Gearbox Question

[MrForbes]

The mini Cim has about 2/3 the torque of the full size CIM

Spool size is also part of the equation...what are you using to wind up whatever it is you're pulling?

[cadandcookies]

Also make sure that your winch release isn't slowing you down-- we found out at our week 0 this weekend that the winch we were using (a COTS boat winch) was introducing so much friction when we released that it cut our shot length to 25% of our new version.

[Ginger Power]

We made our own spool and it has a 2" diameter. Right now it is really holding our shot back but we plan on decreasing the rolling friction it has. Do you think that by decreasing the spool diameter that will significantly help?

[MrForbes]

Decreasing the diameter will increase the force applied to what the winch is pulling. But it will also increase the time it takes to move it.

[golucky66]

Team 4055 had a problem with tensioning our catapult. I don't know exactly what is a problem with yours but we had a few issues.

1) We had one CIM tensioning the catapult

2) There was a large amount of friction because we didn't use bearings (Bad decision)

3) We were applying force to our arm at an extremely small angle.

Fix

1) We designed a completely bolt on mechanism. It was a 4.5 to 1 ratio with two CIMs.

2) We upgraded to a 1/2 in keyed shaft with Oil Impregnated Bronze Bearing
http://www.amazon.com/Spyraflo-PB1-5...bronze+bearing

3)Force has it's maximum efficiency when the force is applying perpendicular to the arm. Relocating our attachment point for our winding strap helped.