Mini-Update On The v2 Ratchet Design

A project log for Hintha Modular Prosthetic Hand

An affordable, durable, bespoke prosthetic hand system developed in and for low-income settings

Jason BenderJason Bender 12/15/2018 at 05:120 Comments

Jason Bender // 15 Dec 2018 // Taunggyi, Myanmar

As I wait for more hardware to arrive from abroad, wanted to update on some small design changes for the ratchet system:

Animated exploded view of new ratchet assembly

If you may remember, the original ratchet system included six printed parts, four screws, and a spring.  By inverting the ratchet (so the gear is external and pawl is internal), having the gear teeth built-in to the body shape, and utilizing two snap-fits (instead of a retaining ring as originally planned for v2) in low-force areas, the part count is reduced to four printed parts and a spring.  The re-design also allows for an increase of about 6mm in the overall diameter of the ratchet, which allows for a increased tooth count and hopefully will help larger hands manipulate the device.

I also realized during testing of the v1 prototype that the ratchet on a right-hand device should really rotate counter-clockwise to accommodate turning with the left hand, so I have also inverted the teeth and pawl to make that change.


All the printed parts for the v2 prototype

The parts for prototype v2 are printed and ready for assembly.  As soon as the hardware arrives, it will be time for another round of testing!

That's all for now. More to come (hopefully) soon.