We were going to use CIM motors for the shooter wheels, but we were concerned about the weight. Are there any other FRC legal motors which would provide the speed at or above that of a CIM, but in a far lighter package?
775Pro. Gear the speed down 2:1. That will give you ~6000 RPM at 8 volts, which will give you headroom for closed-loop speed control.
Do you mean the 775pro? Also, we want to avoid gearing as much as possible as it would complicate our design.
I think he does. Remember that it’s dependent on wheel diameter too, you want a higher angular velocity on a smaller wheel.
Hmmm. We were thinking of a miniCIM as well, would that be a good choice?
It depends on how you intend to use it.
At what operating speed are you intending to run the motor?
At its full RPM, without gearing.
So your team made a conscious decision not to control the shooter wheel speed?
http://www.chiefdelphi.com/forums/showthread.php?p=1521188#post1521188
Speaking from experience, that is a very effective way to ensure you never make the same shot twice.
One important variable to consider is that battery voltage will change throughout the match (not to mention between different matches and batteries), thus changing the motor RPM, and consequently, where the ball goes when you shoot it.
Unless you’re shooting at such a close range it doesn’t matter, or such a high speed that the ball is basically ballistic (something I would think would be frowned upon by the refs, not to mention difficult to achieve without any gearing), you need to have a bit of margin in your RPM and a closed loop program to compensate for battery voltage changes.
There are a ton of sensing options available, and plenty of stock code to make them work. 