Hackaday Prize Semifinalist: OpenBionics Affordable Prosthetic Hands

The human hand is an amazing machine, and duplicating even a fraction of its abilities in a prosthetic is a daunting task. Flexible anthropomorphic prosthetics can reach tens of thousands of dollars and are beyond the means of many of the people who need them. So imagine the impact a $200USD prosthetic hand could have.

For such a low, low price you might expect a simple hook or pincer grip hand, but the OpenBionics initiative designed their hand from the outset to mimic the human hand as much as possible. The fingers are Plexiglas with silicone knuckles that are flexed by tendon cables running in sheaths and extended by energy stored in elastomeric material running along their dorsal aspects. Each finger can be selectively locked in place using a differential based on the whiffletree mechanism, resulting in 16 combinations of finger positions with only a single motor. Combined with 9 unique thumb positions, 144 unique grasp are possible with the open source hand built from hardware store and 3D printed parts. Stay tuned for a video of the hand in action after the break.

3D printing is beginning to prove it’s the next big thing in prosthetics. Hackers are coming up with all kinds of static artificial hands, from the elegant to super-hero themed. Maybe the mechanism that OpenBionics has come up with will find its way into these hands – after all, it is an open source project.

The 2015 Hackaday Prize is sponsored by:

Continue reading “Hackaday Prize Semifinalist: OpenBionics Affordable Prosthetic Hands”

Wiffletree: a mechanical digital to analog converter

This isn’t a hack. But it is a decidedly interesting piece of mechanical technology. The Whiffletree shown above is a way to turn binary data into a mechanical analog value. [Bill Hammack] explains how this assembly is used in a typewriter and how a whiffletree can convert binary data to a set of analog outputs.

These linkages are what makes an IBM Selectrix Typewriter work. You know, the one with the globe stylus instead of individual hammers for each key? [Bill] uses the typewriter as the example in his illustrations that show how each bit of data positions the output in a predictably different location. We’re familiar with other mechanical representations of binary data but converting to an analog value mechanically is a new concept for us. Lukily, the videos that [Bill] put together are fantastic at explaining the concepts. Not surprising, since he is a professor at the University of Illinois at Urbana-Champaign . See them both after the break.

Continue reading “Wiffletree: a mechanical digital to analog converter”