The Kickbike ($259, Amazon) seemed like an obvious choice for the base vehicle because we wanted to do a scooter but also wanted the more stability you get with a larger front wheel, for when we powered it to higher speeds. The Kickbike is basically a scooter with the front of a full sized bike so pretty much right on the money. For the motor/drill we needed the most torque, lowest RPM unit we could find which ended up being the Milwaukee M28 Right Angle Drill 0721-21 ($369, Ohio Power Tool) . This drill is variable speed, based on trigger pull, from 0-400 RPM in low gear (0-1000 RPM in High) . The low RPM even on this unit was still too high so we had to find a gear reducer which could handle the torque and get us even lower. The Hougen reducer 4:1 14008 ($175, Ohio Power Tool) was the best we found for the money and gets the drill speed to 0-100 RPM with some serious torque to carry myself, a 225lb person, no problem.
To get the set up we wanted we found a matching size rear wheel on a kid’s bike and basically cut the entire back half off and inverted it. This kept the chain and rear tire perfectly working together so we really did not have to reinvent the drive mechanism.
The Kickbike rear wheel structure unfortunately was not wide enough to accommodate a wheel with a chain so we had to gently persuade it to expand. We cut the Kickbike rear tire mounts off and welded the kid’s bike to it, using the kid’s bike as the new tire mount.
We had the most difficulty finding a way to attaching the drill to the bottom bracket/crank and staying completely centered. We ended up boring a hole on the lathe and pressing the Hougen adaptor thread where the pedal arm would have gone. By using this thread piece we can easily remove and attach the drill by simply reversing the drill and hitting the trigger a few times.
To hold the drill in place securely we simply welded 3 round tubes to the frame which is pretty sturdy. Currently zip ties keep it from moving side to side but we will soon be welding on more permanent side supports to really hold the drill in place.
The throttle is controlled with the brake caliper from the kid’s bike attached to an extra long tandem brake line and a brake lever mounted on the handle bars. Currently the setup is getting the job done but a more customized piece is also in the works for the trigger of the Milwaukee Drill.
The speed could use some improvement which may could come from switching the Milwaukee Drill to High Gear which is x2.5 the RPM but could require a few manual kicks to get started then use the drill for higher speed cruising. There is also the option of changing out the gear sprockets for different ratios but did not want to do that unless it was really essential.
Total in parts new this would take almost $1000 to build however there are many variations that would reduce the cost tremendously. Hopefully it’s a different enough design to inspire other people to come up with more variations.
YouTube Video of it's first ride: http://www.youtube.com/watch?v=w3fReEuzb4k
Blog Post on Coptool.com: http://www.coptool.com/blog/2011/08/kickbike_scooter_powered_by_mi.html