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Unread 19-02-2010, 01:01
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VEX Robotics Engineer
AKA: Arthur Dutra IV; NERD #18
FRC #0148 (Robowranglers)
Team Role: Engineer
 
Join Date: Mar 2005
Rookie Year: 2002
Location: Greenville, TX
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Re: pic: Window sprocket adaptor

Quote:
Originally Posted by jspatz1 View Post
We would be interested to know if you have any trouble with your Denso motors overheating and cutting out. We had two Densos mated exactly this way for our swerve steering, but had to switch to steering with a CIM because the Densos would overheat and stop. Perhaps on a kicker they do not run enough to be problem. They are window motors so for safety they are designed to cut out when they stall on something and heat up. Not really the ideal motor to build robots with.
We did, but that's because the theoretical load I calculated was between 1/2 and 1/3 of the observed necessary torque*. Using this figure, I found we were loading the Denso motors to 20 amps... and their stall current is about 24 amps. So using the observed torque, I back tracked and redid the gear ratio to maximize the power output and lower the current draw to a reasonable amount.

* I've pinned the reason for the discrepancy down to a few SWAGs at coefficients of friction between different materials not listed in the commonly available engineering tables like Machinery's Handbook. In the future I'll probably perform tests to experimentally ascertain these values instead of guestimating values at 2am...
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Art Dutra IV
Robotics Engineer, VEX Robotics, Inc., a subsidiary of Innovation First International (IFI)
Robowranglers Team 148 | GUS Robotics Team 228 (Alumni) | Rho Beta Epsilon (Alumni) | @arthurdutra

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