The 2-Wheel Scooter Motor Outer Foot Drive

This is a design for a 2-wheel, as opposed to wheel and caster, foot drive powered by a scooter motor. It's a composite design based on a number of R2 Foot Drive designs that I looked at. Very little of the design is either new or original. Physical design constraints, having to fit inside a foot shell, force most of the restrictions (see below, the motor sticks out!). It's designed to be built out of CNC cut .220 in thick styrene sheet.

I choose scooter motors because of their wide availability and low cost. I've seen the 135 watt versions as low as $15, but at this point they are available from a number of suppliers for around $25 each. My other design choice was to use a chain drive, instead of belt drive. In order to fit everything in, there's what I'm calling a jack shaft between the motor and the wheels. The motor drives the jack shaft, the jack shaft drives the wheels. Drive sprockets are 9 tooth, driven sprockets are 22 tooth. That's a 1:2.44 ratio, twice, for an effective ration of 1:5.96 (if I've calculated correctly). The motors will be run at 12v (instead of 24) to keep the speed down. The driven sprocket size was chosen to keep the bottom edge of the sprocket and chain at the same height as the bottom edge of the foot shell. In other words, out of sight unless you are laying on the floor, looking up.

The wheels are 5 inch Colson wheels with internal bearings. I choose chain as I believe it is more compact than the equivalent belt drive and space is at a premium. The wheel sprocket is bolted directly to the wheel using a custom spacer to provide the clearance.  Because of the size of the motor it sticks out into the Battery Box. The prototype of this design appeared at DroidCon II in August 2013. There have been a few changes, mostly simplifications.

8/29/16 Please Note: Although Mechanical Components (motors, wheels, sprockets, chains, etc) are shown in the pages describing the Outer Foot Drive they are for illustration ONLY. I DO NOT supply Mechanical Components with the parts packages I sell for the Outer Foot.


The image links to a 3d pdf file, click on it if you want to be able to rotate the image around and examine it from other angles. (Note, the 3d.pdf file opens in a new window. If you have problems with the 3d feature you may have to upgrade to the latest version of Adobe Reader).

The design drawings are available as both Autocad .dwg files, 3D .step files, and Adobe .pdf files download drawing files with the understanding that the drawings are copyright to Media-Conversions and are not to be used commercially. (That note also appears on each of the drawings). There is one set of drawings that covers both the drive and the shell. I've also put together a set of assembly instructions to help you put the box together. Unlike most of my styrene designs, the Outer Foot Drive has both mechanical  & electrical components to it that require some tinkering to adapt them to our purposes. Those parts are NOT Supplied with the parts package. See the Mechanical & Electrical Parts page for part descriptions and supplier information.
 
Please send me comments, questions, or suggestions on making the design better to me at: fpirz (at) media (dash) conversions (dot) net

 

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