Motor for arm: what should be used when?

[JamesCH95]

Originally Posted by HarveyAce

We have two window motors powering the upper half or our arm. We had the problem of the motors not being able to drive the arm past parallel with the ground due to max torque on the arm due to gravity, which was stalling or window motors. We have two strands of surgical tubing as a counter-balance. An estimation of the torque load would be about 31.5 ft-lbs. (3.5ft*approx 9 lbs weight). Our windows get warm but don't overheat (they did only once due to excessive testing in a short time span). we are using 2 vics to control the motors, using an analog control (a second Attack 3 joystick). this way we can have a little more control of the motor going down (lower voltage), but max voltage going up (it won't move past 90 degrees even with the tubing without the voltage ). besides adding more tubing, what could we do to help get more control and use less voltage? Should we change to an FP with a speed controller? if so, how do we get it to not back-drive?

I would get a stronger motor (RS775 is awesome, as I've mentioned) and gear it way down. You might considering gearing the window motors down even further.