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Unread 17-12-2003, 16:11
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Andy Baker Andy Baker is offline
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Re: Shifting Gears

Quote:
Originally Posted by JVN
Based on my calculations, your above statement is wrong. If you want to achieve Matt's "competitive speed" and his "competitive pushing force" in the same bot, using only 4 motors... you NEED a shifter. Otherwise... you're going to pop the breaker and sit there dead the whole match.
No, you wouldn't be dead the whole match. It would be more like a sputtering car that is in the process of running out of gas. The robot would go full speed for about 30 seconds, you would get an advantage in the match, and then it would start cutting out on you. It would go for about 4-5 seconds and then stop. This would repeat until the end of the match. ... unless you had a shifter. Then you could just shift into low and continue on with the match.

I agree with the above analysis that John made, and I agree that shifters are extremely beneficial. We on team 45 have shifted gears every year since 1999 and we have learned that the #1 advantage to shifting is saving your breakers... and the side benefits are the immediate response of power or speed.

A circuit breaker on a FIRST robot can handle amps above it's rated limit, but just not for too long. If a robot is in high gear for 10-15 seconds, under harsh driving conditions, the breakers will hold up. However, after those 10-15 seconds, the robot driver better start thinking about shifting to low, because the breakers are getting low and starting to give.

The trick with these little circuit breakers is that they don't trip immediately at 40.1 amps. You can overload them for a while, but not too long.

In many matches over the past 5 years, we would run in high gear for the first 40-60 seconds (depending what we were doing) and then shift to low for the latter part of the match. This relief to the breakers would enable us to run in high during the last 5-10 seconds, if needed.

At least, that is from my experience.

Also, on a different note, I would contend that 150 lbs of pushing force may not be enough for a top-tier robot. There were robots which could push with more force than that during the last 2 years. Last year, many robots had unbelievable pushing power on the grating. I would up that number to 200-250 lbs. to be conservative.

Andy B.
 


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