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Unread 21-12-2012, 07:46
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
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Re: pic: 2451 PWNAGE Off-season 2012

Nick,
I have to say this is an amazing assembly. Nice job to everyone involved. Unfortunately, the COTS rule (quoted above) on slip rings seems to take precedent. If team built slip ring assemblies were to be considered, this design surely would be on the top of my list as an allowed item! I like the dual brush assembly design. I doubt that you would experience any wear or deterioration with the use of just one brush per ring either. The CIM brush assembly wears mostly due to the commutator edges and arcing. Neither would be present in this design. Did you design the ring to be the same diameter as the CIM commutator or did you contour the brush to match the ring? Maximum brush contact with the ring is essential to keep resistance and heat to a minimum.
I see nothing that would flag this as contrary to electrical practice, it seems as if the team has thought of everything. Prior to the rule on COTS slip rings, I would have allowed this in and FRC robot.
Did you have to sacrifice CIM motors or were you able to find the brush assemblies as separate items? I would bet that further refinements could bring the cost and weight down as well. In this service, ball bearings are not needed unless you are using the bearing for other purposes. The rotational speed is low and the range of motion over it's lifetime is also very low. The brushes would naturally follow any runout in a simple sleeve bearing. I like the addition of the rotary encoder as well.
All in all a very well thought out design. Congratulations!
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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