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View Full Version : How would you build this? A prosthetic attachment



SimpleSimon
03-12-2012, 06:03 PM
My dad is missing an arm but loves to golf. He has always wanted one of these but they run a goo $800. Basically, it is a tube tapered to fit a golf club but slotted to get the club in and out. It attaches to the prosthetic via standard 1/2 threaded rod.

The hard part is, what to use for the flexible portion? I was thinking of finding a spring of some sort and welding nuts to the end of it for which I could then insert the threaded rod for attachment to the prosthetic. I could then plasticote or cover the spring with vinyl tubing, ??

http://www.oandp.com/products/trs/sports-recreation/golf.asp

bob_s
03-12-2012, 08:39 PM
I would think a piece of steel aircraft cable (1/4" - 5/16" diameter) would work quite well.

Evan
03-12-2012, 08:50 PM
At what height is the amputation? What does he currently have to wear that takes attachments?

How good a golfer is he/was he? If he wants to play for anything more than drinks you may have to consider the energy storage ability of the prosthetic. The guy they call "The blade runner", Oscar Pistorius, aka the fastest man on no legs, has been fighting with the sports establishment over the possible advantage that his carbon fibre lower legs might give him.

I am currently designing energy storage leg prosthetics for myself to help me out when I have to climb stairs or even just spend a lot of time on my feet. There are a lot of considerations and very small seeming particulars that make the difference between something that works and something that works well.

To build something that works well for your Dad I would expect it will take several versions until you get to one that does the job the way he wants.

adatesman
03-12-2012, 09:08 PM
Might want to give the folks at ParadoxSports.org (www.ParadoxSports.org) a holler on this one... They specialize in making the outdoors available to the disabled and there's likely someone on their forum who's already figured out a cheaper solution to this. I've got a couple friends involved with Paradox and they do absolutely fantastic stuff (including adapting my friend Maureen's arm prosthetic for holding an ice climbing axe. :eek: )

darryl
03-12-2012, 09:23 PM
I was thinking of something similar to cable, but I had more pieces of it in mind. Get a piece of rod large enough in diameter to bore and thread, plus drill three, four, maybe five holes surrounding the threaded hole, in the same direction, axially. A piece of cable is epoxied into each hole, then they are twisted into a bundle in the same manner as the cable is made. At the right distance, each cable goes into another similar 'boss', and epoxied as well. As long as each cable does at least one complete 'go around' of the bundle, the bundle will be flexible. You might want to end up with a couple of go-rounds. Work some Plasti-Dip into the cables, then basically encapsulate the bundle.

It's going to be some trial and error to get the right degree of flexibility, regardless of how you make the flexible part. You could use a spring, but in addition to being flexible it will also stretch and shrink. I think you would need to avoid this.

Another possibility is to use some rubber hose with a steel braid in it. That will be strong and flexible, and will have a well-controlled action as you twist it. I'm thinking you should be able to find a size that would give you the right amount of flex. A bigger problem might be finding the best way to attach it elegantly. A couple of hose clamps is going to look pretty awful. On the plus side, most hose is going to have a curl to it, and you might be able to use this to advantage.

Of course, if you made it with multiple cables you could put the bend in it to begin with, then apply the Plasti-Dip. It's going to want to keep some of that bend after it cures.

Some ideas anyway.

Jpfalt
03-12-2012, 11:46 PM
One thing apparent from the web page is that the polyurethane connection between the mount and the club socket is a stiff spring to "store energy" from the backswing. I'd start by making the stud mount and club socket in aluminum or stainless with rectangular sockets for the ends of a graphite fiber leaf spring and then epoxy the assembly together.

SimpleSimon
03-13-2012, 12:01 AM
So I started on this one tonight.

1/2x13TPI threaded rod for attachment into the prosthetic. I bought a 1"x5" heavy duty utility spring that I cut to a smaller lenths to prototype with. The spring is pretty stout but allows just enough deflection to give him some "stored energy". My goal is to build a metal slug to fit into the ends of the spring as caps that I can braze to the spring itself. I'll tap and thread those for the 1/2x13TPI. I intend to cover the spring itself in cloth or vinyl tubing to keep him from catching or pinching on something.

Right now, I see see I'll have some challenge with the depth of the tapered hold as I only have an Atlas 6". I might need to make or buy a longer boring bar. The eccentric piece that attaches to the spring will also have a 1/2x13 TPI.

Also, my first pass with some map gas, flux and some 1/2" nuts didn't work out so well. I may end up TIG welding them. Not sure how that will pan out if I need to affix something to the springs. I purposefully chose steel and non-zinc coated hardware because I knew I'd be trying to work with it later.

On a side note, the old man is already good a good golfer. Not great, but he is retired now and is obsessed with his golf habit.
http://img535.imageshack.us/img535/9272/img0374lq.jpg

Boostinjdm
03-13-2012, 04:22 AM
I think I'd go with a vinyl coated cable between the threaded stud and club handle socket. Then make a mold and cast the whole thing in a polyurethane cover. The cable will make sure it stays attached and has some rigidity, the polyurethane will give some flexibility and energy storage depending on how stiff a mix you find.

I am familiar with that prosthetic as one of the farmers I do work for has me repair his hook on a regular basis. Well.....I used to. I finally made him a new one and he hasn't broken it yet.

sbmathias
03-13-2012, 09:11 PM
The guy they call "The blade runner", Oscar Pistorius, aka the fastest man on no legs, has been fighting with the sports establishment over the possible advantage that his carbon fibre lower legs might give him.

Risking a poor joke, what do you think Oscar's "carbon footprint" is?

Evan
03-13-2012, 10:29 PM
Last I heard is that they will allow him to run but he can't change the blades he uses to any other kind. He is currently right near the top in his field against able bodied athletes. Gives a new perspective on the meaning of "disabled".

Rustybolt
03-14-2012, 09:47 AM
My dad is missing an arm but loves to golf. He has always wanted one of these but they run a goo $800. Basically, it is a tube tapered to fit a golf club but slotted to get the club in and out. It attaches to the prosthetic via standard 1/2 threaded rod.

The hard part is, what to use for the flexible portion? I was thinking of finding a spring of some sort and welding nuts to the end of it for which I could then insert the threaded rod for attachment to the prosthetic. I could then plasticote or cover the spring with vinyl tubing, ??

http://www.oandp.com/products/trs/sports-recreation/golf.asp



The pictures on the bottom.

It looks for all the world like a piece of flexible SS tube used for hazardous area light fixtures. Only the put some shrink tube on theirs.
McMaster Carr sells the stuff. I think it's called 'flexible metal hose' or 'flexible metal conduit.'

Jpfalt
03-14-2012, 03:28 PM
Just thinking this through, why not a clevis or universal joint arrangement with two end plates and studs on the end plates. Then you could put a spring around the joint and between the end plates. Then you could switch out compression springs to get the stiffness desired and control the joint twist at the same time.

I think that it's about time we consider "alternately advantaged" rather than disabled as some of the prosthetics are pretty darned amazing in what they let you do.

Alistair Hosie
03-14-2012, 07:12 PM
I reckon you could fabricate this yourself.I am sorry they charge so much for these things as it seems to be the disabled getting ripped off again. You're the man to do it.I would get as much information as you can and with the help of our pals here more knowledgable than I , I am sure you will suceed. Have fun and the very best of luck. Alistair

SimpleSimon
03-14-2012, 09:31 PM
Just thinking this through, why not a clevis or universal joint arrangement with two end plates and studs on the end plates. Then you could put a spring around the joint and between the end plates. Then you could switch out compression springs to get the stiffness desired and control the joint twist at the same time.

I think that it's about time we consider "alternately advantaged" rather than disabled as some of the prosthetics are pretty darned amazing in what they let you do.

Your cleavis pin idea is interesting. I think I would have to find a spring distributor and get different tensioned springs. I could then pre-cut or somehow adjust preload if it had an impact on the deflection and return of the spring.

Thanks for the ideas guys. As with any problem, its always good to gather input on alternative strategies for a solution whenever possible. :)

armedandsafe
03-14-2012, 09:49 PM
I reckon you could fabricate this yourself.I am sorry they charge so much for these things as it seems to be the disabled getting ripped off again. You're the man to do it.I would get as much information as you can and with the help of our pals here more knowledgable than I , I am sure you will suceed. Have fun and the very best of luck. Alistair


Alistair, it is called economy of scale. When you are building hundreds of thousands, nickles and dimes of profit are acceptable. When you are building tens of ones, five and dime won't pay the rent.

I know this first hand as the tool I designed and am starting to build will maybe sell 200 per year.

Pops

Evan
03-14-2012, 10:09 PM
Products for disabled people are frequently very overpriced. I think the problem is that the assumption is being made that somebody with deep pockets is paying the bill such as insurance companies or the government. The problem then is that the person without that kind of backing is left out in the cold.

TGTool
03-14-2012, 10:26 PM
I'm reminded of a radio program I heard once in which they covered a conference of people with various disabilities. Interestingly they (conference attendees) referred to the rest of us as TAB's - Temporarily Able Bodied. We just assume we will continue to have all of our faculties and abilities because up to this point we always have, but anything could happen to any one of us at any time. No point in being too cocky or swell headed just because we've been lucky so far. :eek:

SimpleSimon
03-18-2012, 12:12 AM
So the old man and I made a day of farting around in the garage. I had my Atlas 618 lathe running overtime as I had to turn two slugs for the spring ends, and use two different turned and bored slugs for the club holder. I then tapped the spring slugs and TIG welded the pieces together. Here is what we ended up with, which worked great! We also chose to blast the final product with a plastic tool dip.

The part that challenged me the most was easily solved while brainstorming with my dad at the hardware store. Rather than have to bore the entire length of a 4" pipe, I made two different tapered slugs and fitted them into the ends of the rod holder. Problem solved!

Not bad for $35 bucks including about 20lbs of scrap steel leftover for my secret stash.

http://img703.imageshack.us/img703/1840/finalproducty.jpg
http://img267.imageshack.us/img267/7002/finalproduct2.jpg
http://img140.imageshack.us/img140/755/prototypem.jpg

Mike Burdick
03-18-2012, 12:28 AM
SimpleSimon,

Kind of an interesting task...

I wonder if one could follow the mechanics of a wire grip and make it light enough to hold a club...

http://t2.gstatic.com/images?q=tbn:ANd9GcR70ZBVJKlC8VAmShzVGJ5pd0YQE-mBaFvRkaNdf-7Vly3GzjXOVw

Your Old Dog
03-18-2012, 07:55 AM
Simon,
Are you sure this project is being "over-thunkted"? :D

I watched a guy giving demonstrations on driving. He had a club shank made of red rubber hose and made spectacular drives. On a right handed golfer, doesn't the wrist (which is what you are trying to make) simply align/guide the club face as the rearward motion of the shoulder pulls the club around?

I seriously think you should first make the receiver for the prosthetic and then the grip for the club and then experiment with different common auto parts store rubber hoses. You don't have to store any energy up in the left wrist grip. All the work is done by the unwinding of the torso and the shoulder coming around.

Don't over think this project.

Your Old Dog
03-18-2012, 08:07 AM
Simon,
Are you sure this project is being "over-thunkted"? :D

I watched a guy giving demonstrations on driving. He had a club shank made of red rubber automotive radiator hose and made spectacular drives. On a right handed golfer, doesn't the left hand simply align/guide the club face to meet the ball as the rearward motion of the shoulder pulls the club around?

I seriously think you should first make the receiver for the prosthetic and then the grip for the club and then experiment with different common auto parts store rubber hoses. You don't have to store any energy up in the left arm grip. All the work is done by the unwinding of the torso and the shoulder coming around.

I wish your dad luck. It's a bear to have the time to do what you want but not be able to do it. I know of what I speak!

Don't over think this project.

SimpleSimon
03-18-2012, 12:22 PM
Simon,
Are you sure this project is being "over-thunkted"? :D

I watched a guy giving demonstrations on driving. He had a club shank made of red rubber automotive radiator hose and made spectacular drives. On a right handed golfer, doesn't the left hand simply align/guide the club face to meet the ball as the rearward motion of the shoulder pulls the club around?

I seriously think you should first make the receiver for the prosthetic and then the grip for the club and then experiment with different common auto parts store rubber hoses. You don't have to store any energy up in the left arm grip. All the work is done by the unwinding of the torso and the shoulder coming around.

I wish your dad luck. It's a bear to have the time to do what you want but not be able to do it. I know of what I speak!

Don't over think this project.

Well its done now! I expect a progress report from hiim today from the driving range. He drove out of here yesterday like a kid who just got a BB gun under the tree for Christmas! :)

Evan
03-18-2012, 02:59 PM
I look forward to his report. A very long time ago when very young I used to caddy at the local country club. A bag of clubs was a lot heavier back then.

Black_Moons
03-18-2012, 03:10 PM
I look forward to his report. A very long time ago when very young I used to caddy at the local country club. A bag of clubs was a lot heavier back then.

Oh really?

http://3.bp.blogspot.com/_vhtrfrPTvs8/S-k0KREqhLI/AAAAAAAAAAc/f9q3sJcfyMQ/s400/giant_driver%5B1%5D.jpg

"Thanks to modren technology, the drivers now have heads the size of infants."

Evan
03-18-2012, 03:20 PM
Yeah, but the shafts are graphite and the heads are titanium.

Black_Moons
03-18-2012, 04:05 PM
Yea, But the screw plugs are a Tungsten/Zirconium alloy to ensure they survive the "high temperature, corrosive environments" of golf.
http://periodictable.com/Items/074.7/index.html

SimpleSimon
03-19-2012, 11:40 AM
SimpleSimon,

Kind of an interesting task...

I wonder if one could follow the mechanics of a wire grip and make it light enough to hold a club...

http://t2.gstatic.com/images?q=tbn:ANd9GcR70ZBVJKlC8VAmShzVGJ5pd0YQE-mBaFvRkaNdf-7Vly3GzjXOVw


I've been thinking on the forces involved in this picture. I think I may do something similar with an eccentric that goes through the channel that holds the club. The only real problem we have now is that the club grips have different diameters (driver, iron, etc). The tapered slugs I used worked....but a more adjustable method would be nice.

flametamer
03-19-2012, 12:41 PM
I think I may do something similar with an eccentric that goes through the channel that holds the club.

http://www.oandp.com/products/trs/sports-recreation/golf.asp

Scroll down to the bottom 4 pictures.


Dt

Evan
03-19-2012, 02:42 PM
The tapered slugs I used worked....but a more adjustable method would be nice.

Like I wrote earlier I figure you will make it to about the Mk III model before it's all good. :D

SimpleSimon
03-20-2012, 12:38 PM
So....he went and hit it yesterday and couldn't get the ball in the air. We were thinking that it might be an issue with the spring length so I'm going to craft a shorter one. I also received some feedback that he wanted it lighter. I could have made it from aluminum but since I had some parts leftover, I started a second version.

In this version, I'm going to use an eccentric cam lock type mechanism since the forces generally only go in one direction. He can slip the club into the tube and pull downward causing the CAM to wedge the club in place.

The little Atlas was groaning trying to cut an eccentric. I had a slow speed with the back gear in place and I used a parting tool like I have seen others do when turning camshafts for hobby engines. I will red-locktite or fusion weld the eccentric onto the shaft later once make a lever and small riser in which to mount it to the tube.

http://img40.imageshack.us/img40/1306/camlock.jpg