Testing a new bearing design and lasercut patterns

by LAURA SHUMAKER February 27, 2014

I finished Dan's third prototype (the first one that used only lasercut rubber and fabric patterns) last night. Before all the adhesive fumes had dispersed, we whisked it to the climbing gym and put it through a round of testing.

The laser does a beautiful job of cauterizing the edges of the Cordura used for the lacing detail.

Dan was finally happy with how the toebox shape felt - a symptom of getting the rubber patterns and application process dialed in. I believe his words were, "Dang son, I want a pair of these," mumbled as he pulled the shoe on the second time. Three of the gym's staff members were kind enough to try on this prototype; their feedback was also positive, citing toebox shape as well.

The biggest hurdle overcome in this prototype was proving out a new bearing design. The adjustment strap of the shoe currently runs from the instep side of the shoe to a "bearing" under the toebox sole, and then to the ladderlock on the outstep of the shoe. Previous bearings tended to become misaligned from the force vector of the adjustment strap, resulting in high stresses in the materials holding the bearings. In Dan's first shoe, these stresses (which are proportional to the climber's weight) were high enough to tear the bearing retention material.

Having seen what happens when a misaligned bearing is subjected to high loading, I sought to design a bearing that would remain aligned or self-align. Since this part was critical, I didn't want to finish the all-lasercut prototype with out it, but that pushed back the completion of the prototype by about a week. A lesson in supply-chain management was learned (most of the delay came from waiting for endmills of the appropriate size to arrive in the mail), and the bearing performed flawlessly last night.

SFT’s prototypes are starting to look more and more real – no more fuschia thread!



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