eBay Hub Motors - might be useful?

http://www.ebay.co.uk/itm/Balance-bo...QAAOSwbsBXmeyE

Nothing to do with me - other than having bought a pair (He accepted an offer of £20 each for two).

I've used quite a lot of 'hover-board' motors & controllers over the last year and found them surprisingly robust (despite what you might read in the press).

The motors are about 250W generally with Hall sensors. They give a top speed of up to 20mph and a respectable amount of torque.

In one application I used the whole of the original controller board. It had two sub-boards with the gyro's on. I just attached each of these to a servo so the servo could tip the board forward & backward - which causes the motor to drive correspondingly. If your robot is reasonably balanced around the wheels - it will also self balance.

The two I bought are to build an 'Electric Bar Stool' which you sit on and shift your weight on the seat to drive & steer. Effectively controlling it entirely with your bottom!

I've bought 3 so far, paid about £12 each. Used these BLDC controllers with them (36V 600W) and got them moving.