jeffr_tech (jeffr_tech) wrote,

wherein I replicate my feet

I sometimes do things unrelated to computers that are probably still considered geeky. I have made reference to being a cyclist before. As you know cyclists are obsessed with all things carbon fiber and I am no different. With the help of a boat builder friend of mine, I finally had an opportunity to make my own composite parts in pursuit of the perfectly fitting shoe. Behind the cut are some pictures and a description of the process.

First, to identify the goal; My feet have very high arches and long toes. This presents a number of challenges which are best solved with orthotic insoles. Unfortunately I couldn't find any I really liked. Cycling is also unusual in that a perfectly stiff insole is not undesirable. The average force on your feet is much lower than most sports and impacts are relatively non-existent.

The solution was to make a plaster of paris mold of my feet. From here I shaped the plaster and then built a plug, or positive mold inside of it. The plug was made of polyester resin and fiberglass. After curing the plaster was removed from the plug and then the plug was shaped further and sanded smooth. I essentially eliminated the toes beyond the metatarsal joints and kept everything else very close to my actual foot shape.

Once I had the mold I made a negative mold from it. Once this was also cured and shaped I sandwiched 8 layers of carbon and epoxy between the two and let them cure over night. After a lot of sanding and shaping this was the result:

Ultimately I had to completely remove the toe area so that this would fit in the shoe. I have since re-added the toe area using 2mm EVA foam. I further used a double-sided adhesive roll to adhere some suede to the insole to add a degree of comfort and traction along with a better looking finish.

Using a 3d motion capture technology I have actually shown that these insoles straightened out my feet and removed lateral motion from my knees. So not only are they exceptionally comfortable but they also improve performance by eliminating some forces applied tangential to the motion of the pedal. The total cost of goods was around $100 and it probably took 15hrs of working time.


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