An Elbow Joint That Can

We’re not certain whether [Paul Gould]’s kid’s prosthetic elbow joint is intended for use by a real kid or is part of a robotics project — but it caught our eye for the way it packs the guts of a beefy-looking motorized joint into such a small space.

At its heart is a cycloidal gearbox, in which the three small shafts which drive the center gear are driven by a toothed belt. The motive power comes from a brushless motor, which is what gives the build that impressive small size. He’s posted a YouTube short showing its internals and it doing a small amount of weight lifting, so it evidently has some pulling power.

If you’re interested in working with this design, it can be downloaded for 3D printing from Thingiverse. We think it could find an application in plenty of other projects, and we’d be interested to see what people do with it. There’s certainly a comparison to be maid over robotic joints which use wires for actuation.

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Give Workshop Pencils A Flush-Mounted Home

Pencils and pens are apt to go wandering in a busy workshop if they don’t have a handy storage spot. For most of us a soup can or an old coffee mug does the trick, but for a prettier and more useful holder [Stuff I Made] has a short video demonstrating a storage unit made from an elbow fitting and a scrap piece of plywood. He cuts a plywood disk that is friction-fit into one end of the elbow, then it gets screwed into a wall making an attractively flush-mounted holder in a convenient spot.

With the right joint the bottom of the holder remains accessible, as a 90 degree bend would be no good. With a shallower joint angle, a regular screwdriver can still reach the mounting screw and it’s possible to access the bottom of the holder just in case it needs cleaning or something small falls inside. You can see the process and results in the video embedded below. Not bad for one screw, a spare joint, and a scrap piece of plywood.

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