Please Explain

[Neo]

Guys,

I know i'm a dumbass for even asking but I can't help myself...take a look at the drawing below and can someone please explain why this doesn't work!

If the overbalanced wheel's mass is greater than all the weights combined how is it not possible that the wheel is unable to lift even five at one time?

[grim]

No you're not a dumbass for asking a question.

One problem up front is that you have one sphere trying to lift five spheres thru a 1:3 (approx) pulley/belt system, a mechanical disadvantage. While this would provided more speed on your sphere elevator than the big cog wheel would turn by 3 times, it would also require 3 times the force (approx).

Will look at the lever advantage of your cog wheel/pulley and refine this answer a bit. Ok.

Center of cog wheel to center of sphere measures 1" on this screen.
Large belt pulley rim to center of cog wheel measures 3/8". 1 divided by 3/8 gives a mechanical advantage of 2.66, so if the one sphere weighs 1 lb, it can turn the belt with a 2.66 lb force max. Now divide that by the 1:3 pulleys ratio, and you get approx. .89 lb lift force at the elevator pulley. With the equivalent of 5 lbs of spheres on the elevator, you have insufficient force to balance one, much less lift five.

The elevator should turn the cog wheel backwards.

Hope this helps.

[jim_mich]

Neo, let me take a crack at an explaination.
You have five balls shown on the left. But you must lift them to the height of six balls before the top ball will roll off. The ramps use up some of this height to make the balls roll away from the lift and back to the lift. So the working part of the wheel is from about 1 o'clock to about 5 o'clock. When the ball enters the 1 o'clock notch it will not produce much torque on the wheel. Then at the 3 o'clock position it reaches its maximum torque. And as it rolls off the wheel at the bottom it again has little torque. When you calculate the average torque and compare it to the torque on the belt you will come up short. If you were to use a second belt in place of the wheel and gear the ratios appropriately then you would improve the situation, but I believe you will still come up short.

[John Lindsay]

To make it as simple as possible and "generally" speaking ;) x weight up y distance needs z force, x weight down y distance yields z force. This is why there is an unlimited amount of arrangements that do not achieve self-rotation. John

[Neo]

Thanks Guys,

Thanks again clearing up my ignorance on these matters...now I have a better understanding of why it doesn't work.