Braking carabiner: aluminium alloy or steel?

[tchudson]

I own two Russian titanium biners that I bought from some visiting Russians in TAG years ago. Used to use them all the time, but now they're on a line I use as a pack tether.

I remember one cave trip where someone mentioned that they would never trust their lives to a Russian titanium biner. I told him that he was going to have a hard time getting out of the entrance pit since it was rigged with two of them....

[cob]

I told him that he was going to have a hard time getting out of the entrance pit since it was rigged with two of them....

Oooofffff.....

[WillemII]

I recall being told to never use alu carabiners on places were friction from a passing rope can create heat.

Repeated heating (and cooling) the alu was said to weaken the internal structure of the alu and thus making it UNrealiable since you don't know it's breaking strength anymore...
Steel is supposed to be less sensitive to this.


It is however long time ago that I looked into this matter, so please correct me if I'm wrong.

[chh]

I recall being told to never use alu carabiners on places were friction from a passing rope can create heat.

Repeated heating (and cooling) the alu was said to weaken the internal structure of the alu and thus making it UNrealiable since you don't know it's breaking strength anymore... Doh!
Steel is supposed to be less sensitive to this.

I'm no metallurgist, and while I'm sure there was (or is) some truth to this as far as the relative sensitivity to heat warping in aluminum vs. steel carabiners, I'd say today's modern aluminum carabiners should be fine. They will get hotter, they might make your rope dirty, and they will wear down faster, but I can't imagine a strength loss that would be caused by the heat associated with repeated rappelling that would'nt otherwise be indicated by grooving or other external signs. Though someone who knows more would probably be able to say for sure.

[icave]

I had heard reports that the use of titanium was stopped in racks as it tends to catch fire if the friction gets it too hot. I'm not sure what temp is needed to start a titanium fire; however, I know that it's a general rule to keep your tools sharp when cutting it to avoid friction fires.

I'm sure that this would apply to other titanium gear where friction can cause heat.

[hunter]

I recall being told to never use alu carabiners on places were friction from a passing rope can create heat.

Anecdotal evidence would suggest that this is not true enough to be a problem. It's not to uncommon to overheat an ATC (aluminum climbing rappel device) to the point of glazing the sheath on the rope and I've never seen a warning related to this damaging the structure of the aluminum.
Likewise most climbing carabiners are aluminum and in top-roping situations they are expected to heat up due to friction from lowering the climber but I've never seen a heat related warning from any manufacturer. I have however seen a biner cut most of the way through and then broken from rope wear.

Same story on rack bars and figure 8s.

I have heard that aluminum bolt hangers are suspect due to stress fracturing over time, I don't know how true this is...

James

[geoff]

Using 10mm here in UK as the norm and Petzl Stop descender, you may like to try a steel "handy" as your braking krab.

this is a purpose designed steel krab where the rope is pulled up into a vee. It does not cause rope wear but gives exceptional control. See Alpine Caving Techniques for the benefit's, including rescue. It is lighter than a steel krab.

I personally dont like the Petzl Freino as by comparison it give poor resistance and not being steel is subject to quick wear on muddy rope.

Geoff

[paul]

Using 10mm here in UK as the norm and Petzl Stop descender, you may like to try a steel "handy" as your braking krab.

this is a purpose designed steel krab where the rope is pulled up into a vee. It does not cause rope wear but gives exceptional control. See Alpine Caving Techniques for the benefit's, including rescue. It is lighter than a steel krab.

I personally dont like the Petzl Freino as by comparison it give poor resistance and not being steel is subject to quick wear on muddy rope.

Geoff

I have been using a Freino for the past few months (I use a Petzl Simple or Bobbin). It is definitely starting to wear on the braking surface and probably will now start to wear quicker.

I found the opposite to you: the Freino gives more friction - often too much friction in constricted pitches (and I weigh 15 and a half stone/217 Pounds/100 Kgs!) I really like the lock-of method as it is quicker than the usual method of feeding a loop of rope through the karabiner and over the top.

I have tried the "Handy" in the past but found it very jerky - that may be a feature of using it with a Bobbin as opposed to a Stop?

[Seamus Decker]

For short pits in the Kentucky Mammoth Cave area, where you have to make long horizontal travel between pitches, and thus minimizing kit weight is a factor, I use a small pear-shaped SMC steel carabiner to abseil in an Munter hitch ("R-knot" I've heard it called). I've never noticed any exceptional effects on the rope. However, after about four years (maybe 120 trips?) of use in this way, my carabiner has slight indentations worn on both sides where the rope wraps around it; probably less than 5% of its diameter worn away. Just barely noticeable, but time to retire it I think, given that I'm getting back into caving after a three year hiatus!

I've seen those titanium u-shape rack bars worn through to produce a hole through the bar and the edges of that hole were razor sharp!

[Mark620]

for true wear resistance has anyone tried ceramic coated rack bars. Such as partially stabilized zirconium?

[Scott McCrea]

for true wear resistance has anyone tried ceramic coated rack bars. Such as partially stabilized zirconium?

Never heard of it being tried. I imagine it wouldn't absorb much heat. Could be somewhat slippery, I imagine. Dunno. Try it and let us know.

[Bob Thrun]

for true wear resistance has anyone tried ceramic coated rack bars. Such as partially stabilized zirconium?

Some brands of figure-8 descenders are hard anodized. Thi is aluminum oxide, which is harder than zirconium oxide. Eventually the anodizing gets worn thru and the edge of the worn spot is like a safety razor or paint scraper. The raw aluminum wears down and the oxide coating overhangs the worn spot slightly

[Seamus Decker]

I've seen that Bob. I would say that that is a bit dangerous isn't it? When it has had a groove and that sharp edge worn into it? I've seen the same thing with those hollow titanium bars for abseiling racks.

[Aaron Addison]

[quote="Bob Thrun"
Some brands of figure-8 descenders are hard anodized. Thi is aluminum oxide, which is harder than zirconium oxide. Eventually the anodizing gets worn thru and the edge of the worn spot is like a safety razor or paint scraper. The raw aluminum wears down and the oxide coating overhangs the worn spot slightly[/quote]


I too have experienced this. I ruined a rescue 8 in Lech many years ago after a weeks use. And never did a drop over 60'! The condition of the rope (dirty/clean) seems to have the most impact on the wear factor of equipment whether steel or aluminum.

AA

[Ralph E. Powers]

A long while back a (caving) friend of mine and I owned a rare Russian/Soviet made hand ascenders that were an exact copy of the (old style) petzl handled ascenders only that it was made from (what else?) Russian Titanium. The plastic handle on it had on it stamped U.S.S.R. thus making it a real collectors piece since the U.S.S.R. doesn't exist anymore.
Was told back then when I had it that how the manufacturers got ahold of the titanium was from cut pieces strewn around the Soviet Submarine yards as they put together those vessels. They got ahold of the pieces from working in the yard(s) or from friends who worked in the yards... and re-worked them and made them into the handled ascender that I had.
The Soviets (then) didn't have access to alum and even rarer good steel thus titanium was easier to come by (for them anyway). So basically any Russian Titanium caving piece is (or should be) the same stuff that is made for Soviet subs. You know the ones, they broke world depth records.

Unfortunately someone else thought they needed my collector's piece more than I did and took it without my knowledge and for damn sure without my permission. So as far as I know my friend still has his piece and is woefully reluctant to part with it though he doesn't cave anymore... (back injury).
I've a darn good idea who took it but that scallywag s.o.b. disappeared... good for him, because I owe him 1 hard buttkick. If you run into a guy showing off a light green colored hand ascender made in the U.S.S.R. let me know.