This simple project showed my kids how simple machine works - electricity, pulley, velocity ratio and mechanical advantage.
Step 1: Step 1 - Fix the Motor
My son has a couple of LEGO sets but none of them are the Technic or those come with a motor. I got one motor from a broken DVD player.
In order to fix it in LEGO blocks, I used some blu tach.
Step 2: Step 2 - Install the Power
Similar to the motor, a 3V battery box cannot fix in LEGO blocks without the help of some blu tack. I got one with an ON/OFF switch.
Step 3: Step 3 - the Power Transmission
Stretch the rubber band and the power can be transmitted from the motor to the wheel.
Step 4: Step 4 - Decoration
My son did the rest of the job. He put one driver and one operator on it. Not bad. You may want to see how it works at my site