Braking carabiner: aluminium alloy or steel?

[Ursus Spelaeus]

I use an aluminium alloy braking carabiner, but some cavers told me that it's better to use a steel braking carabiner.

I think that an aluminium carabiner can brake better.

What do y think about it?

[fuzzy-hair-man]

Aluminium definately provides more braking than steel,
I have tried both stainless steel and aluminium racks and the steel ones are a lot faster.

That said I use a steel carabiner as my brake krab because it is a friction surface and steel will not wear as fast as aluminium.
If you need the extra braking then go aluminium but if not I'd go steel.

If you are likely to be doing high wear trips then I'd definately go for a steel brake krab.

[paul]

Aluminium definately provides more braking than steel, I have tried both stainless steel and aluminium racks and the steel ones are a lot faster.

That said I use a steel carabiner as my brake krab because it is a friction surface and steel will not wear as fast as aluminium. If you need the extra braking then go aluminium but if not I'd go steel.

If you are likely to be doing high wear trips then I'd definately go for a steel brake krab.

I hear what you are saying about racks with regard to the material used for the bars. With racks all the friction is normally produced by the rope rubbing against the bars and the angle of the rope on the bars and amount of rope in contact with the bars (which changes the amount of friction) varies with the spacing of the bars.

But, in my opinion, using a braking carabiner with a bobbin-type descender (Petzl Stop, Petzl Simple or any other similar descenders) the change in braking is caused by pulling the rope harder against the bobbins or capstans on the descender as the rope is pulled up against the braking carabiner - sure, there will be a certain amount of extra friction provided by the carabiner itself bit I don't think it will be as much - the contact area is so much smaller when compared to the total contact area of the capstans. I bet even if you used a pulley in the same place as the braking carabiner, there will be more braking effect provided by the descender when pulling upwards on the controlling rope!

What I'm trying to say is to not worry too much about the material for the braking carabiner with respect to the amount of friction it provides itself - consider weight (seel is heavier), price on how long the braking carabiner will last (steel is more resistant to wear).

[hunter]

What I'm trying to say is to not worry too much about the material for the braking carabiner with respect to the amount of friction it provides itself - consider weight (seel is heavier), price on how long the braking carabiner will last (steel is more resistant to wear).

Paul, this is a good statement. I like al because it is light and I'm willing to throw them out as needed. It seems to me that if the type of metal on your biner makes a big difference in controlling the descent maybe a rack would be a better choice...

It's also worth remembering that friction is a factor of both surface area and force. Just because something has a smaller area of surface contact with the rope doesn't mean it has less breaking.

James

[paul]

It's also worth remembering that friction is a factor of both surface area and force.

and materials and structure and temperature...

Just because something has a smaller area of surface contact with the rope doesn't mean it has less breaking.

Sure - but my main point, put another way, is that to increase the braking effect on a bobbin-type descender you pull harder on the controlling rope. By adding a braking carabiner, the effect of pulling on the controlling rope is increased as the carabiner is acting like a pulley (albeit a not very efficient pulley!) thus supplying a mechanical advantage.

Yes - you are also adding some friction to the system due to the braking carabiner itself, but that is so small when compared to the amount of friction due to the descender (and that supplied by gripping the controlling rope) that using differing materials for the braking carabiner will have a very minimal effect on the total braking effect.

[hunter]

Paul, I agree with your assesment of where the gain is in adding a breaking biner to a bobbin type device. I was just pointing out that equating surface area to friction (i.e. breaking force caused by) is deceptive when you have a constant like mass involved.

James

[NZcaver]

Sure - but my main point, put another way, is that to increase the braking effect on a bobbin-type descender you pull harder on the controlling rope. By adding a braking carabiner, the effect of pulling on the controlling rope is increased as the carabiner is acting like a pulley (albeit a not very efficient pulley!) thus supplying a mechanical advantage.

Nice idea - but I contend that a braking carabiner does not really supply any mechanical advantage.

If you are referring to the wide "V" formed in the rope as it leaves the descender, goes through the braking carabiner, and then to your hand - that's not mechanical advantage. It's just a simple 1:1, with a change of direction. Not only that, but you are braking by pushing the rope away from your body. This is not nearly as effective as applying force by pulling down or toward you.

I realize a braking carabiner is a logical and necessary addition to most bobbin descenders - I just don't think it's particularly efficient OR ergonomic. For a good example of descender braking that does have some mechanical advantage (loosely speaking), try a rack with a hyper-bar some time. If only we could find a more practical alternative to the old bobbin braking carabiner - other than switching descender of course.

In answer to the original post - if I'm using my Petzl Stop, my attachment/braking carabiner is a Freino. But if I had the choice, I would prefer one in stainless steel so it lasts longer, despite the extra weight.

I bet even if you used a pulley in the same place as the braking carabiner, there will be more braking effect provided by the descender when pulling upwards on the controlling rope!

I think not. In fact, I'd be willing to bet against that. ("Pulling upwards?" Isn't that a contradiction in terms?)

But I do agree the difference in practical braking force between an alloy and a steel carabiner is probably negligible. Although rope generally produces more friction against alloys than steel, a single turn around a carabiner is hardly any surface area at all.

[paul]

Sure - but my main point, put another way, is that to increase the braking effect on a bobbin-type descender you pull harder on the controlling rope. By adding a braking carabiner, the effect of pulling on the controlling rope is increased as the carabiner is acting like a pulley (albeit a not very efficient pulley!) thus supplying a mechanical advantage.

Nice idea - but I contend that a braking carabiner does not really supply any mechanical advantage.

If you are referring to the wide "V" formed in the rope as it leaves the descender, goes through the braking carabiner, and then to your hand - that's not mechanical advantage. It's just a simple 1:1, with a change of direction. Not only that, but you are braking by pushing the rope away from your body. This is not nearly as effective as applying force by pulling down or toward you.

Of course you are right - you would only get any mechanical advantage with a single pulley if the pulley was attached to the load and was movable with respect to each end of the rope... Just my brain not working during my lunch break when persuing this Forum!

Mind you, I don't push the rope away from my body, I grip the rope so that the rope leaves the bottom of may hand towards the braking carabiner and descender. To apply more friction to slow down, I raise my arm upwards and grip harder on the rope pulling upwards at an angle to the horizontal.

But I do agree the difference in practical braking force between an alloy and a steel carabiner is probably negligible. Although rope generally produces more friction against alloys than steel, a single turn around a carabiner is hardly any surface area at all.

Well that was I was mainly getting at - so we can agree there and forget the rest!

[NZcaver]

Mind you, I don't push the rope away from my body, I grip the rope so that the rope leaves the bottom of may hand towards the braking carabiner and descender. To apply more friction to slow down, I raise my arm upwards and grip harder on the rope pulling upwards at an angle to the horizontal.

Ah yes - good point.

But still, I've always found the motion of braking this way a little awkward and counter-intuitive. Awkward because the rope below you can be quite heavy to lift on medium-to-longer drops, especially with the 11mm commonly used in the US. And counter-intuitive because lifting the rope is also how you "feed" your descender if necessary - like when thick, dirty rope has you stranded and immobile mid-rope.

However, both these points are virtually non-issues with the ~10mm ropes and shorter, rebelayed drops common in your European-style rigging. And intuition can even be "un-learned" too - a bit like when you realize the Petzl Stop handle is a nice convenience, but really NOT an effective safety (fail-safe) feature.

[potholer]

If the rope was really heavy below, it's fairly rare that I'd actually use the braking krab - even though it'd be in the system, the rope would be passing through it without resistance.

However, YMMV. I suppose there can be a weight issue - depending on people's build, they may find the same descender giving quite different results. I'm around 70Kg, and on 10-11mm use my Stop with only intermittent use of the braking krab, whereas with 9mm or 8mm, I'd really be likely to be using the braking krab much more.
A mate who's ~15Kg lighter sometimes finds himself just not moving on dry 11mm, even with no real weight of rope below. When I started caving, I was nearer his weight and caving on 10mm basically all the time, and it took me a while before I started using a braking crab - I think I originally started when I started rigging, since it made soft+hard-locking easier, and I was descending without any weight of rope below me.

I imagine that someone of a larger build than me *may* find they move uncomfortably fast even with a lot of weight beneath them, and so would have the problem of having to lift a heavy rope in order to use the braking krab.

[NZcaver]

When I started caving, I was nearer his weight and caving on 10mm basically all the time, and it took me a while before I started using a braking crab...

Yeah, me too. Guess I'm a little heavier now than when I started caving...

I imagine that someone of a larger build than me *may* find they move uncomfortably fast even with a lot of weight beneath them, and so would have the problem of having to lift a heavy rope in order to use the braking krab.

Or someone who's dragging a damn 45lb/20kg pack with them drop-after-drop (and climb-after-climb!) on multi-day expeditions... ...

[tchudson]

I use steel as they last longer than aluminum, and on the dirty, muddy ropes that most TAG cavers seem to have, that says a lot. In fact, I had some tubular steel bars that a friend made especially for me - extra thick. Unfortunatly, that rack is lost somewhere in the wilds of Arizona. Anyway, it's never been an issue of which was faster, but which lasted longer.

[NZcaver]

I use steel as they last longer than aluminum, and on the dirty, muddy ropes that most TAG cavers seem to have, that says a lot. In fact, I had some tubular steel bars that a friend made especially for me - extra thick. Unfortunatly, that rack is lost somewhere in the wilds of Arizona. Anyway, it's never been an issue of which was faster, but which lasted longer.

Are you saying you use a steel braking carabiner with your rack? That's unusual - unless you mean you clip it into the top of your rack to substitute for a hyper bar. Or are you referring to something else?

The rest of us were talking about using bobbins. Without a supplemental braking carabiner we would usually be in for a fast rappel!

Another thread showing braking carabiners is here - http://www.caves.org/phpBB2/viewtopic.php?t=2107


PS - I also prefer steel bars whenever I use a rack.

[Uncle Muddy]

Choice of descending devices not withstanding, a steel carabiner can also be used for a munter hitch for short drops. BTW: Are there any titanium biners still available? The Ukrainean cavers who visited the states in the late 80s were swapping them like baseball cards. They're about as light as aluminum and very tough. I've got one that I've used for a munter on Apricot pit that shows only a slight polish where the rope made contact.

[NZcaver]

Choice of descending devices not withstanding, a steel carabiner can also be used for a munter hitch for short drops.

For descending and belaying Munter hitches work OK of course, but in my experience they are less than ideal. Most of the friction is created by nylon-on-nylon contact as the rope loops around itself. Granted this doesn't just happen in one spot on the rope, but it still has to be more detrimental to the rope than a using regular descender - even if the Park does own the ropes.

I used a Munter for a short 40 foot slope rappel on gypsum-encrusted rope once. It wore about 20% of the aluminum off the carabiner in one spot. So I switched back to using the rack, but in a "C" configuration. Another guy used only 2 bars (and back over the hyper bar) on his micro rack for the crusty slope rappels. One or two of the others chose to use those horrible aluminum figure 8's instead.

I haven't seen titanium carabiners around for a while, but you still see other titanium climbing products coming in now and again. I've been told the issue with some of that older stuff is reliability. Batches of raw material offen differed in quality, and controlled load/destruction testing was performed rarely if at all. But then again we don't hear much about them failing and people getting killed, either. So you're probably fairly safe.