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# Power output of a cordless drill attachment (epicyclic gearbox)2

## Power output of a cordless drill attachment (epicyclic gearbox)

(OP)
I'm trying to design an epicyclic gearbox that steps up a cordless drill's rpm ten fold (can't alter the drill itself - it's supposed to attach to the drill to power some attachments). However, I am struggling to find a suitable power value for my calculations (no drill manufacturer shares this information). How can I go about finding a suitable power output (for reference, I'm designing around an 18V, 1.5AH battery) and does it differ under no load and maximum load or should the power stay the same whereas the torque or rotational speed change?

### RE: Power output of a cordless drill attachment (epicyclic gearbox)

Power = torque * rotation rate; units selected as required. It is also proportional to Current * voltage.

Typical power out of a gearbox will be less than power in; depends on the gearbox, but say, 90% for a good one of this type.

Electric motors have varying efficiency. At 0 RPM they have 0 efficiency. At maximum speed there is no torque and again, efficiency is 0. See http://electronics.stackexchange.com/questions/237...

### RE: Power output of a cordless drill attachment (epicyclic gearbox)

Dismantle the cordless drill. It contains an epicyclic (reduction) gearbox. The gears are sized to handle the power of your cordless drill.

If you only need a few gearboxes it would be cheaper to buy cordless drills and steal the gearboxes (using them as step-up) than to design and build your own. If you need large quantities try Alibaba.com

je suis charlie

### RE: Power output of a cordless drill attachment (epicyclic gearbox)

Perhaps you could just remove the gearbox from the drill? It seems a bit redundant to go through a step down box only to go back into a step up box.

### RE: Power output of a cordless drill attachment (epicyclic gearbox)

If you want to know what the actual power characteristics are at the drill output, use a torquemeter and tachometer to take direct measurements at the drill chuck. With torque and rpm you can calculate power. Of course, a single stage epicyclic providing a 10:1 speed increase, with an input speed of up to 1500rpm, is not a simple design task. The mechanical losses in this type of high ratio epicyclic stage would likely be fairly high. Since it would likely use grease lubrication, plain bushings, etc.

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