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Unread 09-12-2012, 15:43
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Ether Ether is offline
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Re: Balancing an Arm



With the high-speed FP motors, it's pretty hard to provide too much speed reduction when used for an arm.

Consider the following rough calculation for an extreme example: an FP 9013 motor with 1000:1 speed reduction

At 0.8 volts, 9013 provides 4.5 oz-in torque @ 4watts & 5 amps when stalled.

That translates to 23.4 ft-lb holding torque (stall) at the arm.

That's equivalent to approx 6 lbs of unbalanced weight at the end of a 4 ft arm, or 12 lbs in the middle.

As Joe mentioned previously, FP should be able to sustain a 4 watt stall condition without overheating.

At 12 volts, the 9013 can drive at that load (4.5 oz-in) at 15580 rpm.

That's equivalent to 94 degrees per second rotation at the arm.


As I mentioned in a previous post, the real concern with these super-high gear ratios is not the speed reduction, but rather the output torque rating of the final gears. This can be mitigated by making the final stage rugged.