Install the front castor and sensor supports. They need to be screwed in. 

Assemble the castor wheel and support

Screw the servo horn with the wheel. The tires are standard 1.9 RC tires. We have used double tape inside the tires and the wheel to give some traction to the wheel.

Install the servo motor in the base of the robot.

Connect the wheels to the servo motors

And we are ready to program. Mount the Arduino using a zip tie and add some sensors for fun!