{"id":1182,"date":"2024-07-09T16:17:11","date_gmt":"2024-07-09T10:47:11","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=1182"},"modified":"2025-07-16T15:03:09","modified_gmt":"2025-07-16T09:33:09","slug":"straight-line-mechanisms","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/me\/theory-of-machines\/straight-line-mechanisms","title":{"rendered":"STRAIGHT LINE MECHANISMS"},"content":{"rendered":"<p style=\"text-align: justify;\">A mechanism built in such a manner that a particular point in it is constrained to trace a straight line path within the possible limits of motion, is known as a straight line motion mechanism.<\/p>\n<p style=\"text-align: justify;\">Straight line motion can be generated by either sliding pairs or turning pairs. Sliding pairs are bulky and gets<br \/>\nworn out rapidly. Therefore, turning pairs are preferred over sliding pairs for generating straight line motion. Straight line motion can be generated either accurately or approximately.<\/p>\n<p style=\"text-align: justify;\"><strong>Exact Straight Line Mechanisms<\/strong><\/p>\n<ul style=\"text-align: justify;\">\n<li>Peaucellier Mechanism<\/li>\n<li>Hart Mechanism<\/li>\n<li>Scott &#8211; Russel Mechanism<\/li>\n<\/ul>\n<p style=\"text-align: justify;\"><strong>Approximate Straight Line Mechanisms<br \/>\n<\/strong><\/p>\n<ul style=\"text-align: justify;\">\n<li>Grasshopper mechanism<\/li>\n<li>Watt mechanism<\/li>\n<li>Tchebicheff Mechanism<\/li>\n<li>Robert\u2019s Mechanism<\/li>\n<\/ul>\n<p style=\"text-align: justify;\"><strong>INTERMITTENT MOTION MECHANISM<\/strong><\/p>\n<p style=\"text-align: justify;\">Intermittent motion is a sequence of motions and dwells. A dwell is a period in which the output link remains\u00a0 stationary while the input link continues to move. Intermittent motion mechanism are used to convert continuous motion into intermittent motion. The mechanisms used for this purpose are the Geneva wheel and the ratchet<br \/>\nmechanism.<\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.madeeasy.in\/study\/me\/theory-of-machines\/straight-line-mechanisms\/#Geneva-Wheel-Geneva-Mechanism\" >Geneva Wheel \/ Geneva Mechanism<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.madeeasy.in\/study\/me\/theory-of-machines\/straight-line-mechanisms\/#Ratchet-and-Pawl-Mechanism\" >Ratchet and Pawl Mechanism<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.madeeasy.in\/study\/me\/theory-of-machines\/straight-line-mechanisms\/#Davis-Steering-Mechanism\" >Davis Steering Mechanism<\/a><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Geneva-Wheel-Geneva-Mechanism\"><\/span><strong>Geneva Wheel \/ Geneva Mechanism<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">The Geneva mechanism is shown in Fig. The input crank is typically a motor driven at a constant speed. The Geneva wheel is fitted with at least three equispaced, radial slots. <img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-1197 alignright\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/four-stop-geneva-mechanism.jpg\" alt=\"Four-stop Geneva Mechanism\" width=\"284\" height=\"243\" \/><\/p>\n<p style=\"text-align: justify;\">The mechanism shown here is having four slots. The crank has a pin that enters a radial slot and causes the Geneva wheel to turn through a portion of a revolution. When the point leaves that slot, the Geneva wheel remains stationary until the pin enters the next slot. This results in the intermittent motion of the Geneva wheel. The crank is also fitted with an arc segment, which engages a matching cutout on the periphery of the Geneva wheel when the pin is out of the slot. This keeps the Geneva wheel stationary and in the proper location for the next entry of the pin. The number of slots determine the number of \u201cstops\u201d of the mechanisms where stop is synonymous with dwell. The slot provided must be tangential to the path of pin while engaging with the pin to reduce shock and jerk.<\/p>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Ratchet-and-Pawl-Mechanism\"><\/span>Ratchet and Pawl Mechanism<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-1199 alignright\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/ratchet-and-pawl-mechanism.jpg\" alt=\"Ratchet and Pawl Mechanism\" width=\"294\" height=\"251\" \/><\/p>\n<p style=\"text-align: justify;\">Fig. shows a Ratchet and Pawl mechanism. The arm pivots about the centre of the toothed ratchet wheel and is moved back and forth to index the wheel. The driving pawl rotates the ratchet wheel (or ratchet) in the counter clockwise direction and does no work on the return (clockwise) trip. The locking pawl prevents the ratchet from reversing direction while the driving pawl returns. Both pawls are usually spring-locked against the ratchet. The mechanism is widely used in devices such as \u201cratchet\u201d wrenches, winches etc.<\/p>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Davis-Steering-Mechanism\"><\/span>Davis Steering Mechanism<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">Davis steering gear is shown in Fig. This type of gear has only sliding pairs. Two arms <em>AG and BH <\/em>are fixed to the stub axles <em>AC <\/em>and <em>BD <\/em>respectively. <em>CAG <\/em>and <em>DBH <\/em>form two similar bell &#8211; crank levers pivoted at <em>A <\/em>and <em>B <\/em>respectively. <em>KL <\/em>is a cross-link which is constrained to slide parallel to <em>AB<\/em>. The ends of the cross-link <em>KL <\/em>are pin-jointed to two sliders <em>S<\/em><sub>1<\/sub> and <em>S<\/em><sub>2<\/sub> as shown in Fig. These sliders are free to slide on links <em>AG <\/em>and <em>BH <\/em>respectively. The whole mechanism is in front of the front wheels.<\/p>\n<p style=\"text-align: justify;\">During the straight motion of the vehicle, the gear is in the mid-position, with equal inclination of the arms <em>AG<\/em> and <em>BH <\/em>with the verticals at <em>A <\/em>and <em>B<\/em>. The steering is achieved by moving cross-link <em>KL<\/em> to the right or left of the mid-position. The steering gear for taking a right turn is shown in Fig. (below). <em>K<\/em>&#8216;<em>L&#8217;<\/em>\u00a0shows the position of the crosslink <em>KL <\/em>while taking a right turn.<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1201\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/davis-steering-gear-straight-drive.jpg\" alt=\"Davis steering gear for straight drive\" width=\"291\" height=\"201\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-gear-straight-drive.jpg 291w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-gear-straight-drive-130x90.jpg 130w\" sizes=\"auto, (max-width: 291px) 100vw, 291px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-1202 alignright\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/davis-steering-gear-taking-right-turn-300x255.jpg\" alt=\"Davis steering gear taking a right turn\" width=\"300\" height=\"255\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-gear-taking-right-turn-300x255.jpg 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-gear-taking-right-turn.jpg 343w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p style=\"text-align: justify;\"><strong>Determination of angle \u03b1<\/strong><\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-1186 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/davis-steering-mechanism.jpg\" alt=\"Davis Steering Mechanism\" width=\"678\" height=\"523\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-mechanism.jpg 678w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/davis-steering-mechanism-300x231.jpg 300w\" sizes=\"auto, (max-width: 678px) 100vw, 678px\" \/><\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-1189 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/equations-300x51.jpg\" alt=\"Equations\" width=\"612\" height=\"104\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/equations-300x51.jpg 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/equations.jpg 649w\" sizes=\"auto, (max-width: 612px) 100vw, 612px\" \/><\/p>\n<p style=\"text-align: justify;\">or<\/p>\n<p style=\"text-align: justify;\">Generally, <em>b\/l <\/em>= 0.4 to 0.5, so that of \u03b1 = 11.3\u00b0 to 14.1\u00b0. There will be friction and more wear due to sliding<br \/>\npairs in the Davis steering gear. It fulfills the fundamental equation of gearing in all the positions. However, due to<br \/>\neasy wearing it becomes inaccurate after some time.<\/p>\n<p style=\"text-align: justify;\"><strong>Ackermann Steering Mechanism<\/strong><\/p>\n<p style=\"text-align: justify;\">The Ackermann steering gear has only turning pairs. Fig. (a) shows the steering gear for straight drive. The turning pairs are : AK, KL, LB and AB. The two short arms AK and BL are of equal length and are connected by pin-joints with front wheel axle AB at A and B respectively. AC and BD are the stub axles so that CAK and DBL form bell-crank levers. ABLK form a four-bar linkage. KL is the track rod.<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-1204\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-straight-line-300x258.jpg\" alt=\"Ackermann steering gear for straight line\" width=\"300\" height=\"258\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-straight-line-300x258.jpg 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-straight-line.jpg 371w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-1205 alignright\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-taking-right-turn-300x212.jpg\" alt=\"Ackermann steering gear taking a right turn \" width=\"344\" height=\"243\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-taking-right-turn-300x212.jpg 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/ackermann-steering-gear-taking-right-turn.jpg 435w\" sizes=\"auto, (max-width: 344px) 100vw, 344px\" \/><\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-1383 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/determination-of-angle-a-300x152.png\" alt=\"determination of angle a\" width=\"300\" height=\"152\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/determination-of-angle-a-300x152.png 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/determination-of-angle-a.png 457w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p style=\"text-align: justify;\"><strong>Determination of angle \u03b1<br \/>\n<\/strong><br \/>\nConsider the Ackermann steering gear, as shown in figure (b) taking a right turn. The instantaneous centre <em>I<\/em><br \/>\nlies on a line parallel to the rear axis at a distance of approximately 0.3 l above the rear axis. It may be seen that the<br \/>\nwhole mechanism of the Ackermann steering gear is on the back of the front wheels. From figure (c), we have,<\/p>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1384 size-full\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-105322.png\" alt=\"\" width=\"863\" height=\"361\" srcset=\"https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-105322.png 863w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-105322-300x125.png 300w, https:\/\/www.madeeasy.in\/study\/wp-content\/uploads\/2024\/07\/Screenshot-2024-07-11-105322-768x321.png 768w\" sizes=\"auto, (max-width: 863px) 100vw, 863px\" \/><\/p>\n<p style=\"text-align: center;\"><a class=\"btn btn-danger\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/me\/theory-of-machines\/pantograph\/\" target=\"_blank\" rel=\"noopener\">&lt;&lt; Previous<\/a> | <a class=\"btn btn-success\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/me\/theory-of-machines\/hooke-joint\/\" target=\"_blank\" rel=\"noopener\"> Next &gt;&gt;<\/a><br \/>\n<strong> Must Read: <\/strong> <a href=\"https:\/\/study.madeeasy.in\/subjects\/what-is-the-theory-of-machines\/\" target=\"_blank\" rel=\"noopener\"><strong>What is the Theory of Machines?<\/strong><\/a><\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A mechanism built in such a manner that a particular point in it is constrained to trace a straight line<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[287,10],"tags":[372,371,370,369,368],"class_list":["post-1182","post","type-post","status-publish","format-standard","hentry","category-theory-of-machines","category-me","tag-ackermann-steering-gear-taking-a-right-turn","tag-davis-steering-gear-taking-a-right-turn","tag-davis-steering-mechanism","tag-geneva-wheel","tag-ratchet-and-pawl-mechanism"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1182","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=1182"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/1182\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=1182"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=1182"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=1182"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}