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diff --git a/39033-h/39033-h.htm b/39033-h/39033-h.htm new file mode 100644 index 0000000..9a34ab1 --- /dev/null +++ b/39033-h/39033-h.htm @@ -0,0 +1,4993 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of An Introduction to Machine Drawing and Design, by David Allan Low. + </title> + <style type="text/css"> + + p { margin-top: .75em; + text-align: justify; + text-indent: 1.5em; + margin-bottom: .75em; + } + h1,h2,h3,h4,h5,h6 { + text-align: center; /* all headings centered */ + clear: both; + } + hr { width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + table {margin-left: auto; margin-right: auto;} + + body{margin-left: 10%; + margin-right: 10%; + } + + .pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + left: 92%; + font-size: smaller; + text-align: right; + } /* page numbers */ + + .marks {position: absolute; left: 90%; text-align: right;} + .notebox {border: solid 2px; padding: 1em; margin-left: 15%; margin-right: 15%; background: #CCCCB2;} + + .blockquot{font-size: 95%; margin-top: 1.5em; margin-bottom: 1.5em;} + .ft20 {font-size: 110%; font-weight: bold;} + + .bb {border-bottom: solid 1px;} + .bl {border-left: solid 1px;} + .bt {border-top: solid 1px;} + .br {border-right: solid 1px;} + .bbox {border: solid 1px;} + + .center {text-indent: 0em; text-align: center;} + .noidt {text-indent: 0em;} + .negidt {text-indent: -2em;} + .smcap {font-variant: small-caps;} + .u {text-decoration: underline;} + .overline {text-decoration: overline;} + + .caption {font-weight: bold; font-variant: small-caps; text-indent: 0em;} + .tabcap {text-indent: 0em; margin-top: 2em; text-align: center;} + + .figcenter {margin: auto; text-align: center; margin-top: 1.5em; margin-bottom: 1.5em;} + + .figleft {float: left; clear: left; margin-left: 0; margin-bottom: 1em; margin-top: + 1em; margin-right: 1em; padding: 0; text-align: center;} + + .figright {float: right; clear: right; margin-left: 1em; margin-bottom: 1em; + margin-top: 1em; margin-right: 0; padding: 0; text-align: center;} + + .footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 84%; text-align: right;} + .fnanchor {vertical-align: super; font-size: .8em; text-decoration: none;} + + .poem {margin-left:4em; margin-right:2em; text-align: left;} + + </style> + </head> +<body> + + +<pre> + +The Project Gutenberg EBook of An Introduction to Machine Drawing and +Design, by David Allan Low + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: An Introduction to Machine Drawing and Design + +Author: David Allan Low + +Release Date: March 4, 2012 [EBook #39033] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK AN INTRODUCTION TO MACHINE *** + + + + +Produced by Juliet Sutherland and the Online Distributed +Proofreading Team at http://www.pgdp.net + + + + + + +</pre> + + + + +<h3>AN INTRODUCTION</h3> +<h5>TO</h5> +<h1>MACHINE DRAWING</h1> +<h5>AND</h5> +<h1>DESIGN</h1> + +<p> </p> +<h5>BY</h5> + +<h3>DAVID ALLAN LOW</h3> + +<p class="center">(WHITWORTH SCHOLAR), M. INST. M.E.</p> + +<p class="center">HEAD MASTER OF THE PEOPLE'S PALACE TECHNICAL SCHOOLS, LONDON<br /> +AUTHOR OF 'A TEXT-BOOK ON PRACTICAL SOLID OR DESCRIPTIVE GEOMETRY'<br /> +'AN ELEMENTARY TEXT-BOOK OF APPLIED MECHANICS' ETC.</p> + +<div class="figcenter" style="width: 397px;"> +<img src="images/illus001.jpg" width="397" height="336" alt="" title="" /> +</div> + +<h4><i>FOURTH EDITION</i></h4> +<p> </p> + +<h4>LONDON<br /> +<big>LONGMANS, GREEN, AND CO.</big><br /> +<small>AND NEW YORK: 15 EAST 16th STREET</small><br /> +1890</h4> + + +<hr style="width: 15%;" /> +<p class="center">PRINTED BY<br /> +SPOTTISWOODE AND CO., NEW-STREET SQUARE<br /> +LONDON</p> + + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_iii" id="Page_iii">[Pg iii]</a></span></p> +<h2>PREFACE.</h2> + + +<p>It is now generally recognised that the old-fashioned method +of teaching machine drawing is very unsatisfactory. In +teaching by this method an undimensioned scale drawing, +often of a very elaborate description, is placed before the +student, who is required to <i>copy</i> it. Very often the student +succeeds in making a good copy of the drawing placed before +him without learning very much about the object represented +by it, and this state of matters is sometimes not much improved +by the presence of the teacher, who is often simply an art +master, knowing nothing about machine design. It is related +of one school that a pupil, after making a copy of a particular +drawing, had a discussion with his teacher as to whether the +object represented was a sewing machine or an electrical +machine. Evidently the publisher of the drawing example in +this case did not adopt the precaution which a backward +student used at an examination in machine design: he put on +a full title above his drawing, for the information of his +examiner.</p> + +<p>Now, if machine drawing is to be of practical use to any +one, he must be able to understand the form and arrangement +of the parts of a machine from an inspection of suitable drawings +of them without seeing the parts themselves. Also he +ought to be able to make suitable drawings of a machine or +parts of a machine from the machine or the parts themselves.<span class='pagenum'><a name="Page_iv" id="Page_iv">[Pg iv]</a></span></p> + +<p>In producing this work the author has aimed at placing +before young engineers and others, who wish to acquire the +skill and knowledge necessary for making the simpler <i>working +drawings</i> such as are produced in engineers' drawing offices, a +number of good exercises in drawing, sufficient for one session's +work, and at the same time a corresponding amount of information +on the design of machine details generally.</p> + +<p>The exercises set are of various kinds. In the first and +simplest certain views of some machine detail are given, generally +drawn to a small scale, which the student is asked to reproduce +<i>to dimensions marked on these views</i>, and he is expected +to keep to these dimensions, and not to measure anything from +the given illustrations. In the second kind of exercise the +student is asked to reproduce certain views shown <i>to dimensions +given in words or in tabular form</i>. In the third kind of +exercise the student is required to make, in addition to certain +views shown to given dimensions, others which he can only +draw correctly if he thoroughly understands the design before +him. In the fourth kind of exercise the student is asked to +make the necessary working drawings for some part of a +machine which has been previously described and illustrated, +<i>the dimensions to be calculated by rules given in the text</i>.</p> + +<p>The illustrations for this work are all new, and have been +specially prepared by the author from <i>working drawings</i>, and +he believes that they will be found to represent the best +modern practice.</p> + +<p>As exercises in drawing, those given in this book are not +numbered exactly in their order of difficulty, but unless on the +recommendation of a teacher, the student should take them up +in the order given, omitting the following:—26, 27, 28, 35, 40, +42, 43, 45, 49, 50, 54, 60, 61, as he comes to them, until he has +been right through the book; afterwards he should work out +those which he omitted on first going over the book.</p> +<p><span class='pagenum'><a name="Page_v" id="Page_v">[Pg v]</a></span></p> +<p>In addition to the exercises given in this work the student +should practise making freehand sketches of machine details +from actual machines or good models of them. Upon these +sketches he should put the proper dimensions, got by direct +measurement from the machine or model by himself. These +sketches should be made in a note-book kept for the purpose, +and no opportunity should be lost of inserting a sketch of any +design which may be new to the student, always putting on +the dimensions if possible. These sketches form excellent +examples from which to make working drawings. The student +should also note any rules which he may meet with for proportioning +machines, taking care, however, in each case to state +the source of such information for his future guidance and +reference.</p> + +<p>As machine drawing is simply the application of the +principles of descriptive geometry to the representation of +machines, the student of the former subject, if he is not +already acquainted with the latter, should commence to study +it at once.</p> + +<p style='text-align: right'>D. A. L.</p> + +<p><span class="smcap">Glasgow</span>: <i>March</i> 1887.</p> + + + +<hr style="width: 15%;" /> +<h3><i>PREFACE TO THE THIRD EDITION.</i></h3> + +<p>To this edition another chapter has been added, containing a +number of miscellaneous exercises, which it is hoped will add +to the usefulness of the work as a text-book in science classes. +The latest examination paper in machine drawing by the +Science and Art Department has also been added to the +Appendix.</p> + +<p style='text-align: right'>D. A. L.</p> + +<p><span class="smcap">London</span>: <i>August</i> 1888.</p> +<p><span class='pagenum'><a name="Page_vi" id="Page_vi">[Pg vi]</a></span></p> + + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_vii" id="Page_vii">[Pg vii]</a></span></p> +<h2>CONTENTS.</h2> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='right'></td><td align='right'></td><td align='right'>PAGE</td></tr> +<tr><td align='right'>I.</td><td align='left'>INTRODUCTION</td><td align='right'><a href="#Page_1">1</a></td></tr> +<tr><td align='right'>II.</td><td align='left'>RIVETED JOINTS</td><td align='right'><a href="#Page_6">6</a></td></tr> +<tr><td align='right'>III.</td><td align='left'>SCREWS, BOLTS, AND NUTS</td><td align='right'><a href="#Page_14">14</a></td></tr> +<tr><td align='right'>IV.</td><td align='left'>KEYS</td><td align='right'><a href="#Page_22">22</a></td></tr> +<tr><td align='right'>V.</td><td align='left'>SHAFTING</td><td align='right'><a href="#Page_24">24</a></td></tr> +<tr><td align='right'>VI.</td><td align='left'>SHAFT COUPLINGS</td><td align='right'><a href="#Page_25">25</a></td></tr> +<tr><td align='right'>VII.</td><td align='left'>BEARINGS FOR SHAFTS</td><td align='right'><a href="#Page_30">30</a></td></tr> +<tr><td align='right'>VIII.</td><td align='left'>PULLEYS</td><td align='right'><a href="#Page_36">36</a></td></tr> +<tr><td align='right'>IX.</td><td align='left'>TOOTHED WHEELS</td><td align='right'><a href="#Page_39">39</a></td></tr> +<tr><td align='right'>X.</td><td align='left'>CRANKS AND CRANKED SHAFTS</td><td align='right'><a href="#Page_43">43</a></td></tr> +<tr><td align='right'>XI.</td><td align='left'>ECCENTRICS</td><td align='right'><a href="#Page_47">47</a></td></tr> +<tr><td align='right'>XII.</td><td align='left'>CONNECTING RODS</td><td align='right'><a href="#Page_49">49</a></td></tr> +<tr><td align='right'>XIII.</td><td align='left'>CROSS-HEADS</td><td align='right'><a href="#Page_56">56</a></td></tr> +<tr><td align='right'>XIV.</td><td align='left'>PISTONS</td><td align='right'><a href="#Page_57">57</a></td></tr> +<tr><td align='right'>XV.</td><td align='left'>STUFFING-BOXES</td><td align='right'><a href="#Page_63">63</a></td></tr> +<tr><td align='right'>XVI.</td><td align='left'>VALVES</td><td align='right'><a href="#Page_68">68</a></td></tr> +<tr><td align='right'>XVII.</td><td align='left'>MATERIALS USED IN MACHINE CONSTRUCTION</td><td align='right'><a href="#Page_76">76</a></td></tr> +<tr><td align='right'>XVIII.</td><td align='left'>MISCELLANEOUS EXERCISES</td><td align='right'><a href="#Page_81">81</a></td></tr> +<tr><td align='right'></td></tr> +<tr><td align='right'></td><td align='left'>APPENDIX A</td><td align='right'><a href="#Page_99">99</a></td></tr> +<tr><td align='right'></td><td align='left'>APPENDIX B</td><td align='right'><a href="#Page_102">102</a></td></tr> +<tr><td align='right'></td><td align='left'>INDEX</td><td align='right'><a href="#Page_113">113</a></td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_viii" id="Page_viii">[Pg viii]</a></span></p> + + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> +<h1>AN INTRODUCTION</h1> + +<h5>TO</h5> + +<h1>MACHINE DRAWING AND DESIGN.</h1> + + + +<hr style="width: 15%;" /> +<h2>I. INTRODUCTION.</h2> + + +<p><i>Drawing Instruments.</i>—For working the exercises in this +book the student should be provided with the following:—A +well-seasoned yellow pine <i>drawing-board</i>, 24 inches long, 17 +inches wide, and <sup>3</sup>⁄<sub>8</sub> inch or <sup>1</sup>⁄<sub>2</sub> inch thick, provided with cross-bars +on the back to give it strength and to prevent warping. +A <b>T</b> <i>square</i>, with a blade 24 inches long attached permanently +to the stock, <i>but not sunk into it</i>. One 45° and one 60° <i>set +square</i>. The short edges of the former may be about 6 inches +and the short edge of the latter about 5 inches long. A <i>pair +of compasses</i> with pen and pencil attachments, and having legs +from 5 inches to 6 inches long. A <i>pair of dividers</i>, with +screw adjustment if possible. A <i>pair of small steel spring +pencil bows</i> for drawing small circles, and a <i>pair of small steel +spring pen bows</i> for inking in the same. A <i>drawing pen</i> for +inking in straight lines. All compasses should have <i>round +points</i>, and if possible <i>needle</i> points. A piece of india-rubber +will also be required, besides two pencils, one marked H or HH +and one marked HB or F; the latter to be used for lining in +a drawing which is not to be inked in, or for freehand work.</p> + +<p>Pencils for mechanical drawing should be sharpened with +a <i>chisel point</i>, and those for freehand work with a <i>round point</i>.<span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span> +<i>Do not wet the pencil</i>, as the lines afterwards made with it are +very difficult to rub out.</p> + +<p>Drawing-paper for working drawings may be secured to +the board by <i>drawing-pins</i>, but the paper for finished drawings +or drawings upon which there is to be a large amount of +colouring should be <i>stretched</i> upon the board.</p> + +<p>The student should get the best instruments he can afford +to buy, and he should rather have a few good instruments than +a large box of inferior ones.</p> + +<p><i>Drawing-paper.</i>—The names and sizes of the sheets of +drawing paper are given in the following table:—</p> + +<div class='center'> +<table border="0" cellpadding="1" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='center'>Inches</td></tr> +<tr><td align='left'>Demy</td><td align='left'>20 × 15</td></tr> +<tr><td align='left'>Medium</td><td align='left'>22 × 17</td></tr> +<tr><td align='left'>Royal</td><td align='left'>24 × 19</td></tr> +<tr><td align='left'>Imperial</td><td align='left'>30 × 22</td></tr> +<tr><td align='left'>Atlas</td><td align='left'>34 × 26</td></tr> +<tr><td align='left'>Double Elephant </td><td align='left'>40 × 27</td></tr> +<tr><td align='left'>Antiquarian</td><td align='left'>52 × 31</td></tr> +</table></div> + +<p>The above sizes must not be taken as exact. In practice +they will be found to vary in some cases as much as an inch.</p> + +<p>Cartridge-paper is made in sheets of various sizes, and also +in rolls.</p> + +<p>Hand-made paper is the best, but it is expensive. Good +cartridge-paper is quite suitable for ordinary drawings.</p> + +<p><i>Centre Lines.</i>—Drawings of most parts of machines will be +found to be symmetrical about certain lines called <i>centre lines</i>. +These lines should be drawn first with great care. On a pencil +drawing centre lines should be thin continuous lines; in this +book they are shown thus — - — - —.</p> + +<p>After drawing the centre line of any part the dimensions +of that part must be marked off from the centre line, so as to +insure that it really is the centre line of that part: thus in +making a drawing of a rivet, such as is shown at (<i>a</i>) fig. 1, +after drawing the centre line, half the diameter of the rivet +would be marked off on each side of that line, in order to +determine the lines for the sides of the rivet.</p> + +<p><i>Inking.</i>—For inking in drawings the best Indian ink +should be used, and not common writing ink. Common ink<span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span> +does not dry quick enough, and rapidly corrodes the drawing +pens. The pen should be filled by means of a brush or a +narrow strip of paper, and not by dipping the pen into the ink.</p> + +<p>In cases where there are straight lines and arcs of circles +touching one another <i>ink in the arcs first</i>, then the straight +lines; in this way it is easier to hide the joints.</p> + +<p><i>Colouring.</i>—Camel's-hair or sable brushes should be used; +the latter are the best, but are much more expensive than the +former. The colour should be rubbed down in a dish, and the +tint should be light. The mistake which a beginner invariably +makes is in having the colour of too dark a tint.</p> + +<p>First go over the part to be coloured with the brush and +<i>clean</i> water for the purpose of damping it. Next dry with +clean blotting-paper to take off any superfluous water. Then +take another brush with the colour, and beginning at the top, +work from left to right and downwards. If it is necessary to +recolour any part let the first coating dry before beginning.</p> + +<p>Engineers have adopted certain colours to represent particular +materials; these are given in the following table:—</p> + +<p class="tabcap"><i>Table showing Colours used to represent Different Materials.</i></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'><span class="smcap">Material</span></td><td align='center'><span class="smcap">Colour</span></td></tr> +<tr><td align='left'>Cast iron</td><td align='left'>Payne's grey or neutral tint.</td></tr> +<tr><td align='left'>Wrought iron</td><td align='left'>Prussian blue.</td></tr> +<tr><td align='left'>Steel</td><td align='left'>Purple (mixture of Prussian blue and crimson lake).</td></tr> +<tr><td align='left'>Brass</td><td align='left'>Gamboge with a little sienna or a very little red added.</td></tr> +<tr><td align='left'>Copper</td><td align='left'>A mixture of crimson lake and gamboge, the former colour predominating.</td></tr> +<tr><td align='left'>Lead</td><td align='left'>Light Indian ink with a very little indigo added.</td></tr> +<tr><td align='left'>Brickwork</td><td align='left'>Crimson lake and burnt sienna.</td></tr> +<tr><td align='left'>Firebrick</td><td align='left'>Yellow and Vandyke brown.</td></tr> +<tr><td align='left'>Greystones</td><td align='left'>Light sepia or pale Indian ink, with a little Prussian blue added.</td></tr> +<tr><td align='left'>Brown freestone </td><td align='left'>Mixture of pale Indian ink, burnt sienna, and carmine.</td></tr> +<tr><td align='left'>Soft woods</td><td align='left'>For ground work, pale tint of sienna.</td></tr> +<tr><td align='left'>Hard woods</td><td align='left'>For ground work, pale tint of sienna with a little red added.</td></tr> +<tr><td align='left'></td><td align='left'>For graining woods use darker tint with a greater proportion of red.</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span></p> + +<p><i>Printing.</i>—A good drawing should have its title printed, +a plain style of letter being used for this purpose, such as the +following:—</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus012a.png" width="800" height="388" alt="" title="" /> +</div> + +<p>The following letters look well <i>if they are well made</i>, but +they are much more difficult to draw.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus012b.png" width="800" height="188" alt="" title="" /> +</div> + +<p>For remarks on a drawing the following style is most suitable:—</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus012.png" width="800" height="68" alt="" title="" /> +</div> + +<p>All printing should be done by freehand.</p> + +<p><i>Border lines</i> are seldom put on engineering drawings.</p> + +<p><i>Working Drawings.</i>—A good working drawing should be +prepared in the following manner. It must first be carefully +outlined in pencil and then inked in. After this all parts cut +by planes of section should be coloured, the colours used +indicating the materials of which the parts are made. Parts +which are round may also be lightly shaded with the brush +and colours to suit the materials. The centre lines are now +inked in with <i>red</i> or <i>blue ink</i>. The red ink may be prepared +by rubbing down the cake of crimson lake, and the blue ink<span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span> +in like manner from the cake of Prussian blue. Next come +the <i>distance</i> or <i>dimension</i> lines, which should be put in with +<i>blue</i> or <i>red ink</i>, depending on which colour was used for the +centre lines. Dimension lines and centre lines are best put in +of different colour. The arrow-heads at the ends of the +dimension lines are now put in with <i>black ink</i>, and so are the +figures for the dimensions. The arrow-heads and the figures +should be made with a common writing pen. The dimensions +should be put on neatly. Many a good drawing has its appearance +spoiled through being slovenly dimensioned.</p> + +<p>We may here point out the importance of putting the +dimensions on a working drawing. If the drawing is not +dimensioned, the workman must get his sizes from the drawing +by applying his rule or a suitable scale. Now this operation +takes time, and is very liable to result in error. Time is +therefore saved, and the chance of error reduced, by marking +the sizes in figures.</p> + +<p>In practice it is not usual to send original drawings from +the drawing office to the workshop, but copies only. The copies +may be produced by various 'processes,' or they may be tracings +drawn by hand. Many engineers do not ink in their +original drawings, but leave them in pencil; especially is this +the case if the drawings are not likely to be much used.</p> + +<p><i>Scales.</i>—The best scales are made of ivory, and are twelve +inches long. Boxwood scales are much cheaper, although +not so durable as those made of ivory. If the student does +not care to go to the expense of ivory or boxwood scales, he +can get paper ones very cheap, which will be quite sufficient +for his purpose. The divisions of the scale should be marked +down to its edge, so that measurements may be made by applying +the scale directly to the drawing. For working such +exercises as are in this book the student should be provided +with the following scales:—</p> + +<div class='center'> +<table border="0" cellpadding="1" cellspacing="0" summary=""> +<tr><td align='center'></td><td align='center'>A scale of</td><td align='center'>1,</td><td align='center'>or</td><td align='center'>12</td><td align='center'>inches to a foot.</td></tr> +<tr><td align='center'></td><td align='center'>”</td><td align='center'><sup>1</sup>⁄<sub>2</sub></td><td align='center'>”</td><td align='center'>6</td><td align='center'>”</td></tr> +<tr><td align='center'></td><td align='center'>”</td><td align='center'><sup>1</sup>⁄<sub>3</sub></td><td align='center'>”</td><td align='center'>4</td><td align='center'>”</td></tr> +<tr><td align='center'></td><td align='center'>”</td><td align='center'><sup>1</sup>⁄<sub>4</sub></td><td align='center'>”</td><td align='center'>3</td><td align='center'>”</td></tr> +<tr><td align='center'></td><td align='center'>”</td><td align='center'><sup>1</sup>⁄<sub>6</sub></td><td align='center'>”</td><td align='center'>2</td><td align='center'>”</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span></p> + +<p>A scale of 1 is spoken of as 'full size,' and a scale of <sup>1</sup>⁄<sub>2</sub> as +'half size.'</p> + +<p>Engineers in this country state dimensions of machines in +feet, inches, and fractions of an inch, the latter being the <sup>1</sup>⁄<sub>2</sub>, <sup>1</sup>⁄<sub>4</sub>, +<sup>1</sup>⁄<sub>8</sub>, <sup>1</sup>⁄<sub>16</sub>, &c. In making calculations it is generally more convenient +to use decimal fractions, and then substitute for the +results the equivalent fractions in eighths, sixteenths, &c. +The following table will be found useful for this purpose:—</p> + +<p class="tabcap"><i>Decimal Equivalents of Fractions of an Inch.</i></p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="groups"> +<colgroup><col width="25%" /></colgroup> +<colgroup><col width="25%" /></colgroup> +<colgroup><col width="25%" /></colgroup> +<colgroup><col width="25%" /></colgroup> +<thead> +<tr> +<th class="bbox"><small>Fraction</small></th> +<th class="bbox"><small>Decimal Equivalent</small></th> +<th class="bbox"><small>Fraction</small></th> +<th class="bbox"><small>Decimal Equivalent</small></th> +</tr> +</thead> +<tbody> +<tr><td align='left'> <sup>1</sup>⁄<sub>32</sub></td><td align='left'> ·03125</td><td align='left'> <sup>17</sup>⁄<sub>32</sub></td><td align='left'> ·53125</td></tr> +<tr><td align='right'> <sup>1</sup>⁄<sub>16</sub></td><td align='left'> ·0625</td><td align='right'> <sup>9</sup>⁄<sub>16</sub></td><td align='left'> ·5625</td></tr> +<tr><td align='left'> <sup>3</sup>⁄<sub>32</sub></td><td align='left'> ·09375</td><td align='left'> <sup>19</sup>⁄<sub>32</sub></td><td align='left'> ·59375</td></tr> +<tr><td align='right'> <sup>1</sup>⁄<sub>8</sub></td><td align='left'> ·125</td><td align='right'> <sup>5</sup>⁄<sub>8</sub></td><td align='left'> ·625</td></tr> +<tr><td align='left'> <sup>5</sup>⁄<sub>32</sub></td><td align='left'> ·15625</td><td align='left'> <sup>21</sup>⁄<sub>32</sub></td><td align='left'> ·65625</td></tr> +<tr><td align='right'> <sup>3</sup>⁄<sub>16</sub></td><td align='left'> ·1875</td><td align='right'> <sup>11</sup>⁄<sub>16</sub></td><td align='left'> ·6875</td></tr> +<tr><td align='left'> <sup>7</sup>⁄<sub>32</sub></td><td align='left'> ·21875</td><td align='left'> <sup>23</sup>⁄<sub>32</sub></td><td align='left'> ·71875</td></tr> +<tr><td align='right'> <sup>1</sup>⁄<sub>4</sub></td><td align='left'> ·25</td><td align='right'> <sup>3</sup>⁄<sub>4</sub></td><td align='left'> ·75</td></tr> +<tr><td align='left'> <sup>9</sup>⁄<sub>32</sub></td><td align='left'> ·28125</td><td align='left'> <sup>25</sup>⁄<sub>32</sub></td><td align='left'> ·78125</td></tr> +<tr><td align='right'> <sup>5</sup>⁄<sub>16</sub></td><td align='left'> ·3125</td><td align='right'> <sup>13</sup>⁄<sub>16</sub></td><td align='left'> ·8125</td></tr> +<tr><td align='left'> <sup>11</sup>⁄<sub>32</sub></td><td align='left'> ·34375</td><td align='left'> <sup>27</sup>⁄<sub>32</sub></td><td align='left'> ·84375</td></tr> +<tr><td align='right'> <sup>3</sup>⁄<sub>8</sub></td><td align='left'> ·375</td><td align='right'> <sup>7</sup>⁄<sub>8</sub></td><td align='left'> ·875</td></tr> +<tr><td align='left'> <sup>13</sup>⁄<sub>32</sub></td><td align='left'> ·40625</td><td align='left'> <sup>29</sup>⁄<sub>32</sub></td><td align='left'> ·90625</td></tr> +<tr><td align='right'> <sup>7</sup>⁄<sub>16</sub></td><td align='left'> ·4375</td><td align='right'> <sup>15</sup>⁄<sub>16</sub></td><td align='left'> ·9375</td></tr> +<tr><td align='left'> <sup>15</sup>⁄<sub>32</sub></td><td align='left'> ·46875</td><td align='left'> <sup>31</sup>⁄<sub>32</sub></td><td align='left'> ·96875</td></tr> +<tr><td align='right'> <sup>1</sup>⁄<sub>2</sub></td><td align='left'> ·5</td><td align='right'> 1</td><td align='left'> 1·0</td></tr> +</tbody> +</table></div> + +<p>Engineers use a single accent (´) to denote <i>feet</i>, and a double +accent (´´) to denote <i>inches</i>. Thus 2´ 9´´ reads two feet nine +inches.</p> + + + +<hr style="width: 15%;" /> +<h2>II. RIVETED JOINTS.</h2> + + +<p>Two plates or pieces to be riveted together have holes +punched or drilled in them in such a manner that one may be +made to overlap the other so that the holes in the one may be +opposite the holes in the other. The rivets, which are round +bars of iron, or steel, or other metal, are heated to redness +and inserted in the holes; the head already formed on the +rivet, and called the tail, is then held up, and the point is hammered +or pressed so as to form another head. This process of<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span> +forming the second head on the rivet is known as riveting, +and may be done by hand-hammering or by a machine.</p> + +<p><i>Forms of Rivet Heads.</i>—In fig. 1 are shown four different +forms of rivet heads: (<i>a</i>) is a <i>snap head</i>, (<i>b</i>) a <i>conical head</i> +(<i>c</i>) a <i>pan head</i>, and (<i>d</i>) <i>a countersunk head</i>.</p> + +<p><i>Proportions of Rivet Heads.</i>—The diameter of the snap +head is about 1·7 times the diameter of the rivet, and its height +about ·6 of the diameter of the rivet. The conical head has a +diameter twice and a height three quarters of the rivet +diameter. The greatest diameter of the pan head is about 1·6, +and its height ·7 of the rivet diameter. The greatest diameter +of the countersunk head may be one and a half, and its depth +a half of the diameter of the rivet.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus015.jpg" width="800" height="353" alt="Fig. 1." title="Fig. 1." /> +<span class="caption">Fig. 1.</span> +</div> + +<p>In fig. 1 at (<i>a</i>) and (<i>b</i>) are shown geometrical constructions +devised by the author for drawing the snap and conical head +for any size of rivet, the proportions being nearly the same as +those given above.</p> + +<p><i>Geometrical Construction for Proportioning Snap Heads.</i>—With +centre A, and radius equal to half diameter of rivet, +describe a circle cutting the centre line of the rivet at B and C. +With centre B and radius BC describe the arc CD. Make +BE equal to AD. With centre E and radius ED describe the +arc DFH.</p> + +<p><i>Construction for Conical Head.</i>—With centre K, and radius +equal to diameter of rivet, describe the semicircle LMN, cutting +the side of the rivet at M. With centre M and radius MN<span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span> +describe the arc NP to cut the centre line of rivet at P. Join +PL and PN.</p> + +<p>When a number of rivets of the same diameter have to be +shown on the same drawing the above constructions need only +be performed on one rivet. After the point E has been discovered +the distance AE may be measured off on all the other +rivets, and the arcs corresponding to DFH drawn with radii +equal to ED. In like manner the height KP of the conical +head may be marked off on all rivets of the same diameter +with conical heads.</p> + +<p><i>Caulking.</i>—In order to make riveted joints steam- or water-tight +the edges of the plates and the edges of the heads of the +rivets are burred down by a blunt chisel or caulking tool as +shown at Q and R.</p> + +<div class="figcenter" style="width: 800px;"> +<div class="figleft" style="width: 331px;"> +<img src="images/illus016a.jpg" width="331" height="640" alt="Fig. 2." title="Fig. 2." /> +<span class="caption">Fig. 2.</span> +</div> +<div class="figright" style="width: 396px;"> +<img src="images/illus016b.jpg" width="396" height="640" alt="Fig. 3." title="Fig. 3." /> +<span class="caption">Fig. 3.</span> +</div> +</div> +<div style="clear: both;"></div> + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 1: <i>Forms of Rivets.</i>—Draw, full size, the rivets and +rivet heads shown in fig. 1. The diameter of the rivet in each case +to be 1<small><sup>1</sup>⁄<sub>8</sub></small> inches, and the thickness of the plates <sup>7</sup>⁄<sub>8</sub> +inch.</p> + +<p><span class="smcap">Exercise</span> 2: <i>Single Riveted Lap Joint.</i>—Draw, full size, the<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span> +plan and sectional elevation of the <i>single riveted lap joint</i> shown +in fig. 2.</p> +</div> + +<p class="tabcap"><i>Table showing the Proportions of Single Riveted Lap Joints for various +Thicknesses of Plates.</i> (<i>Plates and Rivets Wrought Iron.</i>)</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols"> +<thead> +<tr><th class="bbox"><small>Thickness of plates</small></th> +<th class="bbox"> <sup>1</sup>⁄<sub>4</sub></th> +<th class="bbox"> <sup>5</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>3</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>7</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>1</sup>⁄<sub>2</sub></th> +<th class="bbox"> <sup>9</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>5</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>11</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>3</sup>⁄<sub>4</sub></th> +</tr> +</thead> +<tbody> +<tr><td align='left'>Diameter of rivets</td> +<td align='center'> <sup>9</sup>⁄<sub>16</sub></td> +<td align='center'> <sup>5</sup>⁄<sub>8</sub></td> +<td align='center'> <sup>11</sup>⁄<sub>16</sub></td> +<td align='center'> <sup>3</sup>⁄<sub>4</sub></td> +<td align='center'> <sup>13</sup>⁄<sub>16</sub></td> +<td align='center'> <sup>7</sup>⁄<sub>8</sub></td> +<td align='center'> <sup>15</sup>⁄<sub>16</sub></td> +<td align='center'> 1</td> +<td align='center'> 1<small><sup>1</sup>⁄<sub>16</sub></small></td></tr> +<tr><td align='left'>Pitch of rivets</td> +<td align='center'> 1<small><sup>5</sup>⁄<sub>8</sub></small></td> +<td align='center'> 1¾</td> +<td align='center'> 1<small><sup>7</sup>⁄<sub>8</sub></small></td> +<td align='center'> 2</td> +<td align='center'> 2<small><sup>1</sup>⁄<sub>8</sub></small></td> +<td align='center'> 2¼</td> +<td align='center'> 2<small><sup>5</sup>⁄<sub>16</sub></small></td> +<td align='center'> 2<small><sup>3</sup>⁄<sub>8</sub></small></td> +<td align='center'> 2½</td></tr> +<tr><td align='left'>Width of lap</td> +<td align='center'> 1¾</td> +<td align='center'> 2</td> +<td align='center'> 2¼</td> +<td align='center'> 2½</td> +<td align='center'> 2¾</td> +<td align='center'> 2<small><sup>7</sup>⁄<sub>8</sub></small></td> +<td align='center'> 3</td> +<td align='center'> 3<small><sup>1</sup>⁄<sub>8</sub></small></td> +<td align='center'> 3¼</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p class="center">All the dimensions are in inches.</p> + +<div class="figcenter" style="width: 500px;"> +<img src="images/illus017.jpg" width="500" height="800" alt="Fig. 4." title="Fig. 4." /> +<span class="caption">Fig. 4.</span> +</div> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 3.—Draw, half size, a plan and section of a single +riveted lap joint for plates <sup>3</sup>⁄<sub>4</sub>´´ thick to the dimensions given in the +above table.</p> + +<p><span class="smcap">Exercise</span> 4: <i>Double Riveted Lap Joint.</i>—Draw, full size, the +two views of the <i>double riveted lap joint</i> shown in fig. 3.</p> +</div> + +<p><span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> + +<p class="tabcap"><i>Table showing the Proportions of Double Riveted Lap Joints for various +Thicknesses of Plates.</i> (<i>Plates and Rivets Wrought Iron.</i>)</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols"> +<thead> +<tr><th class="bbox"><small>Thickness of plates</small></th> +<th class="bbox"> <sup>3</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>7</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>1</sup>⁄<sub>2</sub></th> +<th class="bbox"> <sup>9</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>5</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>11</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>3</sup>⁄<sub>4</sub></th> +<th class="bbox"> <sup>13</sup>⁄<sub>16</sub></th> +<th class="bbox"> <sup>7</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>15</sup>⁄<sub>16</sub></th> +<th class="bbox"> 1</th> +</tr> +</thead> +<tbody> +<tr><td align='left'>Diameter of rivets</td><td align='center'><sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'><sup>13</sup>⁄<sub>16</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'><sup>15</sup>⁄<sub>16</sub></td><td align='center'> 1</td><td align='center'>1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>3</sup>⁄<sub>16</sub></small></td></tr> +<tr><td align='left'>Pitch of rivets</td><td align='center'>2½</td><td align='center'>2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'>2¾</td><td align='center'>2<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 3</td><td align='center'> 3<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>3¼</td><td align='center'> 3<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 3½</td><td align='center'> 3<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 3¾</td></tr> +<tr><td align='left'>Distance between rows of rivets</td><td align='center'>1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>1¼</td><td align='center'>1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>7</sup>⁄<sub>16</sub></small></td><td align='center'>1<small><sup>9</sup>⁄<sub>16</sub></small></td><td align='center'> 1¾</td><td align='center'>1<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>15</sup>⁄<sub>16</sub></small></td><td align='center'>1<small><sup>15</sup>⁄<sub>16</sub></small></td><td align='center'> 2</td></tr> +<tr><td align='left'>Width of lap</td><td align='center'>3½</td><td align='center'>3¾</td><td align='center'> 4</td><td align='center'>4¼</td><td align='center'>4½</td><td align='center'> 4¾</td><td align='center'> 5</td><td align='center'> 5</td><td align='center'> 5¼</td><td align='center'> 5¼</td><td align='center'> 5½</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<div class="figcenter" style="width: 600px;"> +<img src="images/illus018.jpg" width="600" height="630" alt="Fig. 5." title="Fig. 5." /> +<span class="caption">Fig. 5.</span> +</div> + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 5.—Draw, half size, a plan and section of a double +riveted lap joint for plates <sup>7</sup>⁄<sub>8</sub> inch thick to the dimensions given in +the above table.</p> + +<p><span class="smcap">Exercise</span> 6: <i>Single Riveted Butt Joints.</i>—In fig. 4 are shown +<i>single riveted butt joints</i>. One of the sectional views shows a butt +joint with one <i>cover plate</i> or <i>butt strap</i>; the other sectional view<span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span> +shows the same joint with two cover plates; the third view is a +plan of both arrangements. Draw all these views full size.</p> +</div> + +<div class="figcenter" style="width: 600px;"> +<img src="images/illus019.jpg" width="600" height="703" alt="Fig. 6." title="Fig. 6." /> +<span class="caption">Fig. 6.</span> +</div> + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 7.—Fig. 5 shows a plan and sectional elevation of the +connection of three plates together, which are in the same plane, +by means of single riveted butt joints and single cover plates. The +butt straps where they overlap are forged so as to fit one another +as shown, and thus form a close joint. Draw these views to the +scale of 6 inches to a foot.</p> + +<p>The plates are <sup>1</sup>⁄<sub>2</sub> inch thick and the butt straps <sup>9</sup>⁄<sub>16</sub> inch thick. +All other dimensions must be deduced from the table for single +riveted lap joints.</p> + +<p><span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span></p> + +<p><span class="smcap">Exercise</span> 8.—The connection of three plates by single riveted +lap joints is shown in fig. 6. To make the joint close one plate has +a portion of its edge thinned out, and the plate above it is set up at +this part so as to lie close to the former.</p> + +<p>Draw the three views shown in fig. 6 to the same scale as the +last exercise.</p> + +<p>The plates are <sup>7</sup>⁄<sub>16</sub> inch thick. All other dimensions to be obtained +from table for single riveted lap joints.</p> + +<p><span class="smcap">Exercise</span> 9: <i>Corner of Wrought-iron Tank.</i>—This exercise is +to illustrate the connection of plates which are at right angles to +one another by means of <i>angle irons</i>. Fig. 7 is a plan and elevation +of the corner of a wrought-iron tank. The sides of the tank +are riveted to a vertical angle iron, the cross section of which is +clearly shown in the plan. Another angle iron of the same dimensions +is used in the same way to connect the sides with the bottom. +The sides do not come quite up to the corner of the vertical angle +iron, excepting at the bottom where the horizontal angle iron comes +in. At this point the vertical plates meet one another, and the +edge formed is rounded over to fit the interior of the bend of the +horizontal angle iron so as to make the joint tight. Draw half +size.</p> + +<p>The dimensions are as follows: angle irons 2½ inches × 2½ inches +× <sup>3</sup>⁄<sub>8</sub> inch; plates <sup>3</sup>⁄<sub>8</sub> inch thick; +rivets <sup>11</sup>⁄<sub>16</sub> inch diameter and 2 inches +pitch.</p> + +<p><span class="smcap">Exercise</span> 10: <i>Gusset Stay.</i>—In order that the flat ends of a +steam boiler may not be bulged out by the pressure of the steam +they are strengthened by means of stays. One form of boiler stay, +called a 'gusset stay,' is shown in fig. 8. This stay consists of a +strip of wrought-iron plate which passes in a diagonal direction +from the flat end of the boiler to the cylindrical shell. One end of +this plate is placed between and riveted to two angle irons +which are riveted to the shell of the boiler. A similar arrangement +connects the other end of the stay plate to the flat end of the +boiler. In this example the stay or gusset plate is ¾ of an inch +thick; the angle irons are 4 inches broad and ½ inch thick. The +rivets are 1 inch in diameter. The same figure also illustrates the +most common method of connecting the ends of a boiler to the +shell. The end plates are <i>flanged</i> or bent over at right angles and +riveted to the shell as shown. The radius of the inside curve at +the angle of the flange is 1¼ inches. Draw this example to a scale +of 3 inches to 1 foot.</p> +</div> + +<p><span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<div class="figleft" style="width: 341px;"> +<img src="images/illus021a.jpg" width="341" height="640" alt="Fig. 7." title="Fig. 7." /> +<span class="caption">Fig. 7.</span> +</div> +<div class="figright" style="width: 630px;"> +<img src="images/illus021b.jpg" width="630" height="635" alt="Fig. 8." title="Fig. 8." /> +<span class="caption">Fig. 8.</span> +</div> +</div> + + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span></p> +<h2>III. SCREWS, BOLTS, AND NUTS.</h2> + + +<p><i>Screw Threads.</i>—The various forms of screw threads used +in machine construction are shown in fig. 9. The <i>Whitworth</i> <b>V</b> +thread is shown at (<i>a</i>). This is the standard form of triangular +thread used in this country. The angle between the sides of +the <b>V</b> is 55°, and one-sixth of the total depth is rounded off +both at the top and bottom. At (<i>b</i>) is shown the <i>Sellers</i> <b>V</b> +thread, which is the standard triangular thread used by engineers +in America. In this form of thread the angle between the +sides of the <b>V</b> is 60°, and one-eighth of the total depth is cut +square off at the top and bottom. The <i>Square</i> thread is shown +at (<i>c</i>). This form is principally used for transmitting motion.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus022.jpg" width="800" height="495" alt="Fig. 9." title="Fig. 9." /> +<span class="caption">Fig. 9.</span> +</div> + +<p>Comparing the triangular and square threads, the former is +the stronger of the two; but owing to the normal pressure on +the <b>V</b> thread being inclined to the axis of the screw, that pressure +must be greater than the pressure which is being transmitted +by the screw; and therefore, seeing that the normal +pressure on the square thread is parallel, and therefore equal +to the pressure transmitted in the direction of the axis of the +screw, the friction of the <b>V</b> thread must be greater than the +<span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span>friction of the square thread. In the case of the triangular +thread there is also a tendency of the pressure to burst the +nut. The <i>Buttress</i> thread shown at (<i>e</i>) is designed to combine +the advantages of the <b>V</b> and square threads, but it only has +these advantages when the pressure is transmitted in one +direction; if the direction of the pressure be reversed, the +friction and bursting action on the nut are even greater than +with the <b>V</b> thread, because of the greater inclination of the +slant side of the buttress thread. The angles of the square +thread are frequently rounded to a greater or less extent to +render them less easily damaged. If this rounding is carried to +excess we get the <i>Knuckle</i> thread shown at (<i>d</i>). The rounding +of the angles increases both the strength and the friction.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 11: <i>Forms of Screw Threads.</i>—Draw to a scale of +three times full size the sections of screw threads as shown in +fig. 9. The pitch for the Whitworth, Sellers, and buttress threads +to be <sup>3</sup>⁄<sub>8</sub> inch, and the pitch of the square and knuckle threads to be +<sup>1</sup>⁄<sub>2</sub> inch.</p> +</div> + + +<p class="tabcap"><i>Dimensions of Whitworth Screws.</i></p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols"> +<thead> +<tr> +<th class="bbox"><small>Diameter<br />of screw</small></th> +<th class="bbox"><small>Number of <br />threads per inch</small></th> +<th class="bbox"><small>Diameter at<br />bottom of thread</small></th> +<th class="bbox"><small>Diameter<br />of screw</small></th> +<th class="bbox"><small>Number of <br />threads per inch</small></th> +<th class="bbox"><small>Diameter at<br />bottom of thread</small></th> +<th class="bbox"><small>Diameter<br />of screw</small></th> +<th class="bbox"><small>Number of <br />threads per inch</small></th> +<th class="bbox"><small>Diameter at<br />bottom of thread</small></th> +</tr> +</thead> +<tbody> +<tr><td align='right'> <sup>1</sup>⁄<sub>8</sub></td><td align='right'> 40</td><td align='right'> ·093</td> +<td align='right'> 1¼</td><td align='right'> 7</td><td align='right'> 1·067</td> +<td align='right'> 3½</td><td align='right'> 3¼</td><td align='right'> 3·106</td></tr> + +<tr><td align='left'> <sup>3</sup>⁄<sub>16</sub></td><td align='right'> 24</td><td align='right'> ·134</td> +<td align='left'> 1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='right'> 6</td><td align='right'> 1·162</td> +<td align='left'> 3¾</td><td align='right'> 3</td><td align='right'> 3·323</td></tr> + +<tr><td align='right'> <sup>1</sup>⁄<sub>4</sub></td><td align='right'> 20</td><td align='right'> ·186</td> +<td align='right'> 1½</td><td align='right'> 6</td><td align='right'> 1·286</td> +<td align='right'> 4</td><td align='right'> 3</td><td align='right'> 3·573</td></tr> + +<tr><td align='left'> <sup>5</sup>⁄<sub>16</sub></td><td align='right'> 18</td><td align='right'> ·241</td> +<td align='left'> 1<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='right'> 5</td><td align='right'> 1·369</td> +<td align='left'> 4¼</td><td align='right'> 2<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='right'> 3·805</td></tr> + +<tr><td align='right'> <sup>3</sup>⁄<sub>8</sub></td><td align='right'> 16</td><td align='right'> ·295</td> +<td align='right'> 1¾</td><td align='right'> 5</td><td align='right'> 1·494</td> +<td align='right'> 4½</td><td align='right'> 2<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='right'> 4·055</td></tr> + +<tr><td align='left'> <sup>7</sup>⁄<sub>16</sub></td><td align='right'> 14</td><td align='right'> ·346</td> +<td align='left'> 1<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='right'> 4½</td><td align='right'> 1·590</td> +<td align='left'> 4¾</td><td align='right'> 2¾</td><td align='right'> 4·284</td></tr> + +<tr><td align='right'> <sup>1</sup>⁄<sub>2</sub></td><td align='right'> 12</td><td align='right'> ·393</td> +<td align='right'> 2</td><td align='right'> 4½</td><td align='right'> 1·715</td> +<td align='right'> 5</td><td align='right'> 2¾</td><td align='right'> 4·534</td></tr> + +<tr><td align='left'> <sup>5</sup>⁄<sub>8</sub></td><td align='right'> 11</td><td align='right'> ·508</td> +<td align='left'> 2¼</td><td align='right'> 4</td><td align='right'> 1·930</td> +<td align='left'> 5¼</td><td align='right'> 2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='right'> 4·762</td></tr> + +<tr><td align='right'> <sup>3</sup>⁄<sub>4</sub></td><td align='right'> 10</td><td align='right'> ·622</td> +<td align='right'> 2½</td><td align='right'> 4</td><td align='right'> 2·180</td> +<td align='right'> 5½</td><td align='right'> 2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='right'> 5·012</td></tr> + +<tr><td align='left'> <sup>7</sup>⁄<sub>8</sub></td><td align='right'> 9</td><td align='right'> ·733</td> +<td align='left'> 2¾</td><td align='right'> 3½</td><td align='right'> 2·384</td> +<td align='left'> 5¾</td><td align='right'> 2½</td><td align='right'> 5·238</td></tr> + +<tr><td align='right'> 1</td><td align='right'> 8</td><td align='right'> ·840</td> +<td align='right'> 3</td><td align='right'> 3½</td><td align='right'> 2·634</td> +<td align='right'> 6</td><td align='right'> 2½</td><td align='right'> 5·488</td></tr> + +<tr><td align='left'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='right'> 7</td><td align='right'> ·942</td> +<td align='left'> 3¼</td><td align='right'> 3¼</td><td align='right'> 2·856</td> +<td></td><td></td><td></td></tr> + +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p class="tabcap"><i>Gas Threads</i><a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> (<i>Whitworth Standard</i>).</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols"> +<thead> +<tr><th class="bbox"><small>Diameter of Screw</small></th> +<th class="bbox"> <sup>1</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>1</sup>⁄<sub>4</sub></th> +<th class="bbox"> <sup>3</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>1</sup>⁄<sub>2</sub></th> +<th class="bbox"> <sup>5</sup>⁄<sub>8</sub></th> +<th class="bbox"> <sup>3</sup>⁄<sub>4</sub></th> +<th class="bbox"> 1</th> +<th class="bbox"> 1¼</th> +<th class="bbox"> 1½</th> +<th class="bbox"> 1¾</th> +<th class="bbox"> 2</th> +</tr> +</thead> +<tbody> +<tr><td align='center'>Number of threads per inch</td><td align='center'> 28</td><td align='center'> 19</td><td align='center'> 19</td><td align='center'> 14</td><td align='center'> 14</td><td align='center'> 14</td><td align='center'> 11</td><td align='center'> 11</td><td align='center'> 11</td><td align='center'> 11</td><td align='center'> 11</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> Used for wrought-iron and brass tubes.<span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span></p></div> + +<p><i>Representation of Screws.</i>—The correct method of representing +screw threads involves considerable trouble, and is +seldom adopted by engineers for working drawings. For an +explanation of the method see the author's Text-book on +Practical Solid Geometry, Part II., problem 134. A method +very often adopted on working drawings is shown in fig. 15; +here the thin lines represent the points, and the thick lines +the roots of the threads. At fig. 16 is shown a more complete +method. The simplest method is illustrated by figs. 10, 11, +13, and 14.</p> + +<p>Here dotted lines are drawn parallel to the axis of the +screw as far as it extends, and at a distance from one another +equal to the diameter of the screw at the bottom of the +thread.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus024.jpg" width="800" height="510" alt="Figs. 10, 11." title="Figs. 10, 11." /> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" width="80%"> +<tr><td align='left'><span class="caption">Fig. 10.</span></td><td align='right'><span class="caption">Fig. 11.</span></td></tr> +</table></div> +</div> + +<p><i>Forms of Nuts.</i>—The most common form of nut is the +hexagonal shown in figs. 10, 13, 14, 15, and 16; next to this +comes the square nut shown in fig. 11. The method of drawing +these nuts will be understood by reference to the figures; the +small circles indicate the centres, and the inclined lines passing +through them the radii of the curves which represent the +chamfered or bevelled edge of the nut. In all the figures but<span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span> +the first the chamfer is just sufficient to touch the middle +points of the sides, and in these cases the drawing of the nut is +simpler.</p> + +<div class="figcenter" style="width: 640px;"> +<img src="images/illus025a.jpg" width="640" height="407" alt="Fig. 12." title="Fig. 12." /> +<span class="caption">Fig. 12.</span> +</div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus025b.jpg" width="800" height="388" alt="Figs. 13, 14." title="Figs. 13, 14." /> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" width="80%"> +<tr><td align='left'><span class="caption">Fig. 13.</span></td><td align='right'><span class="caption">Fig. 14.</span></td></tr> +</table></div> +</div> + +<p><i>Forms of Bolts.</i>—At (<i>a</i>), fig. 12, is shown a bolt with a +square head and a square neck. If this form of bolt is passed +through a square hole the square neck prevents the bolt from +turning when the nut is being screwed up. Instead of a +square neck a snug may be used for the same purpose, as shown +on the cup-headed bolt at (<i>b</i>). The snug fits into a short +groove cut in the side of the hole through which the bolt<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span> +passes. At (<i>a</i>) the diagonal lines are used to distinguish the +flat side of the neck from the round part of the bolt above +it. At (<i>c</i>) is shown a tee-headed bolt, and at (<i>d</i>) an eye-bolt. +Fig. 13 represents a hook bolt. A bolt with a countersunk head +is shown in fig. 11. If the countersunk head be lengthened so +as to take up the whole of the unscrewed part of the bolt, we +get the taper bolt shown in fig. 14, which is often used in the +couplings of the screw shafts of steamships. The taper bolt +has the advantage of having no projecting head, and it may +also be made a tight fit in the hole with less trouble than a +parallel bolt. Bolts may also have hexagonal heads.</p> + +<div class="figcenter" style="width: 800px;"> +<div class="figleft" style="width: 390px;"> +<img src="images/illus026a.png" width="390" height="415" alt="Fig. 15." title="Fig. 15." /> +<span class="caption">Fig. 15.</span> +</div> +<div class="figright" style="width: 336px;"> +<img src="images/illus026b.png" width="336" height="414" alt="Fig. 16." title="Fig. 16." /> +<span class="caption">Fig. 16.</span> +</div> +</div> +<div style="clear: both;"></div> + +<p><i>Studs</i>, or <i>stud bolts</i>, are shown in figs. 15 and 16; that in +fig. 15 is a <i>plain stud</i>, while that in fig. 16 has an intermediate +collar forged upon it, and is therefore called a <i>collared stud</i>.</p> + +<p><i>Proportions of Nuts and Bolt-heads.</i>—In the hexagonal nut +the diameter D across the flats is 1½<i>d</i> + <sup>1</sup>⁄<sub>8</sub>, where <i>d</i> is the +diameter of the bolt. The same rule gives the width of a +square nut across the flats. A rule very commonly used in +making drawings of hexagonal nuts is to make the diameter +D, across the angles equal to 2<i>d</i>. H, the height of the nut, +is equal to the diameter of the bolt. In square and hexagonal +headed bolts the height of the head varies from <i>d</i> to <sup>2</sup>⁄<sub>3</sub><i>d</i>; +the other dimensions are the same as for the corresponding +nuts.<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span></p> + +<p><i>Washers</i> are flat, circular, wrought-iron plates, having holes +in their centres of the same diameter as the bolts on which +they are used. The object of the washer is to give a smooth +bearing surface for the nut to turn upon, and it is used when +the surfaces of the pieces to be connected are rough, or when +the bolt passes through a hole larger than itself, as shown in +fig. 10. The diameter of the washer is a little more than the +diameter of the nut across the angles, and its thickness about +<sup>1</sup>⁄<sub>8</sub> of the diameter of the bolt.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 12.—Draw, full size, the views shown in fig. 10 of an +hexagonal nut and washer for a bolt 1¼ inches in diameter. The bolt +passes through a hole 1¾ × 1¼. All the dimensions are to be calculated +from the rules which have just been given.</p> + +<p><span class="smcap">Exercise</span> 13.—Draw, full size, the plan and elevation of the +square nut and bolt with countersunk head shown in fig. 11, to the +dimensions given.</p> + +<p><span class="smcap">Exercise</span> 14.—Draw, full size, the elevation of the hook bolt +with hexagonal nut shown in fig. 13 to the dimensions given, and +show also a plan.</p> + +<p><span class="smcap">Exercise</span> 15.—Draw, to a scale of 4 inches to a foot, the conical +bolt for a marine shaft coupling shown in fig. 14. All the parts are +of wrought iron.</p> + +<p><span class="smcap">Exercise</span> 16.—Fig. 15 is a section of the mouth of a small steam-engine +cylinder, showing how the cover is attached; draw this full +size.</p> + +<p><span class="smcap">Exercise</span> 17.—Fig. 16 shows the central portion of the india-rubber +disc valve which is described on page 68. A is the central +boss of the grating, into which is screwed the stud B, upon which is +forged the collar C. The upper part of the stud is screwed, and +carries the guard D and an hexagonal nut E. F is the india-rubber. +The grating and guard are of brass. The stud and nut are of +wrought iron. Draw full size the view shown.</p> +</div> + + +<p><i>Lock Nuts.</i>—In order that a nut may turn freely upon a +bolt, there is always a very small clearance space between the +threads of the nut and those of the bolt. This clearance is shown +exaggerated at (<i>a</i>), fig. 17, where A is a portion of a bolt within +a nut B. Suppose that the bolt is stretched by a force W. +When the nut B is screwed up, the upper surfaces of the +projecting threads of the nut will press on the under surfaces<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span> +of the threads of the bolt with a force P equal and opposite to +W, as shown at (<i>b</i>), fig. 17. When in this condition the nut +has no tendency to slacken back, because of the friction due to +the pressure on the nut. Now suppose that the tension W +on the bolt is momentarily diminished, then the friction which +opposes the turning of the nut may be so much diminished +that a vibration may cause it to slacken back through a small +angle. If this is repeated a great many times the nut may +slacken back so far as to become useless.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus028.png" width="800" height="317" alt="Figs. 17, 18." title="Figs. 17, 18." /> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" width="70%"> +<tr><td align='left'><span class="caption">Fig. 17.</span></td><td align='right'><span class="caption">Fig. 18.</span></td></tr> +</table></div> +</div> + +<div class="figright" style="width: 412px;"> +<img src="images/illus029.png" width="412" height="640" alt="Fig. 19." title="Fig. 19." /> +<span class="caption">Fig. 19.</span> +</div> + +<p>A very common arrangement for locking a nut is shown at +(<i>a</i>), fig. 18. C is an ordinary nut, and B one having half the +thickness of C. B is first screwed up tight so as to act on the +bolt, as shown at (<i>b</i>), fig. 17. C is then screwed on top of B. +When C is almost as tight as it can be made, it is held by one +spanner, while B is turned back through a small angle with +another. The action of the nuts upon the bolt and upon one +another is now as shown at (<i>b</i>), fig. 18. It will be seen that +the nuts are wedged tight on to the bolt, and that this action +is independent of the tension W in the bolt. The nuts will, +therefore, remain tight after the tension in the bolt is removed.</p> + +<p>It is evident that if the nuts are screwed up in the manner +explained, the outer nut C will carry the whole load on the +bolt; hence C should be the thicker of the two nuts. In +practice, the thin nut, called the lock nut, is often placed on +the outside, for the reason that ordinary spanners are too +thick to act on the thin nut when placed under the other.<span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span></p> + +<p>Another very common arrangement for locking a nut is +shown in fig. 19. A is the bolt and B the nut, the lower part +of which is turned circular. A groove C is also turned on the +nut at this part. The circular part of the nut fits into a +circular recess in one of the parts connected by the bolt. +Through this part passes a set screw D, the point of which can +be made to press on the nut at the bottom of the groove C. D +is turned back when the nut B is being moved, and when B +is tightened up, the set +screw is screwed up so as +to press hard on the bottom +of the groove C. The +nut B is thus prevented +from slackening back. The +screw thread is turned off +the set screw at the point +where it enters the groove +on the nut.</p> + +<p>The use of the groove +for receiving the point of +the set screw is this: The +point of the set screw indents +the nut and raises a +bur which would interfere +with the free turning of +the nut in the recess if +the bur was not at the +bottom of a groove. Additional +security is obtained +by drilling a hole +through the point of the bolt, and fitting it with a split pin E.</p> + +<p>Locking arrangements for nuts are exceedingly numerous, +and many of them are very ingenious, but want of space prevents +us describing them. We may point out, however, that +many very good locking arrangements have the defect of only +locking the nut at certain points of a revolution, say at every +30°. It will be noticed that the two arrangements which we +have described are not open to this objection.<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span></p> + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 18.—Draw, full size, a plan, front elevation, and side +elevation of the arrangement of nuts shown in fig. 18, for a bolt <sup>7</sup>⁄<sub>8</sub> +inch diameter.</p> + +<p><span class="smcap">Exercise</span> 19.—Draw the plan and elevation of the nut and locking +arrangement shown in fig. 19. Make also an elevation looking +in the direction of the arrow. Scale 6 inches to a foot.</p> +</div> + + + +<hr style="width: 15%;" /> +<h2>IV. KEYS.</h2> + + +<p><i>Keys</i> are wedges, generally rectangular in section, but sometimes +circular; they are made of wrought iron or steel, and +are used for securing wheels, pulleys, cranks, &c., to shafts.</p> + +<div class="figcenter" style="width: 640px;"> +<img src="images/illus030.jpg" width="640" height="398" alt="Fig. 20." title="Fig. 20." /> +<span class="caption">Fig. 20.</span> +</div> + +<p>Various sections of keys are shown in fig. 20. At (<i>a</i>) is the +<i>hollow</i> or <i>saddle key</i>. With this form of key it is not necessary +to cut the shaft in any way, but its holding power is small, and +it is therefore only used for light work. At (<i>b</i>) is the <i>key on a +flat</i>, sometimes called a <i>flat key</i>. The holding power of this +key is much greater than that of the saddle key. At (<i>c</i>) is +the <i>sunk key</i>, a very secure and very common form.</p> + +<p>The part of the shaft upon which a key rests is called the +<i>key bed</i> or <i>key way</i>, and the recess in the boss of the wheel or +pulley into which the key fits is called the <i>key way</i>; both are +also called <i>key seats</i>. With saddle, flat, and sunk keys the key +bed is parallel to the axis of the shaft; but the key way is<span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span> +deeper at one end than the other to accommodate the taper of +the key. The sides of the key are parallel.</p> + +<p>The <i>round key</i> or taper pin shown at (<i>d</i>) is in general only +used for wheels or cranks which have been previously shrunk +on to their shafts or forced on by great pressure. After the +wheel or crank has been shrunk on, a hole is drilled, half into +the shaft and half into the wheel or crank, to receive the +pin.</p> + +<p>When the point of a key is inaccessible the other end is +provided with a <i>gib head</i> as shown at (<i>e</i>), to enable the key to +be withdrawn.</p> + +<p>A <i>sliding</i> or <i>feather key</i> secures a piece to a shaft so far as +to prevent the one from rotating without the other, but allows +of relative motion in the direction of the axis of the shaft. +This form of key has no taper, and it is secured to the piece +carried by the shaft, but is made a <i>sliding fit</i> in the key way of +the shaft. In one form of feather key the part within the +piece carried by the shaft is dovetailed as shown at (<i>f</i>). In +another form the key has a round projecting pin forged upon +it, which enters a corresponding hole as shown at (<i>g</i>). The +feather key may also be secured to the piece carried by the +shaft by means of one or more screws as shown at (<i>h</i>). The +key way in the shaft is made long enough to permit of the +necessary sliding motion.</p> + +<p><i>Cone Keys.</i>—These are sometimes fitted to pulleys, and are +shown in fig. 32, page 38. In this case the eye of the pulley +is tapered and is larger than the shaft. The space between +the shaft and the boss of the pulley is filled with three <i>saddle</i> or +<i>cone keys</i>. These keys are made of cast iron and are all cast +together, and before being divided the casting is bored to fit +the shaft and turned to fit the eye of the pulley. By this +arrangement of keys the same pulley may be fixed on shafts of +different diameters by using keys of different thicknesses; also +the pulley may be bored out large enough to pass over any +boss which may be forged on the shaft.</p> + +<p><i>Proportions of Keys.</i>—The following rules are taken from +Unwin's 'Machine Design,' pp. 142-43.<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span></p> + + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='left'>Diameter of eye of wheel, or boss of shaft</td><td align='left'>= <i>d</i>.</td></tr> +<tr><td align='left'>Width of key</td><td align='left'>= <sup>3</sup>⁄<sub>4</sub><i>d</i> + <sup>1</sup>⁄<sub>8</sub>.</td></tr> +<tr><td align='left'>Mean thickness of sunk key</td><td align='left'>= <sup>1</sup>⁄<sub>8</sub><i>d</i> + <sup>1</sup>⁄<sub>8</sub>.</td></tr> +<tr><td align='left'> ” key on flat</td><td align='left'>= <sup>1</sup>⁄<sub>16</sub><i>d</i> + <sup>1</sup>⁄<sub>16</sub>.</td></tr> +</table></div> + +<p>The following table gives dimensions agreeing with average +practice.</p> + +<p class="tabcap"><i>Dimensions of Keys.</i></p> + + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='left'>D</td><td align='left'>=</td><td align='left'>diameter of shaft.</td></tr> +<tr><td align='left'>B</td><td align='left'>=</td><td align='left'>breadth of key.</td></tr> +<tr><td align='left'>T</td><td align='left'>=</td><td align='left'>thickness of sunk key.</td></tr> +<tr><td align='left'>T<sub>1</sub></td><td align='left'>=</td><td align='left'>thickness of flat key, also = thickness of saddle key. Taper of key <sup>1</sup>⁄<sub>8</sub> inch per foot of length, <i>i.e.</i> 1 in 96.</td></tr> +</table></div> + +<p> </p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols" width="90%"> +<thead> +<tr><th class="bbox"><small>D</small></th> +<th class="bbox"> ¾</th> +<th class="bbox"> 1</th> +<th class="bbox"> 1¼</th> +<th class="bbox"> 1½</th> +<th class="bbox"> 1¾</th> +<th class="bbox"> 2</th> +<th class="bbox"> 2¼</th> +<th class="bbox"> 2½</th> +<th class="bbox"> 2¾</th> +<th class="bbox"> 3</th> +<th class="bbox"> 3½</th> +</tr> +</thead> +<tbody> +<tr><td align='left'> B</td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'> <sup>9</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>8</sub></td><td align='center'> <sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'> 1</td></tr> +<tr><td align='left'> T</td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td></tr> +<tr><td align='left'>T<sub>1</sub></td><td align='center'> <sup>3</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>16</sub></td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p> </p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols" width="90%"> +<thead> +<tr><th class="bbox"><small>D</small></th> +<th class="bbox"> 4</th> +<th class="bbox"> 4½</th> +<th class="bbox"> 5</th> +<th class="bbox"> 5½</th> +<th class="bbox"> 6</th> +<th class="bbox"> 7</th> +<th class="bbox"> 8</th> +<th class="bbox"> 9</th> +<th class="bbox"> 10</th> +<th class="bbox"> 11</th> +<th class="bbox"> 12</th> +</tr> +</thead> +<tbody> +<tr><td align='left'> B</td><td align='center'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>4</sub></small></td><td align='center'> 1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>2</sub></small></td><td align='center'> 1<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'>2<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>2<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 3<small><sup>1</sup>⁄<sub>8</sub></small></td></tr> +<tr><td align='left'> T</td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'> <sup>9</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>8</sub></td><td align='center'> <sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> <sup>13</sup>⁄<sub>16</sub></td><td align='center'><sup>15</sup>⁄<sub>16</sub></td><td align='center'> 1</td><td align='center'>1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'>1<small><sup>3</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>4</sub></small></td></tr> +<tr><td align='left'>T<sub>1</sub></td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'> <sup>9</sup>⁄<sub>16</sub></td><td align='center'> <sup>5</sup>⁄<sub>8</sub></td><td align='center'> <sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'> <sup>15</sup>⁄<sub>16</sub></td><td align='center'>1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + + + +<hr style="width: 15%;" /> +<h2>V. SHAFTING.</h2> + + +<p>Shafting is nearly always cylindrical and made of wrought +iron or steel. Cast iron is rarely used for shafting.</p> + +<p><i>Axles</i> are shafts which are subjected to bending without +twisting.</p> + +<p>The parts of a shaft or axle which rest upon the bearings +or supports are called <i>journals</i>, <i>pivots</i>, or <i>collars</i>.</p> + +<p>In journals the supporting pressure is at right angles to the +axis of the shaft, while in pivots and collars the pressure is +parallel to that axis.</p> + +<p>Shafts may be solid or hollow. Hollow shafts are stronger +than solid shafts for the same weight of material. Thus a +hollow shaft having an external diameter of 10¼ inches and an +internal diameter of 7 inches would have about the same weight<span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span> +as a solid shaft of the same material 7½ inches in diameter, but +the former would have about double the strength of the latter. +Hollow shafts are also stiffer and yield less to bending action +than solid shafts, which in some cases, as in propeller shafts, +is an objection.</p> + + + +<hr style="width: 15%;" /> +<h2>VI. SHAFT COUPLINGS.</h2> + + +<p>For convenience of making and handling, shafts used for +transmitting power are generally made in lengths not exceeding +30 feet. These lengths are connected by couplings, of which +we give several examples.</p> + +<div class="figcenter" style="width: 706px;"> +<img src="images/illus033.jpg" width="706" height="600" alt="Figs. 21, 22." title="Figs. 21, 22." /> +<span class="caption">Figs. 21 and 22.</span> +</div> + +<p><i>Solid</i>, <i>Box</i>, or <i>Muff Couplings.</i>—One form of box coupling is +shown in fig. 21. Here the ends of the shafts to be connected +butt against one another, meeting at the centre of the box, +which is made of cast iron. The shafts are made to rotate as<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span> +one by being secured to the box by two wrought-iron or steel +keys, both driven from the same end of the box. A clearance +space is left between the head of the forward key and the +point of the hind one, to facilitate the driving of them out, as +then only one key needs to be started at a time. Sometimes +a single key the whole length of the box is used, in which case +it is necessary that the key ways in the shafts be of exactly +the same depth.</p> + +<p>The half-lap coupling, introduced by Sir William Fairbairn, +is shown in fig. 22. In this form of box coupling the ends of +the shafts overlap within the box. It is evident that one shaft +cannot rotate without the other as long as the box remains over +the lap. To keep the box in its place it is fitted with a saddle +key.</p> + +<p>It will be noticed that the lap joint is sloped in such a +way as to prevent the two lengths of shaft from being +pulled asunder by forces acting in the direction of their length.</p> + +<p>Half-lap couplings are not used for shafts above 5 inches +in diameter.</p> + +<p>It may here be pointed out that the half-lap coupling is +expensive to make, and is now not much used.</p> + +<p>As shafts are weakened by cutting key ways in them, very +often the ends which carry couplings are enlarged in diameter, +as shown in fig. 21, by an amount equal to the thickness of the +key. An objection to this enlargement is that wheels and +pulleys require either that their bosses be bored out large +enough to pass over it, or that they be split into halves, which +are bolted together after being placed on the shaft.</p> + + +<p class="tabcap"><i>Dimensions of Box Couplings.</i></p> + + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="2" summary=""> +<tr><td align='left'>D</td><td align='left'>=</td><td align='left'>diameter of shaft.</td></tr> +<tr><td align='left'>T</td><td align='left'>=</td><td align='left'>thickness of metal in box.</td></tr> +<tr><td align='left'>L</td><td align='left'>=</td><td align='left'>length of box for butt coupling.</td></tr> +<tr><td align='left'>L<sub>1</sub></td><td align='left'>=</td><td align='left'>length of box for lap coupling.</td></tr> +<tr><td align='left'><i>l</i></td><td align='left'>=</td><td align='left'>length of lap.</td></tr> +<tr><td align='left'>D<sub>1</sub></td><td align='left'>=</td><td align='left'>diameter of shaft at lap.</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols" width="90%"> +<thead> +<tr><th class="bbox"><small>D</small></th> +<th class="bbox"> 1½</th> +<th class="bbox"> 2</th> +<th class="bbox"> 2½</th> +<th class="bbox"> 3</th> +<th class="bbox"> 3½</th> +<th class="bbox"> 4</th> +<th class="bbox"> 4½</th> +<th class="bbox"> 5</th> +<th class="bbox"> 5½</th> +<th class="bbox"> 6</th> +</tr> +</thead> +<tbody> +<tr><td align='left'>T</td><td align='center'> 1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 1½</td><td align='center'> 1¾</td><td align='center'>1<small><sup>15</sup>⁄<sub>16</sub></small></td><td align='center'> 2<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 2½</td><td align='center'> 2¾</td><td align='center'>2<small><sup>15</sup>⁄<sub>16</sub></small></td></tr> +<tr><td align='left'>L</td><td align='center'> 5¾</td><td align='center'> 7</td><td align='center'> 8¼</td><td align='center'> 9½</td><td align='center'> 10¾</td><td align='center'> 12</td><td align='center'> 13¼</td><td align='center'>14½</td><td align='center'>15¾</td><td align='center'> 17</td></tr> +<tr><td align='left'>L<sub>1</sub></td><td align='center'> 4<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 5¼</td><td align='center'> 6<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 7½</td><td align='center'> 8<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 9¾</td><td align='center'> 10<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 12</td><td align='center'> —</td><td align='center'> —</td></tr> +<tr><td align='left'><i>l</i></td><td align='center'> 7<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 2¾</td><td align='center'> 3<small><sup>3</sup>⁄<sub>16</sub></small></td><td align='center'> 3<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 4<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 4½</td><td align='center'> —</td><td align='center'> —</td></tr> +<tr><td align='left'>D<sub>2</sub></td><td align='center'> 2<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 3</td><td align='center'>3<small><sup>11</sup>⁄<sub>16</sub></small></td><td align='center'> 4<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 5<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 5¾</td><td align='center'> 6<small><sup>7</sup>⁄<sub>16</sub></small></td><td align='center'> 7<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> —</td><td align='center'> —</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p class="center">Slope of lap 1 in 12.</p> + +<div class="figright" style="width: 600px;"> +<img src="images/illus035.jpg" width="480" height="502" alt="Fig. 23." title="Fig. 23." /><br /> +<span class="caption">Fig. 23.</span> +</div> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 20: <i>Solid Butt Coupling.</i>—From the above table of +dimensions make a longitudinal and a transverse section of a solid +butt coupling for a shaft 2½ inches in diameter. Scale 6 inches to +a foot.</p> + +<p><span class="smcap">Exercise</span> 21: <i>Fairbairn's Half-Lap Coupling.</i>—Make the +same views as in the last exercise of a half-lap coupling for a 3-inch +shaft to the dimensions in the above table. Scale 6 inches to +a foot.</p> +</div> + + +<p><i>Flange Couplings.</i>—The form of coupling used for the +shafts of marine engines is shown in fig. 23. The ends of the +different lengths of shaft +have flanges forged on +them, which are turned +along with the shaft. These +flanges butt against one +another, and are connected +by bolts. These bolts may +be parallel or tapered; +generally they are tapered. +A parallel bolt must have +a head, but a tapered bolt +will act without one. In +fig. 23 the bolts are tapered, +and also provided with +heads. In fig. 14, page 17, +is shown a tapered bolt without a head. The variation of +diameter in tapered bolts is <sup>3</sup>⁄<sub>8</sub> of an inch per foot of length.</p> + +<p>Sometimes a projection is formed on the centre of one +flange which fits into a corresponding recess in the centre of +the other, for the purpose of ensuring the shafts being in line.<span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span></p> + +<p>Occasionally a cross-key is fitted in between the flanges, +being sunk half into each, for the purpose of diminishing the +shearing action on the bolts.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 22: <i>Marine Coupling.</i>—Draw the elevation and +section of the coupling shown in fig. 23; also an elevation looking +in the direction of the arrow. Scale 3 inches to a foot.</p> +</div> + + +<p>The following table gives the dimensions of a few marine +couplings taken from actual practice.</p> +<div style="clear: both;"></div> + + +<p class="tabcap"><i>Examples of Marine Couplings.</i></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols" width="90%"> +<thead> +<tr><th class="bbox"><small>Diameter of shaft</small></th> +<th class="bbox"> 2<small><sup>3</sup>⁄<sub>8</sub></small></th> +<th class="bbox"> 9¾</th> +<th class="bbox"> 12<small><sup>7</sup>⁄<sub>8</sub></small></th> +<th class="bbox"> 16½</th> +<th class="bbox"> 22½</th> +<th class="bbox"> 23</th> +</tr> +</thead> +<tbody> +<tr><td align='left'>Diameter of flange</td><td align='center'> 6</td><td align='center'> 19</td><td align='center'> 24</td><td align='center'> 32</td><td align='center'> 35</td><td align='center'> 38</td></tr> +<tr><td align='left'>Thickness of flange</td><td align='center'> 1</td><td align='center'> 2¾</td><td align='center'> 3<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 4¼</td><td align='center'> 6</td><td align='center'> 5</td></tr> +<tr><td align='left'>Diameter of bolts</td><td align='center'> ¾</td><td align='center'> 2¾</td><td align='center'> 2<small><sup>11</sup>⁄<sub>16</sub></small></td><td align='center'> 3½</td><td align='center'> 4¼</td><td align='center'> 4¼</td></tr> +<tr><td align='left'>Number of bolts</td><td align='center'> 3</td><td align='center'> 6</td><td align='center'> 6</td><td align='center'> 8</td><td align='center'> 9</td><td align='center'> 8</td></tr> +<tr><td align='left'>Diameter of bolt circle</td><td align='center'> 4<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 14<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>18<small><sup>13</sup>⁄<sub>16</sub></small></td><td align='center'> 25</td><td align='center'> 28¾</td><td align='center'>30<small><sup>3</sup>⁄<sub>8</sub></small></td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p class="center">All the above dimensions are in inches.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 23.—Select one of the couplings from the above table, +and make the necessary working drawings for it to a suitable +scale.</p> +</div> + + +<p>The cast-iron flange coupling is shown in fig. 24. In this +kind of coupling a cast-iron centre or boss provided with a +flange is secured to the end of each shaft by a sunk key driven +from the face of the flange. These flanges are then connected +by bolts and nuts as in the marine coupling.</p> + +<p>To ensure the shafts being in line the end of one projects +into the flange of the other.</p> + +<p>In order that the face of each flange may be exactly perpendicular +to the axis of the shaft they should be 'faced' in +the lathe, after being keyed on to the shaft.</p> + +<p>If the coupling is in an exposed position, where the nuts +and bolt-heads would be liable to catch the clothes of workmen +or an idle driving band which might come in the way, the +flanges should be made thicker, and be provided with recesses +for the nuts and bolt-heads.<span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span></p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus037.jpg" width="800" height="582" alt="Fig. 24." title="Fig. 24." /> +<span class="caption">Fig. 24.</span> +</div> + + +<p class="tabcap"><i>Dimensions of Cast-iron Flange Couplings.</i></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols" width="90%"> +<thead> +<tr> +<th class="bbox"><small>Diameter<br />of shaft<br />D</small></th> +<th class="bbox"><small>Diameter<br />of flange<br />F</small></th> +<th class="bbox"><small>Thickness<br />of flange<br />T</small></th> +<th class="bbox"><small>Diameter<br />of boss<br />B</small></th> +<th class="bbox"><small>Depth at<br />boss<br />L</small></th> +<th class="bbox"><small>Number<br />of<br />bolts</small></th> +<th class="bbox"><small>Diameter<br />of bolts<br /><i>d</i></small></th> +<th class="bbox"><small>Diameter of<br />bolt circle<br />C</small></th> +</tr> +</thead> +<tbody> +<tr><td align='center'> 1½</td><td align='center'> 7¼</td><td align='center'> <sup>7</sup>⁄<sub>8</sub> </td><td align='center'> 3½</td><td align='center'> 2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 3</td><td align='center'><sup>5</sup>⁄<sub>8</sub></td><td align='center'> 5½</td></tr> +<tr><td align='center'> 2</td><td align='center'> 8<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 4<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 3<small><sup>3</sup>⁄<sub>16</sub></small></td><td align='center'> 4</td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> 6¾</td></tr> +<tr><td align='center'> 2½</td><td align='center'> 10<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 1¼</td><td align='center'> 5<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 3¾</td><td align='center'> 4</td><td align='center'><sup>7</sup>⁄<sub>8</sub></td><td align='center'> 8<small><sup>1</sup>⁄<sub>8</sub></small></td></tr> +<tr><td align='center'> 3</td><td align='center'> 12<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>7</sup>⁄<sub>16</sub></small></td><td align='center'> 6¼</td><td align='center'> 4<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'> 4</td><td align='center'> 1</td><td align='center'> 9½</td></tr> +<tr><td align='center'> 3½</td><td align='center'> 13<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 1<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 7<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 4<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 4</td><td align='center'> 1</td><td align='center'>10<small><sup>5</sup>⁄<sub>16</sub></small></td></tr> +<tr><td align='center'> 4</td><td align='center'> 14</td><td align='center'> 1¾</td><td align='center'> 8</td><td align='center'> 5<small><sup>7</sup>⁄<sub>16</sub></small></td><td align='center'> 6</td><td align='center'> 1</td><td align='center'>11¼</td></tr> +<tr><td align='center'> 4½</td><td align='center'> 15<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 2</td><td align='center'> 8<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 6</td><td align='center'> 6</td><td align='center'>1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>12½</td></tr> +<tr><td align='center'> 5</td><td align='center'> 17<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 9<small><sup>13</sup>⁄<sub>16</sub></small></td><td align='center'> 6<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 6</td><td align='center'> 1¼</td><td align='center'>13<small><sup>13</sup>⁄<sub>16</sub></small></td></tr> +<tr><td align='center'> 5½</td><td align='center'> 18¼</td><td align='center'> 2<small><sup>5</sup>⁄<sub>16</sub></small></td><td align='center'>10¾</td><td align='center'> 7¼</td><td align='center'> 6</td><td align='center'>1¼</td><td align='center'>14¾</td></tr> +<tr><td align='center'> 6</td><td align='center'> 19<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 2½</td><td align='center'>11<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 7¾</td><td align='center'> 6</td><td align='center'> 1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 16</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p>The projection of the shaft <i>p</i> varies from <sup>1</sup>⁄<sub>4</sub> inch in the small +shafts to <sup>1</sup>⁄<sub>2</sub> inch in the large ones.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise</span> 24: <i>Cast-iron Flange Coupling.</i>—Draw +the views shown in fig. 24 of a cast-iron flange coupling, for a shaft 4½ inches +in diameter, to the dimensions given in the above table. Scale 4 +inches to a foot.</p> +</div> + + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span></p> +<h2>VII. BEARINGS FOR SHAFTS.</h2> + + +<div class="figleft" style="width: 640px;"> +<img src="images/illus038.jpg" width="484" height="480" alt="Fig. 25." title="Fig. 25." /><br /> +<span class="caption">Fig. 25.</span> +</div> + +<p>An example of a very simple form of bearing is shown in +fig. 25, which represents a brake shaft carrier of a locomotive +tender. The bearing in this example is made of cast iron and +in one piece. Through the oval-shaped flange two bolts pass +for attaching the bearing to the wrought-iron framing of the +tender. With this form of bearing there is no adjustment for +wear, so that when it becomes worn it must be renewed.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 25: <i>Brake Shaft Carrier.</i>—Draw the elevation and +sectional plan of the bearing shown in fig. 25. Draw also a vertical +section through the axis. The latter view to be projected from +the first elevation. Scale 6 inches to a foot.</p></div> + + +<p><i>Pillow Block</i>, <i>Plummer Block</i>, or <i>Pedestal</i>.—The ordinary +form of plummer block is represented in fig. 26. A is the +block proper, B the +sole through which +pass the holding-down +bolts. C is the cap. +Between the block +and the cap is the +brass bush, which is in +halves, called <i>brasses</i> +or <i>steps</i>. The bed for +the steps in this example +is cylindrical, +and is prepared by the +easy process of boring. +The steps are not +supported throughout +their whole length, +but at their ends only where fitting strips are provided as +shown. As the wear on a step is generally greatest at the +bottom, it is made thicker there than at the sides, except +where the fitting strips come in. To prevent the steps turning +within the block they are generally furnished with lugs, which +enter corresponding recesses in the block and cover.<span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span></p> + +<div class="figcenter" style="width: 900px;"> +<img src="images/illus039.png" width="900" height="540" alt="Fig. 26." title="Fig. 26." /> +<span class="caption">Fig. 26.</span> +</div> + +<p><span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span></p> + +<p>In the block illustrated the journal is lubricated by a <i>needle +lubricator</i>; this consists of an inverted glass bottle fitted with +a wood stopper, through a hole in which passes a piece of wire, +which has one end in the oil within the bottle, and the other +resting on the journal of the shaft. The wire or needle does +not fill the hole in the stopper, but if the needle is kept from +vibrating the oil does not escape owing to capillary attraction. +When, however, the shaft rotates, the needle begins to vibrate, +and the oil runs down slowly on to the journal; oil is therefore +only used when the shaft is running.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 26: <i>Pillow Block for a Four-inch Shaft.</i>—Draw +the views shown of this block in fig. 26. Make also separate drawings, +full size, of one of the steps. Scale 6 inches to a foot.</p></div> + + +<p><i>Proportions of Pillow Blocks.</i>—The following rules may +be used for proportioning pillow blocks for shafts up to 8 inches +diameter. It should be remembered that the proportions used +by different makers vary considerably, but the following rules +represent average practice.</p> + + + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='left'>Diameter of journal</td><td align='left'>= <i>d</i>.</td></tr> +<tr><td align='left'>Length of journal</td><td align='left'>= <i>l</i>.</td></tr> +<tr><td align='left'>Height to centre</td><td align='left'>= 1·05<i>d</i> + ·5.</td></tr> +<tr><td align='left'>Length of base</td><td align='left'>= 3·6<i>d</i> + 5.</td></tr> +<tr><td align='left'>Width of base</td><td align='left'>= ·8<i>l</i>.</td></tr> +<tr><td align='left'> ” block</td><td align='left'>= ·7<i>l</i>.</td></tr> +<tr><td align='left'>Thickness of base</td><td align='left'>= ·3<i>d</i> + ·3.</td></tr> +<tr><td align='left'> ” cap</td><td align='left'>= ·3<i>d</i> + ·4.</td></tr> +<tr><td align='left'>Diameter of bolts</td><td align='left'>= ·25<i>d</i> + ·25.</td></tr> +<tr><td align='left'>Distance between centres of cap bolts</td><td align='left'>= 1·6<i>d</i> + 1·5.</td></tr> +<tr><td align='left'> ” ” base bolts</td><td align='left'>= 2·7<i>d</i> + 4·2.</td></tr> +<tr><td align='left'>Thickness of step at bottom</td><td align='left'>= <i>t</i> = ·09<i>d</i> + ·15.</td></tr> +<tr><td align='left'> ” ” sides</td><td align='left'>= ¾<i>t</i>.</td></tr> +</table></div> + + +<p>The length of the journal varies very much in different +cases, and depends upon the speed of the shaft, the load which +it carries, the workmanship of the journal and bearing, and the +method of lubrication. For ordinary shafting one rule is to +make <i>l</i> = <i>d</i> + 1. Some makers use the rule <i>l</i> = 1·5<i>d</i>; others +make <i>l</i> = 2<i>d</i>.<span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span></p> + +<div class="figcenter" style="width: 768px;"> +<img src="images/illus041.png" width="768" height="925" alt="Fig. 27." title="Fig. 27." /> +<span class="caption">Fig. 27.</span> +</div> + + +<div class="figleft" style="width: 300px;"> +<img src="images/illus042.png" width="154" height="448" alt="Fig. 28." title="Fig. 28." /><br /> +<span class="caption">Fig. 28.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 27: <i>Design for Pillow Block.</i>—Make the necessary +working drawings for a pillow block for a shaft 5 inches in diameter, +and having a journal 7 inches long.</p></div> + +<p><i>Brackets.</i>—When a pillow block has to be fixed to a wall +or column a bracket such as that shown in figs. 27 and 28 may +be used. The pillow block rests between the <i>joggles</i> A A, +and is bolted down to the bracket and secured in addition +with keys at the ends of the base of the block, in the same<span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span> +manner as is shown, for the attachment of the bracket to the +column.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 28: <i>Pillar Bracket.</i>—Fig. 27 shows a side elevation +and part horizontal section, and fig. 28 shows an end elevation of a +pillar bracket for carrying a pillow block for a 3-inch shaft. Draw +these views <i>properly projected from one another</i>, showing the +pillow block, which is to be proportioned +by the rules given on page +32. Draw also a plan of the whole. +Scale 4 inches to a foot.</p></div> + + +<p><i>Hangers.</i>—When a shaft is suspended +from a ceiling it is carried +by hangers, one form of which is +shown in fig. 29, and which will be +readily understood. The cap of +the bearing, it will be noticed, is +secured by means of a bolt, and +also by a square key.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 29: <i>Shaft Hanger.</i>—Draw +the two elevations shown in +fig. 29, and also a sectional plan. The +section to be taken at a point 5 inches +above the centre of the shaft. Scale +6 inches to a foot.</p></div> + + +<p><i>Wall Boxes.</i>—In passing from +one part of a building to another +a shaft may have to pass through +a wall. In that case a neat appearance +is given to the opening +and a suitable support obtained +for a pillow block by building into +the wall a <i>wall box</i>, one form of +which is shown in fig. 30.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 30: <i>Wall Box.</i>—Draw the views of the wall box +shown in fig. 30, and also a sectional plan; the plane of section to +pass through the box a little above the joggles for the pillow block. +Scale 3 inches to a foot.</p></div> + + +<p><span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span></p> + +<div class="figcenter" style="width: 758px;"> +<img src="images/illus043a.png" width="758" height="600" alt="Fig. 29." title="Fig. 29." /> +<span class="caption">Fig. 29.</span> +</div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus043b.png" width="800" height="475" alt="Fig. 30." title="Fig. 30." /> +<span class="caption">Fig. 30.</span> +</div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span></p> +<h2>VIII. PULLEYS.</h2> + + +<p><i>Velocity Ratio in Belt Gearing.</i>—Let two pulleys A and B +be connected by a belt, and let their diameters be D<sub>1</sub> and D<sub>2</sub>; +and let their speeds, in revolutions per minute, be N<sub>1</sub> and N<sub>2</sub> +respectively. If there is no slipping, the speeds of the rims of +the pulleys will be the same as that of the belt, and will therefore +be equal. Now the speed of the rim of A is evidently += D<sub>1</sub> × 3·1416 × N<sub>1</sub>; while the speed of the rim of B is = +D<sub>2</sub> × 3·1416 × N<sub>2</sub>. Hence D<sub>1</sub> × 3·1416 × N<sub>1</sub> = D<sub>2</sub> × 3·1416 × N<sub>2</sub>, +and therefore</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'> N<sub>1</sub> <br /> —— <br /> N<sub>2</sub> </td><td align='center'> = </td><td align='center'> D<sub>2</sub> <br /> ——. <br /> D<sub>1</sub></td></tr> +</table></div> + +<p><i>Pulleys for Flat Bands.</i>—In cross section the rim of a +pulley for carrying a flat band is generally curved as shown +in figs. 31 and 32, but very often the cross section is straight. +The curved cross section of the rim tends to keep the band +from coming off as long as the pulley is rotating. Sometimes +the rim of the pulley is provided with flanges which keep the +band from falling off.</p> + +<p>Pulleys are generally made entirely of cast iron, but a great +many pulleys are now made in which the centre or nave only +is of cast iron, the arms being of wrought iron cast into the +nave, while the rim is of wrought sheet iron.</p> + +<p>The arms of pulleys when made of wrought iron are +invariably straight, but when made of cast iron they are very +often curved. In fig. 31, which shows an arrangement of two +cast-iron pulleys, the arms are straight; while in fig. 32, which +shows another cast-iron pulley, the arms are curved. Through +unequal cooling, and therefore unequal contraction of a cast-iron, +pulley in the mould, the arms are generally in a state of +tension or compression; and if the arms are straight they are +very unyielding, so that the result of this initial stress is often +the breaking of an arm, or of the rim where it joins an arm. +With the curved arm, however, its shape permits it to yield, +and thus cause a diminution of the stress due to unequal contraction.<span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span></p> + +<p>The cross section of the arms of cast-iron pulleys is generally +elliptical.</p> + +<div class="figcenter" style="width: 718px;"> +<img src="images/illus045.png" width="718" height="600" alt="Fig. 31." title="Fig. 31." /> +<span class="caption">Fig. 31.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 31:</span> <i>Fast and Loose Pulleys</i>.—Fig. 31 shows an +arrangement of fast and loose pulleys. A is the fast pulley, secured +to the shaft C by a sunk key; B is the loose pulley, which turns +freely upon the shaft. The loose pulley is prevented from coming off +by a collar D, which is secured to the shaft by a tapered pin as +shown. The nave or boss of the loose pulley is here fitted with a +brass liner, which may be renewed when it becomes too much worn. +Draw the elevations shown, completing the left-hand one. Scale 6 +inches to a foot.</p> + +<p>By the above arrangement of pulleys a machine may be stopped +or set in motion at pleasure. When the driving band is on the +loose pulley the machine is at rest, and when it is on the fast +pulley the machine is in motion. The driving band is shifted from +the one pulley to the other by pressing on that side of the band +which is advancing towards the pulleys.</p> +</div> +<p><span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span></p> + +<div class="figcenter" style="width: 756px;"> +<img src="images/illus046.png" width="756" height="600" alt="Fig. 32." title="Fig. 32." /> +<span class="caption">Fig. 32.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 32</span>: <i>Cast-iron Pulley with Curved Arms and Cone +Keys</i>.—Draw a complete side elevation and a complete cross section +of the pulley represented in fig. 32 to a scale of 3 inches to a foot. +In drawing the side elevation of the arms first draw the centre lines +as shown; next draw three circles for each arm, one at each end +and one in the middle; the centres of these circles being on the +centre line of the arm, and their diameters equal to the widths of the +arm at the ends and at the middle respectively. Arcs of circles are +then drawn to touch these three circles. The centres and radii of +these arcs may be found by trial. The cone keys for securing the +pulley to the shaft were described on p. 23.</p></div> + +<p><i>Pulleys for Ropes</i>.—Ropes made of hemp are now extensively +used for transmitting power. These ropes vary in +diameter from 1 inch to 2 inches, and are run at a speed of +about 4,500 feet per minute. The pulleys for these ropes are +made of cast iron, and have their rims grooved as shown in +fig. 33, which is a cross section of the rim of a pulley carrying +three ropes. The angle of the V is usually 45°, and the rope<span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span> +rests on the sides of the groove, and not on the bottom, so that +it is wedged in, and has therefore a good hold of the pulley. +The diameter of the pulley should not be less than 30 times +the diameter of the rope. Two pulleys connected by ropes +should not be less than thirty feet apart from centre to centre, +but this distance may be as much as 100 feet.</p> + +<div class="figcenter" style="width: 640px;"> +<img src="images/illus047.jpg" width="640" height="418" alt="Fig. 33." title="Fig. 33." /> +<span class="caption">Fig. 33.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 33</span>: <i>Section of Rim of Rope Pulley.</i>—Draw, half +size, the section of the rim of a rope pulley shown in fig. 33.</p></div> + + + +<hr style="width: 15%;" /> +<h2>IX. TOOTHED WHEELS.</h2> + + +<p><i>Pitch Surfaces of Spur Wheels.</i>—Let two smooth rollers be +placed in contact with their axes parallel, and let one of them +rotate about its axis; then if there is no slipping the other +roller will rotate in the opposite direction with the same +surface velocity; and if D<sub>1</sub>, D<sub>2</sub> be the diameters of the rollers, +and N<sub>1</sub>, N<sub>2</sub> their speeds in revolutions per minute, it follows as +in belt gearing that—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'> N<sub>1</sub> <br /> —— <br /> N<sub>2</sub> </td><td align='center'> = </td><td align='center'> D<sub>2</sub> <br /> ——. <br /> D<sub>1</sub></td></tr> +</table></div> + +<p>If there be considerable resistance to the motion of the +follower slipping may take place, and it may stop. To prevent +this the rollers may be provided with teeth; then they become +<i>spur wheels</i>; and if the teeth be so shaped that the ratio of +the speeds of the toothed rollers at any instant is the same as<span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span> +that of the smooth rollers, the surfaces of the latter are called +the <i>pitch surfaces</i> of the former.</p> + +<p><i>Pitch Circle.</i>—A section of the pitch surface of a toothed +wheel by a plane perpendicular to its axis is a circle, and is +called a <i>pitch circle</i>. We may also say that the pitch circle is +the edge of the pitch surface. The pitch circle is generally +traced on the side of a toothed wheel, and is rather nearer the +points of the teeth than the roots.</p> + +<p><i>Pitch of Teeth.</i>—The distance from the centre of one tooth +to the centre of the next, or from the front of one to the front +of the next, <i>measured at the pitch circle</i>, is called the <i>pitch of +the teeth</i>. If D be the diameter of the pitch circle of a wheel, +<i>n</i> the number of teeth, and <i>p</i> the pitch of the teeth, then +D × 3·1416 = <i>n</i> × <i>p</i>.</p> + +<div class="figcenter" style="width: 640px;"> +<img src="images/illus048.jpg" width="640" height="253" alt="Fig. 34." title="Fig. 34." /> +<span class="caption">Fig. 34.</span> +</div> + +<p>By the diameter of a wheel is meant the diameter of its +pitch circle.</p> + +<p><i>Form and Proportions of Teeth.</i>—The ordinary form of +wheel teeth is shown in fig. 34. The curves of the teeth should +be cycloidal curves, although they are generally drawn in as +arcs of circles. It does not fall within the scope of this work +to discuss the correct forms of wheel teeth. The student will +find the theory of the teeth of wheels clearly and fully explained +in Goodeve's 'Elements of Mechanism,' and in Unwin's +'Machine Design.'</p> + +<p>The following proportions for the teeth of ordinary toothed +wheels may be taken as representing average practice:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Pitch of teeth</td><td align='left'>= <i>p</i> = arc <i>a b c</i> (fig. 34).</td></tr> +<tr><td align='left'>Thickness of tooth</td><td align='left'>= <i>b c</i> = ·48<i>p</i>.</td></tr> +<tr><td align='left'>Width of space</td><td align='left'>= <i>a b</i> = ·52<i>p</i>.</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span>Total height of tooth</td><td align='left'>= <i>h</i> = ·7<i>p</i>.</td></tr> +<tr><td align='left'>Height of tooth above pitch line</td><td align='left'>= <i>k</i> = ·3<i>p</i>.</td></tr> +<tr><td align='left'>Depth of tooth below pitch line</td><td align='left'>= <i>l</i> = ·4<i>p</i>.</td></tr> +<tr><td align='left'>Width of tooth</td><td align='left'>= 2<i>p</i> to 3<i>p</i>.</td></tr> +</table></div> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 34: <i>Spur Wheel.</i>—Fig. 35 shows the elevation and +sectional plan of a portion of a cast-iron spur wheel. The diameter +of the pitch circle is 23<small><sup>7</sup>⁄<sub>8</sub></small> inches, and the pitch of the teeth is 1½ +inches, so that there will be 50 teeth in the wheel. The wheel has +six arms. Draw a complete elevation of the wheel and a half sectional +plan, also a half-plan without any section. Draw also a +cross section of one arm. Scale 4 inches to a foot.</p></div> + +<div class="figcenter" style="width: 600px;"> +<img src="images/illus049.png" width="600" height="600" alt="Fig. 35." title="Fig. 35." /> +<span class="caption">Fig. 35.</span> +</div> + +<p><i>Mortise Wheels.</i>—When two wheels gearing together run +at a high speed the teeth of one are made of wood. These +teeth, or cogs, as they are generally called, have tenons formed +on them, which fit into mortises in the rim of the wheel. This +wheel with the wooden teeth is called a <i>mortise wheel</i>. An +example of a mortise wheel is shown in fig. 36.<span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus050.png" width="1024" height="645" alt="Fig. 36." title="Fig. 36." /> +<span class="caption">Fig. 36.</span> +</div> +<p><span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span></p> + +<p><i>Bevil Wheels.</i>—In bevil wheels the pitch surfaces are parts +of cones. Bevil wheels are used to connect shafts which are +inclined to one another, whereas spur wheels are used to connect +parallel shafts. In fig. 36 is shown a pair of bevil wheels in +gear, one of them being a mortise wheel. At (<i>a</i>) is a separate +drawing, to a smaller scale, of the pitch cones. The pitch +cones are shown on the drawing of the complete wheels by +dotted lines.</p> + +<p>The diameters of bevil wheels are the diameters of the bases +of their pitch cones.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 35: <i>Pair of Bevil Wheels.</i>—Draw the sectional elevation +of the bevil wheels shown in gear in fig. 36. Commence by +drawing the centre lines of the shafts, which in this example are at +right angles to one another; then draw the pitch cones shown by +dotted lines. Next put in the teeth which come into the plane of +the section, then complete the sections of the wheels. The pinion +or smaller wheel has 25 teeth, and the wheel has 50 teeth, which +makes the pitch a little over 3 inches. Each tooth of the mortise +wheel is secured as shown by an iron pin <sup>5</sup>⁄<sub>16</sub> inch diameter. Scale +3 inches to a foot.</p></div> + + + +<hr style="width: 15%;" /> +<h2>X. CRANKS AND CRANKED SHAFTS.</h2> + + +<p>The most important application of the crank is in the +steam-engine, where the reciprocating rectilineal motion of +the piston is converted into the rotary motion of the crank-shaft +by means of the crank and connecting rod.</p> + +<p>At one time steam-engine cranks were largely made of +cast iron, now they are always made of wrought iron or steel. +The crank is either forged in one piece with the shaft, or it is +made separately and then keyed to it.</p> + +<p><i>Overhung Crank.</i>—Fig. 37 shows a wrought-iron overhung +crank. A is the crank-shaft, B the crank arm, provided at +one end with a boss C, which is bored out to fit the shaft; at +the other end of the crank arm is a boss D, which is bored out +to receive the crank-pin E, which works in one end of the +connecting rod. The crank is secured to the shaft by the<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span> +sunk key F. It is also good practice to <i>shrink</i> the crank on +to the shaft. The process of shrinking consists of boring out +the crank a little smaller than the shaft, and then heating it, +which causes it to expand sufficiently to go on to the shaft. +As the crank cools, it shrinks and grips the shaft firmly. The +crank may also be shrunk on to the crank-pin, the latter being +then riveted over as shown in fig. 37.</p> + +<div class="figcenter" style="width: 781px;"> +<img src="images/illus052.png" width="781" height="600" alt="Fig. 37." title="Fig. 37." /> +<span class="caption">Fig. 37.</span> +</div> + +<p>A good plan to adopt in preference to the shrinking process +is to force the parts together by hydraulic pressure. This +method is adopted for placing locomotive wheels on their axles, +and for putting in crank-pins. As to the amount of pressure +to be used, the practice is to allow a force of 10 tons for every +inch of diameter of the pin, axle, or shaft.</p> + +<p>Instead of being riveted in, the crank pin may be prolonged +and screwed, and fitted with a nut. Another plan is to put a +cotter through the crank and the crank-pin.</p> + +<p>The distance from the centre of the crank-shaft to the +centre of the crank-pin is called the radius of the crank. The +<i>throw</i> of the crank is twice the radius. In a direct-acting<span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span> +engine the throw of the crank is equal to the stroke of the +piston.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 36: <i>Wrought-iron Overhung Crank.</i>—Draw the +two elevations shown in fig. 37, also a plan. Scale 1½ inches to a +foot.</p> + +<p class="tabcap"><i>Proportions of Overhung Cranks.</i></p> + +<div class='center'> +<table border="0" cellpadding="2" cellspacing="0" summary=""> +<tr><td align='left' colspan='2'>D = diameter of shaft.</td></tr> +<tr><td align='left' colspan='2'><i>d</i> = ” crank-pin.</td></tr> +<tr><td align='left'>Length of large boss</td><td align='left'>= ·9 D.</td></tr> +<tr><td align='left'>Diameter ”</td><td align='left'>= 1·8 D.</td></tr> +<tr><td align='left'>Length of small boss</td><td align='left'>= 1·1 <i>d</i>.</td></tr> +<tr><td align='left'>Diameter ”</td><td align='left'>= 1·8 <i>d</i>.</td></tr> +<tr><td align='left' colspan='2'>Width of crank arm at centre of shaft</td><td align='left'>= 1·3 D.</td></tr> +<tr><td align='left' colspan='2'> ” ” crank-pin</td><td align='left'>= 1·5 <i>d</i>.</td></tr> +</table></div> + +<p class="center">The thickness of the crank arm may be roughly taken as = ·7 D.</p> + +<p><span class="smcap">Exercise</span> 37.—Design a wrought-iron crank for an engine +having a stroke of 4 feet. The crank-shaft is 9 inches in diameter, +and the crank-pin is 4¾ inches in diameter and 6½ inches long.</p></div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus053.png" width="800" height="350" alt="Fig. 38." title="Fig. 38." /> +<span class="caption">Fig. 38.</span> +</div> + +<p><i>Locomotive Cranked Axle.</i>—As an example of a cranked +shaft we take the cranked axle for a locomotive with inside +cylinders shown in fig. 38; here the crank and shaft or axle +are forged in one piece. A is the wheel seat, B the journal, C +the crank-pin, and D and E the crank arms. Only one half of +the axle is shown in fig. 38, but the other half is exactly the +same. The cranks on the two halves are, however, at right +angles to one another. The ends of the crank arms are turned +in the lathe, the crank-pin ends being turned at the same time<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span> +as the axle, and the other ends at the same time as the crank-pin. +This consideration determines the centres for the arcs +shown in the end view.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 38.—Draw to a scale of 2 inches to a foot the side +and end elevations of the locomotive cranked axle partly shown in +fig. 38. The distance between the centre lines of the cylinders is +2 feet.</p></div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus054.png" width="800" height="476" alt="Fig. 39." title="Fig. 39." /> +<span class="caption">Fig. 39.</span> +</div> + +<p><i>Built-up Cranks.</i>—The form of cranked shaft shown in +fig. 38 is largely used for marine engines, but for the very powerful +engines now fitted in large ships this design of shaft is +very unreliable, the built-up crank shown in fig. 39 being +preferred, although it is much heavier than the other. It will +be seen from the figure that the shaft, crank arms, and crank-pin +are made separately. The arms are shrunk on to the pin +and the shaft, and secured to the latter by sunk keys. These +heavy shafts and cranks are generally made of steel.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 39.—Keeping to the dimensions marked in fig. 39, +draw the views there shown of a built-up crank-shaft for a marine +engine. Scale <sup>3</sup>⁄<sub>4</sub> inch to a foot.</p></div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span></p> +<h2>XI. ECCENTRICS.</h2> + + +<p>The <i>eccentric</i> is a particular form of crank, being a crank in +which the crank-pin is large enough to embrace the crank-shaft. +In the eccentric what corresponds to the crank-pin is called +the sheave or pulley. The advantage which an eccentric +possesses over a crank is that the shaft does not require to be +divided at the point where the eccentric is put on. The crank, +however, has this advantage over the eccentric, namely, that it +can be used for converting circular into reciprocating motion, +or <i>vice versâ</i>, while the eccentric can only be used for converting +circular into reciprocating motion. This is owing to +the great leverage at which the friction of the eccentric +acts.</p> + +<p>The chief application of the eccentric is in the steam-engine, +where it is used for working the valve gear.</p> + +<p>To permit of the sheave being placed on the shaft without +going over the end (which could not be done at all in the case of +a cranked axle, and would be a troublesome operation in most +cases) it is generally made in two pieces, as shown in fig. 40, +which represents one of the eccentrics of a locomotive. The +two parts of the sheave are connected by two cotter bolts. The +part which embraces the sheave is called the eccentric strap, +and corresponds to, and is, in fact, a connecting rod end: the +rod proceeding from this is called the eccentric rod.</p> + +<p>The distance from the centre of the sheave to the centre of +the shaft is called the <i>radius</i> or <i>eccentricity</i> of the eccentric. +The <i>throw</i> is twice the eccentricity.</p> + +<p>The sheave is generally made of cast iron. The strap may +be of brass, cast iron, or wrought iron; when the strap is made +of wrought iron it is commonly lined with brass.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 40: <i>Locomotive Eccentric.</i>—In fig. 40 D E is the +sheave, F H the strap, and K the eccentric rod. The sheave and +strap are made of cast iron, and the eccentric rod is made of wrought +iron. (<i>a</i>) is a vertical cross section through the oil-box of the +strap; (<i>b</i>) is a plan of the end of the eccentric rod and part of the<span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span> +strap. All the nuts are locked by means of cotters. Draw first +the elevation, partly in section as shown. Next draw two end +elevations, one looking each way. Afterwards draw a horizontal +section through the centre, and also a plan. Scale 4 inches to a +foot.</p></div> + +<div class="figcenter" style="width: 751px;"> +<img src="images/illus056.png" width="751" height="1024" alt="Fig. 40." title="Fig. 40." /> +<span class="caption">Fig. 40.</span> +</div> + + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span></p> +<h2>XII. CONNECTING RODS.</h2> + + +<p>The most familiar example of the use of a connecting rod +is in the steam-engine, where it is used to connect the rotating +crank with the reciprocating piston. The rod itself is made of +wrought iron or steel, and is generally circular or rectangular in +section. The ends of the rod are fitted with steps, which are +held together in a variety of ways.</p> + +<p><i>Strap End.</i>—A form of connecting rod end, which is not +so common as it used to be, is shown in fig. 41. At (<i>a</i>) is +shown a longitudinal section with all the parts put together, +while at (<i>b</i>), (<i>c</i>), <i>(d)</i> and (<i>e</i>) the details are shown separately. +A B is the end of the rod which butts against the brass bush +C D, which is in two pieces. A <i>strap</i> E passes round the bush +and on to the end of the rod as shown. The arms of the strap +have rectangular holes in them, which are not quite opposite +a similar hole in the rod when the parts are put together. If +a wedge or <i>cotter</i> F be driven into these three holes they will +tend to come into line, and the parts of the bush will be pressed +together. To prevent the cotter opening out the strap, and to +increase the sliding surface, a <i>gib</i> H is introduced. The gib is +provided with horns at its ends to keep it in its place. Sometimes +two gibs are used, one on each side of the cotter; this +makes the sliding surface on both sides of the cotter the same. +The cotter is secured by a set screw K. The unsectioned +portion of fig. (<i>a</i>) to the right of the gib, or to the left of the +cotter, is called the <i>clearance</i> or <i>draught.</i></p> + + +<div class="blockquot"><p><span class="smcap">Exercise</span> 41: <i>Connecting Rod End.</i>—Make the following views +of the connecting rod end illustrated by fig. 41. First, a vertical +section, the same as shown at (<i>a</i>). Second, a horizontal section. +Third, side elevation. Fourth, a plan. Or the first and third views +may be combined in a half vertical section and half elevation; and +the second and fourth views may be combined in a half horizontal +section and half plan.</p> + +<p>All the dimensions are to be taken from the detail drawings (<i>b</i>), +(<i>c</i>), (<i>d</i>), and (<i>e</i>), <i>but the details need not be drawn separately</i>. The +brass bush is shown at (<i>d</i>) by half elevation, half vertical section, +<span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span>half plan, and half horizontal section. The draught or clearance is +7-16ths of an inch.</p> +</div> + +<div class="figcenter" style="width: 637px;"> +<img src="images/illus058.png" width="637" height="1024" alt="Fig. 41." title="Fig. 41." /> +<span class="caption">Fig. 41.</span> +</div> + +<p><span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span></p> + +<p><i>Box End.</i>—At (<i>a</i>), fig. 42, is shown what is known as a box +end for a connecting rod. The part which corresponds to the +loose strap in the last example is here forged in one piece with +the connecting rod. In this form the brass bush is provided +with a flange all round on one side, but on the opposite side +the flange is omitted except at one end; this is to allow of the +bush being placed within the end of the rod. The construction +of the bush will be understood by reference to the sketch shown +at (<i>b</i>). The bush is in two parts, which are pressed tightly together +by means of a cotter. This cotter is prevented from +slackening back by two set screws. Each set screw is cut off +square at the point, and presses on the flat bottom of a very +shallow groove cut on the side of the cotter.</p> + +<p>The top, bottom, and ends of this box end are turned in +the lathe at the same time as the rod itself; this accounts for +the curved sections of these parts.</p> + +<p>It is clear from the construction of a box end that it is +only suitable for an overhung crank.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 42:</span> <i>Locomotive Connecting Rod.</i>—In fig. 42 is shown +a connecting rod for an outside cylinder locomotive. (<i>a</i>) is the +crank-pin end, and (<i>c</i>) the cross-head end. The end (<i>a</i>) has just +been described under the head 'box end.' We may just add that +in this particular example the brass bush is lined with white metal +as shown, and that the construction of the oil-box is the same as +that on the coupling rod end shown in fig. 44. The end (<i>c</i>) is +forked, and through the prongs of the fork passes the cross-head pin, +of which a separate dimensioned drawing is shown at (<i>d</i>). Observe +that the tapered parts A and B of this pin are parts of the same +cone. The rotation of the pin is prevented by a small key as shown. +The cross-head pin need not be drawn separately, and the isometric +projection of the bush at (<i>b</i>) may be omitted, but all the other +views shown are to be drawn to a scale of 6 inches to a foot.</p></div> + +<p><span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus060.png" width="1024" height="641" alt="Fig. 42." title="Fig. 42." /> +<span class="caption">Fig. 42.</span> +</div> + +<p><span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus061.png" width="1024" height="601" alt="Fig. 43." title="Fig. 43." /> +<span class="caption">Fig. 43.</span> +</div> + +<p><span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span></p> + +<p><i>Marine Connecting Rod.</i>—The form of connecting rod +shown in fig. 43 is that used in marine engines, but it is also +used extensively in land engines. A B is the crank-pin end, +and C the cross-head end. The end A B is forged in one piece, +and after it is turned, planed, and bored it is slotted across, so +as to cut off the cap A. The parts A and B are held together +by two bolts as shown. This end of the rod is fitted with +brass steps, which are lined with white metal. The cross-head +end is forked, and through the prongs of the fork passes a pin +D, which also passes through the cross-head, which is forged on +to the piston rod or attached to it in some other way.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 43:</span> <i>Marine Connecting Rod.</i>—Draw all the views +shown in fig. 43 of one form of marine connecting rod. For detail +drawings of the locking arrangement for the nuts see fig. 19, page +21. Scale 4 inches to a foot.</p></div> + +<p><i>Coupling Rods.</i>—A rod used to transmit the motion of one +crank to another is called a <i>coupling rod</i>. A familiar example +of the use of coupling rods will be found in the locomotive. +Coupling rods are made of wrought iron or steel, and are +generally of rectangular section. The ends are now generally +made solid and lined with solid brass bushes, <i>without any +adjustment for wear</i>. This form of coupling rod end is found +to answer very well in locomotive practice where the workmanship +and arrangements for lubrication are excellent. +When the brass bush becomes worn it is replaced by a new +one.</p> + +<p>Fig. 44 shows an example of a locomotive coupling rod end +for an outside cylinder engine. In this case it is desirable to +have the crank-pin bearings for the coupling rods as short as +possible, for a connecting rod and coupling rod in this kind of +engine work side by side on the same crank-pin, which, being +overhung, should be as short as convenient for the sake of +strength. The requisite bearing surface is obtained by having +a pin of large diameter. The brass bush is prevented from +rotating by means of the square key shown. The oil-box is +cut out of the solid, and has a wrought-iron cover slightly +dovetailed at the edges. This cover fits into a check round +the top inner edge of the box, which is originally parallel, but +is made to close on the dovetailed edges of the cover by riveting. +A hole in the centre of this cover, which gives access to +the oil-box, is fitted with a screwed brass plug. The brass<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span> +plug has a screwed hole in the centre, through which oil may +be introduced to the box. Dust is kept out of the oil-box by +screwing into the hole in the brass plug a common cork. The +oil is carried slowly but regularly from the oil-box over to the +bearing by a piece of cotton wick.</p> + +<div class="figcenter" style="width: 600px;"> +<img src="images/illus063.png" width="600" height="660" alt="Fig. 44." title="Fig. 44." /> +<span class="caption">Fig. 44.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 44:</span> <i>Coupling Rod End.</i>—Draw first the side elevation +and plan, each partly in section as shown in fig. 44. Then instead +of the view to the left, which is an end elevation partly in +section, draw a complete end elevation looking to the right, and also +a complete vertical cross section through the centre of the bearing. +Scale 6 inches to a foot.</p></div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span></p> +<h2>XIII. CROSS-HEADS.</h2> + + +<p>An example of a steam-engine cross-head is shown in +fig. 45. A is the end of the piston rod which has forged upon it +the cross-head B. The cross-head pin shown at (<i>d</i>), fig. 42, and +to which the connecting rod is attached, works in the bearing +C. Projecting pieces D, forged on the top and bottom of the +cross-head, carry the slide blocks E which work on the slide +bars, and thus guide the motion of the piston rod.</p> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus064.png" width="800" height="530" alt="Fig. 45." title="Fig. 45." /> +<span class="caption">Fig. 45.</span> +</div> + + +<div class="blockquot"><p><span class="smcap">Exercise 45:</span> <i>Locomotive Cross-head.</i>—In fig. 45 are shown +side and end elevations, partly in section, of the cross-head and +slide blocks for an outside cylinder locomotive. Draw these views +half size, showing also on the end elevation the cross-head pin and a +vertical section of the connecting rod end from fig. 42. The bush +in the cross-head which forms the bearing for the cross-head pin is +of wrought iron, case-hardened, and is prevented from rotating by the +key shown. The cross-head is of wrought iron, and the slide blocks +are of cast iron, and are fitted with white metal strips as shown. A +short brass tube leads oil from the upper slide block into a hole in +the cross-head as shown, which carries it to a slot in the bush +which distributes it over the cross-head pin.</p></div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span></p> +<h2>XIV. PISTONS.</h2> + + +<p>A <i>piston</i> is generally a cylindrical piece which slides backwards +and forwards inside a hollow cylinder. The piston may +be moved by the action of fluid pressure upon it as in a +steam-engine, or it may be used to give motion to a fluid as in +a pump.</p> + +<p>A piston is usually attached to a rod, called a <i>piston rod</i>, +which passes through the end of the cylinder inside which the +piston works, and which serves to transmit the motion of the +piston to some piece outside the cylinder, or <i>vice versâ</i>.</p> + +<div class="figcenter" style="width: 629px;"> +<img src="images/illus065.png" width="629" height="600" alt="Fig. 46." title="Fig. 46." /> +<span class="caption">Fig. 46.</span> +</div> + +<p>A <i>plunger</i> is a piston made in one piece with its piston rod, +the piston and the rod being of the same diameter.</p> + +<p>A piston which is provided with one or more valves which<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span> +allow the fluid to pass through it from one side to the other is +called a <i>bucket</i>.</p> + +<p><i>Simple Piston.</i>—The simplest form of piston is a plain +cylinder fitting accurately another, inside which it moves. +Such a piston works with very little friction, but as there is +no adjustment for wear, such a piston is not suitable for a high +fluid pressure if it has to work constantly. This simple form of +piston is used in the steam-engine indicator, and also in +pumps.</p> + +<p>Fig. 46 shows the piston of the circulation pump of a marine +engine. A is the cast-iron casing or barrel of the pump; B is +a brass liner fitting tightly into the former at its ends, and +secured by eight screwed Muntz metal pins C, four at each end; +D is the piston, which is made of brass, and is attached to +a Muntz metal piston rod E. The liner is bored out smooth +and true from end to end, and the piston is turned so as to be +a sliding fit to the liner. The wear in this form of piston is +diminished by making the rubbing surface large.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 46:</span> <i>Piston for Circulating Pump.</i>—Draw the +vertical sectional elevation of the piston, &c., shown in fig. 46, also +a half plan and half horizontal section through the centre. Scale 4 +inches to a foot.</p></div> + +<p><i>Pump Bucket.</i>—The next form of piston which we illustrate +is shown in fig. 47. This represents the air-pump bucket of a +marine engine. The bucket is made of brass, and is provided +with six india-rubber disc valves. The rod is in this case +made of Muntz metal. Air-pump rods for marine engines are +very often made of wrought iron cased with brass. It will be +observed that there is a wide groove around the bucket, which +is filled with hempen rope or gasket. This gasket forms an +elastic packing which prevents leakage. This is an old-fashioned +form of packing, and is now only used for pump +buckets.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 47:</span> <i>Air-pump Bucket.</i>—Draw the sectional elevation +of the air-pump bucket shown in fig. 47. Also draw a half plan +looking downwards and a half plan looking upwards. Scale 4 inches +to a foot.</p></div><p><span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus067.png" width="1024" height="523" alt="Fig. 47." title="Fig. 47." /> +<span class="caption">Fig. 47.</span> +</div> +<p><span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span></p> + +<div class="figleft" style="width: 292px;"> +<img src="images/illus068.png" width="292" height="640" alt="Fig. 48." title="Fig. 48." /> +<span class="caption">Fig. 48.</span> +</div> + +<p><i>Ramsbottom's Packing.</i>—The form of packing used in the +air-pump bucket, fig. 47, is not suitable for steam pistons. +For the latter the packing is now always metallic. The +simplest form of metallic packing is that known as Ramsbottom's. +This form is very largely used for locomotive pistons, +and for small pistons in many kinds of engines besides. A +locomotive piston for an 18-inch cylinder with Ramsbottom's +packing is shown in fig. 48. The +particular piston there illustrated +is made of brass, and is secured +to a wrought-iron piston rod by +a brass nut. Two circumferential +grooves of rectangular section are +turned out of the piston, and into +these fit two corresponding rings, +which may be of brass, cast iron, +or steel. In this example the +rings are of cast iron. These rings +are first turned a little larger +in diameter than the bore of the +cylinder (in this example <sup>1</sup>⁄<sub>2</sub> inch), +and then sprung over the piston +into the groves prepared for them. +Their own elasticity causes the +rings to press outwards on the +cylinder. At the point where a +ring is split a leakage of steam +will take place, but with quick-running +pistons this leakage is unimportant. +The points where the +rings are cut should be placed diametrically opposite, so as to +diminish the leakage of steam.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 48:</span> <i>Locomotive Piston.</i>—A part elevation and part +section of a locomotive piston, for a cylinder having a bore 18 inches +in diameter, is shown in fig. 48. Draw this, and also a view looking +on the nut in the direction of the axis of the piston rod. Scale 6 +inches to a foot.</p> + +<p><span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span></p> + +<p><i>Note.</i>—The reason why the part of the piston rod within the +piston has such a quick taper is that the piston has to be taken off +the rod while it is in the cylinder. The cross-head being forged on +the end of the piston rod prevents the piston and piston rod being +withdrawn together.</p></div> + +<p><i>Large Pistons.</i>—Pistons of large diameter are generally +provided with two cast-iron packing rings placed within the +same groove. These rings are pressed outwards against the +cylinder, and also against the sides of the groove by one or +more springs. One form of this packing (Lancaster's) is shown +in fig. 49. Here one spring only is used, and it is first made +a straight spiral spring, and then bent round and its ends united. +The action of the spring will be clearly understood from the +illustration. For the purpose of admitting the packing rings +the piston is divided into two parts, one the piston proper, +and the other the <i>junk ring</i>. In fig. 49, A is the junk ring, +which is secured to the piston by means of bolts as shown.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise 49:</span> <i>Marine Engine Piston.</i>—The piston illustrated by +fig. 49 is for the high-pressure cylinder of a marine engine. The +piston, junk ring, and packing rings are of cast iron. The piston rod +and nut are of wrought iron, so also are the junk ring bolts. The +nuts for the latter are of brass. The spiral spring is made from +steel wire <sup>3</sup>⁄<sub>8</sub> inch diameter. An enlarged section of one of the pack<span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span>ing +rings is shown at (<i>a</i>). A front elevation of the locking arrangement +for the piston rod nut is shown at (<i>b</i>). A sectional plan of +one of the nuts for the junk ring bolts is shown at (<i>c</i>).</p> + +<p>First draw the vertical section of this piston, ne<i>x</i>t draw a plan, +one-third of which is to show the piston complete, one-third to show +the junk ring removed, and the remaining third to be a horizontal +section through between the packing rings. The details (<i>a</i>) and (<i>c</i>) +need not be drawn separately. Scale 3 inches to a foot.</p></div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus069.png" width="800" height="516" alt="Fig. 49." title="Fig. 49." /> +<span class="caption">Fig. 49.</span> +</div> + + +<p><i>Proportions of Marine Engine Pistons.</i>—Mr. Seaton, in his +'Manual of Marine Engineering,' gives the following rules for +designing marine engine pistons:—</p> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='center'> D </td><td align='center'> = </td><td align='left' colspan='2'>diameter of piston in inches.</td></tr> +<tr><td align='center'> <i>p</i> </td><td align='center'> = </td><td align='left' colspan='2'>effective pressure in lbs. per square inch.</td></tr> +<tr><td align='center'> <i>x</i> </td><td align='center'> = </td><td align='left'> D <br /> — <br /> 50 </td><td align='left'> × √<span class="overline"><i>p</i> +</span> 1.</td></tr> +</table></div> + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Thickness of</td><td align='left'>front of piston near boss</td><td align='left'>0·2 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'> ” ” rim</td><td align='left'>0·17 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'>back of piston</td><td align='left'>0·18 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'>boss around rod</td><td align='left'>0·3 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'>flange inside packing ring</td><td align='left'>0·23 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'> ” at edge</td><td align='left'>0·25 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'>junk ring at edge</td><td align='left'>0·23 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'> ” inside packing ring.</td><td align='left'>0·21 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'> ” at bolt-holes</td><td align='left'>0·35 × <i>x</i>.</td></tr> +<tr><td align='center'>”</td><td align='left'>metal around piston edge</td><td align='left'>0·25 × <i>x</i>.</td></tr> +<tr><td align='left' colspan='2'>Breadth of packing ring</td><td align='left'>0·63 × <i>x</i>.</td></tr> +<tr><td align='left' colspan='2'>Depth of piston at centre</td><td align='left'>1·4 × <i>x</i>.</td></tr> +<tr><td align='left' colspan='2'>Lap of junk ring on piston</td><td align='left'>0·45 × <i>x</i>.</td></tr> +<tr><td align='left' colspan='2'>Space between piston body and packing ring</td><td align='left'>0·3 × <i>x</i>.</td></tr> +<tr><td align='left' colspan='2'>Diameter of junk-ring bolts</td><td align='left'>0·1 × <i>x</i> + ·25 inch.</td></tr> +<tr><td align='left' colspan='2'>Pitch of junk-ring bolts</td><td align='left'>10 diameters.</td></tr> +<tr><td align='left' colspan='2'>Number of webs in piston</td><td align='left'>D + 20<br /> ———. <br /> 12</td></tr> +<tr><td align='left'>Thickness</td><td align='left'>”</td><td align='left'>0·18 × <i>x</i>.</td></tr> +</table></div> + +<div class="blockquot"><p><span class="smcap">Exercise 50:</span> <i>Design for Marine Engine Piston.</i>—Calculate +by Seaton's rules the dimensions for a marine engine piston 40 +inches in diameter, and subjected to an effective pressure of 36 lbs. +per square inch. Then make the necessary working drawings for +this piston to a scale of, say, 3 inches to a foot.</p> + +<p><i>Note.</i>—Take the dimensions got by calculation to the nearest +1-16th of an inch.</p></div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span></p> +<h2>XV. STUFFING-BOXES.</h2> + + +<div class="figcenter" style="width: 590px;"> +<img src="images/illus071.png" width="590" height="1024" alt="Fig. 50." title="Fig. 50." /> +<span class="caption">Fig. 50.</span> +</div> + + +<p>In fig. 50 is shown a gland and stuffing-box for the piston +rod of a vertical engine. A B is the piston rod, C D a portion +of the cylinder cover, and E F the <i>stuffing-box</i>. Fitting into +the bottom of the stuffing-box is a brass bush H. The space +K around the rod A B is filled with <i>packing</i>, of which there is<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span> +a variety of kinds, the simplest being greased hempen rope. +The packing is compressed by screwing down the cast-iron +gland L M, which is lined with a brass bush N. In this case +the gland is screwed down by means of three stud-bolts P, +which are screwed into a flange cast on the stuffing-box. +Surrounding the rod on the top of the gland there is a recess +R for holding the lubricant.</p> + +<div class="figcenter" style="width: 768px;"> +<img src="images/illus072.png" width="768" height="881" alt="Figs. 51, 52." title="Figs. 51, 52." /> +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" width="80%"> +<tr><td align='left'><span class="caption">Fig. 51.</span></td><td align='right'><span class="caption">Fig. 52.</span></td></tr> +</table></div> +</div> + +<p>The object of the gland and stuffing-box is to allow the +piston rod to move backwards and forwards freely without any +leakage of steam.<span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span></p> + +<p>Fig. 51 shows a gland and stuffing-box for a horizontal rod. +The essential difference between this example and the last is +in the mode of lubrication. The gland flange has cast within +it an oil-box which is covered by a lid; this lid is kept shut +or open by the action of a small spring as shown. A piece of +cotton wick (not shown in the figure) has one end trailing in the +oil in the oil-box, while the other is carried over and passed +down the hole A B. The wick acts as a siphon, and drops the +oil gradually on to the rod. In this example only two bolts +are used for screwing in the gland; and the flanges of the gland +and stuffing-box are not circular, but oval-shaped.</p> + +<p>In the case of small rods the gland is made entirely of +brass, and no liner is then necessary. Fig. 52 shows a form +of gland and stuffing-box sometimes used for small rods. The +stuffing-box is screwed externally, and carries a nut A B which +moves the gland.</p> + + +<div class="blockquot"><p><span class="smcap">Exercise 51:</span> <i>Gland and Stuffing-box for a Vertical Rod.</i>—Draw +the views shown in fig. 50 to the dimensions given. Scale 6 +inches to a foot.</p> + +<p><span class="smcap">Exercise 52:</span> <i>Gland and Stuffing-box for a Horizontal Rod.</i>—Fig. 51 +shows a plan, half in section, and an elevation half of which +is a section through the gland flange. Draw these to a scale of 6 +inches to a foot, using the dimensions marked in the figure.</p> + +<p><span class="smcap">Exercise 53:</span> <i>Screwed Gland and Stuffing-box.</i>—Draw, full +size, the views shown in fig. 52 to the given dimensions.</p></div> + +<p>A more elaborate form of gland and stuffing-box is shown +in fig. 53. This is for a large marine engine with inverted +cylinders, such as is used on board large ocean steamers. The +stuffing-box is cast separate from the cylinder cover to which +it is afterwards bolted. The lubricant is first introduced to +the oil-boxes marked A, from which it passes to the recess B, +where it comes in contact with the piston rod. To prevent +the lubricant from being wasted by running down the rod, the +main gland is provided with a shallow gland and stuffing-box +which is filled with soft cotton packing, which soaks up the +lubricant.</p> + +<p><span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span></p> + +<div class="figcenter" style="width: 604px;"> +<img src="images/illus074.png" width="604" height="1024" alt="Fig. 53." title="Fig. 53." /> +<span class="caption">Fig. 53.</span> +</div> + +<p>The main gland is screwed up by means of six bolts, and +to prevent the gland from locking itself in the stuffing-box, it<span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span> +is necessary that the nuts should be turned together. This is +done in a simple and ingenious manner. One-half of each +nut is provided with teeth, and these gear with a toothed +wheel which has a rim only; this rim is held up by a ring C. +When one nut is turned, all the rest follow in the same direction.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 54:</span> <i>Gland and Stuffing-box for Piston Rod of Large +Inverted Cylinder Engine.</i>—The lower view in fig. 53 is a half plan +looking upwards, and a half section of the gland looking downwards. +The upper view is a vertical section. Complete all these views and +add an elevation. Scale 3 inches to a foot.</p> + +<p><i>Note.</i>—The large nuts, the wheel, the supporting ring, and small +gland are made of brass.</p></div> + +<p class="tabcap"><i>Dimensions of Stuffing-boxes and Glands.</i></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'><i>d</i></td><td align='left'>= diameter of rod.</td><td align='left'><i>t</i><sub>1</sub> = thickness of stuffing-box flange.</td></tr> +<tr><td align='left'><i>d</i><sub>1</sub></td><td align='left'>= diameter of box (inside).</td><td align='left'><i>t</i><sub>2</sub> = thickness of gland flange.</td></tr> +<tr><td align='left'><i>l</i></td><td align='left'>= length of stuffing-box bush.</td><td align='left'><i>t</i><sub>3</sub> = thickness of bushes in box and gland.</td></tr> +<tr><td align='left'><i>l</i><sub>1</sub></td><td align='left'>= length of packing space.</td><td align='left'><i>d</i><sub>2</sub> = diameter of gland bolts.</td></tr> +<tr><td align='left'><i>l</i><sub>2</sub></td><td align='left'>= length of gland.</td><td align='left'><i>n</i> = number of bolts.</td></tr> +<tr><td align='left'><i>t</i></td><td align='left'>= thickness of metal in stuffing-box.</td></tr> +</table></div> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary="" rules="cols"> +<thead> +<tr> +<th class="bbox"><i>d</i></th> +<th class="bbox"><i>d</i><sub>1</sub></th> +<th class="bbox"><i>l</i></th> +<th class="bbox"><i>l</i><sub>1</sub></th> +<th class="bbox"><i>l</i><sub>2</sub></th> +<th class="bbox"><i>t</i></th> +<th class="bbox"><i>t</i><sub>1</sub></th> +<th class="bbox"><i>t</i><sub>2</sub></th> +<th class="bbox"><i>t</i><sub>3</sub></th> +<th class="bbox"><i>d</i><sub>2</sub></th> +<th class="bbox"><i>n</i></th> +</tr> +</thead> +<tbody> +<tr><td align='center'> 1</td><td align='center'> 1¾</td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> 2</td><td align='center'> 1½</td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'><i>t</i><sub>2</sub>=<i>t</i></td><td align='center'> <sup>3</sup>⁄<sub>16</sub></td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> 2</td></tr> +<tr><td align='center'>1½</td><td align='center'> 2½</td><td align='center'>1¼</td><td align='center'> 2<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 2</td><td align='center'> <sup>9</sup>⁄<sub>16</sub></td><td align='center'> <sup>11</sup>⁄<sub>16</sub></td><td align='center'>when gland</td><td align='center'> <sup>1</sup>⁄<sub>4</sub></td><td align='center'> <sup>5</sup>⁄<sub>8</sub></td><td align='center'> 2</td></tr> +<tr><td align='center'> 2</td><td align='center'> 3½</td><td align='center'>1¾</td><td align='center'> 3¼</td><td align='center'> 2½</td><td align='center'><sup>11</sup>⁄<sub>16</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'>flange is</td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>3</sup>⁄<sub>4</sub></td><td align='center'> 2</td></tr> +<tr><td align='center'>2½</td><td align='center'> 4<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>2¼</td><td align='center'> 3<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'> 2<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'><sup>13</sup>⁄<sub>16</sub></td><td align='center'> 1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'>made of</td><td align='center'> <sup>5</sup>⁄<sub>16</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'> 2</td></tr> +<tr><td align='center'> 3</td><td align='center'> 4¾</td><td align='center'>2¾</td><td align='center'> 4½</td><td align='center'> 3¼</td><td align='center'><sup>15</sup>⁄<sub>16</sub></td><td align='center'> 1¼</td><td align='center'>cast iron</td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> 1</td><td align='center'> 2</td></tr> +<tr><td align='center'>3½</td><td align='center'> 5¼</td><td align='center'> 3</td><td align='center'> 5<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'> 3<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'> 1</td><td align='center'> 1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'>and <i>t</i><sub>2</sub>=<i>t</i><sub>1</sub></td><td align='center'> <sup>3</sup>⁄<sub>8</sub></td><td align='center'> 1</td><td align='center'> 2</td></tr> +<tr><td align='center'> 4</td><td align='center'> 5<small><sup>7</sup>⁄<sub>8</sub></small></td><td align='center'>3¼</td><td align='center'> 5¾</td><td align='center'> 4</td><td align='center'> 1</td><td align='center'> 1<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'>when gland</td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> 1</td><td align='center'> 2</td></tr> +<tr><td align='center'>4½</td><td align='center'> 6<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'>3½</td><td align='center'> 6<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'> 4<small><sup>3</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>9</sup>⁄<sub>16</sub></small></td><td align='center'>flange is</td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> <sup>7</sup>⁄<sub>8</sub></td><td align='center'> 4</td></tr> +<tr><td align='center'> 5</td><td align='center'> 7</td><td align='center'>3¾</td><td align='center'> 7</td><td align='center'> 4<small><sup>5</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>1</sup>⁄<sub>16</sub></small></td><td align='center'> 1<small><sup>9</sup>⁄<sub>16</sub></small></td><td align='center'>made of</td><td align='center'> <sup>7</sup>⁄<sub>16</sub></td><td align='center'> 1</td><td align='center'> 4</td></tr> +<tr><td align='center'> 6</td><td align='center'> 8</td><td align='center'>4¼</td><td align='center'> 8¼</td><td align='center'> 5</td><td align='center'>1<small><sup>1</sup>⁄<sub>8</sub></small></td><td align='center'>1<small><sup>11</sup>⁄<sub>16</sub></small></td><td align='center'>brass.</td><td align='center'> <sup>1</sup>⁄<sub>2</sub></td><td align='center'> 1¼</td><td align='center'> 4</td></tr> +<tr><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td><td class="bb"></td></tr> +</tbody> +</table></div> + +<p>The proportions of glands and stuffing-boxes vary considerably +but the above table represents average practice.</p> + +<div class="blockquot"><p><span class="smcap">Exercise 55:</span>—Make the necessary working drawings for a +gland and stuffing-box for a locomotive engine piston rod 2½ +inches in diameter, to the dimensions given in the table.</p></div> + + + +<hr style="width: 15%;" /> +<p><span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span></p> +<h2>XVI. VALVES.</h2> + + +<p>Professor Unwin divides valves, according to their construction +into three classes as follows:—(1) flap valves, which +bond or turn upon a hinge; (2) lift valves, which rise perpendicularly +to the seat; (3) sliding valves, which move parallel +to the seat.</p> + +<p>Examples of flap valves are shown in figs. 54 and 55; two +forms of lift valves are shown in figs. 56 and 57, and in figs. +58 and 59 are shown two forms of slide valve. The slide valve +shown in fig. 58 moves in a straight line, while that shown in +fig. 59 (called a cock) moves in circle.</p> + +<p><i>India-rubber Valves.</i>—In india-rubber valves there is a +grating covered by a piece of india-rubber, which may be rectangular, +but is generally circular, and which is held down +along one edge if rectangular, or at the centre if circular. +Water or other fluid can pass freely upwards through the +grating, but when it attempts to return the elasticity of the +india-rubber, and the pressure of the water upon it, cause it to lie +close on the grating, and thus prevent the return of the water. +The india-rubber is prevented from rising too high by a perforated +guard. In fig. 54 is shown an example of an india-rubber +disc valve. A is the grating, B the india-rubber, C the +guard secured to the grating or seat by the stud D and nut +E. The grating is held in position by bolts and nuts F. The +grating and guard are generally of brass.</p> + +<p>India-rubber disc valves are also shown on the air-pump +bucket, fig. 47.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 56: <i>India-rubber Disc Valve.</i>—Fig. 54 shows a +vertical section and a plan of an india-rubber disc valve. In the +plan one-half of the guard and india-rubber are supposed to be removed +so as to show the grating or seat. Draw these views, and +also an elevation. A detail drawing of the central stud is shown in +fig. 16, page 18. In fig. 54 the elevation of the guard is drawn as +it is usually drawn in practice, but if the student has a sufficient +knowledge of descriptive geometry he should draw the elevation +completely showing the perforations. Scale 6 inches to a foot.</p></div> +<p><span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> + +<div class="figcenter" style="width: 1050px;"> +<div class="figleft" style="width: 465px;"> +<img src="images/illus077a.png" width="465" height="640" alt="Fig. 54." title="Fig. 54." /> +<span class="caption">Fig. 54.</span> +</div> +<div class="figright" style="width: 534px;"> +<img src="images/illus077b.png" width="534" height="638" alt="Fig. 55." title="Fig. 55." /> +<span class="caption">Fig. 55.</span> +</div> +</div> +<div style="clear: both;"></div> + +<p><span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span></p> + +<p><i>Kinghorn's Metallic Valve.</i>—The action of this valve is the +same as that of an india-rubber valve, but a thin sheet of +metal (phosphor bronze) takes the place of the india-rubber.</p> + +<p>This valve is now largely used in the pumps of marine +engines, and is shown in fig. 55 as applied to an air-pump +bucket. Three valves like the one shown are arranged round +the bucket.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 57: <i>Kinghorn's Metallic Valve.</i>—Fig. 55 shows an +elevation and plan of one form of this valve. In the plan one-half +of the guard and metal sheet are supposed to be removed, so as to +show the grating, which in this case is part of an air-pump bucket. +Draw the views shown, and also a vertical section of the guard +through the centres of the bolts. All the parts are of brass except +the valve proper, which is of phosphor bronze. Scale 6 inches to a +foot.</p></div> + +<p><i>Conical Disc Valves.</i>—A very common form of valve is +that shown in figs. 56 and 57. This form of valve consists of +a disc, the edge of which (called the face) is conical. The +conical edge of this disc fits accurately on a corresponding +seat. The angle which the valve face makes with its axis is +generally 45°. If the disc is raised, either by the action of +the fluid as in the india-rubber valve, or by other means, an +opening is formed around the disc through which the fluid +can pass. The valve is guided in rising and falling either by +three feathers underneath it, as in fig. 56, or by a central +spindle which moves freely through a hole in the centre of a +bridge which stretches across the seat, as in fig. 57. The lift of +the valve is limited by a stop above it, which forms part of the +casing containing the valve. The lift should in no case exceed +one-fourth of the diameter of the valve, and it is generally +much less than this. The guiding feathers (fig. 56) are notched +immediately under the disc for the purpose of making available +the full circumferential opening of the valve for the passage +of the fluid. These notches also prevent the feathers from +interfering with the turning or scraping of the valve face.</p> + +<p>Conical disc valves and their seats are nearly always made +of brass.<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span></p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 58: <i>Conical Disc Valves.</i>—Draw, half size, the plans +and elevations shown in figs. 56 and 57. In fig. 57 the valve is +shown open in the elevation, and in the plan it is removed altogether +in order to show the seat with its guide bridge.</p></div> + +<div class="figcenter" style="width: 1024px;"> +<div class="figleft" style="width: 404px;"> +<img src="images/illus079a.png" width="404" height="800" alt="Fig. 56." title="Fig. 56." /> +<span class="caption">Fig. 56.</span> +</div> +<div class="figright" style="width: 402px;"> +<img src="images/illus079b.png" width="402" height="800" alt="Fig. 57." title="Fig. 57." /> +<span class="caption">Fig. 57.</span> +</div> +</div> +<div style="clear: both;"></div> + +<p><i>Simple Slide Valve.</i>—The form of valve shown in fig. 58, +often called the <i>locomotive slide valve</i>, is very largely used in all +classes of steam-engines for distributing the steam in the +steam cylinders. The valve is shown separately at (<i>d</i>), (<i>e</i>), +and (<i>f</i>), while at (<i>a</i>), (<i>b</i>), and (<i>c</i>) is shown its connection with +the steam cylinder.</p> + +<p>It will be observed that the valve itself is in the shape of +a box with one side open, the edges of the open side being +flanged. When the valve is in its middle position, as shown +at (<i>a</i>), two of these flanged edges completely cover two rectangular +openings S<sub>1</sub> and S<sub>2</sub>, called <i>steam ports</i>, while the hollow +part of the valve is opposite to a third port E, called the <i>exhaust +port</i>. As shown at (<i>a</i>) the piston P would be moving<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span> +upwards and the valve downwards. By the time the piston +has reached the top of its stroke the valve will have moved +so far down as to partly uncover the steam port S<sub>1</sub>, and admit +steam from the valve casing C through S<sub>1</sub> and the passage P<sub>1</sub> +to the top of the piston. The pressure of this steam on the +top of the piston will force the latter down. While the above +action has been going on, the port S<sub>2</sub> will have become uncovered, +and the hollow part of the valve will be opposite both +the steam port S<sub>2</sub> and the exhaust port E, so that the steam +from the under side of the piston, and which forced the piston +up, can now escape by the passage P<sub>2</sub>, the steam port S<sub>2</sub>, and +the exhaust port E to the exhaust outlet O, and thence into +the atmosphere, if it is a non-condensing engine, or into the +condenser if it is a condensing engine, or into another cylinder +if it is a compound engine. After the piston has performed, +a certain part of its downward stroke, the valve, which has +been moving downwards, will commence to move upwards, +and when it has reached a certain point it will cover the port +S<sub>1</sub>, and shut off the supply of steam to the top of the piston. +It is generally arranged that the steam shall be cut off before +the piston reaches the end of the stroke. When the piston +reaches the bottom of its stroke the valve has moved far +enough up to uncover the port S<sub>2</sub> and admit steam to the +bottom of the piston, and to uncover the port S<sub>1</sub> and allow +the steam to escape from the top of the piston through the +passage P<sub>1</sub>, the port S<sub>1</sub>, the port E, and outlet O. In this +way the piston is moved up and down in the cylinder.</p> + +<p>The valve is attached to a valve spindle S by nuts as +shown, the hole in the valve through which the spindle passes +being oval-shaped to permit of the valve adjusting itself so as +to always press on its seat.</p> + +<p>When the valve is in its middle position it generally more +than covers the steam ports. The amount which the valve +projects over the steam port on the outside, the valve being +in its middle position, is called the <i>outside lap</i> of the valve, +and the amount which it projects on the inside is called the +<i>inside lap</i>. When the term lap is used without any qualification, +outside lap is to be understood. In fig. 58 it will be<span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span> +seen that the valve has no inside lap, and that the outside lap +is three-eighths of an inch. The inside lap is generally small +compared with the outside lap.</p> + +<div class="figcenter" style="width: 619px;"> +<img src="images/illus081.png" width="619" height="1024" alt="Fig. 58." title="Fig. 58." /> +<span class="caption">Fig. 58.</span> +</div> + +<p><span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span></p> + +<p>When the piston is at the beginning of its stroke the steam +port is generally open by a small amount called the <i>lead</i> of the +valve.</p> + +<p>The reciprocating motion of the slide valve is nearly always +derived from an eccentric fixed on the crank-shaft of the +engine. Slide valves are generally made of brass, bronze, or +cast iron.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 59: <i>Simple Slide Valve.</i>—At (<i>d</i>), fig. 58, is shown a +sectional elevation of a simple slide valve for a steam-engine, the +section being taken through the centre line of the valve spindle, +while at (<i>e</i>) is shown a cross section and elevation, and at (<i>f</i>) a plan +of the same. Draw all these views full size, and also a sectional +elevation at A B. The valve is made of brass, and the valve spindle +and nuts of wrought iron.</p> + +<p><span class="smcap">Exercise</span> 60: <i>Slide Valve Casing, &c., for Steam-engine.</i>—Draw, +half size, the views shown at (<i>a</i>), (<i>b</i>), and (<i>c</i>), fig. 58; also a +sectional plan at L M. (<i>b</i>) is an elevation of the valve casing with the +cover and the valve removed. (<i>a</i>) is a sectional elevation, the section +being taken through the axes of the steam cylinder and valve spindle. +(<i>c</i>) is a sectional plan, the section being a horizontal one through +the centre of the exhaust port. The inlet and outlet for the steam +are clearly shown in the sectional plan: in the sectional elevation +their positions are shown by dotted circles.</p> + +<p>The stroke of the piston is in this case 12 inches, so that from +the dimensions given at (<i>a</i>) it must come within a quarter of an +inch of each end of the cylinder; this is called the <i>cylinder clearance</i>.</p> + +<p>The piston has three Ramsbottom rings, a quarter of an inch +wide and a quarter of an inch apart.</p> + +<p>The steam cylinder and valve casing are made of cast iron.</p> +</div> + +<p><i>Cocks.</i>—A cock consists of a slightly conical plug which +fits into a corresponding casing cast on a pipe. Through the +plug is a hole which may be made by turning the plug to form +a continuation of the hole in the pipe, and thus allow the fluid +to pass, or it may be turned round so that the solid part of +the plug lies across the hole in the pipe, and thus prevent the<span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span> +fluid from passing. As the student will be quite familiar +with the common water cock or tap such as is used in dwelling-houses +we need not illustrate it here.</p> + +<div class="figcenter" style="width: 560px;"> +<img src="images/illus083.png" width="560" height="1024" alt="Fig. 59." title="Fig. 59." /> +<span class="caption">Fig. 59.</span> +</div> + +<p><span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span></p> + +<p>Fig. 59 shows a cock of considerable size, which may be +used for water or steam under high pressure. The plug in +this example is hollow, and is prevented from coming out by a +cover which is secured to the casing by four stud bolts. An +annular ridge of rectangular section projecting from the under +side of the cover, and fitting into a corresponding recess on the +top of the casing, serves to ensure that the cover and plug are +concentric, and prevents leakage. Leakage at the neck of the +plug is prevented by a gland and stuffing-box. The top end +of the plug is made square to receive a handle for turning it. +The size of a cock is taken from the bore of the pipe in which +it is placed; thus fig. 59 shows a 2¼-inch cock.</p> + +<div class="blockquot"><p><span class="smcap">Exercise</span> 61: 2¼-<i>inch Steam or Water Cock.</i>—First draw the +views of this cock shown in fig. 59, then draw a half end elevation +and half cross section through the centre of the plug. Scale 6 inches +to a foot.</p> + +<p>Instead of drawing the parts of the pipe on the two sides of the +plug in the same straight line as in fig. 59, one may be shown proceeding +from the bottom of the casing, so that the fluid will have to +pass through the bottom of the plug and through one side. This is +a common arrangement.</p> + +<p>All the parts of the valve and casing in this example are made +of brass.</p></div> + + + +<hr style="width: 15%;" /> +<h2>XVII. MATERIALS USED IN MACHINE<br /> +CONSTRUCTION.</h2> + + +<p><i>Cast Iron.</i>—The essential constituents of cast iron are iron +and carbon, the latter forming from 2 to 5 per cent. of the +total weight. Cast iron, however, usually contains varying +small amounts of silicon, sulphur, phosphorus, and manganese.</p> + +<p>In cast iron the carbon may exist partly in the free state +and partly in chemical combination with the iron.<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span></p> + +<p>In <i>white cast iron</i> the whole of the carbon is in chemical +combination with the iron, while in <i>grey cast iron</i> the carbon +is principally in the free state, that is, simply mixed mechanically +with the iron. It is the free carbon which gives the +grey iron its dark appearance. A mixture of the white and +grey varieties of cast iron when melted produces <i>mottled cast +iron</i>. The greater the amount of carbon chemically combined +with the iron, the whiter, harder, and more brittle does it +become.</p> + +<p>The white cast iron is stronger than the grey, but being +more brittle it is not so suitable for resisting suddenly applied +loads. White iron melts at a lower temperature than grey +iron, but after melting it does not flow so well, or is not so +liquid as the grey iron. White iron contracts while grey iron +expands on solidifying. The grey iron, therefore, makes finer +castings than the white. Castings after solidifying contract in +cooling about <sup>1</sup>⁄<sub>8</sub> of an inch per foot. Castings possessing +various degrees of strength and hardness are produced by +melting mixtures of various proportions of white and grey +cast irons. White cast iron has a higher specific gravity than +grey cast iron.</p> + +<p>Cast iron gives little or no warning before breaking. The +thickness of the metal throughout a casting in cast iron +should be as uniform as possible, so that it may cool and +therefore contract uniformly throughout; otherwise some parts +may be in a state of initial strain after the casting has cooled, +and will therefore be easier to fracture. Re-entrant angles +should be avoided; such should be rounded out with fillets.</p> + +<p>The presence of phosphorus in cast iron makes it more +fusible, and also more brittle. The presence of sulphur +diminishes the strength considerably.</p> + +<p>The grey varieties of cast iron are called <i>foundry irons</i> or +<i>foundry pigs</i>, while the white varieties are called <i>forge irons</i> +or <i>forge pigs</i>, from the fact that they are used for conversion +into wrought iron.</p> + +<p>Amongst iron manufacturers the different varieties of cast +iron are designated by the numbers 1, 2, 3, &c., the lowest +number being applied to the greyest variety.<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span></p> + +<p><i>Chilled Castings.</i>—When grey cast iron is melted a portion +of the free carbon combines chemically with the iron; this, +however, separates out again if the iron is allowed to cool +slowly; but if it is suddenly cooled a greater amount of the +carbon remains in chemical combination, and a whiter and +harder iron is produced. Advantage is taken of this in making +<i>chilled castings</i>. In this process the whole or a part of the +mould is lined with cast iron, which, being a comparatively +good conductor of heat, chills a portion of the melted metal +next to it, changing it into a hard white iron to a depth +varying from <sup>1</sup>⁄<sub>8</sub> to <sup>1</sup>⁄<sub>2</sub> an inch. To protect the cast-iron lining +of the mould from the molten metal it is painted with +loam.</p> + +<p><i>Malleable Cast Iron.</i>—This is prepared by imbedding a +casting in powdered red hematite (an oxide of iron), and +keeping it at a bright red heat for a length of time varying +from several hours to several days according to the size of the +casting. By this process a portion of the carbon in the casting +is removed, and the strength and toughness of the latter +become more like the strength and toughness of wrought or +malleable iron.</p> + +<p><i>Wrought or Malleable Iron.</i>—This is nearly pure iron, and +is made from cast iron by the puddling process, which consists +chiefly of raising the cast iron to a high temperature in a +reverberatory furnace in the presence of air, which unites with +the carbon and passes off as gas. In other words the carbon +is burned out. The iron is removed from the puddling +furnace in soft spongy masses called <i>blooms</i>, which are subjected +to a process of squeezing or hammering called <i>shingling</i>. +These shingled blooms still contain enough heat to enable +them to be rolled into rough <i>puddled bars</i>. These puddled +bars are of very inferior quality, having less than half the +strength of good wrought iron. The puddled bars are cut into +pieces which are piled together, reheated, and again rolled +into bars, which are called <i>merchant bars</i>. This process of +piling, reheating, and re-rolling may be repeated several times, +depending on the quality of iron required. Up to a certain +point the quality of the iron is improved by reheating and<span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span> +rolling or hammering, but beyond that a repetition of the +process diminishes the strength of the iron.</p> + +<p>The process of piling and rolling gives wrought iron a +fibrous structure. When subjected to vibrations for a long +time, the structure becomes crystalline and the iron brittle. +The crystalline structure induced in this way may be removed +by the process of <i>annealing</i>, which consists in heating the iron +in a furnace, and then allowing it to cool slowly.</p> + +<p><i>Forging and Welding.</i>—The process of pressing or hammering +wrought iron when at a red or white heat into any +desired shape is called <i>forging</i>. If at a white heat two pieces +of wrought iron be brought together, their surfaces being clean, +they may be pressed or hammered together, so as to form one +piece. This is called <i>welding</i>, and is a very valuable property +of wrought iron.</p> + +<p><i>Steel.</i>—This is a compound of iron with a small per-centage +of carbon, and is made either by adding carbon to wrought +iron, or by removing some of the carbon from cast iron.</p> + +<p>In the <i>cementation</i> process, bars of wrought iron are imbedded +in powdered charcoal in a fireclay trough, and kept +at a high temperature in a furnace for several days. The +iron combines with a portion of the carbon to form <i>blister +steel</i>, so named because of the blisters which are found on +the surface of the bars when they are removed from the +furnace.</p> + +<p>The bars of blister steel are broken into pieces about 18 +inches long, and tied together in bundles by strong steel wire. +These bundles are raised to a welding heat in a furnace, and +then hammered or rolled into bars of <i>shear steel</i>.</p> + +<p>To form <i>cast steel</i> the bars of blister steel are broken into +pieces and melted into crucibles.</p> + +<p>In the <i>Siemens-Martin</i> process for making steel, cast and +wrought iron are melted together on the hearth of a regenerative +gas-furnace.</p> + +<p><i>Bessemer steel</i> is made by pouring melted cast iron into a +vessel called a converter, through which a blast of air is then +urged. By this means the carbon is burned out, and comparatively +pure iron remains. To this is added a certain quantity<span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span> +of 'spiegeleisen,' which is a compound of iron, carbon, and +manganese.</p> + +<p><i>Hardening and Tempering of Steel.</i>—Steel, if heated to +redness and cooled suddenly, as by immersion in water, is +hardened. The degree of hardness produced varies with the +rate of cooling; the more rapidly the heated steel is cooled, +the harder does it become. Hardened steel is softened by the +process of <i>annealing</i>, which consists in heating the hardened +steel to redness, and then allowing it to cool slowly. Hardened +steel is <i>tempered</i>, or has its degree of hardness lowered, by +being heated to a temperature considerably below that of a red +heat, and then cooling suddenly. The higher the temperature +the hardened steel is raised to, the lower does its 'temper' +become.</p> + +<p><i>Case-hardening.</i>—This is the name given to the process +by which the surfaces of articles made of wrought iron are +converted into steel, and consists in heating the articles in +contact with substances rich in carbon, such as bone-dust, +horn shavings, or yellow prussiate of potash. This process +is generally applied to the articles after they are completely +finished by the machine tools or by hand. The coating of +steel produced on the article by this process is hardened by +cooling the article suddenly in water.</p> + +<p><i>Copper.</i>—This metal has a reddish brown colour, and when +pure is very malleable and ductile, either when cold or hot, so +that it may be rolled or hammered into thin plates, or drawn +into wire. Slight traces of impurities cause brittleness, +although from 2 to 4 per cent. of phosphorus increases its +tenacity and fluidity. Copper is a good conductor of heat and +of electricity. Copper is largely used for making alloys.</p> + +<p><i>Alloys.</i>—<i>Brass</i> contains two parts by weight of copper to +one of zinc. <i>Muntz metal</i> consists of three parts of copper to +two of zinc. Alloys consisting of copper and tin are called +<i>bronze</i> or <i>gun-metal</i>. Bronze is harder the greater the proportion +of tin which it contains; five parts of copper to one +of tin produce a very hard bronze, and ten of copper to one +of tin is the composition of a soft bronze. <i>Phosphor bronze</i> +contains copper and tin with a little phosphorus; it has this<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span> +advantage over ordinary bronze, that it may be remelted without +deteriorating in quality. This alloy also has the advantage +that it may be made to possess great strength accompanied with +hardness, or less strength with a high degree of toughness.</p> + +<p><i>Wood.</i>—In the early days of machines wood was largely +used in their construction, but it is now used to a very limited +extent in that direction. <i>Beech</i> and <i>hornbeam</i> are used for +the cogs of mortise wheels. <i>Yellow pine</i> is much used by +pattern-makers. <i>Box</i>, a heavy, hard, yellow-coloured wood, +is used for the sheaves of pulley blocks, and sometimes for +bearings in machines. <i>Lignum-vitæ</i> is a very hard dark-coloured +wood, and remarkable for its high specific gravity, +being 1<small><sup>1</sup>⁄<sub>3</sub></small> times the weight of the same volume of water. This +wood is much used for bearings of machines which are under +water.</p> + + + +<hr style="width: 15%;" /> +<h2>XVIII. MISCELLANEOUS EXERCISES.</h2> + + +<p>The illustrations in this chapter are in most cases not +drawn to scale; they are also in some parts incomplete, and +in others some of the lines are purposely drawn wrong. The +student must keep to the dimensions marked on the drawings, +and where no sizes are given he must use his own judgment +in proportioning the parts. All errors must be corrected, and +any details required, but not shown completely in the illustrations, +must be filled in.</p> + + +<div class="blockquot"> +<p><span class="smcap">Exercise 62:</span> <i>Single Riveted Butt Joint with Tee-iron Cover +Strap.</i>—Two views, one a side elevation and the other a sectional +elevation, of a riveted joint are shown in fig. 60. Draw these views, +and also a plan projected from one of them. Show the rivets completely +in all the views. Scale 4 inches to a foot.</p> +</div> + +<p><span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span></p> + +<div class="figcenter" style="width: 640px;"> +<img src="images/illus090a.png" width="640" height="456" alt="Fig. 60." title="Fig. 60." /> +<span class="caption">Fig. 60.</span> +</div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus090b.png" width="800" height="440" alt="Fig. 61." title="Fig. 61." /> +<span class="caption">Fig. 61.</span> +</div> + + +<div class="blockquot"> +<p><span class="smcap">Exercise 63:</span> <i>Girder Stay for Steam Boiler.</i>—The flat crown +of the fire-box of locomotive and marine boilers is generally supported +or stayed by means of girder stays, an example of which is +shown in fig. 61. A B is the side elevation of a portion of one of +these girders. Each girder is supported at its ends by the plates +forming the vertical sides of the fire-box. The flat crown is bolted +to the girders as shown. Observe that the girders are in contact +with the crown only in the neighbourhood of the bolts. Consider +carefully this part of the design, and then answer the following +<span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span>questions: (1) What objections are there to supporting the girders +at the ends only without the contact pieces at the bolts? (2) What +objections are there to having the girders in contact with the crown +plate of the fire-box throughout their whole length?</p> + +<p>Draw the views shown in fig. 61, and from the right-hand one +project a plan. Scale 4 inches to a foot.</p></div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus091.png" width="800" height="422" alt="Fig. 62." title="Fig. 62." /> +<span class="caption">Fig. 62.</span> +</div> + + +<div class="blockquot"> +<p><span class="smcap">Exercise 64:</span> <i>End of Bar Stay for Steam Boiler.</i>—On page +12 one form of stay for supporting the flat end of a steam boiler is +described. Another form of stay for the same purpose is shown in +fig. 62. A B is a portion of the end of a steam boiler. C D is one +end of a bar which extends from one end of the boiler to the other. +The ends of this bar are screwed, and when the bar is of wrought +iron the screwed parts are generally larger in diameter than the +rest of the bar. When made of steel the bar is generally of uniform +diameter throughout. In the case of wrought-iron bar stays +the enlarged ends are welded on to the smaller parts. Welding is +not so reliable with steel as with wrought iron. Write out answers +to the following questions: (1) What is the advantage of having +the screwed part of the bar larger in diameter than the rest? +(2) Why are steel bar stays not generally enlarged at their screwed +ends?</p> + +<p><span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span></p> + +<p>Draw the views shown in fig. 62, and project from one of them +a third view. Scale 4 inches to a foot.</p> + +<p><span class="smcap">Exercise 65:</span> <i>Knuckle Joint.</i>—Draw the plan and elevation of +this joint shown in fig. 63, and also draw an end elevation looking +in the direction of the arrow. The parts at A and B are octagonal +in cross section. Scale 4 inches to a foot.</p></div> + +<div class="figcenter" style="width: 774px;"> +<img src="images/illus092.png" width="774" height="600" alt="Fig. 63." title="Fig. 63." /> +<span class="caption">Fig. 63.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 66:</span> <i>Locomotive Coupling Rod Ends.</i>—A form +of knuckle joint used on locomotive coupling rods is shown in +fig. 64.</p> + +<p>In this case two rods meet and work on the same pin, as shown +at (a) fig. 64. Draw, in addition to the views shown in fig. 64, a +plan and a vertical section through the axis of the pin. Scale +6 inches to a foot.</p> + +<p>Would it be practicable to replace the two rods A B and B C by +a single rod working on the crank pins at A, B, and C? Give +reasons for your answer.</p> +</div> + +<p><span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span></p> + +<div class="figcenter" style="width: 647px;"> +<img src="images/illus093.png" width="647" height="1024" alt="Fig. 64." title="Fig. 64." /> +<span class="caption">Fig. 64.</span> +</div> +<p><span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span></p> + +<div class="blockquot"><p><span class="smcap">Exercise 67:</span> <i>Bell Crank Lever.</i>—Draw the plan and elevation +of the lever shown in fig. 65. Scale 6 inches to a foot.</p></div> + +<div class="figcenter" style="width: 673px;"> +<img src="images/illus094.png" width="673" height="1024" alt="Fig. 65." title="Fig. 65." /> +<span class="caption">Fig. 65.</span> +</div> + + +<div class="blockquot"><p><span class="smcap">Exercise 68:</span> <i>Back Stay for Lathe.</i>—Draw a plan and two +elevations of the stay shown in fig. 66. Make all necessary corrections +and show all the details in each view. Scale full size.</p></div><p><span class='pagenum'><a name="Page_87" id="Page_87">[Pg 87]</a></span></p> + +<div class="figcenter" style="width: 637px;"> +<img src="images/illus095.png" width="637" height="1024" alt="Fig. 66." title="Fig. 66." /> +<span class="caption">Fig. 66.</span> +</div> +<p><span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span></p> + +<div class="figcenter" style="width: 619px;"> +<img src="images/illus096.png" width="619" height="1024" alt="Fig. 67." title="Fig. 67." /> +<span class="caption">Fig. 67.</span> +</div> +<p><span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span></p> + +<div class="blockquot"><p><span class="smcap">Exercise 69:</span> <i>Conical Disc Valve and Casing.</i>—Draw, half +size, the views shown in fig. 67 of the conical disc valve and casing, +and also add an elevation looking in the direction of the arrow.</p> + +<p><span class="smcap">Exercise 70:</span> <i>Connecting Rod End.</i>—The student should carefully +compare this connecting rod end (fig. 68) with those illustrated +on pages 50 and 52. The lower part of fig. 68 is a half plan and +half horizontal section, and the upper part is a half side elevation +and half vertical section. Draw these views and also an end +elevation. Scale 6 inches to a foot.</p></div> + +<div class="figcenter" style="width: 768px;"> +<img src="images/illus097.png" width="768" height="789" alt="Fig. 68." title="Fig. 68." /> +<span class="caption">Fig. 68.</span> +</div> + +<p><span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span></p> + +<div class="figcenter" style="width: 608px;"> +<img src="images/illus098.png" width="608" height="1024" alt="Fig. 69." title="Fig. 69." /> +<span class="caption">Fig. 69.</span> +</div> +<p><span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span></p> + +<div class="figcenter" style="width: 604px;"> +<img src="images/illus099.png" width="604" height="1024" alt="Fig. 70." title="Fig. 70." /> +<span class="caption">Fig. 70.</span> +</div> +<p><span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span></p> + +<div class="figcenter" style="width: 606px;"> +<img src="images/illus100.png" width="606" height="1024" alt="Fig. 71." title="Fig. 71." /> +<span class="caption">Fig. 71.</span> +</div> +<p><span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus101.png" width="1024" height="617" alt="Fig. 72." title="Fig. 72." /> +<span class="caption">Fig. 72.</span> +</div> + +<p><span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span></p> + +<div class="figcenter" style="width: 1024px;"> +<img src="images/illus102.png" width="1024" height="581" alt="Fig. 73." title="Fig. 73." /> +<span class="caption">Fig. 73.</span> +</div> + +<p><span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span></p> + +<div class="figcenter" style="width: 748px;"> +<img src="images/illus103.png" width="748" height="1024" alt="Fig. 74." title="Fig. 74." /> +<span class="caption">Fig. 74.</span> +</div> + + +<div class="blockquot"><p><span class="smcap">Exercise 71:</span> <i>Engine Cross-head.</i>—The cross-head shown in +fig. 69 is for an inverted cylinder marine engine. A is the piston +rod, and B B are pins, forged in one piece with C, to which the +forked end of the connecting rod is attached. Draw the upper +view with the central part in section as shown. Make the right-hand +half of the lower view a plan without any section, and make<span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span> +the left-hand half a horizontal section through the axis of the pins +B B. Scale 4 inches to a foot.</p> + +<p><span class="smcap">Exercise 72:</span> <i>Ratchet Lever.</i>—The lever shown in fig. 70 is +used for turning the horizontal screw of a traversing screw jack. +Draw the two views shown, and from one of them project a plan. +Scale full size.</p> + +<p><span class="smcap">Exercise 73:</span> <i>Steam Whistle.</i>—Draw, full size, the elevation +and section of the steam whistle shown in fig. 71. Draw also +horizontal sections at A B, C D, and E F.</p></div> + +<div class="figcenter" style="width: 805px;"> +<img src="images/illus104.png" width="805" height="691" alt="Fig. 75." title="Fig. 75." /> +<span class="caption">Fig. 75.</span> +</div> + +<div class="blockquot"><p><span class="smcap">Exercise 74:</span> <i>Screw Coupling for Railway Carriages.</i>—Draw +the three views of the screw coupling shown in fig. 72. Scale 6 +inches to a foot.</p> + +<p>If the link A is fixed, through what distance will the link B +move for two turns of the lever?</p> + +<p><span class="smcap">Exercise 75:</span> <i>Loose Headstock for a 6-inch Lathe.</i>—Two +views of this headstock are shown in fig. 73. On one of these +views a few of the chief dimensions are marked. The details, fully +dimensioned, are shown separately in figs. 74, 75, and 76.</p></div><p><span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span></p> + +<div class="figcenter" style="width: 651px;"> +<img src="images/illus105.png" width="651" height="1024" alt="Fig. 76." title="Fig. 76." /> +<span class="caption">Fig. 76.</span> +</div> + +<p><span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span></p> +<div class="blockquot"> +<p>Explain clearly how the centre is moved backwards and forwards, +and also how the spindle containing it is locked when it is +not required to move.</p> + +<p>Draw, half-size, the views shown in fig. 73, and from the left-hand +view project a plan. Draw also the detail of the locking +arrangement shown in fig. 74.</p> +</div> + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span></p> +<h2>APPENDIX A.</h2> + +<hr style="width: 15%;" /> +<h3><i>SCIENCE AND ART DEPARTMENT, SOUTH<br /> +KENSINGTON.</i></h3> + +<h3><span class="smcap">Syllabus.</span></h3> + +<h4>SUBJECT II.—MACHINE CONSTRUCTION AND<br /> +DRAWING.</h4> + + +<p>It is assumed that the student has already learnt to draw to scale, +and that he can draw two or more views of the same object in +simple or orthographic projection. To pass in machine construction +and drawing, he must be able to apply this knowledge to the representation +of machinery. He must be acquainted with the form and +purpose of the simpler parts of which machines are built up and +must have had some practice in drawing them. To test his knowledge, +rough dimensioned sketches, more or less incomplete, of +simple machine details will be given him, and he will be required to +produce a complete drawing in pencil to a given scale. Two or +more views of at least one subject will be required, and these must +be so drawn as to be properly projected one from the other, <i>in order +to show that the student appreciates that he is producing a representation +of a solid piece of machinery, and not merely copying a +sketch. No credit will be given unless some knowledge of projection +is shown.</i> The centre lines of the drawings should be shown, +and parts cut by planes of section should be indicated by diagonal +shading. Bolts and other fastenings should be carefully shown +where required. Any indication that a candidate has merely +copied the sketches given, without understanding the part represented, +will invalidate his examination.</p> +<p><span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span></p> + +<h4><span class="smcap">First Stage or Elementary Course.</span></h4> + +<p>In the elementary stage, a knowledge is required of the simple +parts only of <i>machines in common use</i>. <i>Some</i> of these are +enumerated in the following list. The student should be practised +in drawing them till he recognises their forms, and the object of the +arrangement should be explained to him. He should also know +the simple technical terms used in describing them.</p> + +<p>A few very simple questions relating to the arrangement, proportions, +and strength of the simplest machine details will be set +in the examination paper.</p> + +<p>In drawing the examples set to test a student's knowledge and +skill in machine drawing, it must be remembered that only a +limited time is available. It is only possible to set an example to +be drawn in pencil, and the points which will receive attention are +(1) accuracy of scale and projection; (2) power of reading a drawing, +shown by the ability to transfer portions of the mechanism +and dimensions from one view to another; (3) knowledge of +machines, as shown by the ability to fill in small details, such as +nuts, keys, etc., omitted in the sketches given. Bearing in mind +the limited time available, the student should try to make his +outline clear and decisive and complete. But the diagonal lines +necessary for sectional parts may be done rapidly, though neatly, +by freehand if necessary.</p> + +<p><i>Riveted Joints.</i>—Forms of rivets and arrangement of rivets in +lap and butt joints with single and double riveting. Junction of +plates by angle and T-irons.</p> + +<p><i>Bolts, Studs, and Set Screws.</i>—Forms of these fastenings. +Forms and proportions of nuts and bolt-heads. Arrangement of +flanges for bolting.</p> + +<p><i>Pins, Keys, and Cotters.</i>—Form of ordinary knuckle joint. Use +of split pins. Connection of parts by a key. Connection of parts by +a cotter. Gib and cotter.</p> + +<p><i>Pipes and Cylinders.</i>—Forms of ordinary pipes and cylinders +and their flanges and covers.</p> + +<p><i>Shafting.</i>—Forms of shafts and axles and of journals and +pivots. Use of collars and bosses. Half-lap coupling. Box +coupling. Flange coupling.</p> + +<p><i>Pedestals and Plummer Blocks.</i>—Simplest forms of pedestals +and hangers for shafts. Form and arrangement of brass steps.<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span> +Arrangements for fixing pedestals and for neutralising the effects of +wear.</p> + +<p><i>Toothed Gearing.</i>—Forms of ordinary spur and bevil wheels. +Meaning of the terms pitch, breadth of face, thickness of tooth, +pitch line, rim, nave, arm. Mode of drawing bevil wheels in +section.</p> + +<p><i>Belt Pulleys.</i>—Forms of belt pulleys for flat and round belts. +Stepped speed cones. Drawing of pulleys with curved arms.</p> + +<p><i>Cranks and Levers.</i>—Forms of ordinary cast-iron and wrought-iron +cranks and levers. Modes of fixing crank pin. Modes of +fixing crank shaft. Double cranks. Form of eccentrics.</p> + +<p><i>Links.</i>—Most simple forms of connecting rod ends, open or +closed. Use of steps in connecting rods. Use of cotters to tighten +the steps.</p> + +<p><i>Pistons.</i>—Simple forms of piston. Use of piston packing. +Modes of attaching piston rod.</p> + +<p><i>Stuffing-Boxes.</i>—Simple form of stuffing-box and gland. Use of +packing. Mode of tightening gland.</p> + +<p><i>Valves.</i>—Simple conical of puppet valve. Simple slide valve. +Cock or conical sliding valve.</p> + + + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span></p> +<h2>APPENDIX B.</h2> + +<hr style="width: 15%;" /> +<h3><i>EXAMINATION PAPERS SET BY THE SCIENCE<br /> +AND ART DEPARTMENT.</i></h3> + + +<h4>SUBJECT II.—MACHINE CONSTRUCTION AND<br /> +DRAWING.</h4> + +<p class="center"><big><i>Examiners</i>, <span class="smcap">Prof. T. A. Hearson</span>, M.Inst.C.E., and<br /> +<span class="smcap">J. Harrison, Esq.</span>, M.Inst.M.E.</big></p> + +<p class="center"><span class="smcap">General Instructions.</span></p> + +<p class="center"><span class="u">If the rules are not attended to, the paper will be cancelled.</span></p> + +<p>You may take the Elementary, or the Advanced, or the +Honours paper, but you must confine yourself to one of them.</p> + +<p>Put the number of the question before your answer.</p> + +<p>You are expected to prove your knowledge of machinery as +well as your power of drawing neatly to scale. You are therefore +to supply details omitted in the sketches, to fill in parts left +incomplete, and to indicate, by diagonal lines, parts cut by planes of +section.</p> + +<p>No credit will be given unless some knowledge of projection is +shown, so that at least two views of one of the examples will be +required properly projected one from the other. The centre lines +should be clearly drawn. The figured dimensions need not be +inserted.</p> + +<p>Your answers should be clearly and cleanly drawn in pencil. +No extra marks will be allowed for inking in.<span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span></p> + +<p>All figures must be drawn on the single sheet of paper supplied, +for no second sheet will be allowed.</p> + +<p>The value attached to each question is shown in brackets after +the question. But a full and correct answer to an easy question will +in all cases secure a larger number of marks than an incomplete or +inexact answer to a more difficult one.</p> + +<p>Your name is not given to the Examiner, and you are forbidden +to write to him about your answers.</p> + +<p>You are to confine your answers <i>strictly</i> to the questions +proposed.</p> + +<p>A single accent (´) signifies <i>feet</i>; a double accent (´´) <i>inches</i>.</p> + +<p><i>The examination in this subject lasts for four hours.</i></p> + +<hr style='width: 15%;' /> + +<h4>First Stage or Elementary Examination. 1885.</h4> + +<p class="center"><span class="smcap">Instructions.</span></p> + +<p>Read the General Instructions above.</p> + +<p>Answer briefly any three, but not more than three, of the +following questions, and draw two, but not more than two, of the +examples.</p> + +<p class="tabcap"><i>Questions.</i></p> + +<div class="poem"> +<p class="negidt">(<i>a.</i>) Show two methods by which a cotter may be prevented +from slacking back. <span class="marks">(6.)</span></p> + +<p class="negidt">(<i>b.</i>) Sketch the brasses for a bearing, and show how they are +prevented from turning in the pedestal. <span class="marks">(6.)</span></p> + +<p class="negidt">(<i>c.</i>) Explain the object of the construction of the connecting rod +end shown in fig. 78. Describe how the adjustment must +be made and how it is locked. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>d.</i>) Show the form of the Whitworth screw thread by drawing +to scale a part section of two or three threads taking a +pitch of 1½ inches. Figure the dimensions on the sketch. +How many threads to the inch are used on an inch bolt? <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>e.</i>) Make a sketch showing how the adjustment is made in +the sliding parts of machine tools: as, for example, in the +slide rest of a lathe. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>f.</i>) Describe with sketches two methods by which the joints +are made in connecting lengths of cast-iron pipes. <span class="marks">(6.)</span></p> +</div> +<p><span class='pagenum'><a name="Page_104" id="Page_104">[Pg 104]</a></span></p> + +<div class="figcenter" style="width: 603px;"> +<img src="images/illus112.png" width="603" height="1024" alt="Figs. 77 and 78." title="Figs. 77 and 78." /> +<span class="caption">Figs. 77 and 78.</span> +</div> + +<p><span class='pagenum'><a name="Page_105" id="Page_105">[Pg 105]</a></span></p> + +<p class="tabcap"><i>Examples to be drawn.</i></p> + +<div class="poem"> +<p class="negidt">1. Jaw for four-screw dog chuck for 5´´ lathe. Draw the two +views as shown (fig. 77). Scale full size.</p> + +<p class="negidt"> (Note.—The other three jaws of the chuck are not to be +drawn.) <span class="marks">(35.)</span></p> +</div> + +<div class="figcenter" style="width: 638px;"> +<img src="images/illus113.png" width="638" height="600" alt="Fig. 79." title="Fig. 79." /> +<span class="caption">Fig. 79.</span> +</div> + +<div class="poem"> +<p class="negidt">2. Connecting rod end. Draw the two views as shown, partly +in section (fig. 78). Draw full size. <span class="marks">(35.)</span></p> + +<p class="negidt">3. Hooke's coupling. Draw the three views shown (fig. 79), +adding any omitted lines where the views are incomplete. +Draw to scale of <sup>1</sup>⁄<sub>4</sub> full size. <span class="marks">(35.)</span></p> +</div> + +<hr style='width: 15%;' /> +<p><span class='pagenum'><a name="Page_106" id="Page_106">[Pg 106]</a></span></p> + +<div class="figcenter" style="width: 616px;"> +<img src="images/illus114.jpg" width="616" height="1024" alt="Figs. 80 and 81." title="Figs. 80 and 81." /> +<span class="caption">Figs. 80 and 81.</span> +</div> + + +<p><span class='pagenum'><a name="Page_107" id="Page_107">[Pg 107]</a></span></p> + + + +<h4>First Stage or Elementary Examination. 1886.</h4> + +<p class="center"><span class="smcap">Instructions.</span></p> + +<p>Read the General Instructions (page 102).</p> + +<p>Answer briefly any three, but not more than three, of the +following questions, and draw two, but not more than two, of the +examples.</p> + +<p class="tabcap"><i>Questions.</i></p> + +<div class="poem"> +<p class="negidt">(<i>a.</i>) Give sketches showing how the cutting tool of a lathe or +other machine is secured in place. <span class="marks">(6.)</span></p> + +<p class="negidt">(<i>b.</i>) Make a sketch of a stud, describe how it is screwed into +place, and state some circumstances under which it is used +in preference to a bolt. <span class="marks">(6.)</span></p> + +<p class="negidt">(<i>c.</i>) Give sketches showing one method of attaching the valve +rod to an ordinary slide valve. <span class="marks">(6.)</span></p> + +<p class="negidt">(<i>d.</i>) Sketch a connecting rod end, with strap, gib, and cotter. +Explain the use of the gib. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>e.</i>) Explain the use of the quadrant for change wheels for a +screw-cutting lathe shown in Example 1, fig. 80, by +making a sketch showing it in place on a lathe with +wheels in gear. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>f.</i>) Sketch one form of hanger suitable for supporting mill-shafting. <span class="marks">(10.)</span></p> +</div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus115.jpg" width="800" height="349" alt="Fig. 82." title="Fig. 82." /> +<span class="caption">Fig. 82.</span> +</div> + + +<p class="tabcap"><i>Examples to be drawn.</i></p> + +<div class="poem"> +<p class="negidt">1. Quadrant for change wheels for screw-cutting lathe. Draw +the two views shown (fig. 80). Scale half-size. <span class="marks">(35.)</span></p> +<p><span class='pagenum'><a name="Page_108" id="Page_108">[Pg 108]</a></span></p> + +<p class="negidt">2. Crank-shaft. Draw the two views as shown, partly in section +(fig 81). Scale <sup>1</sup>⁄<sub>8</sub> full size. <span class="marks">(35.)</span></p> + +<p class="negidt">3. Ball bearing for tricycle. Draw the two views as shown, +partly in section (fig. 82). Draw full size. <span class="marks">(35.)</span></p> +</div> + +<hr style='width: 15%;' /> + +<h4>First Stage or Elementary Examination. 1887.</h4> + +<p class="center"><span class="smcap">Instructions.</span></p> + +<p>Read the General Instructions (page 102).</p> + +<p>Answer briefly any three, but not more than three, of the +following questions, and draw two, but not more than two, of the +examples.</p> + +<p class="tabcap"><i>Questions.</i></p> + +<div class="poem"> +<p class="negidt">(<i>a.</i>) Explain how the piston rings in Example 1, fig. 84, are +made so that the piston may work steam-tight in the +cylinder. How are these rings got into place? <span class="marks">(8.)</span></p> + +<p class="negidt">(<i>b.</i>) Give two views of a double riveted lap joint for boiler-plates. <span class="marks">(8.)</span></p> + +<p class="negidt">(<i>c.</i>) Show by sketches how a wheel is fixed on a shaft by means +of a sunk key. Explain how the key may be withdrawn +when it cannot be driven from the point end. <span class="marks">(8.)</span></p> + +<p class="negidt">(<i>d.</i>) Give sketches showing the construction of a conical metal +lift or puppet valve and seating. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>e.</i>) With the aid of sketches explain how a piston rod is made +to work steam-tight through the end of the cylinder. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>f.</i>) Explain how the slotting machine ram of Example 8, fig. +85, may be made to move up and down when at work. +How is the length of the stroke altered, and what is the +object of the slotway in the upper part of the ram? <span class="marks">(10.)</span></p> +</div> + +<p class="tabcap"><i>Examples to be drawn.</i></p> + +<div class="poem"> +<p class="negidt">1. Piston for steam-engine. Draw and complete the two views +shown (fig. 84), the top half of the left-hand view to be in +section. Scale <sup>1</sup>⁄<sub>2</sub> size. <span class="marks">(30.)</span></p> +</div> +<p><span class='pagenum'><a name="Page_109" id="Page_109">[Pg 109]</a></span></p> + +<div class="figcenter" style="width: 627px;"> +<img src="images/illus117.jpg" width="627" height="1024" alt="Figs. 83 and 84." title="Figs. 83 and 84." /> +<span class="caption">Figs. 83 and 84.</span> +</div> + +<p><span class='pagenum'><a name="Page_110" id="Page_110">[Pg 110]</a></span></p> + +<div class="poem"> +<p class="negidt">2. Plan and sectional elevation of a footstep bearing for an +upright shaft (fig. 83). Draw and complete these views. +Scale <sup>1</sup>⁄<sub>4</sub> size. <span class="marks">(35.)</span></p> +</div> + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus118.jpg" width="800" height="505" alt="Fig. 85." title="Fig. 85." /> +<span class="caption">Fig. 85.</span> +</div> + +<div class="poem"> +<p class="negidt">3. Ram of slotting machine. Draw and complete the two +elevations shown (fig. 85). The tool-holders must be +drawn in their proper positions in the ram, and not +separate as in the diagram. Scale <sup>1</sup>⁄<sub>4</sub> size. <span class="marks">(35.)</span></p> +</div> + +<hr style="width: 15%;" /> +<h4>First Stage or Elementary Examination. 1888.</h4> + +<p class="center"><span class="smcap">Instructions.</span></p> + +<p>Read the General Instructions on p. 102.</p> + +<p>Answer briefly any three, but not more than three, of the +following questions, and draw two, but not more than two, of the +examples.</p> + +<p class="tabcap"><i>Questions.</i></p> + +<div class="poem"> +<p class="negidt">(<i>a.</i>) Give sketches showing how the separate lengths of a line +of shafting may be connected together. <span class="marks">(8.)</span></p> + +<p class="negidt">(<i>b.</i>) What is the object of using chipping or facing strips in fitting +up machine parts? Give one or two examples. <span class="marks">(8.)</span></p> +<p><span class='pagenum'><a name="Page_111" id="Page_111">[Pg 111]</a></span></p> + +<p class="negidt">(<i>c.</i>) Give sketches showing how you would grip and drive a +round iron bar for the purpose of turning it between the +centres of a lathe. <span class="marks">(10.)</span></p> +</div> + + +<div class="figcenter" style="width: 677px;"> +<img src="images/illus119.jpg" width="677" height="1024" alt="Figs. 86 and 87." title="Figs. 86 and 87." /> +<span class="caption">Figs. 86 and 87.</span> +</div> +<p><span class='pagenum'><a name="Page_112" id="Page_112">[Pg 112]</a></span></p> + +<div class="poem"> +<p class="negidt">(<i>d.</i>) Explain the action of the governor shown in Example 1 +(fig. 86). <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>e.</i>) Describe in detail how the mud-hole door in Example 2 +(fig. 88) is removed for the purpose of cleaning the boiler +and how it is replaced and the joint made steam-tight. <span class="marks">(10.)</span></p> + +<p class="negidt">(<i>f.</i>) Describe how the parts of the spur wheel in Example 3 +(fig. 87) are put together, and explain why the wheel is +made in segments. <span class="marks">(10.)</span></p> +</div> + + +<div class="figcenter" style="width: 800px;"> +<img src="images/illus120.jpg" width="800" height="509" alt="Fig. 88." title="Fig. 88." /> +<span class="caption">Fig. 88.</span> +</div> + + + +<p class="tabcap"><i>Examples to be drawn.</i></p> + +<div class="poem"> +<p class="negidt">1. Loaded governor for small gas engine. Draw and complete +the two views, partly in section as shown (fig. 86). Scale +full size. <span class="marks">(35.)</span></p> + +<p class="negidt">2. Mud-hole mouth-piece for Lancashire boiler. Draw and +complete the two views shown (fig. 88). Scale <sup>3</sup>⁄<sub>8</sub>ths. <span class="marks">(35.)</span></p> + +<p class="negidt">3. Point for segments of large spur wheel. Draw and complete +the views shown (fig. 87). Scale <sup>3</sup>⁄<sub>16</sub>ths.</p> + +<p class="negidt"> <i>Note.</i>—As the radius of the wheel is too large for your +instruments, the circumference at the joint may be set out +straight, as in a rack. <span class="marks">(35.)</span></p> +</div> + + +<hr style="width: 100%;" /> +<p><span class='pagenum'><a name="Page_113" id="Page_113">[Pg 113]</a></span></p> +<h2>INDEX</h2> + +<div class="blockquot"> +<p class="noidt"> +Air-pump bucket, <a href="#Page_58">58</a><br /> +Alloys, <a href="#Page_80">80</a><br /> +Angle irons, <a href="#Page_12">12</a><br /> +Annealing, <a href="#Page_79">79</a>, <a href="#Page_80">80</a><br /> +Axles, <a href="#Page_24">24</a><br /> +<br /> +Back stay for lathe, <a href="#Page_86">86</a><br /> +Bar stay, <a href="#Page_83">83</a><br /> +Bearings for shafts, <a href="#Page_30">30</a><br /> +Beech-wood, <a href="#Page_81">81</a><br /> +Bell crank lever, <a href="#Page_86">86</a><br /> +Bessemer steel, <a href="#Page_79">79</a><br /> +Bevil wheels, <a href="#Page_43">43</a><br /> +Blister steel, <a href="#Page_79">79</a><br /> +Blooms, <a href="#Page_78">78</a><br /> +Bolt-heads, proportions of, <a href="#Page_18">18</a><br /> +Bolts, forms of, <a href="#Page_17">17</a><br /> +Border lines, <a href="#Page_4">4</a><br /> +Box couplings, <a href="#Page_25">25</a><br /> +— end, connecting rod, <a href="#Page_51">51</a><br /> +Box-wood, <a href="#Page_81">81</a><br /> +Brackets, <a href="#Page_33">33</a><br /> +Brake shaft carrier, <a href="#Page_30">30</a><br /> +Brass, <a href="#Page_80">80</a><br /> +Brasses, <a href="#Page_30">30</a><br /> +Bucket, <a href="#Page_58">58</a><br /> +Built-up cranks, <a href="#Page_46">46</a><br /> +Bush, <a href="#Page_30">30</a>, <a href="#Page_49">49</a>, <a href="#Page_51">51</a>, <a href="#Page_54">54</a>, <a href="#Page_56">56</a>, <a href="#Page_63">63</a><br /> +Butt joints, <a href="#Page_10">10</a>, <a href="#Page_11">11</a><br /> +— strap, <a href="#Page_10">10</a><br /> +Buttress screw thread, <a href="#Page_15">15</a><br /> +<br /> +Case-hardening, <a href="#Page_80">80</a><br /> +Cast iron, <a href="#Page_76">76</a><br /> +Cast iron flange coupling, <a href="#Page_28">28</a>, <a href="#Page_29">29</a><br /> +— steel, <a href="#Page_79">79</a><br /> +Caulking, <a href="#Page_8">8</a><br /> +Cementation process, <a href="#Page_79">79</a><br /> +Centre lines, <a href="#Page_2">2</a>, <a href="#Page_4">4</a><br /> +Chilled castings, <a href="#Page_78">78</a><br /> +Circulating pump piston, <a href="#Page_58">58</a><br /> +Clearance, cylinder, <a href="#Page_74">74</a><br /> +— of cotter, <a href="#Page_49">49</a><br /> +Cocks, <a href="#Page_74">74</a><br /> +Cogs, <a href="#Page_41">41</a><br /> +— wood for, <a href="#Page_81">81</a><br /> +Collared stud, <a href="#Page_18">18</a><br /> +Collars, <a href="#Page_24">24</a><br /> +Colouring, <a href="#Page_3">3</a><br /> +Colours for different materials, <a href="#Page_3">3</a><br /> +Compasses, <a href="#Page_1">1</a><br /> +Cone keys, <a href="#Page_23">23</a>, <a href="#Page_38">38</a><br /> +Conical disc valve, <a href="#Page_70">70</a>, <a href="#Page_71">71</a>, <a href="#Page_89">89</a><br /> +— head, <a href="#Page_7">7</a><br /> +Connecting rod, locomotive, <a href="#Page_51">51</a><br /> +— — marine, <a href="#Page_51">51</a><br /> +— rods, <a href="#Page_49">49</a>, <a href="#Page_89">89</a><br /> +Construction for rivet heads, <a href="#Page_7">7</a><br /> +Contraction of castings, <a href="#Page_77">77</a><br /> +Copper, <a href="#Page_80">80</a><br /> +Cotters, <a href="#Page_48">48</a>, <a href="#Page_49">49</a><br /> +Countersunk head, <a href="#Page_7">7</a>, <a href="#Page_18">18</a><br /> +Coupling rod ends, <a href="#Page_55">55</a>, <a href="#Page_84">84</a><br /> +— rods, <a href="#Page_54">54</a><br /> +— screw, <a href="#Page_96">96</a><br /> +Couplings, shaft, <a href="#Page_25">25</a><br /> +Cover plate, <a href="#Page_10">10</a><br /> +Cranked axle, <a href="#Page_45">45</a><br /> +Cranks, <a href="#Page_43">43</a><br /> +— built-up, <a href="#Page_46">46</a><br /> +<span class='pagenum'><a name="Page_114" id="Page_114">[Pg 114]</a></span> +Cross-head pin, <a href="#Page_51">51</a><br /> +Cross-heads, <a href="#Page_56">56</a>, <a href="#Page_89">89</a><br /> +Cross-key, <a href="#Page_28">28</a><br /> +Cup-headed bolt, <a href="#Page_17">17</a><br /> +<br /> +Decimal equivalents, <a href="#Page_6">6</a><br /> +Dimension lines, <a href="#Page_5">5</a><br /> +Dimensions, <a href="#Page_5">5</a><br /> +— of box couplings, <a href="#Page_26">26</a><br /> +— cast-iron flange couplings, <a href="#Page_29">29</a><br /> +— keys, <a href="#Page_24">24</a><br /> +— stuffing-boxes and glands, <a href="#Page_67">67</a><br /> +— Whitworth screws, <a href="#Page_15">15</a><br /> +Distance lines, <a href="#Page_5">5</a><br /> +Dividers, <a href="#Page_1">1</a><br /> +Draught of cotter, <a href="#Page_49">49</a><br /> +Drawing board, <a href="#Page_1">1</a><br /> +— instruments, <a href="#Page_1">1</a><br /> +— paper, <a href="#Page_2">2</a><br /> +— pen, <a href="#Page_1">1</a><br /> +— pins, <a href="#Page_2">2</a><br /> +<br /> +Eccentrics, <a href="#Page_47">47</a><br /> +Exhaust port, <a href="#Page_71">71</a><br /> +Eye-bolt, <a href="#Page_18">18</a><br /> +<br /> +Fairbairn's coupling, <a href="#Page_26">26</a><br /> +Fast and loose pulleys, <a href="#Page_37">37</a><br /> +Feather key, <a href="#Page_23">23</a><br /> +Flange couplings, <a href="#Page_27">27</a><br /> +Flap valves, <a href="#Page_68">68</a><br /> +Flat key, <a href="#Page_22">22</a><br /> +Forge irons, <a href="#Page_77">77</a><br /> +Forging, <a href="#Page_79">79</a><br /> +Form of wheel teeth, <a href="#Page_40">40</a><br /> +Forms of nuts, <a href="#Page_16">16</a><br /> +— rivet heads, <a href="#Page_7">7</a><br /> +— screw threads, <a href="#Page_15">15</a><br /> +Foundry irons, <a href="#Page_77">77</a><br /> +<br /> +Gasket, <a href="#Page_58">58</a><br /> +Gas threads, <a href="#Page_15">15</a><br /> +Gib, <a href="#Page_49">49</a><br /> +— head, <a href="#Page_23">23</a><br /> +Girder stay, <a href="#Page_81">81</a><br /> +Gland, <a href="#Page_64">64</a><br /> +Grey cast iron, <a href="#Page_77">77</a><br /> +Gun-metal, <a href="#Page_80">80</a><br /> +Gusset stay, <a href="#Page_12">12</a><br /> +<br /> +Half-lap coupling, <a href="#Page_26">26</a><br /> +Hangers, <a href="#Page_34">34</a><br /> +Hardening of steel, <a href="#Page_80">80</a><br /> +Headstock lathe, <a href="#Page_96">96</a><br /> +Hexagonal nut, <a href="#Page_16">16</a><br /> +Hollow key, <a href="#Page_22">22</a><br /> +Hook bolt, <a href="#Page_18">18</a><br /> +Hornbeam, <a href="#Page_81">81</a><br /> +<br /> +India-rubber disc valves, <a href="#Page_58">58</a>, <a href="#Page_68">68</a><br /> +Inking drawings, <a href="#Page_2">2</a><br /> +Inside lap of valve, <a href="#Page_72">72</a><br /> +<br /> +Joggles, <a href="#Page_33">33</a><br /> +Joint, knuckle, <a href="#Page_84">84</a><br /> +Journals, <a href="#Page_24">24</a><br /> +— length of, <a href="#Page_32">32</a><br /> +Junk ring, <a href="#Page_61">61</a><br /> +<br /> +Keys, <a href="#Page_22">22</a><br /> +— proportions of, <a href="#Page_23">23</a><br /> +Kinghorn's metallic valve, <a href="#Page_70">70</a><br /> +Knuckle joint, <a href="#Page_84">84</a><br /> +— screw thread, <a href="#Page_15">15</a><br /> +<br /> +Lancaster's piston packing, <a href="#Page_61">61</a><br /> +Lap joints, <a href="#Page_8">8</a>, <a href="#Page_9">9</a>, <a href="#Page_10">10</a>, <a href="#Page_12">12</a><br /> +— of slide valve, <a href="#Page_72">72</a><br /> +Lathe headstock, <a href="#Page_96">96</a><br /> +Lead of valve, <a href="#Page_74">74</a><br /> +Lever, bell crank, <a href="#Page_86">86</a><br /> +— ratchet, <a href="#Page_96">96</a><br /> +Lignum-vitæ, <a href="#Page_81">81</a><br /> +Locking arrangements for nuts, <a href="#Page_21">21</a>, <a href="#Page_62">62</a><br /> +Lock nuts, <a href="#Page_19">19</a><br /> +Locomotive connecting rod, <a href="#Page_51">51</a><br /> +— cranked axle, <a href="#Page_45">45</a><br /> +— cross-head, <a href="#Page_56">56</a><br /> +<span class='pagenum'><a name="Page_115" id="Page_115">[Pg 115]</a></span> +Locomotive eccentric, <a href="#Page_47">47</a><br /> +— piston, <a href="#Page_60">60</a><br /> +Lubricator, needle, <a href="#Page_32">32</a><br /> +<br /> +Malleable cast iron, <a href="#Page_78">78</a><br /> +— iron, <a href="#Page_78">78</a><br /> +Marine connecting rod, <a href="#Page_51">51</a><br /> +— coupling, <a href="#Page_28">28</a><br /> +— crank-shaft, <a href="#Page_46">46</a><br /> +— piston, <a href="#Page_61">61</a><br /> +Merchant bars, <a href="#Page_78">78</a><br /> +Mortise wheels, <a href="#Page_41">41</a><br /> +Mottled cast iron, <a href="#Page_77">77</a><br /> +Muff couplings, <a href="#Page_25">25</a><br /> +Muntz metal, <a href="#Page_80">80</a><br /> +<br /> +Needle lubricator, <a href="#Page_32">32</a><br /> +Nuts, forms of, <a href="#Page_16">16</a><br /> +— lock, <a href="#Page_19">19</a><br /> +— proportions of, <a href="#Page_18">18</a><br /> +<br /> +Oil-box, <a href="#Page_54">54</a>, <a href="#Page_65">65</a><br /> +Outside lap of slide valve, <a href="#Page_72">72</a><br /> +Overhung crank, <a href="#Page_43">43</a><br /> +— cranks, proportions of, <a href="#Page_45">45</a><br /> +<br /> +Packing, <a href="#Page_63">63</a><br /> +Pan head, <a href="#Page_7">7</a><br /> +Pedestal, shaft, <a href="#Page_30">30</a><br /> +Pencils, drawing, <a href="#Page_1">1</a><br /> +Phosphor bronze, <a href="#Page_80">80</a><br /> +Pillar bracket, <a href="#Page_34">34</a><br /> +Pillow block, <a href="#Page_30">30</a>, <a href="#Page_32">32</a><br /> +Pin, cross-head, <a href="#Page_51">51</a>, <a href="#Page_54">54</a><br /> +— split, <a href="#Page_21">21</a><br /> +Piston rod, <a href="#Page_57">57</a><br /> +Pistons, <a href="#Page_57">57</a><br /> +Pitch circle, <a href="#Page_40">40</a><br /> +— of wheel teeth, <a href="#Page_40">40</a><br /> +— surfaces of wheels, <a href="#Page_39">39</a>, <a href="#Page_43">43</a><br /> +Pivots, <a href="#Page_24">24</a><br /> +Plummer block, <a href="#Page_30">30</a><br /> +Plunger, <a href="#Page_57">57</a><br /> +Printing, <a href="#Page_4">4</a><br /> +Proportions of bolt-heads, <a href="#Page_18">18</a><br /> +— keys, <a href="#Page_23">23</a><br /> +Proportions of lap joints, <a href="#Page_9">9</a>, <a href="#Page_10">10</a><br /> +— marine engine pistons, <a href="#Page_62">62</a><br /> +— nuts, <a href="#Page_18">18</a><br /> +— overhung cranks, <a href="#Page_45">45</a><br /> +— pillow blocks, <a href="#Page_32">32</a><br /> +— rivet heads, <a href="#Page_7">7</a><br /> +— wheel teeth, <a href="#Page_40">40</a><br /> +Puddled bars, <a href="#Page_78">78</a><br /> +Puddling process, <a href="#Page_78">78</a><br /> +Pulley, eccentric, <a href="#Page_47">47</a><br /> +Pulleys, <a href="#Page_36">36</a><br /> +Pump bucket, <a href="#Page_58">58</a><br /> +<br /> +Ramsbottom's packing, <a href="#Page_60">60</a><br /> +Ratchet lever, <a href="#Page_96">96</a><br /> +Riveted joints, <a href="#Page_8">8</a><br /> +Rivet heads, forms of, <a href="#Page_7">7</a>, <a href="#Page_8">8</a><br /> +— — proportions of, <a href="#Page_7">7</a><br /> +Riveting, <a href="#Page_7">7</a><br /> +Rivets, <a href="#Page_6">6</a><br /> +Rope pulley, <a href="#Page_39">39</a><br /> +Round key, <a href="#Page_23">23</a><br /> +<br /> +Saddle key, <a href="#Page_22">22</a><br /> +Scales, <a href="#Page_5">5</a><br /> +Screw coupling, <a href="#Page_96">96</a><br /> +Screwed gland and stuffing-box, <a href="#Page_65">65</a><br /> +Screw threads, <a href="#Page_14">14</a>, <a href="#Page_15">15</a><br /> +Screws, representation of, <a href="#Page_16">16</a><br /> +Sellers <b>V</b> screw thread, <a href="#Page_14">14</a><br /> +Set screw, <a href="#Page_21">21</a>, <a href="#Page_49">49</a><br /> +— squares, <a href="#Page_1">1</a><br /> +Shaft couplings, <a href="#Page_25">25</a><br /> +— hanger, <a href="#Page_34">34</a><br /> +Shafting, <a href="#Page_24">24</a><br /> +Shear steel, <a href="#Page_79">79</a><br /> +Sheave, eccentric, <a href="#Page_47">47</a><br /> +Shingling, <a href="#Page_78">78</a><br /> +Shrinking, process of, <a href="#Page_44">44</a><br /> +Siemens-Martin steel, <a href="#Page_79">79</a><br /> +Slide blocks, <a href="#Page_56">56</a><br /> +— valves, <a href="#Page_68">68</a>, <a href="#Page_71">71</a><br /> +Sliding key, <a href="#Page_23">23</a><br /> +Snap head, <a href="#Page_7">7</a><br /> +Snug, <a href="#Page_17">17</a><br /> +Spiegeleisen, <a href="#Page_80">80</a><br /> +Spring bows, <a href="#Page_1">1</a><br /> +<span class='pagenum'><a name="Page_116" id="Page_116">[Pg 116]</a></span> +Spur wheel, <a href="#Page_41">41</a><br /> +Square nut, <a href="#Page_16">16</a><br /> +— screw thread, <a href="#Page_14">14</a><br /> +Stay, back, for lathe, <a href="#Page_86">86</a><br /> +— bar, <a href="#Page_83">83</a><br /> +— girder, <a href="#Page_81">81</a><br /> +— gusset, <a href="#Page_12">12</a><br /> +Steam ports, <a href="#Page_71">71</a><br /> +— whistle, <a href="#Page_96">96</a><br /> +Steel, <a href="#Page_79">79</a><br /> +Steps, <a href="#Page_30">30</a><br /> +Strap, <a href="#Page_49">49</a><br /> +— eccentric, <a href="#Page_47">47</a><br /> +— end of connecting rod, <a href="#Page_49">49</a><br /> +Stud bolts, <a href="#Page_18">18</a><br /> +Studs, <a href="#Page_18">18</a><br /> +Stuffing-boxes, <a href="#Page_63">63</a><br /> +Sunk key, <a href="#Page_22">22</a><br /> +<br /> +Taper bolt, <a href="#Page_18">18</a>, <a href="#Page_27">27</a><br /> +— pin, <a href="#Page_23">23</a><br /> +Tee-headed bolt, <a href="#Page_18">18</a><br /> +Tee-iron cover strap, <a href="#Page_81">81</a><br /> +Tee square, <a href="#Page_1">1</a><br /> +Teeth of wheels, form and proportions of, <a href="#Page_40">40</a><br /> +Teeth, pitch of, <a href="#Page_40">40</a><br /> +Tempering of steel, <a href="#Page_80">80</a><br /> +Throw of crank, <a href="#Page_44">44</a><br /> +— eccentric, <a href="#Page_47">47</a><br /> +Toothed wheels, <a href="#Page_39">39</a><br /> +<br /> +Valve Kinghorn's metallic, <a href="#Page_70">70</a><br /> +— slide, <a href="#Page_68">68</a>, <a href="#Page_71">71</a><br /> +Valves, <a href="#Page_68">68</a><br /> +— conical disc, <a href="#Page_70">70</a><br /> +— india-rubber, <a href="#Page_58">58</a>, <a href="#Page_68">68</a><br /> +Velocity ratio in belt gearing, <a href="#Page_36">36</a><br /> +<br /> +Wall boxes, <a href="#Page_34">34</a><br /> +Washers, <a href="#Page_19">19</a><br /> +Welding, <a href="#Page_79">79</a><br /> +Whistle, steam, <a href="#Page_96">96</a><br /> +White cast iron, <a href="#Page_77">77</a><br /> +Whitworth screws, dimensions of, <a href="#Page_15">15</a><br /> +— <b>V</b> screw thread, <a href="#Page_14">14</a><br /> +Wood, <a href="#Page_81">81</a><br /> +Working drawings, <a href="#Page_4">4</a><br /> +Wrought iron, <a href="#Page_78">78</a><br /> +<br /> +Yellow pine, <a href="#Page_81">81</a><br /> +</p> +</div> + + +<h5>PRINTED BY<br /> + +SPOTTISWOODE AND CO., NEW-STREET SQUARE<br /> + +LONDON</h5> + + + +<hr style="width: 100%;" /> +<h2>TEXT-BOOKS OF SCIENCE</h2> + +<div class="poem"> +<p class="negidt"><span class="ft20">PHOTOGRAPHY.</span> By Captain <span class="smcap">W. De Wiveleslie Abney</span>, +C.B. F.R.S. late Instructor in Chemistry and Photography at the School of +Military Engineering, Chatham. With 105 Woodcuts. Price 3<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">The STRENGTH of MATERIALS and STRUCTURES;</span> +the Strength of Materials as depending on their quality and as +ascertained by Testing Apparatus; the Strength of Structures as depending +on their form and arrangement, and on the materials of which they are composed. +By Sir <span class="smcap">J. Anderson</span>, C.E. &c. With 66 Woodcuts. Price 3<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">INTRODUCTION to the STUDY of ORGANIC +CHEMISTRY;</span> the CHEMISTRY of CARBON and its COMPOUNDS. +By <span class="smcap">Henry E. Armstrong</span> Ph.D. F.R.S. With 8 Woodcuts. Price 3<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">ELEMENTS of ASTRONOMY.</span> By Sir R. S. <span class="smcap">Ball</span>, LL.D. +F.R.S. Andrews Professor of Astronomy in the Univ. of Dublin, Royal +Astronomer of Ireland. With 136 Woodcuts. Price 6<i>s.</i></p> + +<p class="negidt"><span class="ft20">RAILWAY APPLIANCES.</span> A Description of Details of +Railway Construction subsequent to the completion of Earthworks and +Structures, including a short Notice of Railway Rolling Stock. By <span class="smcap">John +Wolfe Barry</span>, M.I.C.E. With 207 Woodcuts. Price 3<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">SYSTEMATIC MINERALOGY.</span> By <span class="smcap">Hilary Bauerman</span>, +F.G.S. Associate of the Royal School of Mines. With 373 Woodcuts. +Price 6<i>s.</i></p> + +<p class="negidt"><span class="ft20">DESCRIPTIVE MINERALOGY.</span> By <span class="smcap">Hilary Bauerman</span>, +F.G.S. &c. With 236 Woodcuts. Price 6<i>s.</i></p> + +<p class="negidt"><span class="ft20">METALS, their PROPERTIES and TREATMENT.</span> +By <span class="smcap">C. L. Bloxam</span> and <span class="smcap">A. K. 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Price 6s.</p> + +<p class="negidt"><span class="ft20">PLANE and SOLID GEOMETRY.</span> By <span class="smcap">H. W. Watson</span>, +M.A. formerly Fellow of Trinity College, Cambridge. Price 3<i>s.</i> 6<i>d.</i></p> +</div> + +<hr style="width: 15%;" /> +<h4>London: LONGMANS, GREEN, & CO.</h4> + + + +<hr style="width: 100%;" /> +<h2>SCIENTIFIC CLASS-BOOKS.</h2> + +<div class="poem"> +<p class="negidt"><span class="ft20">GANOT'S NATURAL PHILOSOPHY for GENERAL +READERS and YOUNG PERSONS:</span> a Course of Physics +divested of Mathematical Formulæ, expressed in the language +of daily life. Translated and edited, from Ganot's <i>Cours +Élémentaire de Physique</i>, by <span class="smcap">E. Atkinson</span>, Ph.D. F.C.S. +Sixth Edition, with 34 pages of new matter, 2 Plates, 518 +Woodcuts, and an Appendix of Questions. Crown 8vo. 7<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">GANOT'S ELEMENTARY TREATISE on PHYSICS,</span> +Experimental and Applied, for the use of Colleges and Schools. +Translated and edited, from Ganot's <i>Éléments de Physique</i>, by +<span class="smcap">E. Atkinson</span>, Ph.D. F.C.S. Twelfth Edition, revised and enlarged; +with 5 Coloured Plates and 923 Woodcuts. Cr. 8vo. 15<i>s.</i></p> + +<p class="negidt"><span class="ft20">LESSONS in ELEMENTARY MECHANICS.</span> Designed +for the use of Schools, and of Candidates for the London Matriculation, +and other Examinations; with 52 Examples, nearly +500 Exercises and Examination Questions with Answers, and +124 Woodcuts. By Sir <span class="smcap">Philip Magnus</span>, B.Sc. B.A. Thirteenth +Edition. Fcp. 8vo. 3<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">PRINCIPLES of MECHANICS.</span> By <span class="smcap">T. M. Goodeve</span>, M.A. +Professor of Mechanics at the Royal School of Mines. New +Edition. With 253 Woodcuts. Crown 8vo. 6<i>s.</i></p> + +<p class="negidt"><span class="ft20">The ELEMENTS of MECHANISM.</span> By <span class="smcap">T. M. Goodeve</span>, +M.A. Professor of Mechanics at the Royal School of Mines. +New Edition. With 342 Woodcuts. Crown 8vo. 6<i>s.</i></p> + +<p class="negidt"><span class="ft20">PRACTICAL MECHANICS:</span> an Elementary Introduction +to their Study. With 855 Exercises with Answers and 184 +Diagrams. By the Rev. <span class="smcap">J. F. Twisden</span>. Crown 8vo. 10<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">THEORETICAL MECHANICS.</span> By the Rev. <span class="smcap">J. F. Twisden</span>. +With 172 Examples, numerous Exercises, and 154 Diagrams. +Crown 8vo. 8<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">LESSONS in ELEMENTARY MECHANICS.</span> By +<span class="smcap">W. H. Grieve</span>, Demonstrator in Mechanics to the London +School Board. Fully Illustrated. Stage III. Fcp. 8vo. 1<i>s.</i> 6<i>d.</i> +Stage II. 1<i>s.</i> 6<i>d.</i> Stage I. 1<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">EXPERIMENTAL CHEMISTRY</span> for Junior Students. By +<span class="smcap">J. Emerson Reynolds</span>, M.D. F.R.S. Professor of Chemistry, +University Dublin. Fcp. 8vo. with numerous Woodcuts.</p> + +<p class="center"> +<span class="smcap">Part I. Introductory.</span> 1<i>s.</i> 6<i>d.</i> <span class="smcap">Part II. Non-Metals</span>. 2<i>s.</i> 6<i>d.</i><br /> +<span class="smcap">Part III. Metals and Allied Bodies.</span> 3<i>s.</i> 6<i>d.</i><br /> +<span class="smcap">Part IV. Carbon Compounds.</span> 4<i>s.</i><br /> +</p> +</div> + +<hr style="width: 15%;" /> +<h4>London: LONGMANS, GREEN, & CO.</h4> + + +<hr style="width: 100%;" /> +<h2>LONGMANS' ELEMENTARY SCIENCE MANUALS.</h2> + +<p class="center"><i>Written specially to meet the requirements of the Elementary Stage<br /> +of Science Subjects as laid down in the Syllabus of the Directory<br /> +of the Science and Art Department, South Kensington.</i></p> + +<div class="poem"> +<p class="negidt"><span class="ft20">SOUND, LIGHT, and HEAT.</span> By <span class="smcap">Mark R. Wright</span> +(Hon. Inter. B.Sc. London). With 160 Illustrations. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">An INTRODUCTION to MACHINE DRAWING and +DESIGN.</span> By <span class="smcap">David Allan Low</span>. With 65 Illustrations. Crown 8vo. 2<i>s.</i></p> + +<p class="negidt"><span class="ft20">TEXT-BOOK on PRACTICAL SOLID or DESCRIPTIVE +GEOMETRY.</span> By <span class="smcap">David Allan Low</span>. Part. I. 2<i>s.</i> Part II. 3<i>s.</i></p> + +<p class="negidt"><span class="ft20">ELEMENTARY PHYSIOGRAPHY.</span> By <span class="smcap">J. Thornton</span>, +M.A. With 10 Maps and 150 Illustrations. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">A MANUAL of MECHANICS:</span> an Elementary Text-Book +for Students of Applied Mechanics. With 138 Illustrations and Diagrams, +and 188 Examples taken from the Science Department Examination Papers, +with Answers. By <span class="smcap">T. M. Goodeve</span>, M.A. Fcp. 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">INORGANIC CHEMISTRY,</span> <span class="smcap">Theoretical</span> and <span class="smcap">Practical</span>. +With an Introduction to the Principles of Chemical Analysis. By <span class="smcap">William +Jago</span>. With 49 Woodcuts and Questions and Exercises. Fcp. 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">An INTRODUCTION to PRACTICAL INORGANIC +CHEMISTRY.</span> By <span class="smcap">William +Jago</span>, F.C.S. F.I.C. Crown 8vo. 1<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">PRACTICAL CHEMISTRY:</span> the Principles of Qualitative +Analysis. By <span class="smcap">William A. Tilden</span>, D.Sc. Fcp. 8vo. 1<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">ELEMENTARY INORGANIC CHEMISTRY.</span> Alternative +Course. By <span class="smcap">W. Furneaux</span>, F.R.G.S. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">ELEMENTARY BOTANY,</span> <span class="smcap">Theoretical</span> and <span class="smcap">Practical</span>. +By <span class="smcap">Henry Edmonds</span>, B.Sc. London. With 319 Woodcuts. Cr. 8vo 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">An ELEMENTARY COURSE of MATHEMATICS.</span> +Specially adapted to the requirements of the Science and Art Department. +Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">BUILDING CONSTRUCTION.</span> By <span class="smcap">Edward J. Burrell</span>, +Teacher of Building Construction at the Technical School of the People's +Palace, Mile End. With 308 Illustrations, &c. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">THEORETICAL MECHANICS.</span> BY <span class="smcap">J. Edward Taylor</span>, +M.A. Lond, With 175 Illustrations and Examples and Answers. Cr. 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">ANIMAL PHYSIOLOGY.</span> By <span class="smcap">William S. Furneaux</span>, +Special Science Teacher, London School Board. With 218 Illustrations. +Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">MAGNETISM and ELECTRICITY.</span> By <span class="smcap">A.W. Poyser</span>, +M.A. With 235 Illustrations. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">STEAM.</span> By <span class="smcap">William Ripper</span>, Member of the Institution of +Mechanical Engineers. With 142 Illustrations. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> + +<p class="negidt"><span class="ft20">PHYSICS:</span> Alternative Course. By <span class="smcap">Mark R. Wright</span>. With +242 Illustrations. Crown 8vo. 2<i>s.</i> 6<i>d.</i></p> +</div> + +<hr style="width: 15%;" /> +<h4>London: LONGMANS, GREEN, & CO.</h4> + +<p> </p><p> </p> +<div class="notebox"> +<p class="noidt"><b>Transcriber's Note:</b> Obvious misprints in spelling and punctuation have been silently +corrected.</p> +</div> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of An Introduction to Machine Drawing and +Design, by David Allan Low + +*** END OF THIS PROJECT GUTENBERG EBOOK AN INTRODUCTION TO MACHINE *** + +***** This file should be named 39033-h.htm or 39033-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/9/0/3/39033/ + +Produced by Juliet Sutherland and the Online Distributed +Proofreading Team at http://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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