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Electric Toy Quad Runner Motor Upgrade Version 1

Link to new rebuilt version 2

 My nephew finally managed to wear out the motor drives on his electric quad bike.  My brother was going to give to me for parts but I decided to see what could be done with it.  The original gears were ok but the axle pins on the gears had worn through the plastic mounting blocks and would allow the gears to slip.  There wasn’t much I could do with what was left so I decided to do an upgrade to the drive system with a motor and gear box I had in my stash of junk.

 The motor and gearbox was for a garage door but the a.c. electric motor had died long ago so I used part of it’s case and attached a 12v dc fan motor to the gear box. It works pretty well and is very quiet since it is a worm gear system. It also has steel gears in an oil bath.

 I fabricated a motor mount and cut out the back of the plastic to allow a chain and gear on the axle shaft.
 A 5/8″ bolt was bored out to fit the axle and I brazed the bolt to the center of a bike gear that came from an old rear bike wheel. This gear is pinned to the axle in two places. The reason for two pins is that the axle is only 7/16″ so I didn’t want to weaken it too much and the pins are small.  Since the original gear boxes provided bearings for the axle I kept them but took out everything but the bull gears and the bearing parts and reinstalled them on the axle.  Currently both rear wheels are also pinned to the axle so they will both provide drive but I might release one of them depending on how it steers when my nephew tries it out.
  Here are a couple of pictures of the new setup , the extra parts and the unit reassembled.
 When I put the brace on the rear of the motor mount I also installed another tow hitch connecter too.

front view

rear view

extra parts

side view

rear view

After finally getting a good battery hooked up, it looks like I’m going to have to either put a bigger gear on the axle or use a bigger motor. (I have a few of them)   It would work but was too fast on smooth ground and didn’t have the torque I know it should have had for going over rough ground.  At the moment the gear ratio is 1/1 but I’m going to change it to 1/2.5.   This should solve all the problems and let it drive though loose sand also.