Posted: 2/9/2007 3:01:32 PM EDT
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I have to make a compound machine that has an input force of 2N and an output force of 8N-10N. So far this is what I've got. Its a wheel and axle connected to a block and tackle.  How much bigger will I have to make the wheel than the axle in order to get an output force at least 4x bigger? If it was a frictionless environment the wheel would have to be 2x bigger than the axle or more right? How much should I compensate for friction? I am using metal pulleys I bought that have bearings(or w/e they are called) in them but they do seem to have some friction. I can only get them to make about 3-4 revolutions before they stop. |
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It's not a function of the size of the pulleys...generally for every pulley, you gain a mechanical advantage...except when they're all fixed, the way you've got them layed out If you want a mechanical advantage of 4, 5, or 6...use 4, 5, or 6 pulleys in a vertical configuration...like a block-and-tackle...with 1 fixed pulley..each separate cable that is lifting (apart from the one applying the force) will give you a mech. adv. Use different size pulleys just to keep the cables from tangling up in one another |
No 3 are fixed just to change the dir. of the string. The ones with the weight attached(there are 2 there) are not fixed. |