UKH

There are a few belay devices on the market specifically designed for thin half ropes, the BD ATC Alpine Guide and Edelrid Nano Jul and possibly others.

Is there a diameter of rope (i.e. 8mm and below) where these are worth using over a normal guide plate (BD ATC Guide)?

I assume these smaller belay devices could provide better braking force. I know Jim Titt has done some research into braking force and belay devices too, and found that most (if not all?) manual devices would struggle to hold a significant FF2+ fall? 

In reply to Alpenglow:

I've been mostly using 8.1mm Beal Icelines for nearly twenty years now. I used to be careful to select a compatible device like the Reversino or Bugette, which could be a pain if you have to ab in on an 11mm. Since the modern devices with V-slots came out, I just use a DMM Pivot. Not held any huge falls yet but it gives better control abseiling than the others did.

I have now bought a pair of 7.3mm Beal Gully, not used them yet but it is right on the limit of the Pivot's spec. Likewise interested in any experience...

In reply to Adam Long:

For the last 8 yrs I've been using the Beal Gully 7.3mm with a petzl reverso 4. The device is not rated for less than 7.5mm so I did a 'test' at the climbing wall and found it easy.to use, and it held the falls comfortably.

In action on the Ben the reverso 4 held a factor 1 fall on the shroud - so it works with the beal gully in real world situations IMHO. 

I dropped the reverso into the sea and now have a Black Diamond alpine guide. It's smaller than the reverso 4 and feels more grippy, not held any falls yet but it's OK on abseil.

If my skinny ropes got iced I'd probably use 2 carabiners on the harness to increase the friction. Just my personal experience using the kit, I'm not recommending anyone to do anything!

Cheers.....Jeff

In reply to Alpenglow:

In my opinion, no belay plates have enough friction. Unless abseiling with them is a relaxed affair with one hand on the the ropes then clearly holding any fall is going to be dodgy, and I've not known one that is. I now always put an extra snaplink alongside my screwgate and encourage those belaying me to do the same. This way I can belay safely with any plate and ropes. To me it makes sense not to take the risk.

In reply to Alpenglow:

https://www.lomo.co.uk/products/sailing-gloves-short-finger/

In reply to Alpenglow:

Hoping Jim Titt will jump in if I'm wrong, but I believe belay plates like the pivot are best understood as hand force multipliers. And multiply your grip by about 6 to 8. They don't add a fixed amount of "grip", but multiply your grip. As hand and tricep strength can vary by a factor of 4 (I believe) and climbers' weight by almost 2, what works for some, will not for others and hence I would be cautious. Wet ropes make this even worse. I'm weak. Many of us are weak. On thin ropes I now use two carabiners of equal long axis length as Rupert suggests through both the rope and my belay loop. Or an assisted device.

I found out just how weak I was abseiling down the many pitches of crack baby (an ice climb) with wet icy ropes and gloves. I only just controlled it. My belaying, which felt fine, must have been deeply questionable.

On a side note, does anyone know how DMM and others set the minimum rope diameter? I assume this is informed in part by some kind of measurement 

In reply to David Coley:

Giga Jul initial impressions (Mountain Project). I think page 2 has comments by Jim Titt and others about testing rope diameters in belay devices. Apparently there is no standard for testing and manufacturer's ranges are just guidelines.

In reply to oldie:

And I would guess, therefore, should be taken with a big pinch of salt since diameter range is going to be a selling point.

In reply to David Coley:

Jim discussed a bit about this here: 

https://www.mountainproject.com/forum/topic/120097748/slip-values-of-variou...

In reply to David Coley:

This is correct.

Worth saying that the multiplication factor offered by a device is not necessarily constant as tension of the rope in the device changes.

In reply to oldie:

Indeed. However I was more wondering if manufacturers did some kind of ad hoc tests. They need to generate a minimum diameter to print it on the box. So is this done: playing down the wall, using some math, watching when it slips when loaded with 100kg..... Someone here must work for BD, dmm, petzl. So what actually is done to generate the guesstimate? 

In reply to Robert Durran:

So you don't think f. ex that the pivot and reverso aren't suitable for use as belay devices when used as described in the relevant 'user manuals'? 

In reply to wbo2:

I've not used either of them but, unless the extra ring bit does something fancy I'm not familiar with, they look much the same as ones I have used.

Maybe someone does make one with the holding power of an extra krab built in, in which case I would buy one like a shot.

In reply to Robert Durran:

3 likes, 7 dislikes at time of replying suggests not much consensus on this.  For the people who disagree, what is Robert missing or which bit has he got wrong?

In reply to Ram MkiV:

Maybe people don't like having long held assumptions challenged.

Or maybe it's just that I am a fat bastard.

In reply to wbo2:

One way of putting some detail on this is to try and define "suitable". So imagine a pivot loaded with two 7.3mm ropes. Take a relatively weak handed or weak armed person. Say 1 in 50 weakest.  What is the severity of fall on one strand they can just not hold? I.e. they get burnt or hand trapped in plate. And hence let go. I'm guessing it is not FF2.

Or if one demands a plate must hold a ff1.7 fall say, what percentile of strength must the belayer have for most to consider the plate suitable? At 7.3mm is it one in twenty, one in two hundred...

There is quite a nice test for this. Jump off the top of a cliff on a shiny new thin rope through a belay plate. With a pile of slack at the top of the cliff. I.e. the falling person is belaying herself. Back up knot required. Gloves recommended 

What is clear in such thought or real experiments is that there must be a combination of rope diameter, weakness of belayer and severity of fall that the plate can't work safely with. Hence some people add an extra carabiner,  especially when the ropes are thin or wet or the belayer weak or the fall very severe.

In reply to David Coley:

Not the best of tests.

Only ff1.

No runners to provide additional friction. 

A hard ff2 is only for those teams who neglect to clip a piece above a multi pitch belay.

Edit , might have read better if you had added a smiley.

In reply to Robert Durran:

That plus the fact that belay devices are rarely called upon to hold the big loads that are possible but rarely happen in practice.  System friction around carabiners and rock surfaces combined with typically small fall factors means the usual everyday belay experience is in a completely different category from the extreme examples involving high fall-factor falls with minimal system friction. The everyday experiences lead to the conclusion that a device is adequate when it may not be; the conclusion is based on biased sampling.

I think the already-mentioned rappel test is an excellent indicator.  Remember that if you are climbing with a single rope or are employing half-rope technique, then the test rappel has to be on a single strand.  Make the rappel free-hanging so as not to benefit from boots on the rock. Get a belay and don't use a friction hitch for a backup.  If you can control comfortably, your device might be good enough for a big impact.  If you struggle to control your descent, your chances of stopping a big fall are not good.

I've done this test a number of times with different ropes and devices and agree with Robert that many devices are inadequate for the big cases.  A consequence is that I don't believe the ranges stated by the rope manufacturers can be trusted--probably only the middle third of the stated range is good.  Another interesting point emerging from some DAV testing is that device-rope friction is not simply determined by rope diameter, as some ropes, by construction and/or treatments, are more slippery than others.  This emphasizes the need to test your device with your equipment.

 

In reply to David Coley

Or just do a normal abseil and then apply some imagination.

I accidentally did this experiment for real last year on a sea cliff with about eight metres of slack without back up or gloves.  But fortunately it was with a fat, stiff, furry static rope.....

In reply to Rick Graham:

Regarding fall factors and the usual statement that the maximum load experienced is determined by the fall factor and not the length of fall, all other things being equal.

As an engineer and climber for over 50 years, having held countless falls including long factor 2s, I have always struggled to get my head round this statement and its counter intuity.

It might be the case that in drop tests the maximum load recorded depends on the FF but what is not discussed is that on longer falls, the rope stretching and resultant loads are experienced over a longer period of time.

This longer loading  time will have an effect on how effective any belay device/ belayer / rope combination works, or not.

FWIW , I only tend to use notched belay devices or a Clickup.

To Robert, have you thought about buying a secondhand flat plate?  We never seemed to have this  trouble with the old Sticht, Clog, Bettabrakes.

In reply to Rick Graham:

Agreed, not the best of tests, but it has a certain viscerality the first time one does it. I shat myself. I see it more of a test of whether a person really believes belaying works than of the tech.

In reply to Rick Graham:

Hopefully I  will get some of this right. The FF idea only applies to the fraction of the energy that the rope removes. If the fall is clean, the rope held around bobbins at both ends and belay point fixed, the climber a steel ball this just about all of it. 

If the rope slips through the plate, energy will be lost in heating the plate and melting the skin. This will depend on length of fall not just FF. 

In reply to Rick Graham

I'm pretty sure that many older climbers will have held leader falls with no runners, ie ostensibly F2, using a waist belay. Does that mean this can be a superior method? Adding smiley icon as suggested.😃

In reply to Rick Graham:

Yes, I had been thinking that. Modern plates seem to have moved towards ease of use at the expense of safety. With an extra krab you get both though.

In reply to rgold:

But it's not just the big cases. It's when shit happens - pulled off balance or against the rock, a momentary lapse of concentration, cold hands etc.

In reply to David Coley:

Whatever the correct physics, none of this should distract from the idea that belay plates may well be inadequate for some ropes in some situations, and the rappel test can at least give a rudimentary idea how things will work with the equipment the team actually has.l

The cases of this or that successful factor 2 catch tell us nothing about expected behavior in general, and my guess is that the vast majority of climbers, old or not, have never had to hold a factor 1.8 - 2 type fall. I've caught a factor 2 fall with a hip belay and a near factor-2 fall with a plate on one strand of a pair of half ropes.  In a test situation with weights (we used to do this in the 1960's in the US), I've caught somewhere between 10 and 20 factor 1.8 falls with a hip belay.  For those tests we padded our hips with a canvas backpack wrapped around our waists and of course used burly gloves.  Everyone who tried this failed to stop the weight the first time or two.

As for fall factors, you got almost all of it right.  The remaining part is an assumption that the rope behaves like an idealized spring.  If true, the fallen climber would bounce up and down forever.  So in addition to the features you have mentioned, we have to deal with the damping effects of the internal friction of the rope.  The fall factor still plays a role, as long as there is no slippage at the belay.  Once that happens, the ability of the belay to absorb fall energy does indeed depend on the length of the fall.

I haven't seen a cogent argument for the idea that extra time during the fall arrest reduces peak load. Yates made this unsupported argument about the effectiveness of screamers when his performance claims failed to align with either theoretical computations or actual tests.  If there is no slippage in the belay, then the peak load is determined by the maximum rope tension, which in turn is determined by the percentage elongation of the rope modeled as ideal spring.  If the peak load is lower in some case,  then the work not done in stretching the rope all the way has to be done in some other way.  This means that if extra arresting time causes lower peak loads, then some other energy-absorbing mechanism must be at work, and I've yet to see an account that describes what that mechanism is. 

It is possible that the extra time claims are influenced by considerations of impulse, which is the integral of force over time.  If so, this mistakes the area under the force curve for the maximum value of the force.

Returning to Robert's original point, I think it quite likely that most modern belay plate-thin rope combinations are not up to the demands of all possible falls.  Fortunately, the severe circumstances are quite rare, and we have the simple option of doubling the plate carabiners to increase the friction.

In reply to rgold:

Robert stated he didn't believe a belay plate  would work reliably without a second krab with ANY rope which i think required some justification ( to be polite)

In reply to wbo2:

Well it's hard to be exact because there is some information we don't and are forced to guess, that is we don't actually have values for the impact forces of ropes in a true FF2 fall and we have no idea whether this force holds true for longer falls.

We also don't know for sure exactly how long a belayer can exert maximum grip force on the rope but from personal testing it isn't very long, maybe one or two seconds.

What we do know is that in a severe fall all belay plate/belayer hand force combinations will slip and we also know that for these plate/rope/belayer combinations this reaches catastrophal levels suprisingly quickly. The CAI did a series of tests years ago at their test facility with a very experienced belayer (a guide who has done loads of testing) and he was of the opinion that no belay plate was capable of holding a severe fall even wearing leather gloves. My own tests and calculations agree with this.

The basic problem with these discussions is definitions, a "massive whipper" at Stanage is by the standards of an Italian Alpinist a small stumble. So delving into the techy stuff or why is there no CE/EN test?

Worst case scenario, what's a decently normal rope length? 60m? Okay that sets the length of fall. Plug in the dynamics of a 120m fall, an average hand strength belayer and what do you get? A hospitalised belayer (the faller who knows), this is a big FAIL by both the standards and common sense. Adding a karabiner helps but not enough, adding yet another helps even more but I'll admit laziness stopped me investigating further.

Moving to the assisted thingies the only ones that I know of are that make it are the GriGri and the Edelrid Eddy though there may be others, the Click-Up came close but destroyed my test rope so was a fail as well, rendering part of the safety system unusable isn't really good when you need to continue relying on it.

Basically if your plate stops you when you slump on a bolt at the wall and you are happy then all's fine, when you are wandering around 50m from your belayer completely off route on some Dolomites horror show with only a rusted piton you wouldn't hang your coat on as gear your experience may be different.

In reply to wbo2:

I was thinking of any standard half ropes. I've used a variety of ropes with a variety of plates (currently a Grivel one with V grooves). My ropes are generally at the thicker end of the spectrum and often far from shiny.

There are no downsides to adding an extra krab (okay, a tiny faff), but it makes things so much more secure that it now feels to me a no brainer to do so. 

In reply to wbo2:

Well it is logically kind of true. In that, some belayers have very weak hands. So there must be a hand strength and rope diameter where issues arise for any rope diameter.

My climbing partner has some missing tendons, so has to use an assisted device to hold me. Some belayers are only 12 years old. I wonder if they could hold a tough fall on a half rope of any reasonable diameter. Especially if they were taking in with raised hand at moment of impact. 

For me, the question is, what fraction of the climbing population does it become a real issue, within the manufacturer-recommended diameters? Even 1 in a 100 sounds worrying. And I'd still like a hint at how the manufacturer makes the guesstimate 

In reply to Alpenglow:

I use a DMM Pivot on plenty of 8mm ropes and it's fine and IMO safe, but with new ropes (specifically new Rumbas) it felt pretty slippy and required a definite firmer grip on the dead rope than I'd have liked. With someone newer to belaying, or just not used to half ropes, I must admit it's on my mind a fair bit and I always warn to be extra careful, but with a good belayer I'm still pretty happy (and happy to belay others) with the pivot. That being said - I'm either sport climbing or climbing on pretty skinny halves, so the next device I get will defo be an ATC alpine guide or similar designed for skinnier ropes. 

In reply to jimtitt:

If your mate is 60 mtrs out on a 60 mtrs rope, you don't really need to hold it all surely?!

In reply to TobyA:

This is of course true, however if the pitch is set up for 60m ropes and you actually climbed on an 80...... 

In reply to Alpenglow:

Thanks all for responses so far.

There's a few questions that would be great to get an answer to (if any such answers exist!).

1) In general I like to climb with light kit, without significantly affecting safety. I currently have 8.5mm halfs but wondering if I could move to 8.0-8.2mm halfs in the future. I climb with a lot of different people and everyone just uses standard guide plates for trad, so no-one has any of the smaller plates (BD ATC Alpine Guide etc.). Is there a diameter of half rope where the braking force of a standard guide plate is significantly reduced? As I could buy thin half ropes and a small belay device but then none of my partners would have a small belay device to belay me on!

2) Are there any other manual guide plates on the market that offer better braking performance than the ATC Guide? I know that Jim has previously mentioned his tests showed that the ATC Guide performed as one of the better manual plates, with the Pivot slightly behind.

3) Which parameters of a plate belay device give better braking force? Is it all about the angle the rope passes through the device (so smaller angle/taller belay device is better braking force), do the presence of "teeth" have a big impact, or the width of the 'v-groove' slots? 

In reply to Alpenglow:

Perhaps a solution is for you to buy two thin rope belay devices and for your partner to borrow one if you set out with your thin ropes. Plate type devices are much cheaper than the ropes.

In reply to oldie:

And an extra old snaplink you've got lying around much cheaper again!

In reply to Robert Durran:

For avoidance of any doubt, could you please describe exactly what you use this second snapgate for? I'm assuming you simply clip it through your belay loop and the ropes as you would with the usual single screwgate, but I have seen other ways of adding friction to a belay setup with a carabiner.

In reply to cacheson:

Yes, I just double up with the screwgate. I think you could just clip it in to the ropes, which would stop any disadvantages of the two krabs being different sizes.

In reply to Robert Durran:

Prior to the luxury of belay plates, I would use crossed double karabiners to assist braking. A MR technique I learned from one of the climbers from the original Glencoe MR.

In reply to Robert Durran:

I have not personally tried this - but I have seen it suggested that this actually reduces the 'friction'/'power' of the belay setup. I.e. the opposite of what you are trying to do.

See here https://people.bath.ac.uk/dac33/high/10GettingBackDown.htm#addingfriction

First image shows the double krabs with both going through rope and belay loop, for adding friction.

Second image shows the double krabs with one through the rope and belay loop, but the second krab only through the rope, for reducing friction.

In reply to Robert Durran:

No! Sorry Robert, but if you clip it just through the ropes the two krabs sit on top of each other, not side by side, this pushes the plate away and reduces the breaking effect. This can be useful for very lightweight climbers abseiling down a fat old furry fixed line.

In short, use similar krabs, clipped through ropes and belay loop for adding friction when lead belaying or abseiling 

In reply to Sean Kelly:

I remember once being shown that for abseiling. I later tried to replicate it but found it too topologically challenging to trust it not to just fall apart under load.

In reply to Robert Durran: Anyone doing this needs to do it correctly, so the carabiners are above/below each other to increase the angles the rope goes around. If the carabiners end up one in front of the other it will decrease the friction.

Edit: Beaten to it by David.

In reply to Robert Durran:

I'm not sure about that. My entire climbing friendship group use skinny half ropes. I've held falls with skinny ropes on:

• VC Pro 2 (which I hate).
• ATC XP
• ATC Guide.
• Reverso 2
• Pivot (my current favourite for half ropes).

A few of those were bloody close calls where significant slippage would have resulted in decking and I had to jump back. There wasn't much slippage.

In reply to David Coley and Martin Haworth:

Thanks. That makes sense.

In reply to Alkis:

Yes, of course almost any plate will be fine with almost any rope in the vast majority of situations. But we are talking about exceptional cases or, as I said, "shit happening" and the risk of losing control, not just a bit of slippage.

In reply to Alkis:

If decking is a threat those are presumably all < FF1 falls? So not that severe compared with the worst possible scenario. Also what does 'skinny' mean - 7.5mm or 8.3mm?

I do anecdotally agree with you though, I've not had a problem holding any falls I've had to using whatever belay device/rope combination I've had to. My partner has also held me falling past the belay on a multipitch, so probably roughly FF1 (thinking about it, there was some traversing involved above the last piece, which would reduce the FF a bit compared with going straight up), with no slippage (or at least not enough to pull their hand into the plate), probably using a Pivot and some half ropes I can't remember but I doubt less than 8.3mm.

In reply to Alpenglow:

There has been research done on this, some by Jim Titt, some by universities, possibly some by others I'm unware of.

It's a bit hard to explain without diagrams, I'll try and draw some or dig some out if I have time later. This is from memory so it could be incorrect...

One of the first things to realise is that belay plates don't just provide resistance to a rope being pulled through them because of friction (or at least friction as you'd traditionally think of it). A large proportion of the resistance is as a result of bending/deforming the rope in ways it resists. If you imagine trying to wrap a thin cotton thread around your finger it would be very easy, whereas if you then imagine trying to wrap a ships hawser around your finger it would obviously be impossible. A climbing rope lies somewhere between those two extremes.

To demonstrate this idea I believe Jim has some publicly available information where he constructed a belay device type setup made of rollers, which has very little resistance due to friction, but still has resistance due to the rope being forced to bend around the rollers.

The main factor that influences the 'power' of an atc style belay setup is the tightness of the curves that the rope is forced to go through. So the size and flexibility of the rope has a big influence on the 'power' as well as the belay device and the karabiner.

The tighter the curves the harder it is to bend the rope around them, so the more resistance there is.

Tighter curves in a belay device also typically have a larger angle of wrap, which means you get more friction. See the capstan equation https://en.wikipedia.org/wiki/Capstan_equation

In order for v/u grooves to work they need to be small enough that the rope not under tension can't just sit easily in the bottom of the groove not touching the sides. When the rope is under tension it gets squashed 'downwards' into the v grooves and is supported from the angled sides, rather than just from underneath. Because of physics/vectors this means the normal force on the rope is increased compared to a scenario where it's just supported from underneath. Increasing the normal force increases friction.

I can't remember what the research says about teeth in grooves. I hypothesise that they work in a couple of ways.

They force the rope to deform to fit into the smaller space between them, then the rope can expand again, before being forced to deform again to fit into the space, repeatedly. This has a similar effect to forcing the rope around tight curves it doesn't want to bend around, it takes effort to deform the rope, therefore there is resistance.

Also for teeth in grooves, every time the rope has to deform to fit into the smaller space between teeth it gets a reaction force from the bit of the tooth that sticks out into the v groove, resisting it being pulled through. A diagram would really help with this bit, I've not explained it very well.

Getting the rope past a tooth is a bit like extruding a bit of metal, see the diagram here https://thelibraryofmanufacturing.com/extrusion.html (scroll down to the first image in the Direct Extrusion section). The black bits labelled die are the equivalent of the teeth in the v groove and provide a reaction force opposing the force of the ram (the force of the ram being equivalent in this analogy to the tension in the rope pulling the rope through the belay device).

Still no hints of how manufacturers come up with the minimum diameter guesstimate. Someone must know someone who knows someone. Please.

And in particular does this guesstimate make use of any measurement, of any form, however unofficial or non-standardised? Thanks

In reply to David Coley:

My understanding , with some third hand gossip, is that reputable manufacturers follow whatever they are legally required to do. 

Other than that they do what is prudent, both commercially and whatever lets them sleep at night.

Possibly they do a few test abseils as recommended by Rgold with various rope options.

In reply to David Coley:

Plenty of people know but they sure aren't telling! One method we know from the ex-owner of a well known manufacturer is to suspend the heaviest employee using their belay device and control the belayers hand force by using a basket full of beer bottles, slowly reducing the number until the employee began to descend. The only company I know of that ever scientifically tested a device was Black Diamond who produced some accurate results, their advertising department then made completely (like insanely) wild claims based on these.

Generally the device is thrust into the hands of somebody and they make a guess then the sales guys look at what the competition is claiming and adjust to suit, the fact that different generations of absolutely identical devices suddenly get smaller rope recommendations tells us this.

In reply to the thread in general:

Just some info from a standards point of view:

"Manual" braking devices are covered EN15151-2 and UIAA 129, however, the standard, though ensuring the belay device does not "break" in use, does not measure it's efficacy in "braking".

This has always been a concern for the UIAA Safety Commission and CEN TC135 WG5*. The other EN standard is EN15151-1, which covers assisted belay devices, e.g. the Grigri and this had all the device types covered, if unsatisfactorily.

Then the belay device market changed.

A "third type" of device emerged, the "geometry assisted" belay device (other names are available). This caused concern after a few accidents and, as testing has shown, not all these devices offer the same "braking magnification force" and in some scenarios, become "overcome" and are worse than basic tube device.

The decision was made to create a new standard, the key element of which would be a performance test. This lead to a lot of testing, which gave a lot of interesting results but.....

• the rope impacted the results
• the karabiner impacted the results
• tests were not easy repeatable
• tests were not reproducible

Re the rope, it was just the diameter, but the sheath weave, construction (Beal unicore massively impacts performance of some devices), etc of ropes of the same diameter gave different results.

This posed a problem. The standards committees didn't want to get to a position where a belay device was certified ONLY for specific ropes.

Why? Manufacturers may only pay to certify against certain ropes (certification is not cheap), maybe their own brand, which greatly limits customer choice. Your partner brings their rope but your device is not certified for it etc....

So, the topic is still in development but an answer is not forthcoming!

*This is the CEN working group responsible for the EN specifications relevant to Mountaineering