ive got a problem with my featherweight robot which ive been building, because the 2 drive motors and wheels are each from 2 electric scooters, i didnt know this untill i found out but each motor used to use the scooters chassis as an earth which was fine until i put both motors into a steel chassis and now i cannot operate them at the same time because of the fact that they each end up using the chassis as an earth if i connect one motor to the speed controler it works fine but i cant use both, does anyone have any ideas how to get around this problem? thanks