It took me a long time to find the correct motors and power supply to drive my Dalek. Originally I was going to use two 9v motors powered by 5 D size rechargeable batteries but unfortunately the motors did not have enough torque to drive the wheels. After experimenting with different motors and power supplies I decided to use the motors, gearboxes and batteries from two 12v cordless drills. I removed the chuck from the gearboxes and attached the wheels.

To  control the motors I used two speed controllers which were operated by servos. These allowed me to control the motors independantly and the speed at which the Dalek travels.