Create a robot drive-train from a Jazzy mobility scooter

This old Jazzy mobility scooter cost $50 at auction, this is a fantastic deal since the motors cost over $300 USD a piece new! This unit will make a very powerful and rugged drive system for my robot. Since it is designed to haul a 300 lb person around I think it will be more than enough for the Dalek even with a passenger inside. I am going to post all the steps as I go…

Step 1: or “We don’t need no stinkin’ brakes!”

So I started testing the old Zippy scooter to see if the motors are ok. I found that the scooter has its brakes engaged by default, and it takes 24V (and a lot of amps) to disengage them. Using a 12V battery I could not get the brakes to release. This is no good for efficiency and so it has to go! Also, the motor controller I am using has a brake mode that will be sufficient for the terrain I plan on driving. I will probably need to avoid steep hills… and stairs… until I get the levitation thing figured out!

Here is a pic of the scooter on it’s side with the brake unit about to get disabled.

A close up of the end of one motor, the black cap covers the braking system which is an electromagnet and spring and pad setup.

Removed the 3 screws on the cap with a #1 Phillips head screwdriver.

Now remove the 4 Allen bolts.

Cut the wires and remove the brake unit.

Will need to cover this to prevent corrosion of motor wires before putting it back outside.

Step 2: Plan the circuitry
I need a 5V supply for the Pi. Also connections for the motors and relays that drive the lights, and an Ultrasonic sensor (mounted on a servo) to read distance from objects.

I used Google Docs to create a drawing of a simple wiring diagram for the Robot so that I can remember where each wire goes, it is starting to get complicated.
I would like to eventually have 2 moveable ultrasonic sensors for better coverage, but for now I will build a single one.
Here is the layout so far.

To be continued…