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Staff—A Project Gutenberg eBook - </title> - <link rel="coverpage" href="images/cover.jpg" /> - <style type="text/css"> - -body { margin-left: 10%; margin-right: 10%; } - -h1,h2,h3 { text-align: center; clear: both; } - -p { margin-top: .51em; text-align: justify; text-indent: 1.5em; margin-bottom: .49em; } -p.no-indent { margin-top: .51em; text-align: justify; text-indent: 0em; margin-bottom: .49em;} -p.indent { text-indent: 1.5em;} -p.f120 { font-size: 120%; text-align: center; text-indent: 0em; } -p.f150 { font-size: 150%; text-align: center; text-indent: 0em; } -p.f200 { font-size: 200%; text-align: center; text-indent: 0em; } - -.fontsize_90 { font-size: 85%; } -.fontsize_120 { font-size: 120%; } -.fontsize_150 { font-size: 150%; } - -.space-above1 { margin-top: 1em; } -.space-above2 { margin-top: 2em; } -.space-below2 { margin-bottom: 2em; } - -hr.chap {width: 65%; margin-left: 17.5%; margin-right: 17.5%; margin-top: 2em; margin-bottom: 2em;} - @media print { hr.chap {display: none; visibility: hidden;} } -hr.r5 {width: 5%; margin-top: 0.5em; margin-bottom: 0.5em; margin-left: 47.5%; margin-right: 47.5%;} - -div.chapter {page-break-before: always;} -h2.nobreak {page-break-before: avoid;} - -ul.index { list-style-type: none; } -li.isub2 {text-indent: 2em;} - -table { margin-left: auto; margin-right: auto; white-space: nowrap;} - -.tdl {text-align: left;} -.tdr {text-align: right;} -.tdc {text-align: center;} -.tdl_ws1 {text-align: left; vertical-align: top; padding-left: 1em;} - -.pagenum { - position: absolute; - left: 92%; - font-size: smaller; - text-align: right; - font-style: normal; - font-weight: normal; - font-variant: normal; -} - -.blockquot { margin-left: 10%; margin-right: 10%; } - -.bb {border-bottom: solid thin;} -.bb2 {border-bottom: solid medium;} -.bt2 {border-top: solid medium;} -.bbox {border: solid medium;} - -.center {text-align: center; text-indent: 0em;} -.smcap {font-variant: small-caps;} - -img { max-width: 100%; height: auto; } - -.figcenter { margin: auto; text-align: center; - page-break-inside: avoid; max-width: 100%; } - -div.figcontainer { clear: both; margin: 0em auto; text-align: center; max-width: 100%;} -div.figsub { display: inline-block; margin: 1em 1em; vertical-align: top; max-width: 100%; text-align: center; } - -.transnote {background-color: #E6E6FA; - color: black; - font-size:smaller; - padding:0.5em; - margin-bottom:5em; - font-family:sans-serif, serif; } - -.ws5 {display: inline; margin-left: 0em; padding-left: 5em;} - </style> - </head> -<body> -<p style='text-align:center; font-size:1.2em; font-weight:bold'>The Project Gutenberg eBook of Hoisting Appliances, by Various</p> -<div style='display:block; margin:1em 0'> -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world 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 <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you -are not located in the United States, you will have to check the laws of the -country where you are located before using this eBook. -</div> - -<p style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: Hoisting Appliances</p> -<p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em'>Author: Various</p> -<p style='display:block; text-indent:0; margin:1em 0'>Release Date: April 15, 2022 [eBook #67844]</p> -<p style='display:block; text-indent:0; margin:1em 0'>Language: English</p> - <p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em; text-align:left'>Produced by: deaurider and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)</p> -<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK HOISTING APPLIANCES ***</div> - -<hr class="chap x-ebookmaker-drop" /> -<h1>Hoisting Appliances</h1> - -<p class="center space-above2">By</p> -<p class="f150"><b>I.C.S. STAFF</b></p> - -<p class="f200 space-above2"><b>HOISTING</b></p> -<p class="f120"><b>Parts 3-4</b></p> - -<p class="center space-above2">447<br />Published by<br /> -INTERNATIONAL TEXTBOOK COMPANY<br />SCRANTON, PA.</p> - -<p class="center space-above2">Hoisting, Parts 3 and 4:<br /> -Copyright, 1906,<br />by <span class="smcap">International Textbook Company</span>.</p> - -<p class="center">Entered at Stationers’ Hall, London</p> - -<p class="center">All rights reserved</p> - -<p class="center">Printed in U. S. A.</p> - -<p class="center space-above2"><span class="smcap">International Textbook Press</span><br /> -Scranton, Pa.</p> - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<p><span class="pagenum"><a id="Page_iii"></a>[Pg iii]</span></p> -<h2 class="nobreak">CONTENTS</h2> -</div> - -<p class="blockquot fontsize_90"><span class="smcap">Note.</span>—This -book is made up of separate parts, or sections, as indicated by their -titles, and the page numbers of each usually begin with 1. In this list -of contents the titles of the parts are given in the order in which -they appear in the book, and under each title is a full synopsis of the -subjects treated.</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary="TOC" cellpadding="2" > - <tbody><tr> - <td class="tdc fontsize_150" colspan="2"><b>HOISTING, PART 3</b></td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdr"><i>Pages</i></td> - </tr><tr> - <td class="tdl">Hoisting Appliances</td> - <td class="tdr"><a href="#HOIST_1">1-43</a></td> - </tr><tr> - <td class="tdl">Hoist Indicators</td> - <td class="tdr"><a href="#H_INDIC">1-5</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Column indicators; Dial indicators;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Special indicators.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Drums and Reels</td> - <td class="tdr"><a href="#DRUMS">6-20</a></td> - </tr><tr> - <td class="tdl">Cylindrical Drums</td> - <td class="tdr"><a href="#CYLIND">7-8</a></td> - </tr><tr> - <td class="tdl">Conical Drums</td> - <td class="tdr"><a href="#CONIC">9-16</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Hoisting with cylindrical drums;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Hoisting with conical drums;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Comparison of cylindrical and conical drums.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Flat Rope Reels</td> - <td class="tdr"><a href="#FLAT">17-20</a></td> - </tr><tr> - <td class="tdl">Rope Wheels</td> - <td class="tdr"><a href="#ROPE_WHEEL">21-26</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Koepe system; Whiting system;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Modified Whiting system.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Rope Fastenings</td> - <td class="tdr"><a href="#ROPE_FAST">27</a></td> - </tr><tr> - <td class="tdl">Clutches</td> - <td class="tdr"><a href="#CLUTCH">28-31</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Jaw clutch; Band friction clutches;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Beekman friction clutch.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Brakes</td> - <td class="tdr"><a href="#BRAKE">32-43</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Block brake; Post brake; Strap brake;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Differential brake; Power for brakes;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Differential lever; Power brakes;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Crank brake. - <span class="pagenum"><a id="Page_iv"></a>[Pg iv]</span></td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl" colspan="2"> </td> - </tr><tr> - <td class="tdc fontsize_150" colspan="2"><b>HOISTING, PART 4</b></td> - </tr><tr> - <td class="tdl">Hoisting Appliances</td> - <td class="tdr"><a href="#HOIST_2">1-51</a></td> - </tr><tr> - <td class="tdl">Sheaves</td> - <td class="tdr"><a href="#SHEAVE">1-5</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Cast-iron sheave; Wood-lined sheaves;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Diameter of sheave;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Rollers and carrying sheaves.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Cages for Vertical Shafts</td> - <td class="tdr"><a href="#VERT_CAGE">6-11</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Construction of cage; Safety catches;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Multiple-deck cages.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Automatic Dumping Cages</td> - <td class="tdr"><a href="#AUTO_CAGE">12-16</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Definition; Slope, or inclined shaft</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">hoisting; Slope carriage.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Skips, or Gunboats</td> - <td class="tdr"><a href="#SKIP">17-22</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Definition; Method of loading skips;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Method of dumping skips; Skip cage.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Buckets</td> - <td class="tdr"><a href="#BUCKET">23</a></td> - </tr><tr> - <td class="tdl">Car Locks</td> - <td class="tdr"><a href="#LOCKS">23-24</a></td> - </tr><tr> - <td class="tdl">Cage Guides</td> - <td class="tdr"><a href="#GUIDES">25</a></td> - </tr><tr> - <td class="tdl">Landing Fans, or Keeps</td> - <td class="tdr"><a href="#KEEPS">26-28</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Common forms of fans; Hydrostatic fans;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Pneumatic fans; Cage chairs.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Head-Frames</td> - <td class="tdr"><a href="#HEAD">29-45</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Head-frames in general; Types of head-frames;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Examples of various types;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Head-frame specification.</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl">Detaching Hooks</td> - <td class="tdr"><a href="#HOOKS">46-47</a></td> - </tr><tr> - <td class="tdl">Signaling</td> - <td class="tdr"><a href="#SIGNALS">48-51</a></td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Hammer-and-plate signal; Electric bells;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Speaking tubes; Pneumatic gong signal;</td> - <td class="tdr"> </td> - </tr><tr> - <td class="tdl_ws1 fontsize_90">Telephones.</td> - <td class="tdr"><span class="pagenum"><a id="Page_1"></a>[Pg 1]</span></td> - </tr> - </tbody> -</table> - -<hr class="chap x-ebookmaker-drop" /> -<p class="f200"><b>HOISTING<br /><span class="fontsize_90">(PART 3)</span></b></p> - -<p class="f120">Serial 851C<span class="ws5"> </span>Edition 1</p> - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="HOIST_1">HOISTING APPLIANCES</h2> - -<h3 id="H_INDIC">HOIST INDICATORS</h3> -</div> - -<p><b>1. The hoist indicator</b> is a mechanism attached to the drum -shaft of a hoisting engine to show the hoisting engineer the position -of the cage or skip in the shaft throughout the time of hoisting. The -use of such indicators is sometimes required by law, but there is a -great diversity of opinion as to the advisability of using them. The -objections to them are that they are liable to get out of order, and -that in general the use of any automatic device that tends to relieve -the hoisting engineer of responsibility and constant attention to his -engine is not to be commended. A hoisting engineer, however, depends -for his stopping point mainly on a mark made on the rope, or on the -drum, or on both, and uses an indicator mostly as a guide for the -position of the cage during the hoist.</p> - -<p class="f120"><b>TYPES OF INDICATORS</b></p> - -<p><b>2. Column Indicators.</b>—A very simple indicator, and one that -was formerly very commonly used, is made by inserting a pin into the -center of the end of the drum shaft and using this as a miniature -drum on which to wind and unwind a chain or cord, which corresponds -to the hoisting rope as the pin corresponds to the drum. This chain -or cord is led over a pulley placed at the top of a pair of guides, -<span class="pagenum"><a id="Page_2"></a>[Pg 2]</span> -representing the shaft, and carries at its end a weight, pointer, or -gong, representing the cage or car, as shown in <a href="#FIG_1">Fig. 1</a>.</p> - -<div class="figcontainer"> - <div class="figsub"> - <img id="FIG_1" src="images/i_002a.jpg" alt="" width="400" height="515" /> - <p class="center"><span class="smcap">Fig. 1</span></p> - </div> - <div class="figsub"> - <img id="FIG_2" src="images/i_002b.jpg" alt="" width="150" height="510" /> - <p class="center"><span class="smcap">Fig. 2</span></p> - </div> -</div> - -<p>The different landings in the shaft are marked on the guide; and as -the pointer or gong rises and falls it indicates the position of the -cage in the shaft. If a gong is used, pointer also may be added and -the gong so arranged that it will ring at a point some distance before -the landing is reached and thus attract the engineer’s attention. -Indicators of this kind, though cheap and easily constructed, are not -reliable, for the cord and chain may stretch or they may overlap in -winding on the pin, or may bind in the pulley and thus indicate a wrong -position of the cage.</p> - -<p><b>3.</b> An indicator should have a positive motion and be driven by -gearing or by link belts. <a href="#FIG_2">Fig. 2</a> shows a <b>column indicator</b> -that consists of a screw <i>a</i> working inside of a slotted pipe <i>b</i>, -which may be of any length necessary. This screw is revolved by means -<span class="pagenum"><a id="Page_3"></a>[Pg 3]</span> -of the gears <i>c</i>, which are rotated by the sprocket wheel -<i>d</i>. A nut <i>e</i> travels up and down the screw <i>a</i> and -the pointer <i>f</i> attached to the nut indicates the position of the -cage in the shaft. The pipe standard <i>b</i> is usually painted a dead -black and the different levels may be marked on it with chalk or white -paint. Chalk marks are not safe, as they may be tampered with and the -engineer thus misled.</p> - -<div class="figcenter"> - <img id="FIG_3" src="images/i_003a.jpg" alt="" width="600" height="264" /> - <p class="center"><span class="smcap">Fig. 3</span></p> - </div> - -<p>The pointer <i>a</i>, <a href="#FIG_3">Fig. 3</a>, is moved by the rotation of -the screw shaft <i>b</i>, which is revolved by the bevel gears <i>c</i> and -<i>d</i>. This indicator also registers the number of hoists by means -of the dials <i>e</i>, for at each hoist the lower end of the pointer -a engages a ratchet wheel behind the two dial faces shown and thus -registers on the dial.</p> - -<div class="figcenter"> - <img id="FIG_4" src="images/i_003b.jpg" alt="" width="600" height="260" /> - <p class="center"><span class="smcap">Fig. 4</span></p> - </div> - -<p><b>4. Dial Indicators.</b>—<a href="#FIG_4">Fig. 4</a> shows a positive-motion -indicator that is operated as follows: A worm <i>a</i> on the drum shaft <i>b</i> -<span class="pagenum"><a id="Page_4"></a>[Pg 4]</span> -engages with the worm-wheel <i>c</i> on the small shaft <i>d</i> that -is supported by the bearings <i>e</i>. The pointer <i>f</i> is rigidly -attached to the shaft <i>d</i> and revolves in front of the properly -marked dial <i>g</i>.</p> - -<p id="ART_5"><b>5.</b> <a href="#FIG_5">Fig. 5</a> shows a <b>dial indicator</b> attached to -drum hoists where the speed of rope is constant for each revolution. The wheel -<i>a</i> of this indicator may be a worm-wheel working in a worm on the -drum shaft, as described in connection with the indicator shown in <a href="#FIG_4">Fig. 4</a>, -or it may be a sprocket wheel driven by a link belt from a sprocket -wheel on a drum, or it may be a gear-wheel driven directly from another -gear-wheel on the drum. The gear-wheels <i>b</i> revolve a vertical -shaft <i>c</i> fitted at the upper end with a worm <i>d</i> that drives -the worm-wheel <i>e</i> placed on the end of the pointer spindle. The -different levels from which hoisting is to be done may be painted on -the dial, or better, they may be placed on movable targets that are -clamped to the dial and can thus be moved as occasion requires.</p> - -<div class="figcenter"> - <img id="FIG_5" src="images/i_004.jpg" alt="" width="300" height="540" /> - <p class="center"><span class="smcap">Fig. 5</span></p> -</div> - -<div class="blockquot space-below2"> -<p><span class="smcap">Example.</span>—An indicator is desired -for a shaft 800 feet deep at which the drum of the hoisting engine to -be used is 10 feet in diameter; what ratio of gearing must be used so -that the pointer will make one revolution during the hoist?</p> - -<p><span class="smcap">Solution.</span>—The circumference of the -drum is 31.42 ft. (π<i>D</i> = 10 × 3.1416 = 31.416 ft.); hence, the -revolutions per hoist are 800 ÷ 31.42 = 25.46 revolutions. Then, if the -pointer is to make one revolution per hoist, the ratio of the gearing -will be 25.46 to 1. Ans.</p> -</div> - -<p><b>6. Special Indicators.</b>—One fault of nearly all indicators is -that they give a regular movement throughout the winding, and the space -over which the pointer travels is too small to enable the engineer to -land the cage accurately. Indicators have been made with a differential -motion to the pointer, the motion being greater at the time of landing -and less during the middle of the hoist. They are also made -<span class="pagenum"><a id="Page_5"></a>[Pg 5]</span> with two -pointers, one operating like the dial indicator above described and the -other remaining stationary during all the hoist but the last few feet, -when it moves around its circle.</p> - -<div class="figcenter"> - <img id="FIG_6" src="images/i_005.jpg" alt="" width="600" height="561" /> - <p class="center"><span class="smcap">Fig. 6</span></p> -</div> - -<p><b>7.</b> Where flat ropes are used or where round ropes wind on a -conical drum, the length of rope wound or unwound is different for each -turn of the drum. With all the indicators thus far described, while the -speed with which the indicator moves is proportional to the speed at -which the drum and the drum shaft revolve, it is not proportional to -the speed of the rope when winding and unwinding on a conical drum or -on a flat rope reel. <a href="#FIG_6">Fig. 6 (<i>a</i>) and (<i>b</i>)</a> shows -two views of a compensating dial indicator. By means of the spiral form of sheave -<i>c</i>, the hand <i>d</i> is made to move equal distances around the -<span class="pagenum"><a id="Page_6"></a>[Pg 6]</span> -disk <i>e</i> for equal distances of cage movement in the shaft. The -rope <i>f</i> passes about the spiral sheave and one end is attached at -the small end <i>g</i> of the spiral, while the other end is fastened -to the periphery of the sheave <i>h</i>, which takes its motion from -the drum shaft or crank-shaft of the hoisting engine by means of the -bevel gear <i>i</i>. Consequently, while the sheave <i>h</i> has a -regular motion dependent directly on the revolution of the hoisting -drum, the pointer <i>d</i> moves irregularly, depending on the position -of the spiral sheave <i>c</i>; that is, whether a small or large -diameter of the spiral is presented to the rope. The rope <i>j</i> -carrying the counterweight <i>k</i> is attached to a small circular -drum <i>l</i> that is on the same shaft as the spiral sheave. The -purpose of this cord and counterweight is to keep the indicator line -<i>f</i> taut and to bring the indicator back to position as the cord -<i>f</i> unwinds from the sheave <i>h</i>.</p> - -<p><b>8.</b> In order that the pointer may not stand at exactly the same -point on the dial when the cage is at the top and at the bottom, and -so that the engineer may be able to distinguish between the top and -the bottom positions of the cage by the pointer, the ratio of the -gearing is usually increased by allowing one or two extra teeth on the -worm-wheel. In the example in <a href="#ART_5"><b>Art. 5</b></a>, assume a ratio -of 27: 1; that is, if a worm-gear is used, the worm-wheel will have 27 teeth.</p> - -<p>If the pitch of the teeth is ¾ inch, the circumference of the pitch -circle will be ¾ × 27 = 20.25 inches and the diameter 6.44 inches.</p> - -<p>The pitch of the worm will, of course, be the same as that of the -wheel, and its diameter will be whatever is necessary to give -sufficient strength outside of the shaft, since it bears no relation to -the ratio of the gearing.</p> - -<h3 id="DRUMS">DRUMS AND REELS</h3> - -<p><b>9.</b> The <b>drum</b>, or <b>reel</b>, of a hoisting engine is the -part on which the rope winds. It is either keyed fast to the engine -shaft or is connected to the shaft by means of a clutch, the shaft -being made extra heavy to carry the strain due to the weight of the -drum and the pull of the rope. -<span class="pagenum"><a id="Page_7"></a>[Pg 7]</span></p> - -<h3 id="CYLIND">CYLINDRICAL DRUMS</h3> - -<p><b>10.</b> The outer part, or <b>shell</b>, of a drum <i>a</i>, <a href="#FIG_7">Fig. 7</a>, -is supported on rims <i>b</i>, and these rims are connected by arms -or spiders <i>c</i> with the hubs <i>d</i>. The brake rings <i>e</i> -are for the band brakes, of which there may be one or two. The part -<i>a</i> may be lagged with strips of wood bolted to the rims <i>b</i>, -the heads of the bolts being countersunk. <a href="#FIG_8">Fig. 8</a> shows the -detailed dimensions of a drum 8 feet in diameter having a 4-foot face designed -to carry heavy loads and a large amount of rope. The shell is of boiler -plate and the spiders of cast-steel.</p> - -<div class="figcenter"> - <img id="FIG_7" src="images/i_007.jpg" alt="" width="600" height="306" /> - <p class="center"><span class="smcap">Fig. 7</span></p> -</div> - -<p><b>11.</b> The shell may be cast in one piece for small drums or built -up in sections for large drums, as in Figs. <a href="#FIG_7">7</a> -and <a href="#FIG_8">8</a>. The shell may have -a smooth surface, <a href="#FIG_8">Fig. 8</a>, or it may have grooves, -<a href="#FIG_7">Fig. 7</a>, for the rope -to lie in as it is wound on the drum. On an iron drum without grooves, -the rope will chafe sidewise; and furthermore if the rope winds on a -hard flat surface it bears here and there on a single wire and tends to -flatten, causing internal wear between the wires; while, in the case -of a rope winding in a groove, it is supported on about one-quarter of -its circumference, bringing many more wires to bear on the drum and -dividing the pressure between them. A wooden-lagged drum causes less -<span class="pagenum"><a id="Page_8"></a>[Pg 8]</span> -wear on a rope than an ungrooved iron-shell drum, as grooves are -gradually worn in the lagging, but is not so good as a grooved iron -drum. It is not good practice to allow a rope to wind on itself, and -the drum should be long enough to take the full length of the rope -required for the hoist. At least two turns of the rope should be on -the drum when the load is at the bottom, as the friction between the -rope and drum thus greatly lessens the strain coming on the rope at -the point where it is fastened to the drum. Allowance for two or three -additional turns of the rope should also be made so that the cage may -be hoisted above the landing.</p> - -<div class="figcenter"> - <img id="FIG_8" src="images/i_008a.jpg" alt="" width="600" height="383" /> - <img src="images/i_008b.jpg" alt="" width="600" height="343" /> - <p class="center"><span class="smcap">Fig. 8</span></p> -</div> - -<p>The shell usually has a flange at each end, as shown in -Figs. <a href="#FIG_7">7</a> and <a href="#FIG_8">8</a>, -but it may have a flange at one end only, or may be without flanges -entirely. If, however, the flanges are not used, the drum must be extra -long to prevent the rope running off the end. If the drum is very long, -a third spider is added midway between the other two to stiffen it -against collapse. -<span class="pagenum"><a id="Page_9"></a>[Pg 9]</span></p> - -<div class="blockquot fontsize_90"> -<p><span class="smcap">Example.</span>—Find the length of a drum -6 feet 3 inches in diameter necessary to hold 1,000 feet of 1¼-inch -wire-rope.</p> - -<p><span class="smcap">Solution.</span>—The diameter from center -to center of the rope when wound on the drum is 6 ft. 3 in. plus 1¼ -in., or 6 ft. 4¼ in., which is equal to 19.96 ft. (approximately 20 -ft.) of circumference. Then, to wind 1,000 ft. will require ¹,⁰⁰⁰/₂₀ -= 50 turns on the drum. Allowing two turns of the rope to protect the -fastening and three turns in case of overwinding, gives fifty-five -turns to be allowed for on the drum. If the drum is of iron with -grooves turned in it, ¼ in. must be left between adjacent parts of the -rope, or 1½ in. from the center of one turn to the center of the next. -Then, 55 × 1½ = 82½ in. plus ¾ in. at each end = 84 in., or 7 ft. for -the length of the drum between the flanges. Ans.</p> - -<p>If the drum has wooden lagging, clearance need not be allowed -between two adjacent coils of rope, as in this case the rope winds -against itself and so takes up only 1¼ in. It will then be 55 × 1¼ in. -= 68¾ in., or 5 ft. 8¾ in. long (say 5 ft. 9 in.). Ans.</p> -</div> - -<h3 id="CONIC">CONICAL DRUMS</h3> - -<p><b>12.</b> In hoisting in balance from deep shafts with cylindrical -drums, if no tail-rope is used, or in hoisting from a single shaft -with an unbalanced cage, the hoisting engine is not loaded equally at -different points of the hoist owing to the gradually changing weight of the -unbalanced rope. The following illustrations will further explain this.</p> - -<p id="ART_13"><b>13. Hoisting With a Cylindrical Drum.</b>—Suppose that, from a -single-compartment vertical shaft 1,000 feet deep, it is required to hoist -each trip a load, including friction, of 11,000 pounds made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of material</td> - <td class="tdr">4,000</td> - </tr><tr> - <td class="tdl">Weight of car</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of cage</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Friction, 10 per cent. </td> - <td class="tdr bb2">1,000</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">11,000</td> - </tr> - </tbody> -</table> - -<p>If a 1⅜-inch cast-steel rope weighing 3 pounds per foot is used, -winding about a drum 7 feet in diameter, the weight of rope is then 3 × -1,000 = 3,000 pounds and the load on the rope, when the cage is at the -bottom, is 11,000 + 3,000 = 14,000 pounds, while at the top the load on -the rope is only 11,000 pounds. The moment of the load at the bottom -<span class="pagenum"><a id="Page_10"></a>[Pg 10]</span> -is then the load 14,000 multiplied by the radius 3½, or 14,000 × 3½ = -49,000 foot-pounds; and at the top, 11,000 × 3½ = 38,500 foot-pounds. -This shows that the load against the engine is much greater at the -beginning than at the end of the hoist.</p> - -<p id="ART_14"><b>14.</b> Take now a double-compartment vertical shaft of the same -depth as in <a href="#ART_13"><b>Art. <i>13</i></b></a> and assume the same amount -of material hoisted at a trip, in the same mine car and on the same cage; but that -an empty car and cage are lowered in one compartment while the loaded -car and cage are hoisted in the other. The two cars and the two cages -will balance each other, and the loads will be as follows: At the -beginning of the hoist, when the loaded car and cage are at the bottom, -the gross load is 14,000 pounds, made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of material</td> - <td class="tdr">4,000</td> - </tr><tr> - <td class="tdl">Weight of mine car</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of cage</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Friction, 10 per cent.of above </td> - <td class="tdr">1,000</td> - </tr><tr> - <td class="tdl">Weight of rope</td> - <td class="tdr bb2">3,000</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">14,000</td> - </tr> - </tbody> -</table> - -<p>Multiplying this by the radius of the drum, the gross turning moment is -14,000 pounds × 3½ feet = 49,000 foot-pounds, as before, but there is a -counterbalancing load of 6,000 pounds, made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of mine car</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of cage</td> - <td class="tdr bb">3,000</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">6,000</td> - </tr><tr> - <td class="tdl_ws1">Less friction, 10 per cent. </td> - <td class="tdr">600</td> - </tr><tr> - <td class="tdl"> </td> - <td class="tdr bb2">5,400</td> - </tr> - </tbody> -</table> - -<p class="space-above1">This means a counterbalancing load moment of -5,400 pounds × 3½ feet = 18,900 foot-pounds. The net load moment to be -overcome by the engine at the beginning of the hoist is, therefore, -49,000-18,900 = 30,100 foot-pounds. -<span class="pagenum"><a id="Page_11"></a>[Pg 11]</span></p> - -<p>At the end of the hoist there is a gross load on the loaded -side of 11,000 pounds, made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of material</td> - <td class="tdr">4,000</td> - </tr><tr> - <td class="tdl">Weight of mine car</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of cage</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Friction, 10 per cent. </td> - <td class="tdr bb2">1,000</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">11,000</td> - </tr> - </tbody> -</table> - -<p class="space-above1">This is equal to a gross load moment of 11,000 -pounds × 3½ feet = 38,500 foot-pounds, but there is a counterbalancing -load of 8,100 pounds, made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of mine car</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of cage</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Weight of rope</td> - <td class="tdr bb">3,000</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">9,000</td> - </tr><tr> - <td class="tdl_ws1">Less friction, 10 per cent. of 6,000 </td> - <td class="tdr">600</td> - </tr><tr> - <td class="tdl"> </td> - <td class="tdr bb2">8,400</td> - </tr> - </tbody> -</table> - -<p>This is equal to a counterbalancing load moment of 8,400 pounds × 3½ -feet = 29,400 foot-pounds, and leaves a net load moment against the -engine of 38,500-29,400 = 9,100 foot-pounds. In other words, the load -moment that the engine has to overcome varies from 30,100 foot-pounds -at the beginning of the hoist to 9,100 foot-pounds at the end of the hoist.</p> - -<p><b>15. Hoisting With Conical Drums.—Conical drums</b> are designed to -make the work of the engine as nearly uniform as possible throughout -the hoist. To accomplish this, when the cage is at the bottom of the -shaft, and the load is therefore heaviest, the rope winds on that part -of the drum having the smallest diameter. As hoisting continues, the -rope winds on a gradually increasing diameter of drum, and when the -cage is at the top of the hoist, and the load therefore least, the -rope is winding on that part of the drum having the greatest diameter; -in this way, the moment of the load at every point of the hoist is -approximately the same. The great difference in the loads at different -<span class="pagenum"><a id="Page_12"></a>[Pg 12]</span> -parts of the hoist is due mainly to the variation in the weight of the -rope hanging from the drum; hence, the less the weight of the rope in -proportion to the total load on the engine, the more nearly uniform is -the load on the engine.</p> - -<div class="figcenter"> - <img id="FIG_9" src="images/i_012.jpg" alt="" width="600" height="520" /> - <p class="center"><span class="smcap">Fig. 9</span></p> -</div> - -<p><b>16.</b> <a href="#FIG_9">Fig. 9 (<i>a</i>)</a> shows the condition at the -beginning of the hoist when conical drums are used. Cage <i>a</i> is at the bottom -and carries a loaded car; cage <i>b</i> is at the top and carries an -empty car. The net moment that the engine must overcome is the sum of -the weight of the material to be hoisted, weight of the cage and car at -<i>a</i>, and the weight of the rope attached to <i>a</i>, multiplied -by the small radius <i>r</i> of the drum, minus the weight of the car -and cage at <i>b</i>, multiplied by the large radius <i>R</i> of the drum.</p> - -<p><a href="#FIG_9">Fig. 9 (<i>b</i>)</a> shows the condition of things at the -end of the hoist, when the cage <i>a</i> is at the top and cage <i>b</i> at -the bottom. The loaded car and cage <i>a</i>, whose rope in <a href="#FIG_9">Fig. 9 (<i>a</i>)</a> -<span class="pagenum"><a id="Page_13"></a>[Pg 13]</span> -was winding on the smallest diameter of the drum, is now at -the top and the rope is winding on the largest diameter of the drum. -The cage <i>b</i> with the empty car is now at the bottom and the rope -is unwinding from the smallest diameter of the drum. The net moment -that the engine must overcome in this position is equal to the sum of -the weight of the material hoisted, the weight of the cage <i>a</i> and -the car, multiplied by the larger radius <i>R</i> of the drum, minus -the sum of the weights of the cage <i>b</i>, the car, and the rope, -multiplied by the small radius <i>r</i> of the drum.</p> - -<p id="ART_17"><b>17.</b> If the moment of the load against the engine at the -beginning of the hoist is to equal that at the end of the hoist, it is -possible to determine what relative diameters of drum will produce such -an effect, as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl">Let</td> - <td class="tdc"><i>Wₘ</i></td> - <td class="tdc"> = </td> - <td class="tdl">weight of material hoisted;</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc"><i>Wₖ</i></td> - <td class="tdc">=</td> - <td class="tdl">weight of cage and car;</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc"><i>Wᵣ</i></td> - <td class="tdc">=</td> - <td class="tdl">weight of rope;</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc"><i>R</i></td> - <td class="tdc">=</td> - <td class="tdl">large radius of drum;</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc"><i>r</i></td> - <td class="tdc">=</td> - <td class="tdl">small radius of drum.</td> - </tr> - </tbody> -</table> - -<p>The load moment may be calculated by including friction as ⅒ of the -total weight hoisted, except the weight of the rope, as shown in <a href="#ART_14"><b>Art. 14</b></a>; -or the friction may be disregarded without serious error. Then, -under the conditions shown in <a href="#FIG_9">Fig. 9 (<i>a</i>)</a>, -and disregarding friction,</p> - -<p class="f120">Load moment = (<i>Wₘ</i> + <i>Wₖ</i> + <i>Wᵣ</i>)<i>r</i> - <i>Wₖ</i><i>R</i> (<b>1</b>)</p> - -<p class="no-indent">and under the conditions shown in <a href="#FIG_9">Fig. 9(<i>b</i>)</a>,</p> - -<p class="f120">Load moment = (<i>Wₘ</i> + <i>Wₖ</i>)<i>R</i> - (<i>Wₖ</i> + <i>Wᵣ</i>)<i>r</i> (<b>2</b>)</p> - -<p class="no-indent">Placing formula <b>1</b> = formula <b>2</b>,</p> - -<p class="f120">(<i>Wₘ</i> + <i>Wₖ</i>)<i>R</i> - (<i>Wₖ</i> + <i>Wᵣ</i>)<i>r</i><br /> -<span class="ws5"> </span>= (<i>Wₘ</i> + <i>Wₖ</i> + <i>Wᵣ</i>)<i>r</i> - <i>Wₖ</i><i>R</i>,</p> - -<p class="no-indent">and</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdc">(<i>Wₘ</i> + 2<i>Wₖ</i> + 2<i>Wᵣ</i>)</td> - <td class="tdc"> </td> - </tr><tr> - <td class="tdc"><i>R</i> = </td> - <td class="tdc"><i>r</i> ————————</td> - <td class="tdc">  (<b>3</b>)</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc">(<i>Wₘ</i> + <i>2Wₖ</i>)</td> - <td class="tdc"> </td> - </tr> - </tbody> -</table> - -<p>Since the diameter of a drum is generally given instead of the -radius, it follows that if <i>D</i> = larger diameter, <i>d</i> = -smaller diameter, and then, since <i>D</i> = 2<i>R</i> and <i>d</i> = -2<i>r</i>, formula <b>3</b> may be written</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdc">(<i>Wₘ</i> + 2<i>Wₖ</i> + 2<i>Wᵣ</i>)</td> - <td class="tdc"> </td> - </tr><tr> - <td class="tdc"><i>D</i> = </td> - <td class="tdc"><i>d</i> ————————</td> - <td class="tdc">  (<b>4</b>)</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc">(<i>Wₘ</i> + 2<i>Wₖ</i>)</td> - <td class="tdc"> </td> - </tr> - </tbody> -</table> - -<p><span class="pagenum"><a id="Page_14"></a>[Pg 14]</span> -Formula <b>4</b> gives only approximate results, which are, however, -sufficiently accurate for the mine superintendent’s use, and for this -reason friction has been omitted, as it would make the formula much -more complex. It may be expressed as a rule as follows:</p> - -<p class="blockquot"><b>Rule.</b>—<i>To find the large diameter -of a conical drum, multiply the small diameter by the sum of the -weight of the material to be hoisted, twice the weight of the cage and -car, and twice the weight of the rope; divide this product by the sum -of the weight of the material, and twice the weight of the cage and car.</i></p> - -<div class="figcenter"> - <img id="FIG_10" src="images/i_014a.jpg" alt="" width="600" height="211" /> - <img src="images/i_014b.jpg" alt="" width="600" height="355" /> - <p class="center"><span class="smcap">Fig. 10</span></p> -</div> - -<p>Applying this rule to the problem given in <a href="#ART_14"><b>Art. 14</b></a> and omitting -friction,</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdc">7(4,000 + 12,000 + 6,000)</td> - <td class="tdc"> </td> - </tr><tr> - <td class="tdc"><i>D</i> = </td> - <td class="tdc">————————————</td> - <td class="tdc"> = 9.6 feet</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc">(4,000 + 12,000)</td> - <td class="tdc"> </td> - </tr> - </tbody> -</table> - -<p>The drum would then be 7 feet in diameter at the small end and 9 feet -7¼ inches at the larger end. -<span class="pagenum"><a id="Page_15"></a>[Pg 15]</span></p> - -<p><b>18</b>. <a href="#FIG_10">Fig. 10</a> shows a special form of combined conical -and cylindrical drum designed for hoisting a total balanced load of 25 tons -through a vertical height of 550 feet.</p> - -<p><a href="#FIG_11">Fig. 11</a> shows a combined conical and cylindrical drum; an -unusual feature is the rope reel shown at each end of the drum, which permits -of properly storing a few hundred feet of extra rope, allowing the rope -to be lengthened, when needed, without splicing.</p> - -<div class="figcenter"> - <img id="FIG_11" src="images/i_015.jpg" alt="" width="600" height="448" /> - <p class="center"><span class="smcap">Fig. 11</span></p> -</div> - -<p><b>19. Comparison of Cylindrical and Conical Drums.</b> The -disadvantages of the cylindrical drum lie entirely in the fact that the -load on the engines is variable, but it is possible to overcome this -disadvantage by adding a tail-rope to the cages to balance the weight -of the rope. This system gives its best results where hoisting is done -from one level only, but in deep hoisting it is impracticable because -of the extra weight added and because of possible excessive swaying of -the rope.</p> - -<p>The conical drum has two strong points in its favor: first, the load on -<span class="pagenum"><a id="Page_16"></a>[Pg 16]</span> -the engine may be nearly equalized during the entire hoisting period; -and, second, the starting of the engines with the load requires less power.</p> - -<p>The disadvantages of the conical drum are as follows: To maintain a -certain average speed of hoisting, the speed toward the end of the -hoist is of necessity higher than the average and comes at a time -when a slowing up should be taking place, so that more care must be -exercised when making the landing. To prevent the rope from being -drawn out of the grooves, the latter must be made deep and with a -large pitch, thereby increasing the width of the face or length of -the drum. In making a landing, when the rope is on the conical face, -the rope must be kept taut, as any slackness will permit the rope to -leave the groove, with the result that all the rope will pile up in the -bottom grooves of the drum allowing the cage to drop into the mine, -unless it is resting on the chairs. If there are several levels to be -hoisted from, the equalizing of the load on the engines can only be -realized for one level; for all other levels this advantage will be -lost. For large depths, conical drums become very long and require -correspondingly long leads from head-frame to drum. To hold the same -amount of rope, conical drums are heavier than cylindrical ones, and as -a result, the power required in starting the load is somewhat increased -owing to the greater inertia of the rotating parts.</p> - -<p>Some of these disadvantages have been overcome by making a combination -of cone and cylindrical drums. The drums are so designed that the -landing takes place only when the rope is on the cylindrical portion -of the drum. For deep hoisting, the greater diameter of the drum and -its length must be inconveniently large if the load is equalized. -The length and diameter can be reduced by making one-half of the -drum cylindrical and by having the rope from each end wind on the -same cylindrical portion of the drum. In all cases, however, these -modifications are made at the expense of the equalization of the load -on the engines, and it is not possible to obtain the latter without -including some serious disadvantage.</p> - -<p>There are certain objections to both cylindrical and conical drums: -<span class="pagenum"><a id="Page_17"></a>[Pg 17]</span> -their great size and weight, for large hoists, make them very -expensive; their width necessitates placing the engines far apart, -which adds to the cost of the engines, foundations, and buildings; the -great weight of the drums is also objectionable, because it forms a -large part of the mass to be put in motion and brought to rest at each hoist.</p> - -<h3 id="FLAT">FLAT ROPE REELS</h3> - -<p><b>20</b>. To overcome the objections to conical and cylindrical drums, -several other systems of hoisting have been tried, among them being -one that uses a reel, <a href="#FIG_12">Fig. 12</a>, and a flat rope. The hub -<i>a</i> is increased in diameter, above what is necessary for strength, to -such a size as is suitable to wind the rope on. It is then cored out from the -inside, so as not to contain too great a mass of metal.</p> - -<div class="figcenter"> - <img id="FIG_12" src="images/i_017.jpg" alt="" width="600" height="429" /> - <p class="center"><span class="smcap">Fig. 12</span></p> -</div> - -<p>The arms <i>b</i> of the reel extend radially from the hub to confine -the rope laterally when it is all wound on the drum. These arms are -connected at their outer ends by a continuous flange <i>c</i>, which -flange is flared out, as shown at <i>d</i>, so as to take in the rope -easily, if it is deflected at all sidewise.</p> - -<p>In the larger-sized reels, the arms are bolted to the hub, and often -the outer rim connecting the arms is omitted. Hardwood lining was -<span class="pagenum"><a id="Page_18"></a>[Pg 18]</span> -formerly used on the arms under the impression that the wear on the -rope would be less than with bare iron arms, but sand and grit become -embedded in the wood and grind the rope. Polished iron arms with -rounded corners and lubricated with oil or tar are best. The end of the -rope is fastened in a pocket <i>e</i> provided for it in the hub.</p> - -<p>The rope winds on itself, so that the diameter of the reel increases -as the hoist is made and as the load due to the weight of the rope -decreases. This serves to equalize the load due to the rope in the same -manner as the conical drum. Two reels are generally put on the same -shaft, and while one is hoisting from one compartment of the shaft the -other is lowering into another compartment. The periphery of the hub -where the rope winds should not be round but of gradually increasing -radius, for if a flat rope be wrapped about a round hub the rope will -have to abruptly mount itself at the end of the first revolution and so -on for every revolution. The radius of the hub should increase at such -a rate as to raise the rope an amount equal to its thickness in the -first wrap, so that it will wind on itself without jar at the point of -attachment, as well as on succeeding wraps.</p> - -<p><b>21.</b> In America, it is customary to wind on reels of small -diameter, that is, starting at 3 or 5 feet and increasing to 8 or 12 -feet; but several large plants have been built with reels starting -at 8 feet and increasing to 19 feet. In England, reels have been -made starting at 16 feet and increasing to 20 or 22 feet. Such large -reels are easier on the rope but require large engines, as hoisting -in balance is used to only a slight extent. The large reel is easy on -the rope, both from the fact that it bends the rope but little and -also gives less pressure on the bottom wraps, as each wrap adds to the -pressure. These reels are driven by means of plain jaw or friction clutches.</p> - -<p>The wear of a flat rope is excessive and the rope itself costs more -than a round rope of the same strength, does not last as long, and -requires more care and attention.</p> - -<p id="ART_22"><b>22. Calculating Size of Flat Rope and Reel.</b>—The calculation of -<span class="pagenum"><a id="Page_19"></a>[Pg 19]</span> -the size of a flat rope for given work is not so simple as that of a -round rope, as there is a variable factor in the width and thickness -of the rope that must be taken into account. To illustrate the method -of calculation, suppose that it is required to hoist 5,000 pounds of -material in a 3,000-pound skip from a vertical two-compartment shaft -2,000 feet deep under conditions requiring a factor of safety of about -9 for the rope.</p> - -<p>The determination of the size of the rope and the small and large -diameters of the reels must proceed together. The latter calculations -are performed in much the same manner as for conical drums.</p> - -<p>Referring to Table relating to flat wire ropes in <i>Hoisting</i>, -Part 2, it is found that a flat steel rope 6 inches by ½ inch in size and -with a breaking strength of 150,000 pounds weighs 5.1 pounds per foot; -hence, 2,000 feet of it weighs 2,000 × 5.1 = 10,200 pounds. The total -load on the rope will then be 19,000 pounds, made up as follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of material</td> - <td class="tdr">5,000</td> - </tr><tr> - <td class="tdl">Weight of skip</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Friction, 10 per cent. </td> - <td class="tdr">800</td> - </tr><tr> - <td class="tdl">Weight of rope</td> - <td class="tdr bb2">10,200</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">19,000</td> - </tr> - </tbody> -</table> - -<p>This rope gives a factor of safety of 150,000/19,000 = 7.8, which is -not quite enough when figured from the dead load without that due to -acceleration.</p> - -<p>An 8" × ½" rope with a breaking strength of 200,000 pounds weighs 6.9 -pounds per foot; hence, 2,000 feet of it weighs 2,000 × 6.9 = 13,800 -pounds. The load on the rope will then be 22,600 pounds, made up as -follows:</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdr"><span class="smcap">Pounds</span></td> - </tr><tr> - <td class="tdl">Weight of material</td> - <td class="tdr">5,000</td> - </tr><tr> - <td class="tdl">Weight of skip</td> - <td class="tdr">3,000</td> - </tr><tr> - <td class="tdl">Friction, 10 per cent. </td> - <td class="tdr">800</td> - </tr><tr> - <td class="tdl">Weight of rope</td> - <td class="tdr bb2">13,800</td> - </tr><tr> - <td class="tdl_ws1">Total</td> - <td class="tdr">22,600</td> - </tr> - </tbody> -</table> -<p><span class="pagenum"><a id="Page_20"></a>[Pg 20]</span></p> - -<p>This rope gives a factor of safety of 200,000/22,600 = 8.8.</p> - -<p>Substituting the foregoing weights of material, skip, and rope in -formula <b>4</b>, in <a href="#ART_17"><b>Art. 17</b></a>, gives</p> - -<table class="space-above2 fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdl"> </td> - <td class="tdc"><i>d</i>(5,000 + 6,000 + 27,600)</td> - </tr><tr> - <td class="tdc"><i>D</i> = </td> - <td class="tdc">————————————</td> - </tr><tr> - <td class="tdc"> </td> - <td class="tdc">(5,000 + 6,000)</td> - </tr> - </tbody> -</table> - -<p>Hence, the equation of moments is <i>D</i> = 3.5<i>d</i>. In other -words, the large diameter, or that of the last coil of rope, should be -3.5 times the small diameter, or that of the reel hub.</p> - -<p><b>23.</b> <a href="#FIG_13">Fig. 13</a> represents a coil of flat rope whose -greater diameter <i>D</i> and smaller diameter <i>d</i> are to be determined. -The area of the hub about which the rope is to coil is (¼)π<i>d</i>², -while the area included by the outer coil of rope is (¼)π<i>D</i>² -hence, the area of annular space occupied by the rope is</p> - -<p class="f120">(¼)π<i>D</i>² - (¼)π<i>d</i>² = (¼)π(<i>D</i>² - <i>d</i>²).</p> - -<p>Such values for <i>D</i> and <i>d</i> must be chosen that the -equation of moments in <a href="#ART_22"><b>Art. 22</b></a> is satisfied, while -the area (¼)π(<i>D</i>²-<i>d</i>²) must correspond to the space occupied by the -given rope when rolled.</p> - -<div class="figcenter"> - <img id="FIG_13" src="images/i_020.jpg" alt="" width="400" height="376" /> - <p class="center"><span class="smcap">Fig. 13</span></p> -</div> - -<div class="blockquot"> -<p><span class="smcap">Illustration.</span>—2,000 feet of rope ½ inch thick requires</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="2" > - <tbody><tr> - <td class="tdc">2,000 × 12</td> - <td class="tdc"> </td> - </tr><tr> - <td class="tdc">—————</td> - <td class="tdl"> = 12,000</td> - </tr><tr> - <td class="tdc">2</td> - <td class="tdc"> </td> - </tr> - </tbody> -</table> - -<p class="no-indent">square inches in which to be coiled. To satisfy the equation of -moments, <i>D</i> must equal 3.5 <i>d</i>; hence, to satisfy both -these conditions</p> - -<p class="f120"><b>(¼)π<span class="fontsize_150">[</span>(3.5<i>d</i>)² - - <i>d</i>²<span class="fontsize_150">]</span> = 12,000;</b></p> - -<ul class="index"> -<li class="isub2"><b><i>d</i> = 37 inches, or 3 feet 1 inch;</b></li> -<li class="isub2"><b><i>D</i> = 37 × 3.5 = 129.5 inches, or 10 feet 9½ inches.</b></li> -</ul> - -<p>The dimensions of the reel will then be: diameter of hub 3 feet 1 -inch; width between flanges, 8½ inches, allowing ¼ inch on each side of -the rope for clearance; diameter of the flanges where they flare, 10 -feet 9½ inches.</p> -</div> - -<p><span class="pagenum"><a id="Page_21"></a>[Pg 21]</span></p> -<h3 id="ROPE_WHEEL">ROPE WHEELS</h3> - -<div class="figcenter"> - <img id="FIG_14" src="images/i_021.jpg" alt="" width="450" height="513" /> - <p class="center"><span class="smcap">Fig. 14</span></p> -</div> - -<p><b>24. Koepe System.</b>—In its lightest form, a drum requires a -large amount of power to set it in motion, which power is absorbed by the -brake and lost when it is brought to rest again. Furthermore, with -deep shafts requiring long drums, the fleet, or angle that the rope -makes with the head-sheave due to its traveling from one end of the -drum to the other, is not only a disadvantage and possible cause of -accident, but it is a source of wear. To overcome these objections and -also the great cost of large cylindrical or conical drums, the <b>Koepe -system</b> of hoisting, shown in <a href="#FIG_14">Fig. 14</a>, was devised by Mr. Frederick -<span class="pagenum"><a id="Page_22"></a>[Pg 22]</span> -Koepe. A single grooved driving sheave <i>a</i> is used in place of a -drum. The winding rope <i>b</i> passes from one cage <i>A</i> up over -a head-sheave, thence around the sheave <i>a</i> and back over another -head-sheave, and down to a second cage <i>B</i>; it encircles a little -over half the periphery of the driving sheave and is driven by the -friction between the sheave and rope. A balance rope <i>c</i> beneath -the cages and passing around the sheave <i>d</i> gives an endless-rope -arrangement with the cages fixed at the proper points. The driving -sheave is stronger than an ordinary carrying sheave, as it has to do -the driving and is usually lined with hardwood, which is grooved to -receive the winding rope, the depth of the groove being generally equal -to twice the diameter of the rope. Instead of being placed parallel, -the head-sheaves are placed at an angle with each other, each pointing -to the groove in the driving sheave, thus reducing the side friction of -the rope on the sheaves.</p> - -<p>The system has been in successful operation since 1877, and experiments -made on it have determined that, with a rope passing only one-half -turn around the drum sheave, the coefficient of adhesion with clean -ropes is about .3. If the ropes are oiled, the adhesion becomes -less, and sometimes slippage occurs, producing not only wear of the -driving sheave lining but giving an incorrect reading of the hoist -indicator and thus possibly producing overwinding, unless the position -of the cage is indicated by marks on the rope, or unless the engineer -can see the cage.</p> - -<p>At the end of the hoist, if the upper cage is allowed to rest on the -keep, its weight and the weight of the tail-rope are taken from the -hoisting rope, and there is then not enough pull on the hoisting rope -to produce sufficient friction with the drum sheave to start the next -hoist. To prevent this trouble, the keeps are dispensed with, or the -rope is made continuous and independent of the cage. To do this, -crossheads are placed above and below each cage and connected by ropes -or chains outside of the cages. The bridle chains are then hung from -the top crosshead, and when the cage rests on the keeps, the weight of -the winding and tail-ropes remains on the driving sheaves. -<span class="pagenum"><a id="Page_23"></a>[Pg 23]</span></p> - -<p><b>25. Advantages and Disadvantages of the Koepe System.</b>—With -this system, only one driving sheave is necessary for the operation of two -compartments, and it is light, inexpensive to build, and very narrow, -admitting of a short sheave shaft and small foundations. This system -permits a perfect balance of rope and cage, so that the work to be done -by the engine is uniform, except for the acceleration, and consists -only in lifting the material and overcoming the friction. There is no -fleeting of the rope between the driving sheaves and the head-sheaves.</p> - -<p>The system has the following disadvantages, which prevent its being -used to any considerable extent: Liability to slippage of the rope -on the drum; if the rope breaks, both cages may fall to the bottom; -hoisting from different levels cannot be well done, for, since the -cages are at fixed distances from each other, the length of the rope is -such that when one cage <i>A</i> is at the top, the other cage <i>B</i> -is at the bottom. If hoisting is to be done from the bottom, this is -satisfactory, but if hoisting is to be done from some upper level, cage -<i>B</i>, which is at the bottom, must be hoisted to that level to be -loaded before it can go to the top. Then, when cage <i>B</i> goes to -the top with its load, cage <i>A</i> must go to the bottom, wait there -while cage <i>B</i> is being unloaded, and then be hoisted to the upper -level to receive its load. For each trip, therefore, the time required -for a cage to go from the bottom to the upper level and be loaded -is lost; and two movements of the engines are necessary for a hoist -instead of one.</p> - -<p><b>26. The Whiting System.</b>—This is a system of hoisting with -round ropes, in which two rope wheels placed tandem are used in -place of cylindrical or conical drums. As shown in <a href="#FIG_15">Fig. 15</a>, -for a two-compartment shaft the rope passes from one cage <i>a</i> up over -a head-sheave <i>c</i>, down under a guide sheave <i>d</i>, and is -then wound three times about the rope wheels <i>e</i> and <i>f</i>, to -secure a good hold, then around a fleet sheave <i>g</i>, and back under -another guide sheave <i>h</i>, up over another head-sheave <i>i</i>, -and down to the other cage <i>b</i>. When the system is to be used -for a single-compartment shaft, one end of the rope carries the cage -and the other end carries a balance weight, which is run up and down -in a corner of the shaft. A balance rope below the cages, as shown, -is generally used, though it is not essential to the working of the -system, as it is in the Koepe system. When sinking a shaft, a balance rope -cannot be used as it interferes with the work at the bottom of the shaft. -<span class="pagenum"><a id="Page_24"></a>[Pg 24]</span></p> - -<div class="figcenter"> - <img id="FIG_15" src="images/i_024.jpg" alt="" width="600" height="406" /> - <p class="center"><span class="smcap">Fig. 15</span></p> -</div> - -<p><span class="pagenum"><a id="Page_25"></a>[Pg 25]</span> -The drums or wheels <i>e</i>, <i>f</i> are light, inexpensive, and -narrow, thus permitting short sheave shafts and small foundations. -They are lined with hardwood blocks, each lining having three rope -grooves turned in it. The main wheel <i>e</i> is driven by a hoisting -engine, which may be either first or second motion. The following -wheel <i>f</i> is coupled to the main wheel by a pair of parallel -rods, one on each side, like the drivers of a locomotive. As the rope -wraps about the wheels <i>e</i>, <i>f</i> three times, there are six -semi-circumferences of driving contact with the rope, as compared -with the one semi-circumference in the Koepe system, and there is no -slipping of the rope on the wheels. The following wheel <i>f</i> is -best tilted or inclined from the vertical an amount equal, in the -diameter of the wheels, to the pitch of the rope on the wheel, so that -the rope may not run out of its groove and may run straight from one -wheel to the other without any chafing between the ropes and the sides -of the grooves.</p> - -<p>The capacity of the wheels <i>e</i>, <i>f</i> is unlimited, while -grooved cylindrical drums, conical drums, and reels will hold only the -fixed length of rope for which they are designed.</p> - -<p>As shown by the dotted lines, the fleet sheave <i>g</i> is arranged to -travel backwards and forwards, in order to change the working length of -the rope from time to time to provide for an increased depth of shaft, -and for the changes in the length of rope due to stretching and when -the ends are cut off to resocket the rope. The fleet sheave <i>g</i> is -moved a distance equal to half the change in the length of rope.</p> - -<p><b>27</b>. Hoisting from intermediate levels can be readily done with -the Whiting system; for instance, if the cage <i>a</i> is at the top -and cage <i>b</i> at the bottom, and hoisting is to be done from some -upper level, it is only necessary to run the fleet sheave <i>g</i> out, -<span class="pagenum"><a id="Page_26"></a>[Pg 26]</span> -and thus shorten the working length of the rope until cage <i>b</i> -comes up to the upper level. It can then be loaded and go to the top. -While cage <i>b</i> goes to the top, cage <i>a</i> descends to the same -level, where it can be loaded while cage <i>b</i> is being unloaded, -and can then go directly to the top without any of the lost time, as is -the case in the Koepe system.</p> - -<p>The system permits a perfect balance of rope and cage, so that the work -to be done by the engines is uniform, except for the acceleration, and -consists only in lifting the material and overcoming the friction.</p> - -<p>There is no fleeting of the rope, so the rope wheels can be placed as -close to the shaft as may be desired.</p> - -<p><b>28.</b> This system was tried as early as 1862 in Eastern -Pennsylvania, but it was not used extensively because hoisting from -great depths was not necessary, since, for depths of less than 1,000 -feet, cylindrical and conical drums are quite satisfactory. In the -Lake Superior copper region, there are now three Whiting hoists, two -of which are probably the largest hoisting plants in the world. Each -plant consists of a pair of triple-expansion, vertical, inverted-beam -engines, driving direct a pair of 19-foot drums. The high-pressure -cylinders are 20 inches in diameter, the intermediate cylinders 32 -inches, and the low-pressure cylinders 50 inches, and all six of them -have a 72-inch stroke. The rope used is a 2¼-inch plow-steel rope and -hoists 10 tons of material at a trip, in one case from a depth of 4,980 -feet, the deepest shaft in the world. Several plants on the Whiting -system have been built in England, and two or more are working in South -Africa.</p> - -<p><b>29. Modified Whiting System.</b>—A modification of the Whiting -system is sometimes used in which a large drum keyed to the crank-shaft -replaces the small tandem drums, and even the slight probability of -the rope slipping in the Whiting system is thus obviated. One rope is -fastened to one end of the drum, and the other rope to the other end in -such a way that while one is winding on the other will be winding off -<span class="pagenum"><a id="Page_27"></a>[Pg 27]</span> -the drum. One rope passes directly to the head-sheave while the other -passes first around a fleet sheave, similar to that used for the -Whiting system, but preferably placed horizontal, and thence to the -head-sheave. This system possesses the same advantages as the Whiting -system except that the depth of hoist is limited by the size of the -drum, and that there is a fleet of the rope. Up to the limiting depth, -as determined by the size of the drum, this system can be used with -equal economy for any depth. This hoist, as well as the Whiting, is -therefore especially suitable for a place where one mining company -operates several mines, for it enables the company to select one size -for all their permanent work, with all the advantages that come from -duplicate machinery.</p> - -<h3 id="ROPE_FAST">ROPE FASTENINGS</h3> - -<div class="figcenter"> - <img id="FIG_16" src="images/i_027.jpg" alt="" width="400" height="538" /> - <p class="center"><span class="smcap">Fig. 16</span></p> -</div> - -<p><b>30.</b> A common method of fastening a rope to a drum, <a href="#FIG_16">Fig. 16 (<i>a</i>)</a>, -is to pass the rope through a hole in the drum rim and then -around the shaft, clamping the end to the rope between the shaft and -shell, as shown. Care should be taken to make the radius of curvature -of the hole at <i>a</i> as large as possible so that the rope will not -be bent any sharper than is necessary. When an iron drum is used, the -thickness of the rim does not afford enough depth in which to bend the -rope and it is necessary to build in a pocket for the purpose, as shown -at <a href="#FIG_16">Fig. 16 (<i>b</i>)</a>. It is well to make both sides of -this pocket with a long radius to avoid damaging the rope in case all the rope -is accidentally unwound and the drum backed so as to bring the rope -against the other side of the pocket. -<span class="pagenum"><a id="Page_28"></a>[Pg 28]</span></p> - -<h3 id="CLUTCH">CLUTCHES</h3> - -<p><b>31.</b> It is often desired to have the drum of a hoisting engine -run loosely on the engine shaft, so that it may run independently -of the engine. With such loose-running drums, the engine generally -runs only in the direction required to hoist the load, while the cage -is lowered entirely by means of the brake. In this way, one engine -provided with several drums may be used for hoisting from several -shafts or from several levels in the same shaft at the same time. Such -a loose-running drum is connected to the engine shaft when a load is to -be hoisted by means of a clutch, of which there are two forms commonly -used for hoisting machinery: <i>jaw</i> or <i>piston clutches</i> and -<i>friction clutches</i>.</p> - -<div class="figcenter"> - <img id="FIG_17" src="images/i_028.jpg" alt="" width="500" height="487" /> - <p class="center"><span class="smcap">Fig. 17</span></p> -</div> - -<p><b>32. Jaw Clutch.</b>—<a href="#FIG_17">Fig. 17</a> shows a <b>jaw clutch</b>, -one-half <i>a</i> of which is shown ready to be bolted to a drum or flat rope -reel, which is loose on the shaft <i>b</i>. The other half <i>c</i> of -the clutch is moved back so that the jaws <i>d</i> are not in contact -with the jaws <i>e</i> on the part <i>a</i>. The half <i>c</i> slides -freely on a feather key <i>f</i>, which is driven tightly into a deep -key seat in the shaft <i>b</i>; a collar <i>g</i>, fitting loosely in -a groove in the hub of <i>c</i>, is provided with trunnions <i>h</i> -on each side; levers <i>i</i> connect these trunnions with the lever -<i>j</i> attached to a suitable handle, by means of which the clutch is -made to slide endwise on the shaft so that the jaws <i>d</i> engage -or disengage the jaws <i>e</i> and thus connect or disconnect the drum -or reel from the clutch. There are generally four or six jaws <i>d</i> -that engage the same number of jaws <i>e</i> on the drum, and it is -necessary to have little or no play between <i>d</i> and <i>e</i> when -<span class="pagenum"><a id="Page_29"></a>[Pg 29]</span> -the clutch is connected or there will be too much shock. The clutch is -about 2 feet in diameter, and the jaws are 3 or 4 inches deep for the -average 20" × 48" first-motion hoisting engine. Instead of the clutch -being fastened to the shaft by feather keys, the shaft may be hexagonal -where the clutch slides on it and the clutch is machined to match. Jaw -clutches are made of either cast-iron or cast-steel, and should be in -halves, for convenience of repair, and securely bolted together.</p> - -<div class="figcenter"> - <img id="FIG_18" src="images/i_029.jpg" alt="" width="500" height="538" /> - <p class="center"><span class="smcap">Fig. 18</span></p> -</div> - -<p><b>33. Band Friction Clutches.</b>—<a href="#FIG_18">Fig. 18</a> shows a -<b>band friction clutch</b> that is attached to and revolves with the shaft <i>a</i>. -The winding drum runs loosely on the same shaft and has a driving-band -ring or seat <i>b</i> on one end; when the ring <i>c</i> of the clutch -is tightened by means of the mechanism shown, the clutch and driving -<span class="pagenum"><a id="Page_30"></a>[Pg 30]</span> -band become practically one piece and the drum revolves with the -clutch. The clutch is constructed as follows: The driving disk <i>d</i> -keyed to the driving shaft <i>a</i> is connected to one end of the ring -<i>c</i> by a fixed arm <i>e</i>, which is bolted firmly to the disk -<i>d</i> and revolves with it; a movable arm <i>f</i> that connects -with the other end of the band <i>c</i> turns on the pin <i>g</i>. When -the band <i>c</i> is loose, it can revolve about the seat <i>b</i> -without touching it, but the band can be tightened and made to clamp -<i>b</i> either when revolving or standing still, as follows: The -sliding sleeve <i>h</i> may be caused to slide about 6 inches along -the hub of the disk <i>d</i> by levers (not shown) that take hold of -trunnions <i>i</i> on a ring on the sliding sleeve; this sleeve is -connected to the movable arm <i>f</i> by a link <i>j</i>, and when the -sleeve is on the end of the hub the link stands at an angle of about -60° with the shaft; by sliding the sleeve toward the disk <i>d</i>, -the link is made to move the arm <i>f</i> about 1½ inches at its outer -end and to thus tighten the driving-band <i>c</i>, so that it grips -the ring <i>b</i>. The adjusting nuts <i>k</i> take up the wear of -the wooden blocks with which the ring <i>c</i> is lined. Band lifters -<i>l</i> hold the band clear of the ring when it is loose. The clutch -shown is built to run in the direction indicated by the arrow, but such -clutches may be built to run in either direction; they should always be -run in the direction for which they are designed, so that the load may -always come on the fixed arm. If the band be tightened slowly, there -will be no sudden start or jerk on the rope, as the slip of the band -will prevent the entire force of the grip taking effect at once; and -after the drum reaches full speed, there is little or no slipping of -the driving-band. It is best to keep the band only just tight enough to -do the work, for should the car get off the track, or be overwound, or -should a cage stick in the shaft for any reason, the band will slip and -thus become a safety appliance, and not strain or break the rope, shaft -timbering, or machinery, as would be the case if a positive clutch, -<a href="#FIG_17">Fig. 17</a>, were used.</p> - -<p><b>34. The Beekman Friction Clutch.</b>—A simple friction clutch is -<span class="pagenum"><a id="Page_31"></a>[Pg 31]</span> -shown in <a href="#FIG_19">Fig. 19</a>, in which <i>a</i> is a section of the drum -shell. The wooden blocks <i>b</i> bolted to the side of the gear-wheel <i>c</i> -are made of suitable shape to conform to the <b>V</b>-shaped groove -<i>d</i> in the side of the drum. The steel spring <i>e</i> between the -two steel washers <i>f</i>, <i>f</i> disengages the clutch, as soon as -the pressure is relieved, by reversing the motion of the lever <i>g</i> -and screw <i>h</i> from the opposite end of the drum. When the lever -<i>g</i> is turned, the screw <i>h</i> is forced against the end of the -pin <i>i</i>, which, in turn, presses the cross-key <i>j</i> against -the collar <i>k</i>, forcing the drum against the blocks <i>b</i> and -frictionally engaging the gear-wheel <i>c</i>. This drum shaft is -prevented from moving endwise by means of the collar <i>l</i> and the -grooves <i>m</i> in the babbitted pillow-block. The wide bearings of -the drum on its shaft are lubricated by means of the pipes <i>n</i>.</p> - -<div class="figcenter"> - <img id="FIG_19" src="images/i_031.jpg" alt="" width="600" height="321" /> - <p class="center"><span class="smcap">Fig. 19</span></p> -</div> - -<p>A clutch is often used to change the length of the hoisting rope when -hoisting from two or more lifts or levels. In this case the shaft -carries two drums, one of which is fixed to the shaft, while the other -is provided with a friction clutch. When it is desired to change the -length of the rope, the cage attached to the loose drum is brought -to, say, the upper landing. The cages both resting on the wings, the -clutch is loosened and the other cage attached to the fixed drum is now -brought to the desired level, when the clutch is again tightened and -hoisting proceeds. The change is made in 2 or 3 minutes. -<span class="pagenum"><a id="Page_32"></a>[Pg 32]</span></p> - -<h3 id="BRAKE">BRAKES</h3> - -<p><b>35</b>. A <b>brake</b> is a device by means of which the motion of -a hoisting drum may be retarded or stopped. This is accomplished by -friction of the brake against the circumference of the brake wheel. -There are three types of brakes, known as <i>block brakes</i>, <i>post -brakes</i>, and <i>strap brakes</i>.</p> - -<div class="figcenter"> - <img id="FIG_20" src="images/i_032.jpg" alt="" width="600" height="416" /> - <p class="center"><span class="smcap">Fig. 20</span></p> -</div> - -<p><b>36. The Block Brake.</b>—The <b>block brake</b>, -<a href="#FIG_20">Fig. 20</a>, consists of one or more wooden blocks or -shoes <i>b</i> attached to a lever having a fulcrum at <i>d</i>, and -connected by a rod to the lever <i>c</i>. Block brakes are objected -to mainly because they throw a great load on the journals of the drum -when they are applied; they cannot be relied on when there is a heavy -load on the drum, and they require the application of great force to -the lever <i>c</i> for a given braking power. They are, however, cheap -and easily applied to a drum, and the shoe is readily replaced when worn.</p> - -<p><b>37. The Post Brake.</b>—The <b>post brake</b>, <a href="#FIG_21">Fig. 21</a>, -is composed practically of two block brakes applied at two places on the drum -diametrically opposite each other, thus equalizing the pressure on the -journals. The blocks are generally somewhat longer than in the block -brake, or about one-quarter of the circumference of the drum on each -side. In <a href="#FIG_21">Fig. 21</a>, <i>a</i> is the drum; <i>b</i> are wooden -brake blocks; <i>c</i> are the posts which in the brake shown are of massive, -built-up, steel construction; <i>d</i> are the fulcrums on the plates -<i>e</i>, which plates are adjustable by means of the nuts <i>f</i>; by -means of these nuts, the fulcrums may be brought closer together as the -wooden blocks <i>b</i> wear away; <i>g</i> is a tension rod generally -<span class="pagenum"><a id="Page_33"></a>[Pg 33]</span> -furnished with a turnbuckle to adjust its length as the wooden blocks -wear away. Power is applied at the end of the bent lever <i>h</i>, as -shown by the arrow.</p> - -<div class="figcenter"> - <img id="FIG_21" src="images/i_033a.jpg" alt="" width="600" height="283" /> - <p class="center"><span class="smcap">Fig. 21</span></p> -</div> - -<p>The stops <i>i</i> are adjusted so that the blocks <i>b</i> on each -side are equally distant from the drum when the brake is off. The -fulcrums <i>d</i> should be some distance below the drum and brake -ring, for if they are too near the drum it will be difficult to swing -the lower end of the wooden blocks far enough to clear the drum.</p> - -<div class="figcenter"> - <img id="FIG_22" src="images/i_033b.jpg" alt="" width="600" height="348" /> - <p class="center"><span class="smcap">Fig. 22</span></p> -</div> - -<p><b>38. Improved Post Brake.</b>—In order to have an equal clearance at -<span class="pagenum"><a id="Page_34"></a>[Pg 34]</span> -top and bottom, and to have a more powerful leverage than in the -ordinary post brake, the posts may be made movable at both top and -bottom, <a href="#FIG_22">Fig. 22</a>. The tops of the posts <i>a a′</i> are moved, as in -<a href="#FIG_21">Fig. 21</a>, by the tension rod <i>b</i> and the lever <i>c</i>, the latter -being connected by rod <i>d</i> to lever <i>e</i>. This lever is -pivoted at <i>f</i> and motion is transmitted to the fulcrums <i>j</i> -by the link <i>g</i>, the lever <i>h</i>, and the tension rod <i>i</i>. -The back post <i>a</i> is supported by the uprights <i>k</i>, which are -pivoted at <i>l</i> and swing backwards and forwards like a parallel -ruler. The front post <i>a′</i> is supported by the single upright -<i>m</i>, pivoted at <i>n</i>. The setscrews <i>o</i> regulate the -motion of the bottom of the posts so as to give equal clearance to the -bottom and top of the posts.</p> - -<p>An objection to both the block and the post brake is the fact that, if -the drum surface to which the brake is applied is not perfectly round, -the resistance of the brake will not be uniform when applied while the -drum is in motion.</p> - -<p><b>39. The Strap Brake.</b>—A <b>strap brake</b> consists of a -wrought-iron band or strap that partly encircles the drum and is -connected at its free ends to levers with which the band may be -tightened on the brake wheel and the drum thus firmly held. The iron -or steel band either lies directly against the wooden lagging of the -drum or on wooden blocks bolted to the drum; or else it has bolted to -it a lining of wooden blocks that bear on the drum when the band is -tightened.</p> - -<p>The most efficient forms of strap brakes are those in which the strap -or straps are in contact with 270° or more of the circumference of the -drum. The greater the arc of contact, the more securely is the drum -held by the brake. A single strap is sometimes used, but this is only -satisfactory with small drums, say 8 feet or less in diameter; on large -drums two straps are generally used, each extending half way around -the drum. The levers for transmitting the power from the hand lever or -treadle to the brake strap are variously arranged. In some cases, the -force is multiplied by several short levers; in others, by one long -<span class="pagenum"><a id="Page_35"></a>[Pg 35]</span> -lever. The treadle or foot-lever, however, has been replaced almost -entirely by the hand lever.</p> - -<div class="figcenter"> - <img id="FIG_23" src="images/i_035a.jpg" alt="" width="600" height="245" /> - <p class="center"><span class="smcap">Fig. 23</span></p> -</div> - -<p><b>40.</b> The simplest form of strap brake, <a href="#FIG_23">Fig. 23</a>, -consists of a single strap <i>a</i>, with one end anchored at <i>b</i> and the -free end attached to the brake lever <i>c</i>. This brake acts on the same -principle as the block brake and is open to the objection that it -brings an undue load on the journals, but it is more efficient and -holds the drum more firmly under a heavy load than a block brake.</p> - -<div class="figcenter"> - <img id="FIG_24" src="images/i_035b.jpg" alt="" width="600" height="379" /> - <p class="center"><span class="smcap">Fig. 24</span></p> -</div> - -<p>Block brakes are usually run dry, but in band brakes and post brakes -with ample surfaces and proper leverage the wood may be occasionally -<span class="pagenum"><a id="Page_36"></a>[Pg 36]</span> -slightly oiled with black oil, which greatly adds to the durability of -the blocks without unduly lessening the power of the brake.</p> - -<p><b>41.</b> A two-strap brake is shown in <a href="#FIG_24">Fig. 24</a>. One end -of each strap <i>a</i>, <i>b</i> is fastened to the pedestal <i>c</i> by either of -the methods shown in <a href="#FIG_24">Fig. 24 (<i>a</i>), (<i>b</i>), and (<i>c</i>)</a>. -In the method shown in <a href="#FIG_24">Fig. 24 (<i>a</i>) and (<i>b</i>)</a>, the forgings -<i>d</i>, <i>d′</i>, drawn out to the form of bolts, are riveted to -the ends of the straps and passed through a casting <i>c</i> that is -secured to the foundation. The object in giving one bolt to one strap -and two bolts to the other strap is to allow the straps to pass each -other and yet have their lines of action intersect. The bolts are -fastened to <i>c</i> by four nuts on each bolt, i. e., two principal -nuts and two locknuts. This gives a means of adjustment in the length -of the strap to take up the wear.</p> - -<p>A second method of securing or anchoring the back ends of the straps -is shown at (<i>c</i>). In this case, a wrought-iron angular piece -is riveted to each strap, and these pieces are passed over the bolt -<i>e</i> that takes the place of the casting of the former arrangement. -Nuts are used, as shown, to adjust the straps for wear. The bolt should -be short and stiff, so as to be well able to stand up to its work when -the drum is moving or tending to move in the direction shown by the arrow.</p> - -<p>When the brake is applied, the friction between the brake strap and -the circumference of the brake wheel produces a great strain on the -pedestal <i>c</i>, which must be securely anchored.</p> - -<p>The front ends of the straps are worked into eyes, as shown at -<i>f</i>, and by these eyes and suitable pins passing through them the -ends are fastened to the brake lever <i>g</i>. This lever is supported -on and rotates about a pin <i>h</i>, so that when the braking force is -applied at <i>i</i>, in the direction of the arrow, the brake lever -rotates, pulling down on strap <i>a</i> and up on strap <i>b</i>; and, -if the straps are held firmly at the back end, the more force that is -applied at <i>i</i> the tighter will the drum be gripped by <i>a</i> -and <i>b</i>.</p> - -<p>The ends of the straps should be brought in as close to the drum as is -<span class="pagenum"><a id="Page_37"></a>[Pg 37]</span> -practicable, both front and back, so as to give the greatest amount of -contact between the drum and the straps and to get the best effect from -the force applied. The springs <i>j</i> are used with straps that are -not stiff enough to clear the drum when the brake is released.</p> - -<p><b>42.</b> The rotation of the drum may assist or retard the action of -the lever in applying the drop brake. For instance, if, in <a href="#FIG_23">Fig. 23</a>, -the drum revolves in the direction indicated by the arrow, the pull -of the drum at the brake strap is in the same direction as the pull -of the lever when applying the brake and the action of the lever is -then assisted by the motion of the drum. On the other hand, if the -drum is revolving in the opposite direction, it opposes the action of -the lever and a greater force must be applied to the lever to overcome -this opposing pull of the drum. Hence, in the case of strap brakes, if -possible, that end should be anchored which will cause the revolution -of the drum to assist the lever in applying the brake and throw the -strain on the anchor bolt instead of on the lever.</p> - -<div class="figcenter"> - <img id="FIG_25" src="images/i_037.jpg" alt="" width="600" height="369" /> - <p class="center"><span class="smcap">Fig. 25</span></p> -</div> - -<p><b>43.</b> If a brake is required to work with the drum running in -either direction, there are several ways of bringing the strain due -to the load on the anchorage in whichever way the drum runs. One of -the simplest of these is shown in <a href="#FIG_25">Fig. 25</a>, where <i>a</i> is -a drum with a strap brake <i>b</i> embracing nearly the entire circumference; -<i>c</i> is a lever bar that is attached to the ends of the brake strap -by pins <i>d</i> and <i>e</i>, which work in the slots <i>f</i> in the -iron anchor plates <i>g</i>. One anchor plate is on each side of the -lever, and both are bolted to the foundation. If the band is kept of -the proper length, then, no matter which way the drum is turning, the -pull of the drum will come on the anchorage, and the pull on the lever -<span class="pagenum"><a id="Page_38"></a>[Pg 38]</span> -need be only sufficient to take up the slack end of the band. To -illustrate: If the drum is turning in the direction indicated by the -arrow, the pin <i>e</i> holding the lower end of the band will be on -the bottom of its slot and the pin <i>d</i> will be free in its slot -and engaged in tightening the slack end of the band through the motion -of the lever <i>c</i>. Were the drum running the other way, the pin -<i>d</i> connected with the upper half of the band would move to the -upper end of its slot and take the main load, while the pin <i>e</i> -at the lower end of the band would only have to take up the slack. -The outer, or long, end of the lever moves downwards in all cases to -tighten the band. Provision must be made to lift the band clear of the -drum when slack, but no anchorage other than at <i>g</i> should be -attempted.</p> - -<div class="figcenter"> - <img id="FIG_26" src="images/i_038.jpg" alt="" width="600" height="243" /> - <p class="center"><span class="smcap">Fig. 26</span></p> -</div> - -<p><b>44. The Differential Brake.</b>—The differential brake has both -ends of the brake strap attached to short lever arms operated by -the brake lever, but these arms are of different lengths and are so -arranged that as the longer arm tightens the brake strap the shorter -arm yields and loosens the strap. The tightening, however, is more than -the loosening or yielding and, as a result, the brake band is tightened -about the brake wheel. The form of the lever arm is immaterial so long -as the differential principle is retained, that is, that the shorter -arm yields when the longer pulls, when the brake is thrown into action. -This principle is illustrated in <a href="#FIG_26">Fig. 26</a>. In this brake, -no provision is made for anchoring either end of the brake strap, but the entire -load is thrown on the lever arms <i>a</i> and <i>b</i>. These lever -<span class="pagenum"><a id="Page_39"></a>[Pg 39]</span> -arms are connected with the arm <i>c</i>, which revolves on the -same shaft <i>d</i> and is operated by the reach rod <i>e</i>. The -revolution of the drum is thus resisted by the shaft <i>d</i>.</p> - -<p>This brake is self-acting when the drum revolves so as to pull on the -shorter arm, as indicated by the arrows; that is, the motion of the -drum helps to set the brake when the latter is once applied. When, -however, the drum revolves in the opposite direction, the action of -the brake is opposed, instead of being assisted, by the motion of the -drum. As a consequence, this particular form of brake is not adapted to -hoisting drums that revolve in opposite directions at each alternate -hoist. Differential brakes are not generally used.</p> - -<div class="figcenter"> - <img id="FIG_27" src="images/i_039.jpg" alt="" width="600" height="258" /> - <p class="center"><span class="smcap">Fig. 27</span></p> -</div> - -<p><b>45. Power for Brakes.</b>—For small drums and light loads, the -brakes are usually applied by hand power through suitable lever -connections. The force that a man can exert can be multiplied -indefinitely by levers and combinations of levers; but while the force -is multiplied, the distance through which it can act is divided in the -same ratio. A certain amount of motion is required to free the brake -band from the drum, when the brake is off; this, then, limits the -leverage that a man can use. Suppose, for instance, that with a strap -brake the band moves from the drum ½ inch, thus increasing the diameter -1 inch, or the circumference about 3 inches. Then, supposing that a -man can exert his force to advantage through 3 feet, or 36 inches, the -available leverage is ³⁶/₃ = 12. That is, if a man can pull 50 pounds -<span class="pagenum"><a id="Page_40"></a>[Pg 40]</span> -on his hand lever, he can exert 50 × 12 = 600 pounds circumferentially -on the brake band, with simple levers. If any form of differential -levers is used, the ratio by which the force applied at the hand lever -can be increased will be considerably larger. A diagram will explain -this more clearly.</p> - -<p><b>46.</b> In <a href="#FIG_27">Fig. 27</a>, <i>a</i> is the hand lever, with a fulcrum -at <i>b</i> and a pin at <i>c</i> by which it takes hold of a reach rod or connection -<i>d</i>. This rod is connected to the end <i>h</i> of the brake lever -<i>e</i>, which is connected by pins at <i>f</i>, <i>g</i> to the brake -bands. If the leverage of the hand lever <i>a</i> is made 6 to 1, that -is, if</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" > - <tbody><tr> - <td class="tdc"><i>ab</i></td> - <td class="tdc"> </td> - <td class="tdc"> 6 </td> - </tr><tr> - <td class="tdc">——</td> - <td class="tdl"> = </td> - <td class="tdc">——</td> - </tr><tr> - <td class="tdc"><i>cb</i></td> - <td class="tdc"> </td> - <td class="tdc">1</td> - </tr> - </tbody> -</table> - -<p class="no-indent">and a force of 50 pounds is applied at <i>a</i>, -a pull of 300 pounds will be exerted at the pin <i>c</i> and, -consequently, along the rod <i>d</i> to the end of the brake lever -<i>e</i>. Then, if the brake lever is made with a ratio of 4 to 1, that -is, if</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" > - <tbody><tr> - <td class="tdc"><i>eh</i></td> - <td class="tdc"> </td> - <td class="tdc"> 4 </td> - <td class="tdc"> </td> - <td class="tdc"><i>eh</i></td> - </tr><tr> - <td class="tdc">——</td> - <td class="tdl"> = </td> - <td class="tdc">——</td> - <td class="tdl"> = </td> - <td class="tdc">——</td> - </tr><tr> - <td class="tdc"><i>eg</i></td> - <td class="tdc"> </td> - <td class="tdc">1</td> - <td class="tdc"> </td> - <td class="tdc"><i>ef</i></td> - </tr> - </tbody> -</table> - -<p class="no-indent">a pull of 300 pounds × 4 = 1,200 pounds will -be exerted at the pin <i>f</i> or <i>g</i>. This total pull must be -divided equally between the arms <i>eg</i> and <i>ef</i>, giving 600 -pounds pull on each. According to the principle of the lever, the -distances through which these forces act are inversely proportional -to the forces acting. It is assumed that the brakeman can exert the -force of 50 pounds through 36 inches; if this is the motion of the end -of the hand lever <i>a</i>, one-sixth of this, or 6 inches, will be -the motion at <i>c</i> and, therefore, at <i>h</i>; one-fourth of 6 -inches or 1½ inches will be the motion at <i>f</i> and <i>g</i>; that -is, <i>f</i> will increase its half of the brake band 1½ inches in -circumference, and <i>g</i> will do likewise with its half, making the -total circumference 3 inches more, or the diameter 1 inch more, and -thereby moving the band away from the drum ½ inch radially. The levers -are all shown in mid-position to make the figure more simple, but the -relative leverages remain the same at all points in the motion.</p> - -<p>This is an example of simple levers, but the force applied at the hand -lever may be increased in a much greater ratio by the use of a device -known as a <i>differential lever</i>. -<span class="pagenum"><a id="Page_41"></a>[Pg 41]</span></p> - -<div class="figcenter"> - <img id="FIG_28" src="images/i_041.jpg" alt="" width="600" height="401" /> - <p class="center"><span class="smcap">Fig. 28</span></p> -</div> - -<p><b>47. The Differential Lever.</b>—The principle of the -operation of the <b>differential lever</b> with which a constantly -increasing force can be applied to the brake strap is illustrated in -<a href="#FIG_28">Fig. 28</a>. Let <i>a o</i> represent a straight lever whose -fulcrum is at <i>o</i>; and let the reach rod be attached at <i>e</i>. In this -position, if</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" > - <tbody><tr> - <td class="tdc"><i>a o</i></td> - <td class="tdc"> </td> - <td class="tdc"> 6 </td> - </tr><tr> - <td class="tdc">——</td> - <td class="tdl"> = </td> - <td class="tdc">——</td> - </tr><tr> - <td class="tdc"><i>e o</i></td> - <td class="tdc"> </td> - <td class="tdc">1</td> - </tr> - </tbody> -</table> - -<p class="no-indent">the effective lever is 6 to 1. If, now, the lever -is moved through 30° to the position <i>b o</i>, the force applied -at <i>a</i> moves through the distance <i>a b</i>, and the reach rod -through the horizontal distance <i>k f</i>, so that the effective -leverage is increased a small amount <i>e k</i> and the ratio of the -arms becomes</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" > - <tbody><tr> - <td class="tdc"><i>a o</i> </td> - </tr><tr> - <td class="tdc">—— .</td> - </tr><tr> - <td class="tdc"><i>k o</i> </td> - </tr> - </tbody> -</table> - -<p class="no-indent">When the lever is moved another 30° to the -position <i>c o</i>, the reach rod moves a distance <i>i g</i>, which -is less than <i>k f</i>, so that the effective leverage is increased by -the amount <i>k l</i> and the ratio of the arms becomes</p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" > - <tbody><tr> - <td class="tdc"><i>a o</i> </td> - </tr><tr> - <td class="tdc">—— .</td> - </tr><tr> - <td class="tdc"><i>l o</i> </td> - </tr> - </tbody> -</table> - -<p class="no-indent">Again, moving the lever 30° more to the position -<i>d o</i>, the reach rod moves through the still shorter distance -<i>j h</i>, which is less than <i>i g</i>, and the effective leverage -becomes very great. It is evident from this that the farther the lever -is moved toward <i>d</i> <span class="pagenum"><a id="Page_42"></a>[Pg -42]</span> the greater becomes the effective leverage. In practice, -it would be impossible to move the lever through the entire quadrant -to advantage, and there would also be more movement of the reach rod -at the beginning of the stroke and less at the end than is needed to -produce the desired effect.</p> - -<div class="figcenter"> - <img id="FIG_29" src="images/i_042.jpg" alt="" width="400" height="558" /> - <p class="center"><span class="smcap">Fig. 29</span></p> -</div> - -<p>From the principle just given, it is plain that, if <i>p o</i>, <a href="#FIG_28">Fig. 28</a>, -represents a brake lever with the reach rod attached at <i>q</i>, -a smaller pull will be exerted on the brake band if the lever is moved -to the position <i>b o</i> than would be exerted if a lever were moved -through the same angle from <i>b o</i> to <i>d o</i>. The movement -from <i>p o</i> to <i>b o</i> is a convenient and easy one for the -engineer to make, while the movement from <i>b o</i> to <i>d o</i> is -inconvenient. To overcome the inconvenience and still to obtain the -advantage of this latter movement, the differential lever shown in -<a href="#FIG_29">Fig. 29</a> is used. By means of an arm placed on the lever, -the point of attaching the reach rod is at <i>l</i> instead of <i>p</i>; hence, -when the handle <i>r b</i> is moved to the position <i>s b</i>, the -point <i>l</i> moves to <i>m</i>, thus securing a greater and gradually -increasing pull with the easier movement of the handle.</p> - -<p>A differential lever may be advantageously used in connection with any -band or post brake and on a drum running in either direction. Such -levers are considered by many preferable to the differential brake.</p> - -<p><b>48. Power Brakes.</b>—Large drums and heavily loaded drums -<span class="pagenum"><a id="Page_43"></a>[Pg 43]</span> -cannot be controlled by hand-power brakes, and in such a case some other -form of power, such as steam, compressed air, or water, must be used.</p> - -<div class="figcenter"> - <img id="FIG_30" src="images/i_043.jpg" alt="" width="600" height="244" /> - <p class="center"><span class="smcap">Fig. 30</span></p> -</div> - -<p><a href="#FIG_30">Fig. 30</a> shows, in outline, how such power is applied. -The movements of the hand lever <i>A</i>, instead of being directly -communicated to the lever operating the brake, merely control the -valve <i>v</i> connected with the cylinder <i>a</i>. By means of this -valve, steam, compressed air, or water is admitted to either end of -the cylinder and this moves the piston in the direction necessary to -apply or release the brake. There are a number of varieties of such -power brakes, differing in structural details, but the action of all -is essentially the same. With steam or air power, the brake would be -applied with its full force almost instantaneously, thus subjecting -the various parts of the mechanism to very severe and objectionable -strains, unless the valves were modified so as to regulate the -admission of the steam or air. One method of controlling this action -is the use of a valve that requires a long travel to give it a full -opening. Such a valve can be opened a little, so as to allow the steam -to leak through and thereby increase the pressure in the cylinder -gradually. As the motion is difficult to regulate, a better method is -by means of a floating valve, described in <i>Hoisting</i>, Part 1.</p> - -<p><b>49. Crank Brake.</b>—In addition to the brake applied to the -drum and intended for use mainly in emergencies, many hoisting engines -are also fitted with a strap brake applied to the crank-disk. In some -states, crank-brakes are required by law. In order to give a large -bearing surface, the crank-disk is made very large. -<span class="pagenum"><a id="Page_1A"></a>[Pg 1]</span></p> - -<hr class="chap x-ebookmaker-drop" /> -<p class="f200"><b>HOISTING<br /><span class="fontsize_90">(PART 4)</span></b></p> - -<p class="f120">Serial 851D<span class="ws5"> </span>Edition 1</p> - -<hr class="chap x-ebookmaker-drop" /> - -<div class="chapter"> -<h2 class="nobreak" id="HOIST_2">HOISTING APPLIANCES</h2> -</div> - -<h3 id="SHEAVE">SHEAVES</h3> - -<p><b>1. Sheaves</b> are grooved iron or steel wheels used to -carry or guide a rope. The general method of mounting them on a frame -for hoisting light loads is shown in <a href="#FIG_1A">Fig. 1</a>. The journal -boxes are so constructed as to be easily taken apart for inspection or repair. -For hoisting heavy loads, the timbers must be braced, as is explained -under the heading Head-Frames in this Section. Sheaves are of two -styles—those composed entirely of cast-iron and those with cast-iron -hubs and rims and wrought-iron or soft-steel arms or spokes.</p> - -<div class="figcenter"> - <img id="FIG_1A" src="images/i_101.jpg" alt="" width="500" height="530" /> - <p class="center"><span class="smcap">Fig. 1</span></p> -</div> - -<p><b>2.</b> The <b>cast-iron sheave</b>, <a href="#FIG_2A">Fig. 2</a>, has arms -with a cross-section, as shown at <i>a b</i>, and with the flanges of the arms -<span class="pagenum"><a id="Page_2A"></a>[Pg 2]</span> -tapering from the hub to the rim; that is, <i>d</i> is greater than -<i>c</i> and <i>f</i> is greater than <i>e</i>. The bottom of the -groove <i>g</i> in the rim should be a circular arc, whose radius is a -little larger than that of the rope used over the sheave, to allow for -the angling of the rope due to its fleeting on the drum. The flanges -<i>h</i> are made quite deep to prevent the rope jumping off.</p> - -<p>This sheave is cheaper than a combined cast-iron and wrought-iron or -steel sheave, and for many purposes it is entirely satisfactory. Its -great weight is an objection, because it adds to the weight on the -journals and also offers considerable resistance to being set in motion -and stopped.</p> - -<div class="figcenter"> - <img id="FIG_2A" src="images/i_102.jpg" alt="" width="600" height="452" /> - <p class="center"><span class="smcap">Fig. 2</span></p> -</div> - -<p>If a sheave is merely used to carry the rope or to deflect it only a -little, the contact and pressure between the rope and the sheave is -small; consequently, the power of the rope to turn the sheave will be -slight. In such a case, when the rope starts or stops quickly, as it -usually does in modern hoisting plants, the heavier the sheave the more -will it lag behind the rope and the greater will be the wear on the -rope due to slipping.</p> - -<p><b>3.</b> The sheave with a cast-iron hub and rim and wrought-iron or -soft-steel spokes, <a href="#FIG_3A">Fig. 3</a>, is an excellent and extensively -<span class="pagenum"><a id="Page_3A"></a>[Pg 3]</span> -used sheave, especially the larger diameters. The spokes are screwed -into the hub and rim and are carried to the right and to the left of -the hub alternately, as shown in <a href="#FIG_3A">Fig. 3 (<i>b</i>)</a>, so as to -take hold of the opposite ends of the hub, thereby giving stiffness to the sheave -against any side stress.</p> - -<div class="figcenter"> - <img id="FIG_3A" src="images/i_103.jpg" alt="" width="500" height="378" /> - <p class="center"><span class="smcap">Fig. 3</span></p> -</div> - -<p>With a sheave having cast-iron arms, the load from the rope is -transmitted to the shaft by a compressive stress through the arms -directly under the load; that is, if a rope runs over the sheave, -<a href="#FIG_2A">Fig. 2</a>, putting a load on it from <i>j</i> to <i>k</i>, -this load will be transmitted as a compressive stress through the arms <i>l</i> -and <i>m</i> to the hub and the shaft. Of course, a part of this load -is carried around the rim to the lower arms and is supported by them -in tension, but these lower arms are not considered in designing the -sheave because cast-iron is of comparatively little value in tension, -whereas it is of great value in compression. In the case of the sheave -with wrought-iron arms, or spokes, <a href="#FIG_3A">Fig. 3</a>, the load is -transmitted around the rim to the side opposite its point of application and is -carried from there to the hub and shaft by the tension of the spokes; -in fact, from the method of construction, the spokes in this sheave act -only by tension. The sheave is strong and rigid, and much lighter than -<span class="pagenum"><a id="Page_4A"></a>[Pg 4]</span> -a cast-iron sheave of the same strength, so that there is less wear -between it and the rope due to any slipping action when it is started -or stopped.</p> - -<div class="figcontainer"> - <div class="figsub"> - <img id="FIG_4A" src="images/i_104a.jpg" alt="" width="300" height="293" /> - <p class="center"><span class="smcap">Fig. 4</span></p> - </div> - - <div class="figsub"> - <img id="FIG_5A" src="images/i_104b.jpg" alt="" width="150" height="300" /> - <p class="center"><span class="smcap">Fig. 5</span></p> - </div> -</div> - -<p><b>4.</b> Sometimes, the spokes, instead of being radial as in <a href="#FIG_3A">Fig. 3</a>, -are made tangent at the center of the wheel, <a href="#FIG_4A">Fig. 4</a>, to an imaginary -circle, which is about 2 inches in diameter for a 10-foot sheave. -Alternate pairs of spokes are made tangent to the opposite sides of -the circle, so that they pull against each other, and this makes the -sheave rigid in both directions. That is, spoke <i>A</i> is tangent to -the right side of the tangent circle and <i>A′</i> to the left side, -while spoke <i>B</i> is tangent to the right side of the circle and -<i>B′</i> to the left side. The pair <i>B B′</i> is joined to one end -of the hub, while the pair <i>A A′</i> is joined to the other end, thus -giving lateral stiffness to the sheave. This arranges the spokes in -groups of four, so that the total number must be some multiple of four. -The tangential direction of the spokes is often necessary in very large -sheaves carrying heavy loads, because with such a sheave it requires -considerable force to turn the shaft in its bearings, and while radial -spokes act only as long levers in turning the shaft, with tangential -spokes there is also a direct pull to do it.</p> - -<p><b>5. Wood-Lined Sheaves.</b>—The rims of all sheaves are made -<span class="pagenum"><a id="Page_5A"></a>[Pg 5]</span> -either solid or with wooden lining, as shown in section in <a href="#FIG_5A">Fig. 5</a>. -One flange <i>a</i> of the rim is a separate piece that is held on by -bolts <i>b</i>. The wooden lining is in the form of blocks placed with -the grain of the wood running radially and held securely by clamping -together the two flanges with bolts, as shown. With such a sheave, -there is much less wear on the rope than there is with one that has a -plain cast-iron rim. The wear of the sheave proper is also avoided, -because as the blocks wear down they are taken out and replaced by new -ones.</p> - -<p><b>6. Diameter of Sheave.</b>—The size of a sheave about which -a rope bends is determined generally by the size of the rope to be -used, as explained under Wire Ropes in <i>Hoisting</i>, Part 2; but, -if the rope is simply to be supported in a straight line, the space -available for setting the sheave and its cost and weight usually -determine the size used. The minimum allowable diameter of sheave -should not be used unless it is necessary to do so, for the larger the -sheave the less will be the wear of the rope due to the bending, and -the longer the life of the rope, but the cost of the sheave, which -increases with the size, puts a limit in the other direction.</p> - -<p><b>7. Rollers and Carrying Sheaves.</b>—Wooden or iron -rollers are sometimes used for rope carriers or guides, instead of -light sheaves, when the rope has merely to be supported and there -is no bending of the rope, excepting the slight amount due to the -sagging between the rollers. The diameter of the rollers is of little -importance in such cases so far as the rope is concerned. If they -are for use on a slope to keep the rope from dragging on the ground, -they must be small, because the cars must run over them, and mine -cars are usually made low because of restricted headroom in the mine. -Rollers and carrying sheaves are fully described and illustrated in -<i>Haulage</i>.</p> - -<p>If a hoisting rope changes its course from a straight line, even if -the deflection is only a small amount, a roller is not advisable and a -sheave should be used, if possible. -<span class="pagenum"><a id="Page_6A"></a>[Pg 6]</span></p> - -<p class="f150 space-above2"><b>CAGES</b></p> - -<h3 id="VERT_CAGE">CAGES FOR VERTICAL SHAFTS</h3> - -<p><b>8.</b> A <b>cage</b> is a carriage used for hoisting mine cars -and their contents, men, timber, etc., in both vertical and inclined -shafts. Cages are built of wood strengthened with iron or steel, or -entirely of iron or steel.</p> - -<div class="figcenter"> - <img id="FIG_6A" src="images/i_106.jpg" alt="" width="500" height="585" /> - <p class="center"><span class="smcap">Fig. 6</span></p> -</div> - -<p><b>9.</b> The cage shown in <a href="#FIG_6A">Fig. 6</a> is much used in the -anthracite region of Pennsylvania. It is made largely of oak strengthened with -<span class="pagenum"><a id="Page_7A"></a>[Pg 7]</span> -iron and the size varies to suit the shaft, being sometimes as large as -6 feet wide by 12 feet long. The general construction of the cage is -evident from the figure, but several appliances that should be common -to all cages in some form or other require detailed explanation.</p> - -<p>A covering <i>a</i>, called a <b>bonnet</b>, protects persons on the -cage from objects falling down the shaft, and is required by law in -some States. This bonnet is made of steel plate with flanges or angle -irons to stiffen it, and is usually inclined. To prevent objects of -moderate size from wedging between the edge of the bonnet and the shaft -lining, the former is sometimes made shorter than the cage, so that -a space of about a foot is left between its lower edge and the shaft -lining. A short bonnet of this character does not, however, fully -protect persons on the cage. The upper part of the bonnet is fastened -to the upper cross-bar of the cage by two hinges and is held up by rods -<i>b</i> that are attached to the bonnet and have sockets at their -lower ends, which fit over pins bolted to the uprights of the cage. By -raising the rods from the pins the bonnet can be lowered so that pipes -or long timbers may be lowered on the cage.</p> - -<p><b>10. Safety catches</b> are intended to prevent a cage falling -in case the hoisting rope breaks. A common form, shown at <i>c</i>, -<a href="#FIG_6A">Fig. 6</a>, and in detail in <a href="#FIG_7A">Fig. 7</a>, -consists of a pair of toothed cams <i>j</i>, <a href="#FIG_7A">Fig. 7</a>, -fastened on each side of the cage near the shaft -guides. The drawbar <i>b</i> to which the rope is attached extends -through the top cross-piece of the cage and through the cylinder -<i>d</i>, at the bottom of which is a plate <i>c</i> supplied with -lugs for the rods <i>f</i> that connect it with the levers <i>g</i>. -Inside the cylinder are three powerful rubber springs, which are in -compression so long as the cage hangs from the rope, but are extended -if the rope breaks, drawing the rods <i>f</i> down and with them the -ends of the levers <i>g</i> to which they are attached; and, since the -levers are pivoted, their other ends are moved upwards and with them -the rods <i>k</i>. The cams <i>j</i> are each attached to one end of -the rods <i>k</i> in such a manner that as the rods move upwards they -rotate the cams inwards until they come in contact with the shaft -<span class="pagenum"><a id="Page_8A"></a>[Pg 8]</span> -guides. The teeth of the cams grasp the wooden shaft guides and stop -the descent of the cage. The cams are provided with projections -<i>a</i> and <i>l</i> that strike the guide and thus prevent the cams -turning entirely around. <a href="#FIG_7A">Fig. 7 (<i>a</i>)</a> shows the springs -extended and the dogs <i>j</i> just about to grasp the shaft guides, while -<a href="#FIG_7A">Fig. 7 (<i>c</i>)</a> shows the position of the dogs when -the springs are compressed as they are when hoisting. At <i>e</i> in cylinder -<i>d</i>, <a href="#FIG_7A">Fig. 7 (<i>b</i>)</a>, there are slots for the -lugs of plate <i>c</i> to move up and down as the spring is compressed -or extended. Instead of rubber springs, helical steel springs are -sometimes used, and with a somewhat different design flat steel springs -are used.</p> - -<div class="figcenter"> - <img id="FIG_7A" src="images/i_108.jpg" alt="" width="600" height="430" /> - <p class="center"><span class="smcap">Fig. 7</span></p> -</div> - -<div class="figcenter"> - <p> </p> - <img id="FIG_8A" src="images/i_109.jpg" alt="" width="450" height="576" /> - <p class="center"><span class="smcap">Fig. 8</span></p> -</div> - -<p>The cams, or dogs, may be placed at any point along the upright post -of the cage, and in some cases two sets of cams are used on each side, -one set at the top and another in the middle, both sets being connected -by rods so that they work together. Practical tests of these catches, -made by allowing the cage to drop, show that they are, as a rule, -very efficient devices. The cams usually take hold at once, the cage -<span class="pagenum"><a id="Page_9A"></a>[Pg 9]</span> -dropping only a few inches, or, at most, a few feet if the guides are -dry and free from oil. When the guides are very greasy or wet, the cage -may drop several feet before the cams take a firm hold and stop it, and -with ice-covered guides, instances are given where the cage has fallen -15 feet before the cams ploughed their way through the ice and took firm -<span class="pagenum"><a id="Page_10A"></a>[Pg 10]</span> -hold of the guides; but in so doing the momentum the cage acquired was -so great that the guides were destroyed. Fortunately for the utility of -safety catches, ropes are usually broken while a loaded cage is being -raised, and the cage has an upward momentum; if a rope breaks when the -cage is descending at a speed of 30 or 40 feet a second, its momentum -is so great that either the catches or guides break. The catches -generally hold and either the guides or cage suffer more or less injury -under such circumstances. Instead of being placed near the top of -the cage the dogs are frequently placed near the center, or near the -bottom; in some cases two sets of dogs have been used, one set being at -the top and the other at the bottom. Instead of being cam-shaped with -a number of small teeth on the rim of the cam, as shown in <a href="#FIG_7A">Fig. 7</a>, -the dogs are now frequently made consisting of one or more strong straight -teeth on each side of the guide. These teeth are operated similarly -to those shown in <a href="#FIG_7A">Fig. 7</a>, and are driven into the -guides if the rope breaks, thus holding the cage more firmly than the -cam-shaped guides, particularly where the guides are wet.</p> - -<p id="TABLE_I" class="f120 space-above2"><b>TABLE I</b></p> - -<table class="fontsize_120" border="0" cellspacing="0" summary=" " cellpadding="0" rules="cols" > - <thead><tr> - <th class="tdc bb2" colspan="8"> </th> - </tr><tr> - <th class="tdc bb" colspan="3">Platform</th> - <th class="tdc bb" colspan="3">Guides</th> - <th class="tdc bb" rowspan="3"> Safe Load <br />Pounds</th> - <th class="tdc bb" rowspan="3"> Weight<br />Pounds</th> - </tr><tr> - <th class="tdc bb" colspan="2">Width</th> - <th class="tdc bb" rowspan="2"> Length <br />Feet</th> - <th class="tdc bb" rowspan="2">Size<br /> Inches </th> - <th class="tdc bb" colspan="2"> Distance Between </th> - </tr><tr> - <th class="tdc bb">Feet </th> - <th class="tdc bb"> Inches </th> - <th class="tdc bb">Feet</th> - <th class="tdc bb"> Inches </th> - </tr> - </thead> - <tbody><tr> - <td class="tdc">4</td> - <td class="tdc">3</td> - <td class="tdc">6</td> - <td class="tdc">6 × 6</td> - <td class="tdc">4</td> - <td class="tdc">6</td> - <td class="tdc">5,000</td> - <td class="tdc">2,000</td> - </tr><tr> - <td class="tdc">6</td> - <td class="tdc"> </td> - <td class="tdc">10</td> - <td class="tdc">6 × 10</td> - <td class="tdc">6</td> - <td class="tdc">3</td> - <td class="tdc">8,000</td> - <td class="tdc">3,800</td> - </tr><tr> - <th class="tdc bt2" colspan="8"> </th> - </tr> - </tbody> -</table> - -<p><b>11. The Heavy Steel Cage.</b>—The cage that is shown in <a href="#FIG_8A">Fig. 8</a> -is made of iron and steel except the wood flooring, which is laid in -two courses, one lengthwise and one diagonal. The joints should not be -driven too tightly, as the wood is likely to swell. The track is bolted -to the floor, or <b>deck</b>, of the cage. The cast-steel safety dogs -are operated by steel springs <i>a</i>, coiled about the bars <i>b</i>, -<span class="pagenum"><a id="Page_11A"></a>[Pg 11]</span> -which are connected to the drawbar <i>c</i> by chains, as shown. The -drawbar drops if the rope breaks and thus assists the action of the -springs <i>a</i>. This cage is in use at both coal and iron mines, and -is built to suit any size of shaft and guides. Standard sizes are given -in <a href="#TABLE_I">Table I</a>.</p> - -<p><b>12. The Light Steel Cage.</b>—<a href="#FIG_9A">Fig. 9</a> shows a -light steel cage much used at gold and silver mines. It has a spring drawbar and -steel safety dogs, operated by steel springs, as in <a href="#FIG_8A">Fig. 8</a>, -but the floor is of steel grating in order to give as little air -pressure as possible against the cage. The openings <i>a</i> in the -side frames are provided so that through them the nuts can be tightened -on the bolts that hold the shaft guides. The cage is provided with -bails <i>b</i> that swing down over each end of a car to hold it on the -cage.</p> - -<div class="figcenter"> - <img id="FIG_9A" src="images/i_111.jpg" alt="" width="400" height="668" /> - <p class="center"><span class="smcap">Fig. 9</span></p> -</div> - -<p><b>13. Multiple-Deck Cages.</b>—Cages are sometimes built that -have two or more decks or platforms one above the other, thus giving -greater hoisting capacity to a shaft. A two-deck, safety, hoisting cage -is shown in <a href="#FIG_10A">Fig. 10</a>. The upper deck is heavier than in a -single-deck cage of similar construction. The lower deck is suspended from the -<span class="pagenum"><a id="Page_12A"></a>[Pg 12]</span> -upper deck by means of pins so that it may be removed at any time. A -double-deck cage may be used by first changing the car on the upper -deck and then bringing the lower deck to the track level and changing -the other car. Time can be saved by having two track levels, both at -the loading and landing stations, enabling both decks to be loaded and -unloaded at the same time.</p> - -<div class="figcenter"> - <img id="FIG_10A" src="images/i_112.jpg" alt="" width="250" height="714" /> - <p class="center"><span class="smcap">Fig. 10</span></p> -</div> - -<p><b>Multiple-deck cages</b> have been mainly used at ore mines in -America and very few coal mines have been equipped with them. Cages are -also built to accommodate two cars placed either side by side or end to end.</p> - -<div class="figcenter"> - <img id="FIG_11A" src="images/i_113.jpg" alt="" width="275" height="721" /> - <p class="center"><span class="smcap">Fig. 11</span></p> -</div> - -<h3 id="AUTO_CAGE" class="space-above2">AUTOMATIC DUMPING CAGES</h3> - -<p><b>14.</b> A <b>dumping cage</b> is a cage so constructed that at the -proper place it can be automatically tipped sufficiently to dump the -contents of a car that is on it and will then right itself for the down -<span class="pagenum"><a id="Page_13A"></a>[Pg 13]</span> -trip, thus avoiding the necessity of removing the car from the cage, -and saving time at the head. The construction of the cage is such -that the car is held firmly in place while dumping. The principle of -the self-dumping cage is illustrated in <a href="#FIG_11A">Fig. 11</a>, the cage -being shown in its highest and lowest positions. The cage is made in two parts -<i>a</i> and <i>b</i>. The fixed frames <i>b</i> slide on the guides -<i>k</i> and have attached to them the safety catches and hoisting -gear. The movable part <i>a</i> is united to the frame <i>b</i> by -the hinge <i>c</i>. The platform <i>d</i>, on which the car rests, -is fastened to the movable part <i>a</i> by the support <i>e</i> -and further secured by the braces <i>f</i>. At the top of <i>a</i> -is attached the wheel <i>g</i> that runs along the rail <i>h</i>, -keeping <i>a</i> in an upright position until it reaches the dumping -place <i>i</i>. Here the rail <i>h</i> is bent as shown and the wheel -<span class="pagenum"><a id="Page_14A"></a>[Pg 14]</span> -<i>g</i> is made to follow it by means of the guide <i>j</i>. This -throws the top of <i>a</i> over so as to incline the platform and -dump the car that is on it. On lowering, the cage rights itself when -<i>g</i> passes below the point <i>i</i>. The part <i>b</i> is kept in -a vertical position by means of shoes that slide on the main guides <i>k</i>.</p> - -<p>It is possible to dispense with the guide rail <i>h</i> by attaching a -flange to the top of <i>a</i> at the back, to slide on the main guide -<i>k</i>. This flange should be shorter than the shoe on <i>b</i>. The -main guide is cut away at the point where this flange comes when the -wheel <i>g</i> enters the curved guide <i>j</i>, leaving an opening -just large enough to allow the flange on <i>a</i> to pass through. The -shoe on <i>b</i>, being longer, completely spans the space and cannot -pass through, but makes <i>b</i> move straight up on the main guides.</p> - -<p>The bottom of the cage in <a href="#FIG_11A">Fig. 11</a> has an interrupted track, -and at the bottom of the shaft the track is also interrupted, as shown in the -plan at the bottom of the figure, but in such a way that when the cage -is resting at the bottom this portion of the track <i>n</i> projects -up through the bottom of the cage and makes a continuous track. When -the cage is raised the wheels of the car drop into the spaces <i>n</i> -in the cage bottom, thus preventing the car from running off the cage -during hoisting or dumping.</p> - -<p><b>15. Slope, or Inclined-Shaft, Hoisting.</b>—In a slope, or -inclined shaft, the mine cars are attached directly to the hoisting -rope and hoisted singly or in trains for inclinations less than 35°, -at which inclination the material will begin to fall from the top of -the car. For steeper slopes, it is customary to use a slope cage or -carriage on which the mine car is hoisted, or else to dump one or -more cars of the material into a gunboat, or skip, at the bottom of -the slope or at some landing along the slope, and to then hoist the -gunboat, or skip.</p> - -<p><a href="#FIG_12A">Fig. 12</a> shows a cage for use in a slope or steeply inclined -shaft. It is made of steel with timber platform and differs from a vertical shaft -cage mainly in having its upper frame inclined and in running on four -<span class="pagenum"><a id="Page_15A"></a>[Pg 15]</span> -wheels <i>a, b</i>. These wheels usually run on timber guides, so that -the safety dogs <i>c</i> will take hold of the guide in case the rope -breaks. For slopes of variable inclination, the platform <i>d</i> may -be made adjustable by means of a hand lever so as to be always level.</p> - -<div class="figcenter"> - <img id="FIG_12A" src="images/i_115.jpg" alt="" width="500" height="536" /> - <p class="center"><span class="smcap">Fig. 12</span></p> -</div> - -<p><b>16.</b> A <b>slope carriage</b> is a frame so constructed that when -rails are placed on the top and a mine car run on them the car will be -practically horizontal. The carriage is mounted on wheels and axles in -order to follow the slope tracks, and is supplied with a drawbar, or -with hooks, as shown in <a href="#FIG_13A">Fig. 13</a>, for attachment -to the hoisting rope. -<span class="pagenum"><a id="Page_16A"></a>[Pg 16]</span></p> - -<p>These carriages are sometimes built to run on a slope track of the same -gauge as the mine cars, but to insure stability they have generally a -broader gauge. The headroom necessary is governed not so much by the -form of the carriage as by the length of the car and the inclination -of the seam. This height is less when the cars are placed on the -carriage with their length across the slope than when they are run on -lengthwise; but this arrangement increases the width of the slope. When -the inclination is very steep, the wheels are sometimes placed on the -sides of the carriage and above its center of gravity and run between -two tracks or guides, on each side of the slope.</p> - -<div class="figcenter"> - <img id="FIG_13A" src="images/i_116.jpg" alt="" width="600" height="442" /> - <p class="center"><span class="smcap">Fig. 13</span></p> -</div> - -<p>The carriage, <a href="#FIG_13A">Fig. 13</a>, is for use on slopes of a uniform -inclination. It is made almost entirely of heavy timber, is stiff and simple of -construction, and is easy to repair. Its details will be readily -understood from the illustrations, except perhaps, the device for -locking the car to prevent its running off during the hoist. The middle -portion of the platform <i>a</i> having a piece of the car track on it, -<span class="pagenum"><a id="Page_17A"></a>[Pg 17]</span> -may move vertically up or down. As shown in the side elevation, it -is resting on the horizontal timbers <i>b</i> of the carriage in a -position ready for hoisting. At the end of the hoist, when the cage -settles on the keeps <i>c</i>, shown in the end elevation, this -platform reaches them first and is supported by them while the rest of -the carriage descends still farther until the timbers <i>d</i> rest -on the keeps also. The track on the platform <i>a</i> is then at the -same level as that on <i>d</i>, and the car can be run off and replaced -by another. When the empty car is on, the carriage is lifted from the -keeps, but the platform <i>a</i> remains until the timbers <i>b</i> -pick it up, when the keeps are swung back out of the way and the -carriage is lowered.</p> - -<p>Slope carriages usually have the tracks running crosswise so that the -car is pushed on from the side instead of from the end.</p> - -<h3 id="SKIP">SKIPS, OR GUNBOATS</h3> - -<p><b>17. Skips</b> are self-dumping cars used for hoisting -material from shafts or slopes. In a vertical shaft, they run in -guide tracks; but in a slope they have wheels and run on a track like -a car. In the anthracite region of Pennsylvania, skips are called -<b>gunboats</b>.</p> - -<p>As the skip is not detached from the hoisting rope, time is saved at -the top over that needed to unhook and hook the cars to the rope or to -remove and place the cars on the cage. But since dumping the material -into the skip and again on the surface produces considerable fine -material, skips, or gunboats, are seldom used for any material, such -as coal, that is often lessened in value by being broken. The skip, or -gunboat, shown in <a href="#FIG_14A">Fig. 14</a> is closed along the top <i>a</i> -and open at the end <i>b</i>, which is cut at about the angle of the slope in which -it is to be used, so as to remain practically level during the hoist. -It is made of sheet iron, the bottom, sides, and top being stiffened by -angle or <b>T</b> irons, and the back stiffened and protected by 3-inch -planks, backed by 3" × 6" timbers. The wheels of a skip are fixed on -the axles, which run in journal boxes, thus insuring smoother running -<span class="pagenum"><a id="Page_18A"></a>[Pg 18]</span> -than is obtained with loose wheels. The details of the journal -bearings, as shown in <a href="#FIG_15A">Fig. 15</a>, consist of three castings, -the bracket <i>a</i>, which is bolted or riveted to the gunboat, a pivot casting -<i>b</i>, and the bearing proper <i>c</i>. The bearing <i>c</i> rests -on the axle and carries, by means of trunnions <i>d</i>, the pivot -casting <i>b</i>, on the top of which is placed a rubber cushion -<i>e</i> to lessen the shocks between the casting and the bracket.</p> - -<div class="figcenter"> - <img id="FIG_14A" src="images/i_118a.jpg" alt="" width="500" height="425" /> - <p class="center"><span class="smcap">Fig. 14</span></p> - <p> </p> - <img id="FIG_15A" src="images/i_118b.jpg" alt="" width="500" height="450" /> - <p class="center"><span class="smcap">Fig. 15</span></p> -</div> - -<p><b>18. Method of Loading Skips.</b>—In <a href="#FIG_16A">Fig. 16</a>, a skip <i>a</i> -<span class="pagenum"><a id="Page_19A"></a>[Pg 19]</span> -is shown in a slope standing immediately below a level where a car -<i>b</i> is ready to have its load dumped into the skip. Instead of -dumping the mine car directly into the skip, a bin is frequently -provided at the level station, or landing, into which the mine cars -are dumped and from which the material is loaded into the skip through -suitable chutes. The use of such bins makes the hoisting of material -largely independent of the working conditions on the levels and the -hoisting can be more systematically and satisfactorily carried on.</p> - -<div class="figcontainer"> - <div class="figsub"> - <img id="FIG_16A" src="images/i_119a.jpg" alt="" width="250" height="251" /> - <p> </p> - <p class="center"><span class="smcap">Fig. 16</span></p> - </div> - <div class="figsub"> - <img id="FIG_17A" src="images/i_119b.jpg" alt="" width="250" height="281" /> - <p class="center"><span class="smcap">Fig. 17</span></p> - </div> -</div> - -<p>If the material comes to the slope as shown in <a href="#FIG_17A">Fig. 17</a>, it -is necessary to let down a bridge <i>a</i>, on which the car runs, in order to reach -the skip. After the car is dumped, the bridge is lifted out of the way -into the dotted position, so as to leave the slope unobstructed.</p> - -<p><b>19. Method of Dumping Skips.</b> To dump a skip at the -surface, the tracks are extended above the slope mouth, as shown in -Figs. <a href="#FIG_18A">18</a> and <a href="#FIG_19A">19</a>, and are arranged -so that the material may be dumped directly into a bin or into cars as desired. -<span class="pagenum"><a id="Page_20A"></a>[Pg 20]</span></p> - -<p>In the arrangement shown in <a href="#FIG_18A">Fig. 18</a>, the front wheel of -the skip strikes a stop <i>a</i> and, since the bail of the skip is pivoted far -down toward the lower end, as the rope continues to pull, the rear of -the skip is raised and the material is dumped. The objection to this -method is that if the rope is slightly overwound the skip is pulled off -the track and does not then right itself on the track when the rope is released.</p> - -<div class="figcenter"> - <img id="FIG_18A" src="images/i_120.jpg" alt="" width="600" height="571" /> - <p class="center"><span class="smcap">Fig. 18</span></p> -</div> - -<p>In the Lake Superior iron and copper region, many of the dumps are -built as shown in <a href="#FIG_19A">Fig. 19</a>. In this dump, the rails of the -main track <i>a</i> are curved as shown at <i>b</i>; a short distance back of the -beginning of this curve, another track <i>c</i> begins outside the -track <i>a</i> and runs in a straight line parallel to the inclination -of the hoist. The track <i>c</i> is of a wider gauge than <i>a</i>, and -the rear wheels of the skip have a wider tread than the front, so that -they will run on <i>c</i> while the front wheels take the curved track -until they strike the stop <i>d</i>. The rear of the skip will thus be -raised and the material dumped. There are but two tracks in the main -part of the slope. -<span class="pagenum"><a id="Page_21A"></a>[Pg 21]</span></p> - -<div class="figcenter"> - <img id="FIG_19A" src="images/i_121a.jpg" alt="" width="500" height="529" /> - <p class="center"><span class="smcap">Fig. 19</span></p> - <img id="FIG_20A" src="images/i_121b.jpg" alt="" width="500" height="462" /> - <p class="center"><span class="smcap">Fig. 20</span></p> -</div> -<p class="space-above2"><span class="pagenum"><a id="Page_22A"></a>[Pg 22]</span></p> - -<div class="figcenter"> - <img id="FIG_21A" src="images/i_122.jpg" alt="" width="400" height="663" /> - <p class="center"><span class="smcap">Fig. 21</span></p> -</div> - -<p><span class="pagenum"><a id="Page_23A"></a>[Pg 23]</span> -In the method illustrated in <a href="#FIG_20A">Fig. 20</a>, the rear and front -wheels have the same tread, but the rear axle is longer than the front and has -rollers <i>a</i> on each side. These strike the track <i>b</i>, and -while the front wheels follow the curved track <i>c</i> these rollers -run on the track <i>b</i> and thus raise the rear end of the skip.</p> - -<p><b>20. Skip Cage.</b>—Where a self-dumping skip is to be used -in a vertical or highly inclined shaft and it is desired to use safety -catches, the skip <i>a</i> is mounted in a cage or frame <i>b</i>, <a href="#FIG_21A">Fig. 21</a>, -similar to the self-dumping cage, <a href="#FIG_11A">Fig. 11</a>. The skip being pivoted -at <i>c</i> one side of the center, and resting on the frame of the -cage, tends to remain upright until it reaches the dump; but for safety -it is sometimes locked in place by the latch <i>d</i>, which hooks -over the pin <i>e</i>. When near the top, the roller <i>f</i> on the -end of the latch <i>d</i> comes in contact with a bar that depresses -the roller and thus unhooks the latch. The roller <i>g</i> enters and -travels along the guide rails <i>h</i>, tipping the skip. There are two -rollers <i>g</i>, one on either side of the skip. The nose <i>i</i> is -temporarily caught on the roller <i>j</i>, thus stopping the movement -of the skip sidewise and away from the upright guide.</p> - -<h3 id="BUCKET">BUCKETS</h3> - -<p><b>21. Buckets</b>, such as are used for hoisting material -during shaft sinking, are continued in use after mining begins when the -amount of material to be hoisted is small.</p> - -<h3 id="LOCKS">CAR LOCKS</h3> - -<p><b>22.</b> Several methods of keeping the car on the cage have already -been illustrated: by chains, <a href="#FIG_8A">Fig. 8</a>; by bails, -Figs. <a href="#FIG_9A">9</a>, <a href="#FIG_10A">10</a>, and -<a href="#FIG_12A">12</a>; by omitting sections of the rail under -the car wheels, <a href="#FIG_11A">Fig. 11</a>; and by -<span class="pagenum"><a id="Page_24A"></a>[Pg 24]</span> -dropping a portion of the platform, <a href="#FIG_13A">Fig. 13</a>. A very common -way is merely to put a pin through the hole in the drawbar and into the floor -of the cage. Another common device consists of a brake block that fits -between the wheels and can be thrown in from the side by a lever when -the car is in place. Another device consists of a yoke, which, by -means of a lever, is raised when the car is in place so that it passes -about the axle and thus holds the car. A device frequently used on -self-dumping cages is shown in <a href="#FIG_22A">Fig. 22</a>.</p> - -<div class="figcenter"> - <img id="FIG_22A" src="images/i_124.jpg" alt="" width="350" height="656" /> - <p class="center"><span class="smcap">Fig. 22</span></p> -</div> - -<p>The curved bars <i>a</i> of iron, which just fit around the car wheels -as shown, are attached to the loose bars <i>b</i>, on the ends of which -are the weights <i>c</i>. When the cage is at the bottom, these weights -strike on a cross-piece and are raised to the position shown by the -dotted lines, throwing out the bars <i>b</i>, as shown by the dotted -line, thus releasing the wheels. The devices shown in -Figs. <a href="#FIG_11A">11</a>, <a href="#FIG_13A">13</a>, and -<a href="#FIG_22A">22</a> do not come into action until the cage leaves -the landing and the cars must, therefore, be watched until that time. -<span class="pagenum"><a id="Page_25A"></a>[Pg 25]</span></p> - -<h3 id="GUIDES">CAGE GUIDES</h3> - -<p><b>23. Guides</b> are used in all vertical shafts of any -considerable depth and in many highly inclined shafts to keep the cage -from swinging about and striking the sides of the shaft. They are made -of wooden rails, iron rails, or wire ropes. In American mines, timber -guides predominate, although some iron ones are used, and for small -shafts at ore mines wire-rope guides are common. In English mines, wire -ropes, called <i>conductors</i>, are very largely used. This difference -in practice is probably due to the fact that in English mines the -shafts are usually round and the cages are rectangular. In such a -shaft, the wire-rope conductors hang from the head-frame without any -cross-bracing, but they require a strong support, as both the weight -of the ropes and the strain to give the necessary tension come on the -head-frame. When both the shaft and the cage are rectangular, as in -most American mines, timber guides are easily put in and they offer a -good surface for the safety catches to grip.</p> - -<div class="figcenter"> - <img id="FIG_23A" src="images/i_125.jpg" alt="" width="500" height="445" /> - <p class="center"><span class="smcap">Fig. 23</span></p> -</div> - -<p>Wooden guides are always rectangular in cross-section and in the United -States are usually made of yellow pine or other long-grained wood that -does not splinter easily; in some localities, oak or some of the other -harder woods are used. There is no fixed size for cage guides, but 4" × -4", 6" × 8", 8" × 10", and 4¼" × 11" timbers are frequently used.</p> - -<p>The guides are firmly fastened to the shaft buntons with lagscrews or -with bolts countersunk into the guide so as to be clear of the shoes, -and, to secure safety with speed in hoisting, the ends of the guides -must be put together with joints that are not liable to displacement -<span class="pagenum"><a id="Page_26A"></a>[Pg 26]</span> -and that offer no projections to the shoes in passing. The buntons -to which the guides are secured must be so firmly fastened that they -cannot get out of place, and the guides must be set as nearly as -possible in a straight line, because if they are crooked the cage -is thrown back and forth as it travels along them and this not only -increases the strain on the hoisting rope and engine, but sooner or -later loosens and misplaces the guide. <a href="#FIG_23A">Fig. 23</a> -shows a plan of a cage with the bunton <i>A</i>, guides <i>B</i>, and -cage shoes <i>C</i> in their normal positions.</p> - -<h3 id="KEEPS">LANDING FANS OR KEEPS</h3> - -<p><b>24.</b> In order to take the strain off the hoisting rope while a -cage or skip is being loaded or unloaded, a mechanism to support the -cage is placed at the top and at any level of the mine where loading is -done, excepting at the bottom level where all that is usually required -are the cross-timbers for the cage to rest on. These supports have -different names in various localities, being known as <i>fans</i>, -<i>keeps</i>, <i>cage rests</i>, <i>landing dogs</i>, <i>landing -chairs</i>, <i>wings</i>, etc. Their use increases the safety of caging.</p> - -<p><b>25.</b> A common form of keeps is shown in <a href="#FIG_24A">Fig. 24</a>. -The cage <i>a</i> rests on four square bars of iron <i>b</i>, one under each -corner of the cage. These bars have an eye or hub at the lower end -and are keyed to the shafts <i>d</i>, which rest in cast-steel boxes. -The levers <i>e</i> and <i>f</i>, which are also keyed to the ends of -the shafts <i>d</i>, are connected by a rod <i>g</i>. Chains <i>h</i> -prevent the fans from moving too far under the cage. When the cage -is to be lowered, it is first lifted clear of the fans and the lever -<i>e</i> is moved into the dotted position, thus moving the fans -<i>b</i> out of the way and permitting the cage to be lowered. The -inside of the fans have no projections, and the operating mechanism -is such that no harm would come if they were left in the shaft and a -hoist were made, as the cage would open out the fans and pass through -them without any trouble. If, however, the fans are not drawn back at -all the headings in the shaft when the cage is lowered, great damage -results when the cage strikes the projecting fans. To avoid the -<span class="pagenum"><a id="Page_27A"></a>[Pg 27]</span> -possibility of such an accident, fans have been devised that fall back -out of line of the shaft as soon as the weight of the cage is removed -from them.</p> - -<div class="figcenter"> - <img id="FIG_24A" src="images/i_127.jpg" alt="" width="500" height="555" /> - <p class="center"><span class="smcap">Fig. 24</span></p> -</div> - -<p><b>26. Hydrostatic Fans.</b>—Most fans in use are built on the -same principle as those just described, although the details of their -construction may vary. An objection that can be raised against them is -that, with large cages and heavy loads, the jar caused by letting the -cage down on such a rigid support is very hard on the cage. All cages, -particularly heavy ones, suffer much more wear from being landed too -suddenly than from the strains of hoisting. For this reason, it is -advisable to make the upper parts as light as compatible with strength -and the side pieces stronger than needed for the actual strains to -which they are subjected. Hydraulic fans, <a href="#FIG_25A">Fig. 25</a>, have successfully -<span class="pagenum"><a id="Page_28A"></a>[Pg 28]</span> -overcome this trouble. The cylinder shown is one of four on which the -cage rests. The eye at the lower end fits on a bar by means of which -the cylinders are moved backwards and forwards similar to the motion of -the fans <i>b</i>, <a href="#FIG_24A">Fig. 24</a>. In <a href="#FIG_25A">Fig. 25 (<i>a</i>)</a>, -the cage is shown as about to rest on the jaw <i>a</i>. As the cage -settles, it pushes the plunger <i>b</i> downwards, but this action is -resisted by oil in the cylinder at <i>c</i>. At first, this resistance -is very slight, because the <b>V</b>-shaped grooves <i>d</i> in the -plunger, which are of considerable size at the end of the plunger, -allow the oil to escape freely into the upper chamber <i>e</i>. These -grooves, however, taper down to nothing, so that the flow of oil -through them decreases until none can pass except by leakage around the -plunger. This allows the plunger with its load to settle slowly to the -bottom, as shown in <a href="#FIG_25A">Fig. 25 (<i>b</i>)</a>.</p> - -<div class="figcenter"> - <img id="FIG_25A" src="images/i_128.jpg" alt="" width="600" height="388" /> - <p class="center"><span class="smcap">Fig. 25</span></p> -</div> - -<p>If now the cage is lifted and the weight thus removed from the jaw -<i>a</i>, the spring <i>g</i> pushes the plunger <i>b</i> outwards and -allows the oil to run from <i>e</i> back into <i>c</i>.</p> - -<p><b>27. Pneumatic Fans.</b>—A pneumatic fan, shown in section in -<a href="#FIG_26A">Fig. 26</a>, is one in which the shock of the landing is partially -relieved by a cushion of compressed air. The fan is keyed at the bottom to the -<span class="pagenum"><a id="Page_29A"></a>[Pg 29]</span> -shaft <i>a</i> that rotates it, as in <a href="#FIG_24A">Fig. 24</a>. The cylinder -<i>b</i> contains the plunger <i>c</i>, which is kept at the top limit of its -motion by the spring <i>d</i>. When the cage lands in the jaw <i>e</i>, -the plunger descends, compressing the air in the cylinder <i>b</i>. The -air escapes slowly through the ¹/₁₆-inch hole <i>f</i>, thus allowing -the cage to settle into place with very little shock. These fans should -be made of wrought-iron or cast-steel so as not to be easily broken.</p> - -<div class="figcenter"> - <img id="FIG_26A" src="images/i_129.jpg" alt="" width="400" height="557" /> - <p class="center"><span class="smcap">Fig. 26</span></p> -</div> - -<p><b>28. Cage Chairs.</b>—In the case of a cage required to stop at a -large number of levels, it is expensive to provide fans at each level, -and to obviate this a strong steel bar or dog may be used under each -corner of the cage, all four bars being connected to a lever on the -cage, by means of which they can be thrown out at will so as to rest -on supports provided at each level. <a href="#FIG_27A">Fig. 27</a> shows Gray’s patent -cage chair, which operates on this principle. The sliding bars <i>a</i> are -connected by the cross-bars <i>b</i>, which are pivoted at the center -and operated by the bar <i>c</i> through the links <i>d</i>. By moving -the lever <i>e</i> into the position shown, the bars <i>a</i> are -thrown out so as to rest in notches or on wall plates in the shaft. The -springs <i>f</i>, through the cross-bars <i>b</i>, force the sliding -bars <i>a</i> back under the cage when the lever <i>e</i> is released.</p> - -<h3 id="HEAD">HEAD-FRAMES</h3> - -<p><b>29.</b> A <b>head-frame</b> of wood, iron, or steel is built over a -shaft or slope mouth to carry the sheaves over which the hoisting ropes -are conducted from the mine to the drum of the hoisting engine; it also -usually carries the upper portion of the cage guides or, in the case of -a slope, the tracks for cars. -<span class="pagenum"><a id="Page_30A"></a>[Pg 30]</span></p> - -<div class="figcenter"> - <img id="FIG_27A" src="images/i_130a.jpg" alt="" width="500" height="515" /> - <img src="images/i_130b.jpg" alt="" width="500" height="487" /> - <p class="center"><span class="smcap">Fig. 27</span></p> -</div> - -<p><span class="pagenum"><a id="Page_31A"></a>[Pg 31]</span> -A head-frame must be strong enough to bear the strain brought on it due -to the total load hoisted and the pull of the engine in hoisting this -load; it must also be rigid in construction to withstand the severe -vibration and shock to which it is subjected on account of the rapid -hoisting and the jar due to the landing of the cages.</p> - -<div class="figcenter"> - <img id="FIG_28A" src="images/i_131.jpg" alt="" width="600" height="369" /> - <p class="center"><span class="smcap">Fig. 28</span></p> -</div> - -<p>The amount and direction of stresses that a head-frame must resist are -usually determined by applying the parallelogram of forces as follows: -<a href="#FIG_28A">Fig. 28</a> is a simple head-frame at a slope; <i>a</i> is the -drum of the hoisting engine with the rope coming from its upper side and running -over the head-sheave <i>b</i> down to the slope cage <i>c</i>. Assuming -that the angles <i>e</i>, <i>f</i> made by the two portions of the -rope with the horizontal are equal, and that the pull on each part of -the rope is 20,000 pounds, to determine the amount and direction of -the resultant of the two rope pulls, proceed as follows: Extend the -rope lines to the point of intersection <i>g</i> and from there lay -off the two lines <i>g h</i> and <i>g k</i>, to some definite scale, -representing the pull of the rope. If a scale of 2,000 pounds to ⅒ inch -is taken (⅒ inch = 2,000 pounds), <i>g h</i> and <i>g k</i> will each be -<span class="pagenum"><a id="Page_32A"></a>[Pg 32]</span> -1 inch long. Complete the parallelogram by drawing <i>h l</i> parallel -to <i>g k</i> and <i>k l</i> parallel to <i>g h</i>. The diagonal -<i>g l</i> represents the direction and amount of the force acting on -the head-frame due to the pull of the two portions of the rope. The -diagonal, by measurement, is 1½ inches or ¹⁵/₁₀ inches long, and since -each tenth inch equals 2,000 pounds, the stress on the head-frame in -the line of the diagonal <i>g l</i> is 2,000 × 15 = 30,000 pounds. The -figure also shows that the direction of this force is vertical, hence -there is no tendency for the frame to be pulled over to either side -and, theoretically, side bracing is not needed.</p> - -<div class="figcenter"> - <img id="FIG_29A" src="images/i_132.jpg" alt="" width="400" height="541" /> - <p class="center"><span class="smcap">Fig. 29</span></p> -</div> - -<p><b>30.</b> Consider now the case of a vertical shaft, <a href="#FIG_29A">Fig. 29</a>, -in which, as before, <i>a</i> is the drum, <i>b</i> the head-sheave, -<i>c</i> the cage, and <i>d</i> the head-frame, and assume the same -pull of 20,000 pounds on each part of the rope. As before, extend the -lines of the rope, which are the lines of force along which the pulls -due to the engine and the load act, until they intersect at <i>g</i>. -From this point lay off on these lines distances representing the -stresses in the rope to any scale. Using the same scale as before, ⅒ -inch = 2,000 pounds, the lines <i>g h</i> and <i>g k</i> representing -the two forces will be each 1 inch long. Completing the parallelogram -by drawing <i>h l</i> parallel to <i>g k</i>, and <i>k l</i> parallel -to <i>g h</i>, and drawing the diagonal <i>g l</i> through <i>g</i>, -the resultant, <i>g l</i> = ¹⁹/₁₀ inches, represents a stress of 38,000 -pounds. The direction of the resultant is also determined, being in the -line of the diagonal <i>g l</i>. If the head-frame shown in <a href="#FIG_28A">Fig. 28</a> -<span class="pagenum"><a id="Page_33A"></a>[Pg 33]</span> -were used for this case, it would be overturned by this resultant force, -unless the leg on the opposite side of the shaft from the engine -were securely anchored, so an inclined brace <i>m</i> is added to -resist this overturning action. The resultant of all forces acting -on the head-frame should generally fall within the structure if the -greatest stability is to be secured, but when this cannot be done it is -necessary to resist the overturning pull by anchoring the head-frame to -its foundations much more securely than is the case where the resultant -falls within the structure.</p> - -<p>The direction of the resultant force may be obtained by drawing a -line through the intersection of the lines of action of the forces at -<i>g</i> and the center of the head-sheave <i>b</i>, as may be seen in -Figs. <a href="#FIG_28A">28</a> and <a href="#FIG_29A">29</a>.</p> - -<div class="figcenter"> - <img id="FIG_30A" src="images/i_133.jpg" alt="" width="600" height="407" /> - <p class="center"><span class="smcap">Fig. 30</span></p> -</div> - -<p><b>31.</b> In Figs. <a href="#FIG_28A">28</a> and -<a href="#FIG_29A">29</a>, the pull of one hoisting rope running -from the top of the drum was considered, but in most cases it is -necessary to consider the pull from two hoisting ropes, one running -from the top and one from the bottom of the drum <i>f</i>, as shown in -<a href="#FIG_30A">Fig. 30</a>. <i>a b</i> and <i>a′ b′</i> represent the directions -<span class="pagenum"><a id="Page_34A"></a>[Pg 34]</span> -of action of the two forces acting on the hoisting ropes, while the two -vertical forces <i>a c</i> and <i>a′ c</i> acting down the shaft are -approximately equal to the two forces acting toward the drum. There -are, therefore, two resultants <i>a d</i> and <i>a′ d′</i>, the -directions of which are determined by lines from <i>a</i> and <i>a′</i> -through the center of the sheave <i>e</i>. The amounts of these -resultant forces can be determined by the parallelogram of forces as -shown in Figs. 28 and 29. A resultant that is a mean between <i>a d</i> -and <i>a′ d′</i>, both in position and amount, is sometimes taken, or -the greater value as determined from <i>a d</i> or <i>a′ d′</i> and the -greatest inclination as given by <i>a′ d′</i> may be used, as being -the worst theoretical conditions to which the frame may be subjected. -A head-frame usually has a vertical post approximately parallel to -the vertical pull of the rope in the shaft, and an inclined member -<i>g h</i> approximately parallel to the resultant determined by the -parallelogram of forces. If <i>g h</i>, <a href="#FIG_30A">Fig. 30</a>, is parallel -to the resultant, the vertical leg <i>h i</i> is under no strain and merely -supports the end of <i>g h</i>. If the resultant falls between <i>g -h</i> and <i>h i</i>, both of these legs will be under compression. -If the resultant falls outside of <i>g h</i>, the leg <i>g h</i> will -be under compression and <i>h i</i> will be under tension. The head -frame will be most stable when the resultant falls between <i>g h</i> -and <i>h i</i>, but this cannot always be accomplished in building the -frame on account of the conditions at the head of the shaft; nor is it -always advisable to do so from structural considerations.</p> - -<p id="ART_32"><b>32.</b> Since wood is much better adapted to withstand compressive -than tensile stresses and since steel is adapted to withstand either -tensile or compressive stresses, it is much more important that -the members of timber frame conform as closely as possible to the -theoretical line worked out in Figs. 28, 29, and 30 than in the case -of a steel frame. Take, for instance, the case shown in <a href="#FIG_31A">Fig. 31</a>, -where for some local reason it is impossible to put an inclined strut in or -near the line of the resultant stress to withstand the pull that tends -to overturn the head-frame. In a steel structure, <i>a</i> can very -easily be made a tension member by anchoring its lower end to a heavy -<span class="pagenum"><a id="Page_35A"></a>[Pg 35]</span> -foundation. This resists the tendency to overturn and makes a very -stable structure. In practice, braces can generally be located parallel -to the line of resultant strain, <a href="#FIG_29A">Fig. 29</a>, or outside this -line, as shown in <a href="#FIG_30A">Fig. 30</a>, so that the strain due to the pull -of the rope will come mainly on the inclined brace and not on the upright. To distribute -the stress on the foot of the different parts of the frame, an inclined -brace is usually set farther from the shaft than the parallelogram of -forces locates it, and so placed that about two-thirds of the strain -due to the pull of the rope comes on the brace and one-third on the -upright parts of the frame. In order to give the frame a more stable -base and because the base must be larger than the top of the frame to -bring the foundations back from the shaft mouth, usually the members -<i>h i</i> are also slightly inclined.</p> - -<div class="figcenter"> - <img id="FIG_31A" src="images/i_135.jpg" alt="" width="500" height="575" /> - <p class="center"><span class="smcap">Fig. 31</span></p> -</div> - -<p>Wherever permanency of head-frames is required, if steel is obtainable -at a price at all comparable with wood, steel structures are being -used, as timber frames rot. -<span class="pagenum"><a id="Page_36A"></a>[Pg 36]</span></p> - -<p class="f120"><b>TYPES OF HEAD-FRAMES</b></p> - -<p><b>33.</b> There are three types of head-frame construction—<i>the</i> -<b>A</b> <i>type</i>, the <i>square type without an inclined brace</i>, -and the <i>square type with an inclined brace</i>.</p> - -<p><b>34. A Type of Head-Frame</b>.—<a href="#FIG_32A">Fig. 32</a> -shows the construction of a triangular, or <b>A</b>-shaped, head-frame -of which (<i>a</i>) is a side elevation and (<i>b</i>) an end view. -This particular frame is largely used at anthracite mines, but the type -is one quite commonly used for timber frames, though the details of -construction vary in different localities. The height of the frame is -from 30 to 50 feet, and with direct-acting engines this height should -be sufficient to allow a play of at least two-thirds of a revolution -between the cage landing and the overwinding point. The posts <i>a</i> -are parallel to the hoisting rope <i>b</i> as it hangs down the shaft -and the inclined brace <i>c</i>, which resists any thrust that would -tend to rotate the head-frame, is parallel to the resultant pull of -the two parts of this rope <i>b</i>; the inclined braces <i>d</i> -stiffen the frame and help support the cross-timbers <i>m</i> that -support the cage guides <i>e</i>. The sills <i>f</i> are made of three -pieces of timber 8 inches by 14 inches in cross-section. The posts -<i>a</i> rest in cast-iron shoes <i>g</i> that are firmly bolted to -the posts and sills. The inclined braces <i>c</i>, <i>d</i> are fitted -with cast-iron shoes <i>h</i>, <i>i</i>. The post <i>a</i> and the two -braces <i>c</i>, <i>d</i> are held in place at the top of the frame by -the casting <i>j</i>, which also supports the pillow-block <i>k</i>.</p> - -<p>The posts <i>a</i> and the brace <i>c</i> are made up of two pieces of -timber each 8 inches by 14 inches in cross-section. The brace <i>d</i> -consists of one piece of timber 8 inches by 14 inches in cross-section. -The transverse braces <i>l</i> consist of two pieces of timber 6 inches -by 14 inches in cross-section, bolted through the timbers <i>a</i> and -<i>c</i>. The supports <i>m</i> for the guides are single pieces of -8" × 8" timber. The center post, as shown in <a href="#FIG_32A">Fig. 32 (<i>b</i>)</a>, -is braced by the two pieces <i>n</i>, <i>o</i>, which are supported by two -timbers <i>p</i>, <i>q</i> bolted to the two outside posts. The posts -<i>a</i> and the inclined braces <i>c</i> are further braced by the -tie-rods <i>r</i>, <i>s</i>, <i>t</i>, and <i>u</i>, all of which are -fitted with turnbuckles, as shown at <i>v</i>. The different posts are -firmly bolted together, the bolts being fitted with cast-iron washers. -<span class="pagenum"><a id="Page_37A"></a>[Pg 37]</span></p> - -<div class="figcenter"> - <img id="FIG_32A" src="images/i_137.jpg" alt="" width="600" height="441" /> - <p class="center"><span class="smcap">Fig. 32</span></p> -</div> - -<p class="space-above2"><span class="pagenum"><a id="Page_38A"></a>[Pg 38]</span></p> - -<div class="figcenter"> - <img id="FIG_33A" src="images/i_138.jpg" alt="" width="600" height="355" /> - <p class="center"><span class="smcap">Fig. 33</span></p> -</div> - -<p><a href="#FIG_33A">Fig. 33</a> shows the construction of the ordinary -timber gallows frame used at many ore mines.</p> - -<p><a href="#FIG_34A">Fig. 34</a> shows a steel <b>A</b> frame, of which the principal -dimensions are as follows: height to sheave center 48 feet; base 33 feet 10 inches -by 56 feet. Legs <i>a</i> and <i>b</i> are made of laced channels, as -are also the central upright posts and cross-braces. The forward -inclined legs are made of <b>I</b> beams. The weight of the frame is -98,000 pounds without the sheaves. The advantages claimed for this type -of design are that it gives a very strongly braced frame while using a -minimum of material. Also, in cases of overwinding, the cage goes over -the top of the frame without injury to the frame, and should men be -overwound they would fall only the height of the frame instead of being -crushed against the top.</p> - -<p><b>35. Square Type Without Inclined Brace.</b>—<a href="#FIG_35A">Fig. 35</a> -shows a steel frame in which the tendency to be overturned by the pull of -the rope is resisted by a nearly vertical tension leg as explained -in <a href="#ART_32"><b>Art. 32</b></a>. Each leg of the frame is built of channel -bars connected by lattice bracing, as shown, and the legs are stiffened by -horizontal channel cross-bars similarly braced and also by diagonal -tie-rods, provided with turnbuckles.</p> - -<div class="figcenter"> - <img id="FIG_35A" src="images/i_platetop.jpg" alt="" width="600" height="278" /> - <img src="images/i_platebott.jpg" alt="" width="600" height="258" /> - <p class="center"><span class="smcap">Fig. 35</span></p> -</div> -<p class="space-above2"><span class="pagenum"><a id="Page_39A"></a>[Pg 39]</span></p> - -<div class="figcenter"> - <img id="FIG_34A" src="images/i_139.jpg" alt="" width="500" height="556" /> - <p class="center"><span class="smcap">Fig. 34</span></p> -</div> - -<p>Springs are sometimes placed under the journals of the head-sheaves -to lessen the strain on the rope while starting the load; the 15-foot -head-sheaves of the Robinson deep mine at Johannesburg have locomotive -springs under the journal boxes, the actual load on each spring due to -the weight of the sheave, rope, skip, and rock being equal to about -<span class="pagenum"><a id="Page_40A"></a>[Pg 40]</span> -20,000 pounds; it was estimated that the sheave would thus be lowered -by the load on it, about 3 inches, which would be equal to an action -of a spring giving motion of 6 inches at the cage. Springs can often -be used both on the rope and under the sheave in the same plant to advantage.</p> - -<div class="figcenter"> - <img id="FIG_36A" src="images/i_140.jpg" alt="" width="500" height="638" /> - <p class="center"><span class="smcap">Fig. 36</span></p> -</div> - -<p><b>36. Square Type With Inclined Brace.</b>—<a href="#FIG_36A">Fig. 36</a> -shows a very substantial frame with square tower and inclined brace. -<span class="pagenum"><a id="Page_41A"></a>[Pg 41]</span></p> - -<div class="figcenter"> - <img id="FIG_37A" src="images/i_141.jpg" alt="" width="500" height="602" /> - <p class="center"><span class="smcap">Fig. 37</span></p> -</div> - -<p>Its principal dimensions are as follows: height to sheave center 59 -feet 6 inches; base of tower 15 feet 8 inches by 14 feet; distance -of bottom of inclined leg from vertical post 48 feet. Each end post -<i>a</i> is composed of two channels, double-latticed. The horizontal -members <i>b</i> are <b>I</b> beams and each inclined member <i>c</i> -is made up of two angles. The inclined leg <i>d</i> is trussed as shown -and built of channel and angle beams, the main member being made of two -<span class="pagenum"><a id="Page_42A"></a>[Pg 42]</span> -channels, the incline and base members of the truss being made up of -two angles, and the short vertical member of two channels. The center -post of the tower is similar to the end posts, except that the uprights -are <b>I</b> beams instead of channels. The frame is designed for a -static weight of 16,000 pounds and for a maximum strain on the cable of -32,000 pounds.</p> - -<p><a href="#FIG_37A">Fig. 37</a> shows a frame of similar form, but in which the -landing platform is placed at a height above the surface, so that the cars -hoisted can be run off on a trestle and thus be delivered at the top of -a car, breaker, tipple, or ore house. Its principal dimensions are as -follows: height to sheave center 75 feet; base 40 feet 11¾ inches by -21 feet 8½ inches. The leg <i>a</i> is made of two angles. The bracing -leg <i>b</i> is built of two angles. The diagonal braces <i>c</i> are -single angles. The horizontal braces are angles or channels of various -sizes depending on the stresses.</p> - -<p><b>37.</b> The <b>head-sheave</b> is supported directly on top of -the main frame, as shown in Figs. 32, 34, 36, and 37, or a small -superstructure <i>a</i> is built on top of the main frame, as shown in -<a href="#FIG_38A">Fig. 38</a>, so that the base of the sheave journals is -perpendicular to the resultant pull on the frame, that is, to the -theoretical direction of the inclined leg of the frame if one is used.</p> - -<p><b>38.</b> Timber frames are usually built by the mining company from -its own designs. Steel frames are generally built by the structural -steel companies from detailed plans and designs furnished by the mining -company, or from a skeleton diagram furnished by the mining company, -giving the loads on the rope and the general conditions about the shaft -to which the frame must conform, the frame being then designed and -erected in detail by the steel company.</p> - -<p><b>39. Enclosing Head-Frames.</b>—Head-frames are sometimes wholly -or partially enclosed to protect them and the men from the weather. -A covering of boards is warmest. All woodwork should be painted with -fireproof paint and ample means for extinguishing fire should be -provided. A covering of corrugated sheet iron well painted on both sides -<span class="pagenum"><a id="Page_43A"></a>[Pg 43]</span> -to prevent rusting is often used instead of wood and lessens the danger -of fire, but is not as warm a covering as wood.</p> - -<div class="figcenter"> - <img id="FIG_38A" src="images/i_143.jpg" alt="" width="500" height="565" /> - <p class="center"><span class="smcap">Fig. 38</span></p> -</div> - -<p><b>40.</b> In many states, it is required by law that the top of the -shaft be protected by a fence or by gates to prevent persons falling -down the shaft. This protection is secured at the sides of head-frames -by extra timbers or beams forming part of the frame, or by means of a -fence placed near the sides of the frame. The ends of the shaft are -protected by a bar placed across uprights, by gates that swing like an -<span class="pagenum"><a id="Page_44A"></a>[Pg 44]</span> -ordinary door, or more generally by vertical sliding gates that are -raised by the cage when it comes to the surface and drop into place -when the cage descends. Similar gates, doors, or bars should be used at -all landings below the surface.</p> - -<p class="f120"><b>HEAD-FRAME SPECIFICATIONS</b></p> - -<p><b>41.</b> The following is a sample set of specifications for a steel -head-frame to be built from detailed plans furnished by the mining company.</p> - -<p>This head-frame to be made from drawings to be furnished by the—— -Coal Company, and placed on foundations furnished by said company.</p> - -<p><b>Material.</b>—Structure to be built throughout of soft structural -steel, net strength 55,000 to 62,000 pounds per square inch; elastic -limit not less than 30,000 pounds per square inch; elongation, 25 per -cent.; bending test, bend flat on itself without fracture.</p> - -<p>Builder agrees to guarantee structure to withstand strains specified -on drawings with factor of safety of 10, to provide for possible -overwinding or sticking in shaft.</p> - -<p>No steel shall be used less than ¼ inch thick except for lining or -filling vacant places.</p> - -<p><b>Workmanship.</b>—The tower to be built in a neat and workman-like -manner. The pitch of the rivets (distance between centers) shall not -exceed 6 inches or sixteen times the thinnest plate, nor be less than -three diameters of the rivets.</p> - -<p>The rivets used shall generally be ½ inch, ¾ inch, and ⅞ inch in -diameter.</p> - -<p>The distance between edges of any piece and the center of rivet hole -shall not be less than 1¼ inches, except for bars less than 2½ inches -wide; when practicable it shall be at least two diameters of the -rivet. All rivet holes shall be spaced and punched, so that when the -several parts are assembled together a rivet of ¹/₁₆ inch less diameter -than the hole can be entered hot into any hole, without reaming or -drifting. The rivets when driven should fill the holes. The heads must -be rounded; they must be full and neatly made, and be concentric to -the rivet hole, and thoroughly pinch the connecting pieces together. -Field riveting must be reduced to a minimum. All joints and connections -shall be neatly made, the several parts to be brought together without -twists, bends, or open joints.</p> - -<p><b>Inspection.</b>—All facilities for inspecting the material and -workmanship shall be given by the builders during the erection of the -head-frame. The company reserves the right to reject any or all parts -not built in accordance with the plans or these specifications. Final -inspection of work 1 month after being in actual service. -<span class="pagenum"><a id="Page_45A"></a>[Pg 45]</span></p> - -<p><b>Painting.</b>—All work, before leaving the shops, shall be -thoroughly cleaned from all loose rust and scale, and be given one good -coat of paint well worked into all joints and open spaces. In riveted -ironwork, the surfaces coming in contact shall each be painted before -being riveted together. Bottoms of bearing plates and any parts that -are not accessible for painting after erection shall have two coats of -paint. After the structure is erected in place, it shall be given one -coat of paint. All recesses that will retain water, or through which -water can enter, must be filled with thick paint or some waterproof -cement before receiving the final painting. The paint shall be a -lampblack paint, mixed with pure linseed oil, or of red lead mixed with -raw linseed oil containing Japan dryer.</p> - -<p><b>General Clauses.</b>—The specifications and drawings are intended -to cooperate and to indicate the principal dimensions and requirements -necessary to the complete structure. It being understood that -while some work may be shown in the plans and not described in the -specifications, or vice versa, and some minor details and fastenings -are omitted from both plans and specifications, the work is to be -executed without extra charge therefor, the same as if the minutest -details were set forth in full in both drawings and specifications. -The contractor is to make good any defects of material or workmanship -developing within 1 year after final acceptance.</p> - -<p>The contractor shall furnish a location plan and also two copies of the -detail shop drawings for convenience in making future alterations and -repairs.</p> - -<p><b>Erection.</b>—The head-frame is to be erected complete, secured to -foundations provided by the _______ Company.</p> - -<p>Contractor shall furnish all foundation bolts and washers. Iron -stairway with hand rails beside main back bracers and platform with -wooden floor under sheaves, also iron stairs from platform under -sheaves to back sheave pedestal for oiling. Wood furnished by -the ______ Company.</p> - -<p>Price includes all material for completion of work delivered, erected, -and riveted in place and painted.</p> - -<p>The ______ Company will furnish and place in position the sheaves, with -the shafts and boxes belonging to the same, also the wooden guides.</p> - -<p><b>Delivery.</b>—The head-frame to be erected, complete, and secured -to foundations in ______ weeks from date of order. -<span class="pagenum"><a id="Page_46A"></a>[Pg 46]</span></p> - -<h3 id="HOOKS">DETACHING HOOKS</h3> - -<div class="figcenter"> - <img id="FIG_39A" src="images/i_146.jpg" alt="" width="600" height="525" /> - <p class="center"><span class="smcap">Fig. 39</span></p> -</div> - -<p><b>42.</b> In hoisting, there is more or less danger of overwinding -or lifting the cage too far, and dashing it against the top of the -head-frame, or if the top is open the cage may be pulled entirely over -the top. <b>Detaching hooks</b> are intended to prevent this. Several -varieties of such hooks are made, which differ from each other only -in their smaller details. In all of them, detachment is effected by -passing the rope through a circular hole in an iron plate or through an -iron cylinder, the diameter of which is sufficient to allow the upper -portion of the hooks to pass through when passing upwards, but the -lower portion is made larger and so arranged that when this larger part -strikes the plate the upper portion is forced open and the hoisting -rope released. After the upper part has been thus opened, it is too -<span class="pagenum"><a id="Page_47A"></a>[Pg 47]</span> -large to pass back through the opening and the plate and the cage is -therefore held suspended. <a href="#FIG_39A">Fig. 39</a> shows such -a hook. It consists of two outside fixed plates slightly narrower -at the top than the diameter of the hole in the disengaging plate -<i>h</i>. Between the frame plates <i>a</i> are two inner plates -<i>b</i> that move about a strong pin <i>c</i> passing through both -plates <i>a</i> and <i>b</i>, but near the bottoms there are two -projections <i>d</i> to prevent the hook from passing entirely through -the hole. The winding rope is attached to the top shackle <i>e</i> and -the cage to the lower shackle <i>f</i>. When the two movable plates -<i>b</i> are closed as tightly as possible at the top about the pin -of the shackle <i>e</i>, they are secured by a copper pin <i>g</i>. -In case of overwinding, when the hook passes into the hole of the -disengaging plate <i>h</i>, the two projections <i>k</i> on plates -<i>b</i> are pressed inwards, shearing off the copper pin <i>g</i> and -allowing the plates <i>b</i> to turn about the central bolt <i>c</i>, -thus releasing the shackle <i>e</i>. The plates <i>b</i> are then in -such a position that the projections <i>l</i> on them cannot pass down -through the hole. The cage then hangs by the hooks from the disengaging -plate, and the rope passes on. An objection raised against this hook -is that, being constructed of plates, there is considerable surface in -contact between the moving parts, and unless they are regularly taken -apart and oiled, there is danger of their rusting firmly together.</p> - -<p>In England, detaching hooks are used quite commonly, and also in -certain parts of the Central Basin in the United States, but they have -not yet been generally adopted throughout the United States.</p> - -<p><b>43.</b> It is claimed by many that such devices inspire the -engineer with a misleading feeling of security; that they are more or -less complicated in construction and so need care, and destroy the -simplicity of the plant; that they may be the direct cause of accident -by introducing new elements of danger; that they add to the cost; and -that they are not thoroughly reliable. Again, it is held that the -surest prevention of overwinding is obtained by the employment of a -sober, reliable, and competent engineer, who is held personally -<span class="pagenum"><a id="Page_48A"></a>[Pg 48]</span> -responsible for overwinding accidents; by having a good brake and an -engine thoroughly under the control of the engineer; by a reliable -method of indicating the position of the cage; by sufficient height -to head-sheaves to allow of considerable hoisting over and above that -necessary for landing.</p> - -<h3 id="SIGNALS">SIGNALING</h3> - -<p><b>44.</b> Some method must be provided for communicating between the -bottom or any level of a shaft and the top landing or the engine room, -also between the top landing and the engine room, so that the hoisting -engineer may be notified when both the head-man and foot-man are ready -for him to hoist. A common method of signaling is by means of a gong, -bell, or triangle placed in the engine room and connected by a wire -or small wire-rope with the point from which it is desired to signal. -Attempts have been made in different localities and by different -associations to adopt a standard code of hoisting signals, and while it -would be advantageous if this could be done, none of the attempts made -have been entirely successful. Although there is no uniform system of -signals, one bell generally means stop, two bells lower, three bells -hoist, and four bells hoist men.</p> - -<div class="figcenter"> - <img id="FIG_40A" src="images/i_148.jpg" alt="" width="600" height="353" /> - <p class="center"><span class="smcap">Fig. 40</span></p> -</div> - -<p><b>45. Hammer-and-Plate Signal.</b>—<a href="#FIG_40A">Fig. 40</a> shows a -hammer-and-plate signal, the plate being a piece of boiler iron or steel. The hammer is -<span class="pagenum"><a id="Page_49"></a>[Pg 49]</span> -often located beneath the plate instead of above, as shown. Another -style of hammer-and-plate is shown in <a href="#FIG_41A">Fig. 41</a>. The hammer -is made of 2-inch square iron and heavy enough to balance the weight of wire -hanging in the shaft and to take the sag out of the horizontal wire -connecting the top of the shaft with the lever <i>a</i>. A simple dial -turned by a ratchet motion attached to the lever <i>a</i> is sometimes -used to show the number of strokes, and thus check the number counted -by the engineer. The dial is reset by the engineer as soon as he -understands the signal.</p> - -<div class="figcontainer"> - <div class="figsub"> - <img id="FIG_41A" src="images/i_149a.jpg" alt="" width="200" height="555" /> - <p class="center"><span class="smcap">Fig. 41</span></p> - </div> - <div class="figsub"> - <img id="FIG_42A" src="images/i_149b.jpg" alt="" width="375" height="540" /> - <p class="center"><span class="smcap">Fig. 42</span></p> - </div> -</div> - -<p><b>46. Electric Bells.</b>—Electric bells operated by push buttons are -rapidly coming into use for mine signaling on account of the ease and -completeness with which such a system can be installed. Electric flash -lights are also extensively used for signaling purposes. The principle -<span class="pagenum"><a id="Page_50A"></a>[Pg 50]</span> -of action and details of the wiring for electric signals and flash -lights have been described in <i>Transmission, Signaling, and Lighting</i>.</p> - -<p><b>47. Speaking Tubes.</b>—The laws of certain states require -speaking tubes, in addition to the ordinary means of signaling. These -speaking tubes are generally made of 2-inch iron pipe and are from 300 -to 1,500 feet long, and are often provided with whistles at the end -of the pipe and at each level of the mine, by which the attention of -persons at any level can be attracted or the whistle may be omitted and -the attention of persons attracted merely by rapping on the pipe with a -piece of iron.</p> - -<div class="figcenter"> - <img id="FIG_43A" src="images/i_150.jpg" alt="" width="350" height="579" /> - <p class="center"><span class="smcap">Fig. 43</span></p> -</div> - -<p><b>48. Pneumatic Gong Signal.</b>—<a href="#FIG_42A">Fig. 42</a> shows an -attachment that can be connected to a speaking tube and that is widely used for -signaling. It consists of a brass cylinder <i>a</i> fitted with a piston <i>b</i> -containing valves <i>c</i>. The gong <i>d</i> is attached to the -cylinder <i>e</i> inside of which the clapper <i>f</i> fits loosely. -When the piston is pushed inwards, as shown by the arrow, by means -of the handle, the air in the cylinder and in the pipe <i>h</i> is -compressed and forces the clapper <i>f</i> upwards against the gong -<i>d</i>. The arrangement of these gongs in the mine is shown in <a href="#FIG_43A">Fig.43.</a> -A cylinder and whistle are usually placed at each landing -<span class="pagenum"><a id="Page_51A"></a>[Pg 51]</span> and a -gong and whistle in the engine room, though, if desired, a cylinder, -whistle, and gong may be placed at each landing and in the engine room.</p> - -<p><b>49. Telephones.</b>—Telephones connecting the different -levels with the top and the engine room are now frequently used in -connection with other signal systems, but they are not as well adapted -as bells or gongs for rapid-hoisting signaling.</p> - -<div class="transnote bbox space-above2"> -<p class="f120 space-above1">Transcriber’s Notes:</p> -<hr class="r5" /> -<p class="indent">The illustrations have been moved so that they do not break up - paragraphs and so that they are next to the text they illustrate.</p> -<p class="indent">Typographical and punctuation errors have been silently corrected.</p> -</div> -<div style='display:block; margin-top:4em'>*** END OF THE PROJECT GUTENBERG EBOOK HOISTING APPLIANCES ***</div> -<div style='text-align:left'> - -<div style='display:block; margin:1em 0'> -Updated editions will replace the previous one—the old editions will -be renamed. -</div> - -<div style='display:block; margin:1em 0'> -Creating the works from print editions not protected by U.S. copyright -law 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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