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Comment by pingswept | Hacker News Reader

Maxon is a Swiss company that makes very high power-density motors that are commonly used in high-end robots.

(I don't know if they're the quietest.)

http://www.maxonmotor.com

I suspect most of the noise is generated by the gearbox. That makes this seem hopeful: http://www.maxonmotorusa.com/media_releases_maxon-Koax-Drive...

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This is exactly my problem. I can look at the picture and see the information, but how do I figure out if that motor will do what I want it to do without buying it and programming it?

I need to move 2kg through space in a natural manner - is there any series of numbers I can apply that will allow me tell if that motor would be suitable for this?

Call them, tell them what you're making, and ask for a sample. If it doesn't work, "adjust" your story. Most suppliers will gladly ship out a sample if it is likely that you would buy in bulk in the future. Some will gladly ship to hobbyists. Depends on the person you talk to.

I'm unlikely to buy bulk later. You sure that they will give me a free motor just because I ask for it? Sounds...too good to be true :)

http://www.ladyada.net/library/procure/samples.html

If money isn't an issue, just buy one and if it doesn't work, find another one and buy it, etc.

The suggestion to use Maxon motor is a pointer in the right direction. I think a brushless DC motor will give you the best power in a small package. Most of these motors have a rating in Watts. one good place to start is with the microchip motor control demo board. They will also sell you a Hurst brushless DC motor. http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_P...

Mind you, this is just the system I used, Several chip makers offer similar demo boards. Here is another: http://www.silabs.com/products/mcu/Pages/SensorlessBLDCMotor...

You can figure out how to properly size a motor from the load you'll be carrying, how fast you want it to accelerate, what sort of power supply you have available, etc.

Here's a link to a good, easy-to-parse reference:

http://www.amazon.ca/Build-Your-Own-Combat-Robot/dp/00721946...

Yes, but it's a nontrivial calculation, especially if you're moving in more than one dimension. What you want to do, roughly, is this:

1. Pick the largest motor you can stomach in your robot.

2. Figure out how much current it can handle when stalled. This will be proportional to the square root of the power, because P = I^2 * R.

3. From the motor specifications, you can figure out how much torque you'll get when the motor is stalled, which it will be when you first start accelerating your 2 kg.

4. Figure out how much force on the load will result from the torque.

5. Once you know force, you'll know how fast the load will accelerate.

6. Assume the load accelerates for 0.01 s (or some small time step) and then recalculate all your parameters.

7. If it's not fast enough, pick a more powerful motor.

Really, you're trying to solve a system of differential equations, so the actual answer might be "go to engineering school and take a class in dynamics" or "find an engineer who will do some system modeling in Matlab for you."

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