I recently found an old Knex pinball kit that didn't work anymore, so I took it apart, hoping I could find stuff for arduino. During the "dissection" :) I found most of the pieces used for this, a 4 digit 7 segment display, and a motor box that works the same way as any other knex motor. I connected the center piece of the board and connected it to a motor, as well as some pvc pipe and a battery box from a remote control. Have fun!

Step 1: What You Need...

1. Knex electronic arcade.........$20 to $40 on ebay
2. PVC Pipe...........three "3 sided parts" and about 24 in. 3/4 and {1 inch (optional)}
3. Soldering iron
4. Hot glue gun
5. Battery pack..................I used one from a remote control, which was disconnected
6. 2 wires, about 6 in.
7. Drill
8. Paper
9. Paint and brush
10. Tape

Step 2: Getting the Pieces

Open up the center peice (the one that rotates in the middle), there should be a motor with a rubber-like band connected to the center. Take out the motor (you don't need the plastic around it) and don't take off the rings. Now, unscrew the large middle piece and take it out. It should look something like the picture above. Hot glue the piece you unscrewed to the bottom, and then hot glue the motor to the whole.

Step 3: PVC

On one 2 in. piece of pvc, drill a whole as close to the center as possible, making sure you don't drill all the way through. Then connect the rest in the fashion in the picture. It should look like an H, however with a stick in the middle. At the top of the "stick" should be the drilled pvc.

Step 4: Connecting

Now......solder the wires to the motor, place the wires through the hole in the pvc, and hot glue the motor in it. Glue the battery pack to the pvc close to the motor, and solder the other ends of the wires to it. If you place the battery in the battery pack, the current should flow, and the "centerpiece" should spin.