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Unread 01-06-2014, 17:51
Andrew Lawrence
 
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Re: Offseason WCD with 3 CIM inverted transmission design

Quote:
Originally Posted by Travis Schuh View Post
Backing up a bit, why did you choose 6 CIMs over 4? For me, there is a very real cost to going with a 6 CIM drive, yet after two seasons of there being bots with 6 CIM drives, I do not see strong evidence that 6 CIMs has a large advantage over 4 CIM. The tradeoff is that you can't use the CIMs elsewhere, they add weight, and they greatly increases breaker tripping risks. We ran 4 CIMs this year after trying 6 last year, and were very pleased with our decision to do so (it would have been much much harder to build the robot we did if we had not done such).

Also, why belts in a WCD? My rough estimate is that you are saving less than 0.5lb by using belts over #25 chain, yet a WCD drive does not have a good answer of how to change a broken belt between elimination matches. If you are going to bet on the belts not breaking, I would recommend sizing up to the 15mm wide. We have broken belts on our robot (albeit most frequently on our practice robot and in the after season), and find that it is an important design priority to be able to quickly change belts. Our calculations have also shown that with 9mm wide GT2, we are a running the belts a good bit out of the belt's specs.
The goal with the six cims was simply a design challenge for myself - not pure intent for use in competition.

The belts were chosen out of lack of experience using 25 chain and sprockets in this kind of setup. Of course the pulleys can be changed out with sprockets if we really wanted to.

I appreciate the advice, though!
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