{"id":1969,"date":"2024-07-30T22:00:07","date_gmt":"2024-07-30T22:00:07","guid":{"rendered":"https:\/\/workhouse.sweetdishy.com\/?p=1969"},"modified":"2024-07-30T22:00:07","modified_gmt":"2024-07-30T22:00:07","slug":"reversible-and-irreversible-machines","status":"publish","type":"post","link":"https:\/\/workhouse.sweetdishy.com\/index.php\/2024\/07\/30\/reversible-and-irreversible-machines\/","title":{"rendered":"\u00a0REVERSIBLE AND IRREVERSIBLE MACHINES"},"content":{"rendered":"\n

The machine which starts to move in reverse direction after removal of effort, is called reversible machine. Simple rope and pulley drive is a reversible machine<\/em>. The machine, which does not move in reverse direction after removal of effort, is called irreversible<\/em> or self-locking machine<\/em>. Screw jack, worm and worm wheel, and winch crab are examples of irreversible machine.<\/p>\n\n\n\n

13.3.1  Condition for Reversibility of Machine<\/h4>\n\n\n\n

 <\/p>\n\n\n\n

Frictional loss = Input \u2013 Output = P<\/em> \u00d7 y<\/em> \u2013 W<\/em> \u00d7 x<\/em><\/p>\n\n\n\n

 <\/p>\n\n\n\n

When effort is removed, i.e., P<\/em> = 0. The work done by the load exceeds the frictional loss and load starts to move in reverse direction.<\/p>\n\n\n\n

\"equation\"\/<\/figure>\n\n\n\n

Thus for a reversible machine the efficiency must be greater than 50%.<\/p>\n\n\n\n

13.3.2  Condition for Irreversibility or Self-locking of Machine<\/h4>\n\n\n\n

In the case of self-locking machine, after load removal friction force overcomes the work done by the load in reverse direction.<\/p>\n\n\n\n

\"equation\"\/<\/figure>\n\n\n\n

Thus for an irreversible of self-locking machine efficiency should be less than 50%.<\/p>\n\n\n\n

Example 13.1:<\/strong> In a lifting machine, it was found that the effort was moved by 300 mm to lift a load by 10 mm. This machine is used to lift a load of 50,000 N by an effort of 2,000 N. Determine (i) velocity ratio, (ii) mechanical advantage, (iii) efficiency, (iv) ideal effort, (v) effort lost in friction, (vi) the load which could have been lifted with the given effort under the ideal conditions, and (vii) friction of the machine.<\/p>\n\n\n\n

Solution:<\/p>\n\n\n\n

    \n
  1. \"equation\"<\/li>\n\n\n\n
  2. \"equation\"<\/li>\n\n\n\n
  3. \"equation\"<\/li>\n\n\n\n
  4. \"equation\"<\/li>\n\n\n\n
  5. Effort lost in friction = Actual effort \u2013 Ideal effort = 2,000 \u2013 1,666.66 = 333.33 N<\/li>\n\n\n\n
  6.  \"equation\"<\/li>\n\n\n\n
  7. Friction of machine = Ideal load \u2013 Actual load = 60,000 \u2013 50,000 = 10,000 N<\/li>\n<\/ol>\n\n\n\n

    Example 13.2:<\/strong> In a lifting machine, an effort of 100 N raised a load of 1,000 N and an another effort of 500 N raised a load of 6,000 N. Find (i) law of machine, (ii) effort required to lift a load of 8,000 N, and (iii) maximum mechanical advantage.<\/p>\n\n\n\n

    Solution:<\/p>\n\n\n\n

    Let\u00a0P<\/em>\u00a0be the effort,\u00a0W<\/em>\u00a0be the load, and m be the slope of the graph as shown in\u00a0Figure 13.4.<\/p>\n\n\n\n

    \"Figure<\/figure>\n\n\n\n

    Figure 13.4<\/strong> Law of Machine<\/p>\n\n\n\n

    \"Equation\"\/<\/figure>\n\n\n\n
      \n
    1. Law of the machine, \"Equation\"C<\/em> can be determined from first or second loading conditions of the question.\"Equation\"<\/li>\n\n\n\n
    2. P<\/em> = 0.08W<\/em> + 20 = 0.08 \u00d7 8,000 + 20 = 660 N<\/li>\n\n\n\n
    3. Maximum mechanical advantage \"Equation\"<\/li>\n<\/ol>\n\n\n\n

      <\/a>Example 13.3:<\/strong> In a lifting machine, an effort of 1 kN was required to lift a load of 30 kN, the velocity ratio of the machine being 50. Is the machine reversible? If so what effort can be removed so that the machine is at the point of reversing?<\/p>\n\n\n\n

      Solution:<\/p>\n\n\n\n

      \"Equation\"\/<\/figure>\n\n\n\n

      Since the efficiency is more than 50%, the machine is reversible.<\/p>\n\n\n\n

      Ideal load that can be lifted with an effort of 1 kN.<\/p>\n\n\n\n

      \"Equation\"\/<\/figure>\n\n\n\n

      Example 13.4:<\/strong> In a lifting machine, the effort required to lift loads 200 N and 300 N were 50 N and 60 N, respectively. If the velocity ratio of the machine is 20, determine (i) law of machine, (ii) efficiencies corresponding to loads of 200 and 300 N, (iii) effort lost in friction in both the cases, and (iv) the maximum efficiency which can be expected from the machine.<\/p>\n\n\n\n

      Solution:<\/p>\n\n\n\n

        \n
      1.   \"Equation\"<\/li>\n\n\n\n
      2.   \"Equation\"<\/li>\n\n\n\n
      3.  \"Equation\"Effort lost in friction for 200 N load, P<\/em>f<\/em>200<\/sub> = 50 \u2013 10 = 40 NEffort lost in friction for 300 N load, P<\/em>f<\/em>300<\/sub> = 60 \u2013 30 = 30 N<\/li>\n\n\n\n
      4.   \"Equation\"<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

        The machine which starts to move in reverse direction after removal of effort, is called reversible machine. Simple rope and pulley drive is a reversible machine. The machine, which does not move in reverse direction after removal of effort, is called irreversible or self-locking machine. Screw jack, worm and worm wheel, and winch crab are examples of irreversible machine. […]<\/p>\n","protected":false},"author":1,"featured_media":1967,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[345],"tags":[],"class_list":["post-1969","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-lifting-machines"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/07\/mechanical-gears-.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/1969","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=1969"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/1969\/revisions"}],"predecessor-version":[{"id":1970,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/1969\/revisions\/1970"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/1967"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=1969"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=1969"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=1969"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}