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Unread 24-02-2014, 09:29
Jefferson Jefferson is offline
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AKA: Jeff Clements
FRC #0016 (Bomb Squad)
Team Role: Mentor
 
Join Date: Jan 2011
Rookie Year: 2010
Location: Mountain Home, AR
Posts: 258
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Re: Baxter Bomb Squad 2014 ~ Nighthawk

Quote:
Originally Posted by Rob Stehlik View Post
Nice to see another cam based catapult! We came up with a different solution to back driving that you may be interested in: The final 30 degrees of our cam profile is circular, so there is no reaction torque from the catapult springs. Once the cam follower gets to the circular part of the cam, there is no chance of back driving.

As a side note, we built a small cam driven catapult last year for a non FRC project, and experimented with a notch in the cam to prevent back driving. It worked, but we found there to be a large current spike when the motor was trying to get the follower out of the notch.
The reliability and repeatability of the cam driven catapult was the deciding factor for us.

We had a similar profile you describe, just not as long on the flat. Hitting that small window right before the roll over was tough. We also like the idea of being mechanically locked in there.

We do get a pretty significant current spike coming out of the notch. I watched our practice bit spike over 60A the other night. It took us several rounds to get the slope flat enough come back out to reliably fire.

Btw, y'all's robot looks very nice again this year. Good luck out there.