Are you having the red battery motor of knex and are tired of changing batteries all the time? This is the solution! With this you modify the motors to ones to be plugged in!
Step 1: Gather Materials
First gather the materials.
Step 2: Prepare the cable
First you preper the cable.
Step 3: Unscrew the motor
Now you unscrew the motor. You just need that red half.
Step 4: Prepare the red lead
Veary simple, just screwing a hole.
Step 5: Using the soldering gun
Step 6: Putting it together
After you made this step you'll have to put 3Volt on the other end of the cable. Polarity is irrelevant because it still goes through the switch.