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Unread 16-09-2014, 15:36
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Re: Experience With 6 Cim Drive train

Quote:
Originally Posted by Andrew Lawrence View Post
At higher speeds - regardless of target distance - my calculators show that the extra motors can save a tenth of a second or so (nothing significant), and at lower speeds (especially around your sweet spot) the calculator shows improvements of a few hundredths of a second at best.
I see a difference of .15 secs to travel 20ft geared around 12ft/sec. Not significant like you said at these lower ratios.

But I also see a cim speed of 2850 rpm with 6 cims versus 2134 rpm with 4 cims to spin the tires of our 2014 robot in high gear in a model I built. Thus, it seems adding more cims decreases speed drop under load making the drivetrain "feel" stronger while consuming the same current? This may seem odd until you understand the cim motor efficiency curve...

http://www.usfirst.org/uploadedFiles...rves_Rev_A.pdf

Ideally, we'd always run our motors at peak efficiency instead of peak power. Only caveat is when you gear so aggressively you stall the motors where adding motors only makes the problem worse.