A construction guide built and photographed by Pieran in Year 4

Make a differential gearbox. I used a crown gear to connect the motor.
 

Make a ratchet on one side that will stop the wheel turning when the motor goes the other way.

This is what the gearbox should look like.

Time for some armour!!!!!

Fit the RCX unit on top.

This is the view from underneath. It looks complicated doesn't it?

To steer your robot just reverse the robot. Then it will spin. Reverse the motor again and both tracks go forward.