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Unread 09-05-2003, 17:34
Jnadke Jnadke is offline
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Quote:
Originally posted by sanddrag
Why is everyone thinking of having one motor engaged only some of the time? Besides current draw, I can't understand how this would be advantagous over having all the motors engaged and powered all the time.
The Chiaphua alone spins at a free speed of 5,500 RPM with a stall torque of 2.45 Nm. The Drill motor spins at a free speed of ~20,000 RPM with a stall torque of 0.80 Nm. As you can see, the easiest way to set this up would be to put the Chiaphua on a clutch bearing, and gear both motors to a shaft with no reduction. Then, you'd gear from there normally as if you were gearing the chiaphua alone for high-torque. It'd be easier, however, to do it the other way around and use the drill with bosch gearbox, for compactness. A 50:1 gear ratio is a lot harder to create than a 15:1 gear ratio.

As for your question, the reason you wouldn't want to operate the high-speed motor all the time is because, in the area of the high-torque motor, it is going to draw anywhere from 80A to 120A. Obviously, the motor will trip a few breakers. Also, in this range the motor is less than 30% efficient. A lot of the current is going to waste heat. As you know, as a motor heats up, its resistance becomes higher. Therefore, as the high speed motor heats up, it becomes less powerful. Also, more heat means you're closer to letting the magic smoke out.
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