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Originally Posted by Spencer295
Richard because your test results vary so drastically from the specs on previous posts on motor wattage, would you mind testing the old cim motors on your dyno so I can make an accurate comparison.
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I finally got my hands on an old CIM motor, to measure speed and current vs. torque on my dynamometer. [N.B.: had to order some spares in case the team burns one up testing.]
Your suspicion that my measurements are low compared with published specs is correct: I measured peak power about 270 Watts (c.f. 337 published) at about 2700 RPM, drawing 50 Amperes.
There are several reasons my measurements might be low, but accurate dynamometer torque calibration is not one of them. The most likely (IMO) reasons are (1) I let the terminal voltage drop off at higher current draw due to lead resistance, about 5 ft. of 10 qmm (~7 AWG) for each lead from the supply terminals to the motor lead connection point, and (2) I let the motor get hot while taking readings. Imperfect shaft alignment and residual drag torque in the magnetic brake probably amount to about 25 Watts.
It has been my experience that the above loss mechanisms are also present, to about the same degree, in drivetrains that I have built for FRC robots.
__________________
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)