[Kit Gerhart]

Originally Posted by John Wanninger

We're also using the 42mm, 256:1 FisherPrice/Banebot combo to drive our arm through a a 54:14 (sprocket/chain/sprocket) reduction. Our arm load is approximately 100 in-lb max static load, with tube. We're using dynamic braking, no counterbalancing and closed loop proportional control. We limit maximum PWM signal to stay within the 100 to 160 command range. Our arm is fairly flexible and has some 'whip' to it - I think that may help to limit peak loads.

It's interesting to hear that some of you have had much better success with the 256:1 F/P combo than we did. We were using about a 4:1 reduction from the BaneBots to our arm, but with very little flexibility anywhere in the system. Also, our closed-loop position control, at times, probably put the motor from full speed forward to near full speed reverse when the arm reaches position. Basically, we were putting extreme shock loads on the B/B. We switched to a home made gear set using a big CIM for our arm. The gear stuff is fine, but we ran into structural problems with the arm itself (now fixed) due to the shock loads. All of this gives me a real appreciation for the tricks they use to soften the shock load in car and motorcycle drive trains to keep from breaking things.