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Unread 13-07-2007, 01:30
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Dan Petrovic Dan Petrovic is offline
Got my degree and ready for more!
FRC #0166 (Chop Shop)
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Re: what motor did you use(arm)

Quote:
Originally Posted by Doug G View Post
I can't emphasize this enough. Over design the power transmission on the arm. If calculations show that you need 30 ft-lbs of torque to lift the arm and object at the end of the arm, then design a motor/transmission combination that can supply that while drawing < 10 Amps! (somewhat dependant on the motor choice)

If you need 30 ft-lbs, then stall torque should be at least 120-150!! Also this way, you can throw in some feedback and PID will have lots of headroom for tuning and working correctly.

In the 7 years of doing FIRST ... In my opinion the ratio of "under-designed arms" to "over-designed (or simply well-designed) arms" is at least 25 to 1.
We made the mistake of calculating the reduction required when the motor is being run with ~60 amps. These motors were only ran with 20 amps. So we ordered new Banebots transmissions and that set us back a whole week... (good thing we were doing pretty well schedule-wise until then ).

Well, that's what happens when you make mistakes: you learn from them.
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