What's a roller quickdraw?

Is is pretty scary on those runouts?
The fall is quite big—especially from the last sideways reach, which is harder if you have a shorter span—but it is safe, especially with a soft catch and a roller quickdraw.

What is a "roller quickdraw?"  I've never heard of this before.

Source: rockandice.com/climbing-new…

Definitely a great tool to have.

​https://www.backcountry.com/dmm-revolver-locking-carabiners?CMP_SKU=DMM0039&MER=0406&skid=DMM0039-SCR-ONESIZ&mr:trackingCode=CC3E50DB-F061-DF11-9DA0-002219319097&mr:referralID=NA&mr:device=c&mr:adType=plaonline&CMP_ID=PLA_GOc001&utm_source=Google&utm_medium=PLA&k_clickid=_k_CjwKCAjwy7vlBRACEiwAZvdx9k_1zFsL7I9Ouz48_8DHrQXJ7Y_IYfRYR3ShTDZB0ahQSDF8WT-iaRoCvxIQAvD_BwE_k_&rmatt=tsid:1042790|cid:213417517|agid:13362830437|tid:aud-483074737321:pla-438889299755|crid:92885919877|nw:g|rnd:347122789893102521|dvc:c|adp:1o2|mt:|loc:9009266&gclid=CjwKCAjwy7vlBRACEiwAZvdx9k_1zFsL7I9Ouz48_8DHrQXJ7Y_IYfRYR3ShTDZB0ahQSDF8WT-iaRoCvxIQAvD_BwE​

John RB wrote: What is a "roller quickdraw?"  I've never heard of this before.

Source: rockandice.com/climbing-new…

DMM revolver

Aldo comes in a locking version

QD with DMM Revolver or Petzl Rollclip A on the rope side. For rock climbing I would prefer Revolver.

It seems that a pulley-equipped carabiner like the Revolver would increase the loads to the climber, the belayer and to the top point. With a normal carabiner a significant amount of the force of the fall is converted to heat energy through the friction of the rope running over the carabiner. When you put a pulley in the system your loads are going to increase, not decrease.

Here's the text in DMM's user manual:
14. Revolver Carabiner It is critical that users of the Revolver have a full understanding of the factors affecting the
dynamics and forces involved in a rope system. This includes:- chosen belaying system, weight of belayer/climber, type/
condition/diameter of rope, length of rope out, number and position of anchorage points in the system, additional
external factors effecting friction within the system i.e. rock type angle of rock etc., Whether the belayer is anchored or
not.
The use of the Revolver in the initial stages as a running belay could in some circumstances increase the load on the
belayer.

Being mostly a trad climber I'm not a big user of the soft catch. Perhaps the benefits of soft catch and a pulley n the system can actually reduce the loads? Somehow I don't think so. Jim Titt and RGold, perhaps you can chime in?

Climb safe,
Mal

I have a couple of the DMM Revolver carabiners...nice, especially for ascending if need be.

For runout slab, the advantages I can think of are the leader has less rope drag whilst on point.  Also, maybe the "Stone Mountain belay" would be easier with less friction for the belayer as well.  I know when I've had leaders fall on lower angle slabs, I've been able to reel in some slack prior to them finishing their fall.  Maybe the revolver would make this easier?  Dunno.  Interesting to ponder...but...I don't see it reducing loads.  

Edit to add:  Maybe it helps keep the rope from whipping the gear out of the thin crack?  Or loading the biner/draw attached to the gear?  Keeps the load in a more of a straight downward pull by allowing the rope to run straighter?  

The purpose of something like the Revolver in this case is to reduce peak force on gear by making the catch softer. Many people think a soft catch means extra slack out, more rope to stretch, more time to stop a fall--not necessarily a softer catch since the climber falls farther and so has more kinetic energy.

A true soft catch involves a dynamic belayer and minimal extra slack out. The force that the climber feels is the belayer pulling the rope plus any additional friction in the system (carabiners, rope drag on rock) minus how much the rope stretches and how much the belayer moves. With the addition of a rolling carabiner at a key point (read: first draw as a redirect before a traverse), the friction in the system is reduced which reduces the peak force and leads to a longer, "softer" catch. This can be useful in trad climbing too (see link in OP)!

Malcolm, you might be thinking of the pulley effect (which is at play even if there is only a carabiner and not a pulley/rolling carabiner), which is when the top piece of gear experiences higher loading because both the climber and the belayer are hanging off of it (example: a fall while top roping vs a fall while a leader who is not weighting the anchor brings up a second or the load on the rope while rapping solo vs lowering or simul-rapping).

tl;dr and back on topic: "rolling quickdraws" are a useful tool when you want to reduce peak forces but not when you are relying on normal friction in the system (TRing a short route, for example) to arrest a fall quickly.

Edit to add: friction dissipated as heat in a fall is still load that the gear is experiencing, the catch should be soft to protect the climber--normally the belayer isn't in danger when catching a fall unless it is a higher FF but in this case (traverse), that's not super likely especially with a nice redirect near the belay.

Aidan Raviv wrote: With the addition of a rolling carabiner at a key point (read: first draw as a redirect before a traverse), the friction in the system is reduced which reduces the peak force and leads to a longer, "softer" catch. 

I guess I'd expect an increase in peak force with less friction in the system? 

From a paper on climbing loads:

http://lamountaineers.org/pdf/xRopes.pdf

Testing has shown that the friction on a rope that bends 180 degrees over a carabiner will reduce the load that the belayer feels by 52 percent (Soles, 1995). This friction can reduce the overall anchor load because the force in the belay side will not be as high. (see Figure 10) This effect is offset somewhat by the reduction in stretch of the rope as the climber falls.

When discussing peak forces on "the system," we need to be specific about what part of the system you're talking about.  Do you mean the force felt by the falling climber (the subjective "softness" of the catch as felt by the climber), the force on the top piece (very important for marginal trad gear, not really important for sport climbing) or force felt by the belayer.  So be specific. 

The actual effect is something I discusssed  investigating wirh DMM but in reality with the rope 180 over a Revolver the reduction in friction is minimal compared with all the rest that's happening, something like 8%.

Jim Titt wrote: The actual effect is something I discusssed  investigating wirh DMM but in reality with the rope 180 over a Revolver the reduction in friction is minimal compared with all the rest that's happening, something like 8%.

To my understanding those binners (Revolver, Rollclip A) are designed to be used to reduce rope drag or carabiner to rope friction when rope bends not that much around the binner. E.g., somewhat waving pitch (Revolver) or arboristic speedline (autolocker Rollclip A).

I and folks I have climbed with have always used them on the first clip or an extended clip around a roof or feature to reduce rope drag.

have you ever whipped in a revolver on the 1st bolt, or a low bilt on a route?

A decrease in friction at the top piece will yield less force on the leader and top piece and will transmit more force to the belayer side.

Imagine the friction at the top piece is so high, it is the same as just tying a knot. A leader fall would transmit all energy into the leader and the leader side of the rope.  No energy is able to go to the belayer side of the top piece.  Forces would be high on the leader and top piece.

Now imagine the friction at the top piece is next to nothing. A leader fall would transmit energy to the leader, the leader side of the rope and much more easily to the belayer side of the rope and the belayer. Much more rope in the system to absorb the energy. Lower forces on the leader and top piece. But greater force on the belayer.

This is similar to calculated fall factor vs effective fall factor. More friction in the system will give a higher effective fall factor.

slim wrote: have you ever whipped in a revolver on the 1st bolt, or a low bilt on a route?

Would be especially exciting with a light belayer.

So, from the interview:

The fall is quite big—especially from the last sideways reach, which is harder if you have a shorter span—but it is safe, especially with a soft catch and a roller quickdraw.

Hard for me to understand if the fall is "safe" because the load is less on the gear or the fall isn't as hard on the leader.  My guess is she's trying to relate that the gear, RP's, won't fail?

Still, counter intuitive to me.  A decrease in friction in the system would increase the load on the piece, or, is the effect of the "soft catch" reducing the peak load enough that it negates the force at the gear?  Sounds like minimal system effect as Jim pointed out.  Wouldn't take much to rip an RP placement, though!

Cool physics problem!  At any rate, she sent after a couple of falls so even if its psyche pro, it worked!

Brian in SLC wrote:
Still, counter intuitive to me.  A decrease in friction in the system would increase the load on the piece, 

No.  See my post above. 

Brian in SLC wrote: Hard for me to understand if the fall is "safe" because the load is less on the gear or the fall isn't as hard on the leader.  My guess is she's trying to relate that the gear, RP's, won't fail?

Still, counter intuitive to me.  A decrease in friction in the system would increase the load on the piece, or, is the effect of the "soft catch" reducing the peak load enough that it negates the force at the gear?  Sounds like minimal system effect as Jim pointed out.

To start: both of these things make the fall safe. In this situation, the belayer isn't going to be in danger either way, so why not have a lower peak force on the gear and a lower peak force on the leader?

Here's where things diverge: a decrease in friction does not increase load on the piece of gear. The load experienced by the gear is the apparent weight of both climber and belayer plus the friction caused by the rope bending/rubbing around the carabiner. When the carabiner or whatever the top piece is creates less friction, the load on the piece of the gear is reduced. If the belayer is moving upwards (small jump when rope tightens or lighter belayer), the top piece experiences a lower peak force because the apparent weight of the belayer is lower (so the climber is not stopped as quickly and the "weight" "felt" by the piece is lower overall).

We know from physics that Impulse (change in momentum) = Force * Time, so if our momentum changes, we can either have that happen over a longer time (falls with moving belayers take more time to come to a stop) for a lower peak force or we can have it happen in a shorter time for a higher peak force.

Aidan Raviv wrote:

To start: both of these things make the fall safe. In this situation, the belayer isn't going to be in danger either way, so why not have a lower peak force on the gear and a lower peak force on the leader?

Here's where things diverge: a decrease in friction does not increase load on the piece of gear. The load experienced by the gear is the apparent weight of both climber and belayer plus the friction caused by the rope bending/rubbing around the carabiner. When the carabiner or whatever the top piece is creates less friction, the load on the piece of the gear is reduced. If the belayer is moving upwards (small jump when rope tightens or lighter belayer), the top piece experiences a lower peak force because the apparent weight of the belayer is lower (so the climber is not stopped as quickly and the "weight" "felt" by the piece is lower overall).

We know from physics that Impulse (change in momentum) = Force * Time, so if our momentum changes, we can either have that happen over a longer time (falls with moving belayers take more time to come to a stop) for a lower peak force or we can have it happen in a shorter time for a higher peak force.

you sure about this?  i thought it was the sum of the weights of the climbers, minus the friction fighting against the "heavier" side..., which would explain why a twiggy person can still generally keep their feet on the ground when their fat partner is dogging.  think about it.  if you have both people tied in, and the rope is clove hitched to the biner (really high friction) one person could weight the anchor and the anchor would only see that load the "belayer" would see no load if they were standing on the ground.

here's an easier analogy.  imagine we have 2 steep, but same angle, inclined planes that each have  an anchor at the top.  inclined plane "A" is made out of glass and coated with vaseline.  inclined plane B is made out of wood and has grip tape on it.  now, imagine we place identical rubber cubes on each inclined plane and they have a rope up to the anchor.  which anchor will see more load do you think?  probably the vaseline coated glass...

all of this isn't as straight forward as greg's summary.  there are 2 things that are kind of competing against each other, but also fucking with each other.  friction is damping.  but it is also affecting the stiffness of the rope.  increasing the friction would decrease the total load on the anchor as it will fight against the climbers weight and reduce the load on the belayer's side, but it would also effectively shorten the rope which will make the system stiffer, which would increase the force on the anchor.

the answer is that we don't really know without testing.

that being said, revolvers are so crappy that it doesn't really matter anyway.

I think this is all moot. Somewhere on here or RC there’s a note that the Revolver pulley locks up at relatively low loads so there’s zero pulley effect in a fall where the revolver is the top draw. It’s basically just a round bar biner.  The benefit is mostly realized in drag reduction for the rope. I carry one or two with me to add in places where the rope zig zags back and forth more than a runner would help (or where I want to minimize fall length). Here they can help with smoother rope running. Likely beneficial as it allows more rope to be involved and/or the belayer and rope slip to reduce impact force (see Jim’s posts on the semi static thread recently). In fact, I believe it was Jim who may have noted this on the old topic years back. RC com archives perhaps.

Found it. Jim Notes “That's about it, the shape of the biner was optimised for use as a runner, wrap the rope 180 and more load and there's no real benefit. The friction is about the same as a 12mm biner”

Jim covers this a year ago as well - “The revolver is designed to reduce friction in a lead rope with small angles of bend and light loads and for this it works well, with a 180° bend and a high load ... the reduced friction is minimal, it´s better than a typical quickdraw karabiner as the diameter is 11mm but no better than the usual 12mm round stock belay karabiner. At higher loads the rope flattens and runs more on the body of the karabiner anyway which negates any advantage the pulley might have had.”

That’s getting a bit fuzzy slim. It is as simple as I stated.

We are not talking about the belayer weighting the rope. We are talking about a leader fall. All of the energy comes from this fall. In a zero friction top piece scenario, yes the belayer must oppose with an equal and opposite force, yielding approximately double the force on the top piece that the leader experiences and that the belayer experiences if a truly friction free setup.  Also there will be at least twice, if not much more rope in system to absorb energy and increase time to arrest the fall.  Both of these factors leads to lower forces on the top piece when friction is reduced at the top piece. 

In a very high friction top piece scenario, the amount of energy is no different if it is an equal fall. The big difference here is, much less rope and less time to arrest the fall. 
In a “tied off biner” fall you are guaranteeing a FF 2.  Allowing even a small amount of rope on the belayer side to participate drops the FF potentially quite a bit.