Designing brackets for cLeg cosmetic fairings

Colten Jackson
Nov 29, 2015 · 3 min read
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A continuation of: Blending and Bending Prosthetic Leg Fairings

I wanted to design a 3D printable file that would allow me to clamp my acrylic fairings to the cLeg. Luckily Kay and Gabe created a pretty solid model of the cLeg itself so I could use its contours in my design. Again, I had to cut the model down manually in Blender because netfabb does an awful job of exporting STL (hadn’t yet investigated if this is an actual or a free-demo-imposed limitation of the software).

I also used Blender to multiply the scale by 1,000 before importing into Tinkercad.

I like Tinkercad because it makes it super easy to perform boolean functions on complex stuff like our leg here. If you’re a tinkercadder, try ungrouping the model so you can see how I made a cross section of the leg: Tinker This

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And I went on to improvise a way to screw two parts together — this is very much a test fit, to see if the idea makes any sense, to see if screwing two plastic pieces on with pressure is enough to keep it from falling off.

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I went back and forth about 3D printing holes for nuts and bolts, but decided I would drill it out of the finished plastic — “machining” is way more accurate than printing for this kind of thing.

OK, the original Kinect scan was not very dimensionally accurate…I guess I could have compared measurements of the model with measurements of the object, that’s what I get for trusting technology -.- I can still use the blocks of plastic for practice fitting, though. They don’t clamp around the c-Leg, but I tested screwing the pieces together and drilling into the plastic to insert a brass threaded insert, and with a few taps of a hammer that turned our really nice.

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Of course, the chunky tinkercad design isn’t so fashionable, but it served its purpose to confirm that I need to press the shape of the leg more accurately (the front fairing doesn’t sit flush with the printed model at all) and that countersunk M5 screws will do a nice job of securing the fairing to the bracket, though I’ll have to play with melting a countersink so the head of the screw doesn’t stick out the back.

Continued here:

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