The Center Foot

I have designed a center foot assembly built using a structural frame of .22 styrene sheeting. I've used a stock Colson 3 inch stem caster although you could easily substitute an Omni-Caster if you wanted to. See my note below about additional parts used in this design. I used a standard 3D model of the caster, kindly provided by Colson.

This is the full center Foot (with one side panel skin missing)

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).

After 'activating' the 3d mode by clicking on the display
select a part by left clicking on it (the part will be highlighted)
then right clicking brings up a window.  Follow the sequence
-> part options -> part render mode -> transparent
to make the outer parts transparent and the inner
details visible.

Or you can use the views below which also link to .pdf files.

This is a view of the center foot shell with parts color coded so you can see the detail. The center section of the side panel is held on with magnets that attach to the structural ribs (see below).

The image, like the one above, links to a 3d pdf file.

This is a view of the Center Foot Structural components, fabricated from .220 Styrene. Tab & Slot interlocking design adds strength.

The image, like the one above, links to a 3d pdf file.


As with any design, there are limitations to what can be reasonably accomplished by CNC machining. I initially thought I would cut the bevels on the foot shells using the CNC machine. My first attempt at doing did not work out as I had hoped. The tabs holding the parts to the panel, now also beveled, became much harder to separate and trim. As a result the bevels on the foot shell are done in a separate cutting process. I had attempted to cut apron pieces from the same .220 styrene I use for the structural parts. The resulting parts would have been difficult to fit, requiring significant filing on the edges to fit properly. As a result I've made those parts on my 3D printer.

Additional parts: I have an aversion to installing bolts in holes threaded into styrene parts when the bolts are under stress. In order to attach the Center Foot to the Center Ankle I'm using a 3/8 x 1 in. aluminum spacer in the ankle and a pair of 3/8 shoulder bolts in the foot shell. You will also need a caster for the foot. There is a list of parts and suppliers here. Note: if you are thinking of using my design for the outer feet then you might want to purchase the wheels at the same time. The larger the order the bigger discount you are likely to get and you only pay for shipping once.

The design drawings are available as both Autocad .dwg 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 download also includes .stp 3D drawings of the Apron. (That note also appears on each of the drawings). I've also put together a set of assembly instructions to help you put the foot together.
 
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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