Wrenchin'

[bluedogz]

Hi all-

I have a new rig... a thermoplastic socket ending in a simple wrist unit that functions as an elbow. The wrist/elbow (which is located at the end of the socket where my elbow used to be) has a 1/2" threaded receptacle for a forearm or terminal device.

Trouble is, the 'forearm' I am using is a 7/8" aluminum tube, which obviously does not have screw threads on the end of it to attach to the elbow. I have managed to rig a 1/2" bolt to the end of the tube by drilling laterally through the forearm into the bolt that provides the threads, then using sheet metal screws to hold the bolt into the forearm. However, this is creating a weak spot, and the bolt rips out of the forearm every couple of weeks, requiring me to cut the tube a bit shorter and drill new holes.

I am trying to find a better way to get threads on the end on the forearm so I can screw it to my elbow. I'm a pretty handy fellow but this seems beyond me.

If my description is too vague there's a photo here... www.triumphtorque.com/media/file/67747.aspx

[snowyh]

Excellent, Blue! But, where did you get all this slick stuff if not from a prosthetist? And, if you got it from a prosthetist, why didn't they rig the connection between the socket and the forearm? I'm having trouble figuring why you're the one who has to wield the wrench.

Helen

[bluedogz]

The prosthetist is 100 miles away in DC, my new job is 100 miles the other direction in New Jersey, and I cannot afford several days off to travel around having it fixed. So I want to just open my toolbox and do it.

[cherylm]

Blue, is the "weak spot" caused by a gap between the diameter of the bolt and the diameter of the pipe for the forearm? If that's the case, is there any way that you could use something to fill the gap and stabilize the holes you've drilled through the forearm pipe?

Just throwing out thoughts...............

[bluedogz]

Yes, Cheryl, this is one source of weakness... in a perfect world, I'd use a good old 3/8" bolt with a tall crown, and drill a 1/8" or 3/16" hole all the way through the crown side to side, and put a long bolt through the whole shebang and crank it down with a nut. However, this is an operation that works better with time, tools, and... two hands.

I'm just thinking there has to be a better-engineered way than the Rube Goldberg solution above. I was hoping a CPO might chime in....