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Unread 25-12-2014, 03:39
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RoboChair RoboChair is offline
He who fixes with hammers #tsimfd
AKA: Devin Castellucci
FRC #1678 (Citrus Circuits and 5458 Digital Minds)
Team Role: Mentor
 
Join Date: Jan 2007
Rookie Year: 2005
Location: Davis, CA
Posts: 628
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Re: One speed vs Two speed gearboxes

Quote:
Originally Posted by Abhishek R View Post
So we've been thinking about auto-shifting some more, and how to increase our efficiency. I've also heard that 1678 achieved speeds of 22 ft/s on the field and wondered how they did that, especially if they started in first gear then shifted or if they were in 2nd the entire time (assuming they used shifters). We were happy with our auto-shifting system last year and would like to improve it further. This led to a few questions:

How do we figure out the correct gearing for the low gear supposing we know we want to have a high gear of 17 ft/s? This needs to maximize acceleration as well as battery life.

What exactly does it mean to be traction-limited and what are the physics equations and calculations surrounding that?

We are planning on using either 4 CIMs, 4 CIMs and 2 MiniCIMs, or straight up 6 CIMs, so any advice on those configurations would help as well. I didn't want to start a new thread since there has been so much discussion on the topic, but since using auto-shifting as a method of avoiding blowing the main breaker was discussed here, I figured it was apt. We didn't have to worry about that last year since we only had 4 CIMs on the main drivetrain.
We were GEARED for 22fps(no loss), we measured somewhere between 17 and 18 actual. About 12 miles per hour or if you want to give a good value to some pit scouts, that's 5.3% the speed of sound!