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Re: DeWALT Transmission After Action Report
931 built two NBD units using 2004 FP motors and 10-tooth #35 sprockets, following the white paper recipe almost exactly. We did adjust the pinion hole diameter slightly to get an easier press fit. Based on gage pin tests I think we ended up with about 0.1255".
One NBD-FP is on our robot actuating the arm pivot chain, the other is a spare that we have not needed yet. Arm radius measured sprocket-to-hook is about 4 ft. Sprocket reduction is two stages for 36:1 and then the XRP gearbox in low. Motor current measurements while lifting a vision tetra indicate less than 25A average draw [note: motor current is discontinuous with instantaneous peaks to about 45A, chopped at Victor modulation frequency], and our PWM code limits the average motor voltage to about 9V max. So far no problems, but we did have to remove the anti-backdrive pins to permit stable lowering; having the pins out makes our arm operator much happier while capping.
I'll report again after the championship.
__________________
Richard Wallace
Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
 since 2003
I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
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