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Unread 03-09-2013, 09:34
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AKA: Carl Springli
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Re: Motors/Gearboxes required to move a 20 kg/44 lb robot

Quote:
Originally Posted by magnets View Post
Lets say that you have the motor spinning at 15000 rpm. With a 50:1 reduction, that's 300 rpm for the wheels. The wheel circumference is about 7.9", so that gives you a max of 2370 feet per minute of travel, or 40 feet per second, which is too much.
Aside from the motor spec being incorrect, this math is also flawed. Divide by 12 to convert from inches to feet. Also the incorrect formula for circumference was used.

C = pi*d = 3.14*5 in.
C = 15.7"
300 rpm = 5 rps
speed (inches per second) = 5 rps * 15.7"/revolution = 78.5 in./s
speed (feet per second) = 78.5/12 = 6.5 fps

This is on the slow side of somewhat reasonable speeds for a robot using FRC motors. That being said, I have no practical experience with RS775-18 in a drive system, so use at your own risk.
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