Thread: RS775 Gearboxes
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Unread 17-01-2011, 10:31
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Re: RS775 Gearboxes

Quote:
Originally Posted by rahilm View Post
~390 if I did my math correctly; ~(voltage)*(stall current)/4 = (12)*(130)/4 = 390 (not factoring in motor inefficiency)

Also, the 2010 FPs had roughly 190w. This year's have 290w. (Both figures from the FIRST motor curves)




The reduction we're going with is a 512:1 (256:1 with banebots gearbox, and then 2:1 with sprocket). This gives us ~576 lb-ft of torque if you go with 65% gearbox efficiency, which is more than enough to lift it, while we still have 25RPM, which is 150deg/s.
DON'T DO THIS. That is, unless you've carefully considered the following.

Banebots suggests a maximum torque output of 85 ft-lbs for the P80 CIM gearbox. If your mechanism is actually going to require anything close to 576 ft-lbs of torque, you'd destroy a P80 gearbox rather quickly. And P80s are tougher than the P60, which is smaller with an aluminum ring gear. BB doesn't list the max recommended torque for the P60s, but it's going to be less. At least half, possibly a quarter. So I strongly urge you to look at the maximum safe output of your gearbox and make sure you plan your gear reductions accordingly. You may want to decrease the reduction in your gearbox and add an additional reduction stage of sprockets. 256:1 gear reductions provide surprisingly little torque once the gears have failed.
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