Thin Ropes in ATC Guide = Danger

Jim Titt wrote: Two different things, if you haven´t enough braking power when abseiling then the ropes are too thin or you are too fat.

I guess I don't get the issue. What I am speaking of really doesn't directly have to do with braking power or rope thickness... it's the dry treat making the rope so slippery the device can't produce enough friction to lock the rope. Rope thickness would play a factor in friction obviously but I guess you guys are talking about something other then a lack of friction and autolocking NOT working, ma bad.

I think using either a Reverso or an ATC-guide with 7.8 mm half ropes is asking for trouble. If you have to start messing around with extra biners for friction when rappelling on two strands, how the hell are you going to hold a high-load fall on one strand? The answer is the rope is going to run through the device---better be wearing gloves.

I think both manufacturers give unrealistic ranges for rope diameters; probably only the middle third is reasonable for both adequate friction and decent handling.

Although BD doesn't say, the Reverso specifications give a clue to the device's inadequacy for belaying leader falls with small-diameter ropes. Petzl says, "effective braking for half/twin ropes 7.5mm diameter or larger and for single ropes 8.9mm diameter or larger." But when you use half ropes, you typically have to catch falls on a single strand, and according to Petzl's own specifications, you won't get "effective braking" with a single 7.8mm strand, in fact you aren't even close to the specified minimum of 8.9mm, which itself is probably overly optimistic. All of these deficits are going to be magnified by rope treatements that decrease friction.

With 7.8mm doubles, I'd use one of the assisted-locking devices. For half-rope technique, I think the Alpine Up is the best of the lot when it comes to handling, although it is expensive relatively large, and heavy.

This is about belaying the leader. You already know the device doesn't work for autoblocking belay of the second.

CaptainMo wrote: I guess I don't get the issue. What I am speaking of really doesn't directly have to do with braking power or rope thickness... it's the dry treat making the rope so slippery the device can't produce enough friction to lock the rope. Rope thickness would play a factor in friction obviously but I guess you guys are talking about something other then a lack of friction and autolocking NOT working, ma bad.

Autobloc failure is exactly how the OP described it;- "My follower fell, and instead of the climbing strands cinching down on top of the belay strands, they fell next to the belay strands in the cage of the ATC, and began to slip, slowly lowering the climber."
The loaded rope strand is supposed to lie on top of the braking strand and supply the braking force, the thinner the rope the more likely it is that the loaded strand goes to the side of the loaded strand and unltimately underneath it and you have no autolocking and an extremely poorly functioning belay device, the rope is also jammed.

Richard Gold is correct in his views on some of the wilder claims by manufacturers about the suitability of rope diameters with various devices, some manufacturers claims being both completely untrue and physically impossible but advertising is advertising and rarely had much to do with reality.

Ouray ran some primary research on them and use in plaquetting with rescue mainlines. The Guide performed within rescue, the Reverso had some questionable results, the Toucan failed. I don't recall if the smaller dyneema rescue lines were looked at. Granted, these are dynamic hits on somewhat static systems (thereby outside of their manufacturers' model), but the diameter is still a concern. RMRG has also indicated problems in climbing accidents with smaller rope diameters, not using smaller devices, not using gloves, leading to belay failure when used with attentive belaying.

Another thing to consider, when using the dual rope system, my interval spacing is larger than typical trad lead; to cover ground quicker in alpine terrain. Any fall is gonna be a big. I question in that falling while leading is probably not an option to begin with; the rope & belay being a last chance; maybe.

Jim Titt wrote: Autobloc failure is exactly how the OP described it;- "My follower fell, and instead of the climbing strands cinching down on top of the belay strands, they fell next to the belay strands in the cage of the ATC, and began to slip, slowly lowering the climber." The loaded rope strand is supposed to lie on top of the braking strand and supply the braking force, the thinner the rope the more likely it is that the loaded strand goes to the side of the loaded strand and unltimately underneath it and you have no autolocking and an extremely poorly functioning belay device, the rope is also jammed. Richard Gold is correct in his views on some of the wilder claims by manufacturers about the suitability of rope diameters with various devices, some manufacturers claims being both completely untrue and physically impossible but advertising is advertising and rarely had much to do with reality.

now i get it ... i am dense.