Securing the cable quick lock for body powered prosthetic arms - PVC outer cable sheath as lock cover

Securing cable quick locks is a major issue as there are no useful commercially available solutions that really work well over an extended period of time, or that offer good performance with fast degradation and cheap and available replacement.

Previous materials tested:

  • Metal cylinders are not useful as small deformations may render them useless and as that area of the prosthesis may be subject to repeated physical contacts (i.e., bangs, to be exact), you don't want to go that route. Steel or aluminum tubes did not work out to be efficient. Otto Bock metal covers contain a small screw that is thought to fix the metal cover in place but either the cylinder is too narrow, or a small deformation gets abraded too fast, or it is too wide. Mostly and at any given time, the metal cylinder will be too wide, and the cable will disconnect from the lock as the cylinder displaces itself.
  • Rubber tubes of any suitable diameter are cumbersome as they start out too narrow initially. They are very hard to get on, and to swap terminal devices initially is time consuming and painful as fingers need to exert full force. And you don't want to use lube there. Later, rubbers get damaged and tear easily. Over a period of 3-4 weeks, the slightly damaged and dusty rubber assumes the perfect stiffness but period of initiation (while the rubber is too stiff and too narrow) is too long, period of usage (mostly 3 weeks) too short in relation to that. They are better than nothing, better than metal, but they still suck.

The ideal solution are PVC outer cable sheaths of appropriate diameter, for me these are 5-line power cord cables. This find was the consequence of an ever alert visit to a construction site where such cable sheath ends were lying around amidst the rubbish. I saw one of these, went "hey", picked one up, saw the 5-leave-shaped cross section that allows for a mild tension of the sheath while allowing for dust or other small particles to be easily displaced. And it was love on first sight.

Here is the cable quick lock with the PVC securing cover pushed to the side:

Here is the quick lock cover in place:

Here is how to round them up yourself:

These are the DISTRELEC order details for the cable:

The clipped end of the cable shows the five-leaf-shaped inner contour of the black PVC sheath. The five ridges give the sheath the required tension so it stays on the metal lock - and while it still slides on an off, I found this one is sturdy enough for rock'n'roll.

The cable part used as lock cover gets clipped:

All inner cables are pushed or pulled out:

The resulting PVC covers:

Usage report:

So far, the material is easy to push on / off the cable lock but does not displace accidentally. It glides very well on both prosthetic socket and under most clothes without discoloration, rub-off, without generating friction noise or other problems. Also it is very affordable. But it survived all major incidents so far, and did not slide off when it would have been unintended.

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Securing the cable quick lock for body powered prosthetic arms - PVC outer cable sheath as lock cover; published 25/11/2010, 14:19; URL: https://www.swisswuff.ch/tech/?p=370.

BibTeX: @MISC{schweitzer_wolf_1602784721, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Securing the cable quick lock for body powered prosthetic arms - PVC outer cable sheath as lock cover}}, month = {November},year = {2010}, url = {https://www.swisswuff.ch/tech/?p=370}}