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Re: Dual CIMs and #25 Chain
Our team has used 6wd, 3/16in drop center, AndyMark plactions, 4cim, AndyMark Supershifters, and #35 chain with aluminum sprockets for two years. We used the standard kitbot frame our rookie year, and this year we build a custom chassis out of 1x1x1/8in aluminum box.
Using this setup, we have NEVER had an issue with throwing chain and I can't remember throwing chains on my old team of 3 years and they too used 4cims, AM Toughboxes or Shifters, and #35 chain.
As some have suggested it could be your supplier of #25 chain. We use AndyMark which I'm sure is what a majority of teams used.
We did throw one chain run on our Fall Robot that we built for a one day competition. The reason it came off was because it wasn't tensioned properly. In 2011 we used pieces of pvc to provide tension to our chains and added spacers as needed. 2012 we used pieces of pvc with springs underneath them so we just had to loosen the mounting bolts to tension our chain.
Check the alignment of your sprockets and chain runs, everything should be straight with no bending. If you don't have perfectly straight chain runs they will come off with use or when you go into high torque applications.
I would highly recommend that you do not remove a set of CIMS from your drive. The only year that teams used 1 cim per side was 2009 when the floor was a low friction surface. A four cim drive gives you more torque and is a fail safe in case you loose a cim or jaguar in a match which happens a lot more than people think.
As for your robot being very jumpy as a four cim drive. Is your center of gravity high/on the higher side? Is your robot a full 120lbs? Both of these can contribute to why your robot is jumpy with more power in your drivebase.
My personal recommendation is to upgrade to #35. You'd be surprised by the forces at work in your drivebase.
You are running a very standard setup these days (6wd w/4cims), removing two cims will not fix your problems it sounds like your problem lies in the transferring of power between wheels. If you post some detailed pictures of your drivebase when you get your robot back I'm sure we can offer more help.
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