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Mulyiplying the effect on the load in a rope system?

  1. Dec 8, 2007 #1
    Alright, so this is a crude drawing of my current system set-up:

    [​IMG]

    So what I want is a "multiplication" effect, like a 2 inch movement on the "A" side will cause a 4 inch movement on the load side.

    So what should I put in the red circle to get this effect?
     
  2. jcsd
  3. Dec 8, 2007 #2

    Danger

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    Welcome to PF, Desmond.
    The setup as shown will simply give you a reversal of force. That is, you will need to pull down on the user end of the rope with a force in excess of the load's weight. It doesn't matter what sort of wheel you put at the top.
    To gain (or in your case lose) mechanical advantage, you need a compound pulley system.
    Note that pulley systems are usually applied for the opposite of your goal. Pulling the rope 1 foot will result in a 6 inch movement of the load, but requires only half of the force.
    Your goal is usually achieved by other means.
     
  4. Dec 8, 2007 #3

    brewnog

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    This sounds like homework.

    Desmond, have a think about how you could use another pulley to lift the load more quickly than you're pulling. If not; have a look at some simple lifting arrangements on cranes.
     
  5. Dec 8, 2007 #4
    Thanks a lot guys, I just looked at some diagrams of compound pulley systems and now I have what I need (well, I still gotta put the system in a braced position).

    You guys have been really helpful, I'm glad I joined PF.

    My physics course at school in gonna start soon so I'll probably be here more often then.
     
  6. Dec 8, 2007 #5

    brewnog

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    No problem.

    Danger - you need to clear out your PM box.
     
  7. Dec 8, 2007 #6

    Danger

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    Tell me about it. :rolleyes:
    The problem is that I keep all of my PM's, because they're important to me. I used to clean out the box by saving them to HD. Then W killed my computer a couple of months ago, so I have to use either this one at work or hers at home. Either way, I don't have a place to stash them. I'm thinking to relocate one of my desktop or tower Mac's to a room with an electrical outlet and drop my stuff in there.
    Unfortunately, my e-mail account is similarly plagued, so you can't even get hold of me that way. I'll gladly PM you my phone #, but there might be a problem with the time zones. It's a cell, so I have it on all of the time, but I might not be awake.
     
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