Tolerances

[Wolf Schweitzer]

Does anyone know the tolerances allowed for bolts that fit into regular wrist units (cable controlled prostheses)?

A friend milled me a couple (so we could start playing with modified terminal devices) and they range from sturdy fit to loose so we wondered if tolerances are something you could easily name.

I use a standard Otto Bock wrist unit.

Thank you, Wolf / rbe

[Wolf Schweitzer]

http://www.swisswuff.ch/tech/?p=65

OK we designed our bolts, no problem (see link). Currently we are considering the tolerances and wondered whether the wrist unit by Otto Bock was at all good enough.

We figured that Otto Bock's bolt tolerance specs (which they didn't want to give out) were probably very wide. Also their wrists seem to contain a metal bolt bearing that is constructed in a way that it dilates over time - metal too soft, too thin, whatever. Due to that combination I now have some bolts that sit snug and one that rotates rather freely.

So if we start to build high quality bolts we figured we'd redo the wrist at the same time. After all that thing is simply screwed into the prosthetic socket and one can obviously remove and reinsert or swap it.

Anyone with experience in building your own wrist unit?

[Wolf Schweitzer]

http://www.swisswuff.ch/tech/?p=65

We documented:
- bolt diameters
- wrist mechanism

Seems like wide variances of factory issue bolts distend that spring that locks the bolt into place.

[Wolf Schweitzer]

We are currently building a new wrist unit that can replace the current one. Is anyone aware of patent regulations?

If I do not want anyone to patent what we are developing, would it be enough to publish the design so it can be freely accessed? Publish where? I think we'd just want the final step files etc. be freely accessible such as through Open Prosthetics but I am not sure if this is the right audience as y'all seem to be exclusively Hosmer and TRC based, whereas I am using / replacing Otto Bock parts.