MSM wrist [road map]
We started to develop a wrist joint - or a mechanical wrist joint - for my cable controlled arm prosthesis (or body powered arm prosthesis). The wrist joint should contain a quick release mechanism to allow fast switching of hook, hooks, hands, terminal devices, experimental tools or anything of that nature.
If you are interested in the time line of previous and future developments of our MSM wrist, here's the right place to check.
Contact me for further details (email address ~ wuff *@@@* swisswuff.ch).
Simple very sturdy design to wear and use on Otto Bock wrist matching sockets or terminal devices.
December 20, 2008. The idea is conceptualized to design our own wrist after taking apart an Otto Bock standard wrist and being very surprised by what we saw.
March 2008. The first parts are ready to wear. Subsequently, details of advantages and flaws become apparent.
April 2008. With simple modifications, significant issues of the MSM wrist 0.1 design are fixed; initial setup is extremely sturdy but with only three M3 inbus screws one easily comes loose through repeated shaking and requires frequent fastening, with M3 not being hard enough to allow for full inbus screwdriver action so six M4 screws are used instead. Secondly, the cable pull direction working well with the Otto Bock hook requires a mirrored sprocket for the Otto Bock system hand and due to the advances of high tech milling, the model is simply mirrored on the machine and produced again once more. Technically very simple, solves the problem very well.
The most accessible design idea to fully lock this wrist is by employing a simple pin that can be operated by a spring switch. However, pins and springs may end up not overly stable and so we may be looking into other ideas.
March 10th 2009. We are currently revising drafts for the prototype 0.2. Both our idea of one handed operation and a theoretically wide tolerance of one part of the lock were improved.
March 22nd 2009. All revisions of a concise draft 0.2 are finished, three independent reviews (M, S, M) now agree that this can be done with a good prospect of achieving what we are after. This will take about 7 months time (did I mention that we really revised the drafts and the new prototype is going to be more complex).
October 2009. The first prototype arrived. This was a lot more complicated to materialize. The parts were built to include troubleshooting features.
April 2010. Detailed trouble shooting finished.
June 2010. Extensive testing, 3D draft revision and improvement of a range of critical points is now done and completed. Awaiting production of final wrist.
July 2010. "All pigs fed and ready to fly." Perfect machining, perfect design. Thank you!
MSM stands for Müller Schweitzer Meili. In reality, five people now work on parts, Stephan Müller, Roman Meili, Peter Schneider, Remo Quinter and Wolf Schweitzer. A good slogan to use would be "MSM FUNCTIONAL PROSTHETICS - GET A GRIP ON REALITY".