Titanium

[BIGNASTY]

I have a problem with my new leg the manufacture said that I can only have one heal height on my shoes something to do with the way the knee is set up, the length of the shaft from the bottom of the knee to the top of the foot and the heal is figured into the length. My question The knee is part Titanium and Part Aluminum but its all got some kind of anodizing on it to make it look the same. Titanium in a non-magnetic metal like aluminum so how can I tell the difference without scraping off some of the finish. The manufacture said whats the big deal with one heal height? 12 pairs of lucchese boots is a pretty big deal to me!!!!! And how would it look to go to the barn with 501's, chaps,denim shirt, and Reebok tennis shoes!!! Not to say what the guys at the saloon would do to me for coming in with that on. My idea was to make new leg shafts for different heal heights the manufacture said it would work but for some reason wouldn't tell me what the shaft is made of I cant see the leg shaft being made of Titanium isn't that stuff pretty expensive? This is what im looking at, the machining can be done by my gunsmith but its the shaft from the bottom of the knee to the top of the foot that is in question.



Thanks

BIG

 

[JR]

BIG, I would think the flexing parts would be titanium, just reasoning that critical components would be higher strength? thats only speculation i know nothing about em. I dont understand why only one heel though. They do have insoles to make up for heighth differences my fathers left hip is half inch shorter than his right when he buys new shoes he takes them to a specialist and they add a half inch to his right shoe sole so that he walks evenly.

 

[goodguys75]

I like my suppressors made out of titanium... . aircraft grade of course... very light and worth the price... ...

 

[BIGNASTY]

The way this leg works is kind of sci-fi to me anyway. The leg has motors and foot has sensores. The foot sensores tell when the motors should run and in what direction. When you lift your heal first it tell the microprocessor that you moving forward and the motors run in one direction so when you lift your stump the leg will move the foot forward. The opposite happens when the toe sensores feel less weight on them the run the motors in another direction because when you back up (your toes lift first). Its pretty neat the way they got it figured out its as natural a stride or gate that an amputee can get. Some of the people that have had it for awhile when they just walk you can hardly tell that they have a prosthesis. When they step over something is where its pretty visible you lift your stump and the leg will move the foot in an unnatural motion. WHO THE HELL CARE'S BEATS THE CRAP OUT OF CRAWLING. The problem is that when the heal height is changed the sensors react at a different rate (early or late ) because the pressure on the heal or toe has changed because of the height. Also the change will be more noticeable with the height change because the foot/leg will be longer or shorter like you said the one guy took his shoe to a store to have it worked on how many times have you seen that one shoe with normal sole and the other like inches thick its so they dont limp, same thing. Personally I dont think that the manufacture likes to have people think about this kind of thing. On my other leg before surgery my BIL seen what a PITA it was for me to change shoes so he made a quick disconnect almost like an air fitting on air hose to air tool pull the slide the boot and foot would fall off and stick it in another foot/boot combo and let the slide go and it connected. He has a patten on that and has made some pretty serious change off his idea for helping his BIL. On that leg it was pretty easy just make the shaft short or longer it was aluminum and was not a big deal.

 

[JR]

Thanks for sharing that, BIG. I had no idea they were that technical.

 

[BIGNASTY]

They aren't really, this is new to this country. I have to learn to walk with this and then another leg combo that is Mechanical in nature because the Microprocessor leg cant take the weight and what I do to it with the mules and packing equipment and then to be able to change back and forth is going to be fun for the winter. The physical therapist said CANT BE DONE!!! Wife told him she has $500. 00 that says I can

 

[goodguys75]

very neat stuff.....

 

[GHarman]

Titanium and Aluminum

BIG!
There are several types of titanium and titanium alloys in use. They each have their purpose. From a practical standpoint! I would second the idea that the titanium is used in the wear and high stress areas.
BTW it is not a completely accurate statement to say that Titanium is "non magnetic". It is considered "paramagnetic" in itself and especially if it is alloyed with iron, can be identified with a strong magnet. This will not have the same attraction as steel, but will be slightly noticeable.
http://en.wikipedia.org/wiki/Paramagnetism
http://en.wikipedia.org/wiki/Titanium
The leg shafts are probably made from aluminum as it is 1/2 the weight of Titanium and the greatest mass in the prosthetic.
I would think that Aluminum alloys such as 6061 T-6 and 7075 T-6 would work for leg shafts. No welding the 6061, or the heat treat(T-6) will be destroyed at the weld zone (although the 6061 can be "re heat treated" after welding) . Generally, 7075 is not considered weldable. A cylindrical tube for would be an ideal shape, but there are other extruded structural shapes available. Calculating diameter and wall thickness for the best load bearing and stress loading application will be the chore.
Here are a few general information links on those aluminum alloys;

http://en.wikipedia.org/wiki/6061_aluminium_alloy
http://en.wikipedia.org/wiki/7075_aluminium_alloy

You can go deeper into the metallurgy. This just gives you a basic idea.
GregH

 

[Wayne M.]

BIG. that's an amazing piece of equipment there. The only experience I have with titanium is race engine valve spring retainers and bicycle frames. Guy at work does long distance lance Armstrong type biking. His frame is titanium. I know it's very brittle and the tubes have a certain ring when knocked as opposed to mild steel or cro-mo. They are known to crack. The retainers are so light, lighter than plastic, and have a texture like it. Al& Ti are similar in natural color.

 

[Wayne M.]

Mr. Greg, had I seen your post, I wouldn't have posted at all.

 

[GHarman]

Wayne M.

Why not, Buddy? Your opinion is just as good as mine!

GregH

 

[BIGNASTY]

Greg

Thanks for the help the leg shaft is not hollow (I think) I tapped on it to see what it sounded like it didn't sound hollow to me! I have had no experience with titanium other than in some of the aircraft parts that were to heavy for me to pick up anyway so I didnt know that it is heavier than aluminum if its solid it has to be aluminum because the inertia of heavy weight would use the motor and battery power pretty fast.



Wayne

I kind of know about Lance Armstrong type of bikes some of the parts could be titanium but most of those type of bikes that are in the Tour de France are built of carbon fiber they weigh less than 20lbs and some have to add weight to make the minimum. But I could be wrong its happen before.

 

[GHarman]

BIG!

IMHO, A Chrome moly tube would be very strong and given a thinner cross section than aluminum bar stock or tube with a thick wall. Steel is about 3X heavier than Aluminum given the same volume of material. However a 4140 Chrome moly tube with a 1/16" wall (as an example), would be the same weight as a similar diameter aluminum tube with a 3/16" wall thickness. Examples; 1' of 1" diameter aluminum tube weighs 0. 5615#. A piece of 1' X 1" diameter 4140 Chrome Moly tube with a . 062" wall weighs 0. 6182#. A 6061 aluminum bar at 1' X 1" diameter weighs 0. 9231# and a 4140 Chrome moly tube with a 0. 09375" (3/32") wall weighs 0. 9032#. The rigidity of the alloy steel, tensile strength and load bearing capability would be something to consider. Welding fittings and adapters onto the tube would be less troublesome.

Course you would have to blue the steel and oil it daily. Hmmm. You could rifle it too:-laf Naaah, that would require a larger diameter tube for what I was thinking!

GregH

 

[BIGNASTY]

GMan I will have to go to the hospital shop for prosthesis repair and talk to that guy he can tell me what it is. The reason that I dont think its a tube is because to remove it there is a set screw at the top and bottom of the shaft. That is not a collar its part of the shaft on the upper part where it goes into the knee is the same but it also has a collar with a 2 screw clamp. I think that is a place to add some sort of add on that I dont have or need. but on the end of the shaft there is a slot cut all the way AROUND the shaft and the set screw locks it in place. Like I said the repair guy should know at the hospital for a doughnut and coffee they will talk your ear off they dont get many visitors in shop.

 

[GHarman]

BIG!
Love to hear what he has to say!
It sounds like a FUN project. If ya can work it right? Patent it!
Make sure you copyright any notes you make!
Yer Pard!
Greg

 

[BigPapa]

Did you say there are some kind of sensors in the foot? If so, I would wager the shaft is hollow with the wiring running through it.



I would also guess that the foot angle has to be set for the single heel height in order to work properly.



Just my opinion, but I'd try it with the tallest and the shortest heels I had and just see for yourself if it makes a huge difference in how it functions.

 

[BIGNASTY]

BIG!
Love to hear what he has to say!
It sounds like a FUN project. If ya can work it right? Patent it!
Make sure you copyright any notes you make!
Yer Pard!
Greg

I would just like to be able to ride my mule again Pard money is not that big of an agenda for us anymore.

 

[GHarman]

BIG!
I know! Just sayin!
You will ride again!
Greg

 

[BIGNASTY]

Did you say there are some kind of sensors in the foot? If so, I would wager the shaft is hollow with the wiring running through it.



I would also guess that the foot angle has to be set for the single heel height in order to work properly.



Just my opinion, but I'd try it with the tallest and the shortest heels I had and just see for yourself if it makes a huge difference in how it functions.

SURE it's not YOUR FACE!!!! that gets drove into the floor :-laf:-laf that could be, have to pull the foot off and look around the bottom. Could be a hole drilled in bar stock also. Right now they are kind of weird about ME doing ANYTHING other than walking, and exploring on a $35K knee would be kind of expensive if something went south. They make adjustment to it all the time in rehab its not the final setting by any means. But he did say it could be done so there is hope.

 

[BIGNASTY]

BIG!

I know! Just sayin!

You will ride again!

Greg

I know Pard If there is money to be made we will find it. Im still getting use to the sounds it makes I went to the barn today and the gang kind of got weird when I walked up to them we can just hear the motors but they must hear it pretty well cause Daisy kept walking away from me and the BOY'S left the barn!!! The cow was the only one glad to see me she likes me playing with her T****s :-laf Nora my Daughter said Daddy-O your one sick puppy but she still loves me.