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-   -   Best motor for direct drive shooter wheels (http://www.chiefdelphi.com/forums/showthread.php?t=141936)

viggy96 16-01-2016 23:53

Best motor for direct drive shooter wheels
 
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?

Ether 16-01-2016 23:59

Re: Best motor for direct drive shooter wheels
 
Quote:

Originally Posted by viggy96 (Post 1525179)
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.



viggy96 17-01-2016 00:04

Re: Best motor for direct drive shooter wheels
 
Do you mean the 775pro? Also, we want to avoid gearing as much as possible as it would complicate our design.

Knufire 17-01-2016 00:06

Re: Best motor for direct drive shooter wheels
 
Quote:

Originally Posted by viggy96 (Post 1525192)
Do you mean the 775pro?

I think he does. Remember that it's dependent on wheel diameter too, you want a higher angular velocity on a smaller wheel.

viggy96 17-01-2016 00:16

Re: Best motor for direct drive shooter wheels
 
Hmmm. We were thinking of a miniCIM as well, would that be a good choice?

Ether 17-01-2016 00:18

Re: Best motor for direct drive shooter wheels
 
Quote:

Originally Posted by viggy96 (Post 1525199)
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?



viggy96 17-01-2016 00:30

Re: Best motor for direct drive shooter wheels
 
At its full RPM, without gearing.

Ether 17-01-2016 00:39

Re: Best motor for direct drive shooter wheels
 
Quote:

Originally Posted by viggy96 (Post 1525205)
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/sh...88#post1521188




cbale2000 17-01-2016 01:06

Re: Best motor for direct drive shooter wheels
 
Quote:

Originally Posted by viggy96 (Post 1525205)
At its full RPM, without gearing.

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. ;)


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