My Invention

[TinselKoala]

@johnny: some research terms for you:

Moment
Arm
Moment arm
Torque

You might also like to take a look at a book called "Statics and Dynamics: Vector mechanics for engineers" by Beer and Johnston (get a used copy if you can find one) and their "supersite" here:

http://www.mhhe.com/engcs/engmech/beerjohnston/

You do have some calculus under your belt, I hope.

keep building, cheers....
--TK

[zoelra]

Sorry, I posted before finishing my thoughts.  This build will assume the bob has already been trapped by the cord and will test the falling of the counter weight and lifting of the bob.  I plan on testing different pulley positions, bob heights, and counter/bob weights to see if I can find the right combination.  The way the two weights are interconnected with the cord, this looks to be a basic 1:1 pulley setup.  As the counter weight falls, the bob is lifted.

I hope to complete a few tests this evening.

[johnny874]

  Rick,
with something like this, modifying things shouldn't be to difficult.
It may be lifting at a 2:1 ratio might work.
One thing I thought of is that when the pendulum swings outward, it landing on a ramp might help. It would be some what of a trade off.
It would lose some force because the ramp would be pushing it further out. But as long as it has more force than the counter weight, then that's okay. It could be that it would take a two step process.

[zoelra]

James,

The first test I wanted to do was a 1:1 setup to see if the 2.5lb counter weight would lift the 2.5lb bob.  One end of the cord is fixed to the center of the counter weight and the other end to the center of the bob.  Well there was no lift with this setup.  In fact the bob actually pulled down slightly raising the counter weight.  However, when I added some weight to the counter weight, the reset action ocurred as you predicted.  I need to take the mechanism off the wall and drill new holes to get the setup close to your specs.  I also need to adjust the pulley mechanisms as the cord kept getting caught between the bearings and the side washers.  See my second post for a short video of this first test.

[zoelra]

The video is too large to attach.  I will work on reducing the size.