If you can't find inexpensive LEGO motors online, you can make your own LEGO motors for almost FREE!
You'll need:
Hot Glue Gun / Glue Sticks
DC Motor
Wires
Batteries
The DC Motor wires and battery pack can all be had for free if you take apart some old battery powered toy cars. But you can also buy DC motors, wires, and battery holders at Radio Shack (sometimes under a dollar).
Here are some examples of DC motors taken from old toy cars etc:
Step 1.
Get an axle pin and the DC motor:
Get the the "Hot Glue Gun" these can be purchased from a craft hobby store:
Take the DC motor and hot glue an axle-pin to the shaft. Make sure to center the pin as close as possible on the DC motor's shaft.
Take the DC motor and hot glue an axle-pin to the shaft. Make sure to center the pin as close as possible on the DC motor's shaft.
Step 2.
Insert the motor's shaft (now an axle-pin shaft) into a brick with holes.
Use more LEGO to connect this brick to a flat platform LEGO to which the motor can be glued. Here, the DC motor is not yet glued to the platform :
Step 3.
Glue the flat platform to the motor. Make sure the axle-pin shaft can turn easily before the glue dries.
Step 4.
Connect the battery to test that the motor spins freely:
Step 5.
You now have a motor that can power your LEGO creations!
Here is a DC motor powering a lego rock polisher!