DMM Revolver carabiners don’t work very well as pulleys

Short version: a simple test shows that a Revolver carabiner is about the same as a round stock carabiner in terms of hauling efficiency.

Long version: Revolver carabiners, according to the DMM website, are designed to lessen rope drag when you’re leading a pitch that wanders around. Some of us, myself included, have been tempted to use them as a replacement for a pulley in some sort of lifting or mechanical advantage system, thinking that that little wheel must help you in some way.  

DMM claims the carabiner “reduce rope drag 40-47%” so that should help, right? 
Well, it might reduce rope drag when you’re leading, but it doesn't seem to do squat as a pulley.
In fact, I did a few simple observational studies that show they’re not any better than a round stock carabiner. 

This is summarized in greater detail on my website, that has a series of posts on mechanical advantage for climbers. Here’s the link: 
https://www.alpinesavvy.com/blog/progress-capture-efficiencies-of-various-devices

This study is easy to replicate by anyone else, all you need is an inexpensive $11 digital spring scale from Amazon. Here’s a link to the one I used. https://www.amazon.com/Dr-Meter-Upgraded-Fishing-Measuring-Batteries/dp/B078KP5YGP/

There are various ways to set this up, but here’s about the simplest:
A 1:1 upward pull with the redirect through the carabiner so you are pulling downward, just like you would set up for a 1:1 haul on a big wall.

Here’s what I used:

• 10 pound barbell plate
• Length of approximately 9 mm climbing rope
• DMM revolver carabiner, Petzl Attaché round stock carabiner, Camp Nano carabiner, new rescue pulley 
• Digital spring scale

Here’s a picture of the set up:


And here’s a summary of the results:

Approximate force needed to lift a 10 pound load through a redirect

sealed bearing rescue pulley - 13 pounds - 77% efficient
round stock petal Attache biner - 20 pounds - 50% efficient 
DMM Revolver carabiner - 21 pounds -  48% efficient
Camp Nano carabiner -  23 pounds - 43% efficient

As you can see, the Revolver carabiner was essentially the same as the round stock carabiner. So, the Revolver gives you no increased efficiency, and is probably not worth spending the money on it if you don’t have one already.

And, it also shows that a pulley is going to be better than any kind of a carabiner, no surprise there. 

Takeaway - the Revolver carabiner seems to offer no increased pulling efficiency over a round stock biner, and a real pulley is much better.

You're testing something outside of its performance requirements - part of your takeaway should be that it works well for its intended use.

Thanks. I've wondered about using the revolver in an ascending system in place of a real pulley.  

"Long version: Revolver carabiners, according to the DMM website, are designed to lessen rope drag when you’re leading a pitch that wanders from left to right"

I have a revolver, but I haven't used it much because I keep finding myself on pitches that go from right to left. Have you tried it in this configuration? Thanks!

My problem with the revolvers is the rope will rarely seat itself in the pulley grove but rather to the gate side of the puley.  With a slight redesign, it could be a much better tool.

On a side note, you should re-do your test with 100 lbs., free hanging and see what you come up with.

Xan Calonne wrote: "Long version: Revolver carabiners, according to the DMM website, are designed to lessen rope drag when you’re leading a pitch that wanders from left to right"

I have a revolver, but I haven't used it much because I keep finding myself on pitches that go from right to left. Have you tried it in this configuration? Thanks!

Well, they are Welsh carabiners, and the Welsh drive on the left side of the road, so those carabiners are clearly designed to only go from left to right. :-)

Good catch, I changed it.  =^)

Chris Owen wrote: You're testing something outside of its performance requirements - part of your takeaway should be that it works well for its intended use.

Hey Chris, 

That very well might be true, that they reduce rope drag when you are leading. But I could not find any quantitative info on that on the web, I did not test myself, and that's why I did not include it in the takeaway. If anyone has a link to some solid data on this, feel free to post it up here.

I think DMM equipment is totally solid and I've use their gear for years, and I in no way intended this to be a slam on them. I simply wanted to point out that using a Revolver to replace a proper pulley is probably not going to give you very good results.

Don Ferris III wrote: My problem with the revolvers is the rope will rarely seat itself in the pulley grove but rather to the gate side of the puley.  With a slight redesign, it could be a much better tool.

On a side note, you should re-do your test with 100 lbs., free hanging and see what you come up with.

Don, I think you describe the issue perfectly. I was was also curious how the results might be different with a much bigger load. The inexpensive digital scale that I had is not go up to hundred pounds, or I would've tried that too. 

If anyone here has a better scale, or access to even a proper testing facility and wants to try this and report back, I'd be very curious.

If anyone doesn't want their Revolvers anymore as a result of these findings, feel free to ship them to me.

Thanks

I've always believed that using TWO biners (same size)  is more efficient in a hauling setup than a single one, roundstock or otherwise. That would be interesting to test. As would something like 100 lb lift. It shouldn't be too hard to do - just stand on the bathroom scale as you pull down.

Gunkiemike wrote: It shouldn't be too hard to do - just stand on the bathroom scale as you pull down.

Props for creative application of physics to a practical problem. 

Jared Chrysostom wrote:

Props for creative application of physics to a practical problem. 

I thought it was more of a practical solution to a physics problem.  :-)

I tested all this stuff years ago, some is on RC.com and some on MP. (2 biners give more friction).

I got mine in the mail today and just got done playing it just before seeing this. I got it to help feed rope into a backpack and I felt a noticable difference when it would actually seat on the pulley which was only half the time. For my use I guess I could just throw some gromets on it to direct the rope but its a bit annoying when the biner fucking expensive. I wonder how it handles hauling loads.

Justice Holloway wrote: I wonder how it handles hauling loads.

Did you read the OP?

Jim Titt wrote: I tested all this stuff years ago, some is on RC.com and some on MP. (2 biners give more friction).

Jim,

I have gathered you've done a lot of research into this area, and I'd be glad to reference your work if I knew where to find it. Too bad RC.com has died, that was a pretty sweet resource for a lot of stuff. I'm not saying I'm discovering anything new here, just doing my own little observational study and sharing the results in case folks find it helpful.

Thanks for your contributions and comments.

Gunkiemike wrote: I've always believed that using TWO biners (same size)  is more efficient in a hauling setup than a single one, roundstock or otherwise. That would be interesting to test. As would something like 100 lb lift. It shouldn't be too hard to do - just stand on the bathroom scale as you pull down.

Gunkie, Hey, good thinking! I might give that a try.

And I tested the two biners also - they add more friction. Which can be good in certain situations. Say you are rappelling on a single strand of rope, and you want to add friction to increase your control of the rappel. Add two identical biners to your belay loop and it should slow down your rap. 

https://www.alpinesavvy.com/blog/adding-friction-to-a-rappel

Marc801 C wrote: Did you read the OP?

Hauling loads as in the weight of a haul bag. Anyways I think I'm done commenting on stuff for a while. 

I recall hearing something about a light plastic bushing instead of actual sealed bearing that binds under load and creates more friction than a normal carabiner,  seams to line up with your findings.

Great tool for a very specific application, which to credit DMM, is their advertised use.

Nice work on the testing!

You need this one. The revolver rig twin

From the DMM web site: "The Revolver can be used in an improvised hauling system to help your second over a crux, haul kit bags, or rescue your partner from a crevasse. Where normal carabiners in these systems cause energy to be lost as friction, the Revolver's pulley wheel makes hauling easier by converting more of your energy into movement. "

So I would say hauling is definately part of the stated capability of the Revolver. I would certainly expect it to perform better than a fat carabiner, and if it does not I am a bit disappointed.

How about a test with a really big load, say 200 lb?