Prosthetic Arm - Calling For Harness-Makers!

[StrayDogLamont]

Greetings Folks,

I'm a living historian (F&I War, RevWar, 1812, and 1830's.) I volunteer at an historic village in NJ (blacksmith, militia, and leathershop). I am the only volunteer who has done any leatherwork. We have a new 16 year old volunteer who was born without most of his right forearm. He is currently interpreting the Carpenter Shop, and wants to be able to do more. We thought that it would be nice to try and fabricate a prosthetic arm which would fit in the period (1836) and would have the ability to hold a chisel securely so that this young lad can work - in "period."

The lad's upper arm is a bit more slender than usual, and his forearm terminates about 3 inches from the crease of his elbow. His forearm is tapered/conical in shape, and it is therefore necessary to secure the appendage to some sort of cuff which is attached to the upper arm. At the end of the forearm I have designed what will be a relatively lightweight "hand" that uses a strap-clamp like mechanism to secure a chisel or similar tool. My concern is that even though the hand is not heavy, striking the chisel with a mallet could cause the forearm portion to move out of place. I have attached my preliminary sketch (since this sketch, I have revised the tool-clamping device.)

So, the advice I'm looking for has to do with ensuring the stability of the forearm prosthetic under semi-strenuous conditions.

I would be very grateful for any ideas or advice in this regard. I figured that harness-makers would likely be the most knowledgeable.

Thank you, and may God bless.

[electrathon]

Cool and interesting project. My input is it needs a better hindge on the elbow, you seem to have more of a pivot area. I would also strap the top over to the other shoulder (like a shoulder holster) so it does not simply slide forward and off.

Aaron

[StrayDogLamont]

Thanks Aaron. Yes, a shoulder strap would seem to keep the whole rig in place more securely. I also thought that if the upper cuff were actually connected (as one piece of leather) under the elbow to the forearm, this would cause the forearm portion to tighten if the elbow was bent. Combine this with the shoulder strap, and perhaps were are getting somewhere for a reasonable and practical prosthetic.

Thanks again!

Cool and interesting project. My input is it needs a better hindge on the elbow, you seem to have more of a pivot area. I would also strap the top over to the other shoulder (like a shoulder holster) so it does not simply slide forward and off.

Aaron

[electrathon]

If the strap goes behind the elbow it will pull the cuff off as you are bending it back and forth. It will also rub the elbow raw after a while.

I would suggest having the blacksmith make a hinge out of band iron (long and slender) then you embed it in the leather arm band. I would envision it looking a little bit antique crossed with some steam-punk styling.

[amuckart]

There are pictures of extant ACW-era prosthetics online. Have you looked at those to see how the prostheses of the period were done?

[StrayDogLamont]

Getting the blacksmith to make hinges would probably be the way to go. The tangs of those hinges should run nearly the length of the cuff and forearm piece, I imagine. As I said, the concern is that his forearm is quite short, and stability is crucial. I suppose that the best method of attachment for such hinges would be rivets. I do plan to line the cuff and forearm piece with sheep hide (hair inward.) Even though I intend to line the pieces with sheep hide, you're right that under the elbow could pose its own problems.

Thanks again Aaron.

If the strap goes behind the elbow it will pull the cuff off as you are bending it back and forth. It will also rub the elbow raw after a while.

I would suggest having the blacksmith make a hinge out of band iron (long and slender) then you embed it in the leather arm band. I would envision it looking a little bit antique crossed with some steam-punk styling.

[StrayDogLamont]

I have done quite a bit of research for early 19th Century prosthetics, and have found a few pictures, and that's how I came up with the basic harness design. The pivot of the elbow has apparently been a difficulty for those folks as well. I had found one which used crossed straps which may work, but could cause some rubbing. And there is one with hinges, but like myself, most of our blacksmiths are amateur blacksmiths, and I'm not so sure we could pull off good flat hinges. I'll be talking to them to see what we can do. Thanks for your input.

There are pictures of extant ACW-era prosthetics online. Have you looked at those to see how the prostheses of the period were done?

[electrathon]

As far as the hinge is concerned I don't think it could get any simpler to make. You use two pieces of band iron. Drill a hole near the end of both. Fasten them togeather with one rivit.