MYOG Titanium/Carbon Fiber Ice Axe

> You could very well be correct about the CF insert being the key to better performance. I really should try it out before knocking it.
Yeah, I would REALLY like to see this experiment done. I am quite sure myself it would add greatly to the strength of the head connection, to the point that the shaft might then be adequate. I would recommend that the insert be 1.5 times the length of the current ferrule and a fairly tight fit.

> Looking at it from the another view, if we increased the diameter of the shaft, we could shorten the ferrule
Won't work! Check it on the FEA by all means, but shortening the length of the ferrule will ALWAYS reduce the strength of the joint severely. You could probably taper the ferrule wall thickness down significantly though – but keep that length!!!

Cheers

Besides adding strength, adding a thin cf insert inside the ferrule extending a couple inches out would spread the stress on the shaft over a larger area. CF will flex quite a bit and when bending, a large amount of force is applied to the hard edge at the end of the ferrule.

When you look at the end of a power cable the usually have a ribbed area to allow the cord to bend at the plug rather terminating at a hard corner. Same idea.

Hi Chris – good questions.

(1) Current shaft legnth at 19" = 45.2 grams

(2) I calculated early on that the max stress to be 122,000, but after testing found that it is almost exaclty half that at ~61000psi.

(3) A shaft with the same wall thickness as the original shaft having a I.D. of 0.875" and an O.D. of 0.9575" would weigh 57 grams.

Assuming the larger shaft was built the same and had the same properties, it would hold about 80lbs before breaking. This would add 12 grams to the weight of the axe.

Comparing a few more numbers, to get at the 135 lb UIAA requirement, we would need to find out how to increase the 61000 psi number. The numbers just aren't working out as we would need to have a huge (and heavy) shaft.

The Ti on the axe spike was actually made from 3Al-2.5V for ease, but when I sent out for quotes, no one could source a tube with the required dimensions…and I mean not one. They all came back stating a material change of 6Al-4V. I know I can get the stuff from Ti Joe, but the problem is that he isn't a reliable source for material because he deals with scrap. Therefore, sometimes he has the stuff, and sometimes he doesn't. For a short production run, I could get away with it, but most places just wanted to order one piece of .875 bar stock, put it in the machine and come back later when all the parts are done…it was very difficult to even get guys to quote the stuff. Other then Ti Joe, I couldn't source the stuff from any of my suppliers. Even now, I'm getting the stuff shipped in from California.

"I'm not sure if he can supply an insert with an outer diameter within the tolerances required to fit the shaft without a second operation. For instance, the upper 1.4" of the current shaft (where the ferrule is placed over) is ground accurate to +/-0.001".

See what Kevin says but Roger's "fairly tight fit" sounds good enough to me. This bond does not have to take tension as great as the ferrule joint after all, it just has to transfer some bending forces. It might not even need such expensive glue. I was hoping that glued in it would add about 8 gram and cost about $5

> Assuming the larger shaft was built the same and had the same properties, it would hold about 80lbs before breaking. This would add 12 grams to the weight of the axe.

I would buy that increase. I think the wall is a shade too thin at present.

OK, I heard back from Kevin, who happens to be away from work at this moment. He is going to verify that he has the tooling available at his work to manufacture the required insert. He is familiar with the insert technique being used in situations like the one we have with the axe, however, he stated that it is not common practice.
In the meantime, I am going to run some numbers to get an idea of how long it needs to be, how much strength it will give us, and how best to go about the process.

Fun I want to play that game, my guess 50%

edit or 55% if the insert is inserted flush to the end then pushed in another 1/3rd ferrule length. Insert length 1.5 ferrule length

Hey Steve,
I know this is a fairly new and who knows how expensive, but is it possible to use / get a CF tube that is made with the new Nanotube technology?

The company's that have switched to them have not changed there prices that much with the same product using the Nano.

I would think that since the CF tube is strong and just needs to flex more before breaking, the Nano just may be the trick.

This may be a $10 addition cost to you but you could add it as a $25 option to make up for low cost gain that you have.

Just thought I would give a quick update for those interested. I have all the material for the axes, I'm just waiting to hear from Kevin on the carbon insert. He told me he was away for the next week or so, but was going to let me know if and when he could provide them…he has been very helpful, so I don't want to hound him. :)

I did run some numbers but I believe they were not very conclusive. I am getting about a 10% increase in strength, which would equate to about 4 lbs of additional load capability…hopefully I am wrong. I do realize that we will be relying on the insert to spread the stress over a larger area, and this is very difficult (for me) to calculate, and I can't run it through my software as I don't have all the required material properties…so we may have to wait for the test to see solid numbers.

So we hurry up and wait…

Thanks Steve,
I am glad to have the update. We are off to the Pyrenees on the 9th july. It would great to have a just in case axe for then but it sounds as if they wont quite be available by then.

Derek

Derek, amazingly enough, I just got an email from Kevin stating that he has built the inserts and is shipping them tomorrow. I should have them by the end of the week, but I wouldn't be able to promise anything by the 9th…I'm STILL struggling with getting some of the pieces quoted.
Then again, I'd really like to get one out there for someone to review it in the field. We'll see…