Quote:
Originally Posted by ToddF
No matter what motor you end up using, the first thing you can do to help yourselves is to add a spring to counter balance the weight of your arm. This could be as simple as a piece of surgical tubing wrapped around a pulley that's attached to your arm pivot axis. Attach the other end of the surgical tubing to your frame so that the weight of the arm is supported by the stretched tubing, not your motor. Then, the motor just has to handle arm motion, not carry the weight.
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Can't believe it took this long to suggest this. This is a great method to reduce the load on any motor, and the worm-drive mechanism in the window motor is a great way to sidestep any backdriving issues caused by changes in the spring force as your arm travels.
Quote:
Originally Posted by ToddF
Properly counterbalanced, a window motor just MIGHT work. But, the teams at our last FRC summit concluded that window motors are supplied as object lessons for rookie teams to learn what NOT to use. Most of us just throw them in the trash. With their limited capabilities, there are much better options available. Not to mention that the thermal cutoff will kick in at the most inopportune moment, leaving you motionless until the motor cools down.
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I disagree that they're useless. There are plenty of low-load applications where window motors work just fine, and their worm gear reduction offers a great deal of resistance to backdriving (which is often very useful). Rather than heavily reduce a high power 500-series motor for a low-speed, low-power application, we often use window motors. In 2012, we used a window motor to power our final stage roller, that would load the balls into our shooting wheels. Not much speed or power required, and with a tight compression, high CoF, and the worm gear combined, we prevented ourselves from "accidentally" shooting a ball early when the loader stacked up. In 2013, our original loading cam was powered by a window motor as well, but this entire loading mechanism was eventually replaced by a pneumatic system.
Don't take that to mean that the window motor is the correct choice for this application, though.
The throttle motors, on the other hand....