Step 1: The plan
Any 24V scooter has two 12V batteries, a motor and a speed control. Why not pull out the parts and attach it to a push mower to make a variable speed cutter that can be push around the yard. It seemed simple enough.
The motor is way to fast, and finding a simple way to connect the drive belt to the mower did not work for me. The mower runs at about 80 rotations of the cutter for every one of the wheel (WAG estimate). Adding the scooter motor would shoot that high enough to make the mower take-off. Unsafe and unwise.
Use a windshield wiper motor (12V) and one scooter battery (using the other as a spare) to power the motor.
Simple and cheap...except that the windshield wiper motor why strong is about half the speed you will need. It cuts, but the process of trimming even a 10' X 12' lawn becomes a chore.
After destroying the batteries by accidentally overcharging them, I found a powered window motor for $12 online. The RPMs were roughly double, and I could always order the other rotation is I completely ruined one side of the motor.
What a plan! Through a little tinkering, this works very well, and cuts just a little slower than I would like.
Step 2: Acquire Materials
mower (mine was $5 on Craigslist)
12V battery (I had to use an alarm battery from Radioshack for $30. A doner scooter would be better)
12V power windows motor 150RPMs or better ($14.99)
Wire and battery connectors
4" angle brackets
10-24 tap kit
1/2 and 1-1/2" 10-24 screws
steel spacer the diameter of your mower shaft
bolt and nuts for your new wheel
steel strapping and pop rivets for battery case
1" rubber spacer