Describe the ultimate rappel safety

[Tim White]

If you were looking for the perfect rappel safety/back-up device how would you describe it?

Here is a start:

1. Inexpensive
2. Simple to operate
3. Easy to learn
4. Self engaging
5. Hands free operation
6. Allow rope to be positioned between legs or over hip (without effort)
7. Ability to disengage if loaded/locked
8. Able to withstand abuse (mud, etc.)

What would you want to see in such a device?

I’m not looking to turn this discussing into the pros vs. cons of rappel safeties or whether they are needed or not. You can carry that discussing on here French Wrap Self-Belay Article among other locations.

What I want to know: If you HAD the ultimate rappel safety, what would it be?

[MessedUpMike]

Something single handed to operate with a dead man's function. Preferably that would work in conjunction with my main device. I haven't had time to mess with them much, but bobbin type descenders look most like they would fit the bill, but are to bulky to use as a backup.

The inherent problem with most rappelling equipment, at least that I'm familiar with is, is that most of won't pass a "whistle test".

Off the cuff I"m not sure if they're used much in caving, but you might be able to put a 540 device in you system above you main descender. That way if it locks up you can unlock it and keep going. the problem is they're kinda big.

I'm going to need to think on this one.

[Brian Roebuck]

Many times a rappel rapidly becomes out of control and the rappeller cannot react fast enough to keep from being injured or killed. Thus electronics that can sense the dangerous situation could become a viable alternative to manual control. I can foresee a simple device activated by an inexpensive accelerometer (such as is used in the controllers of games like the wii etc). These devices use very little energy and are cheap and reliable. Put into a hardened case they would make an ideal sensor to determine when a rappell has gone out of control by the acceleration forces measured in the downward direction. This could be adjustable to some extent for beginers etc. The device would attach mechanically to the top of a rack (or be built in) and have the rope pass through it. In case of a fall or uncontrolled decent it would activate a small friction lock (brake) quickly before too much speed is built up and slow or stop the rappeller. The power source for the brake could be a CO2 cartidge since it should only be needed once in any out of control situation. It needs to be simple, easy to use, and reliable. Now all you have to do is design one!

[MessedUpMike]

Dr Beaner,
540 devices do that mechanically, which is sort of what I was thinking, I'm just not sure how effective they'd be for rappelling. I've used them in the past on 2 line rappels as a belay to great success. as a matter of fact I know one instance where it prevented a rappelling accident, where the rappeller panicked and let go of his rope 20 feet up, and the 540 auto locked almost instantly.

If you could adjust the way the rope comes into the device I think they'd work really well.
storrick.cnchost.com/VerticalDevicesPage/Belay/MiscBelayPages/MiscBelay756.html
www.cmcrescue.com/product.php?CatalogID=1&dept_id=1509&rootNode=0&pid=20307

[Brian Roebuck]

I suppose you could build one of the 540 degree type devices into a rack in much the same way I envision an accelerometer brake device being positioned. I see either one at the top of the rack since you would need to still have access to the bars and be able to change where the rope feeds due to how many bars are in use. Either system would be heavier and more complex. Extra time would have to be taken to rig before a drop. Most cavers would not go for such a thing considering it would significantly raise the cost, complexity, and weight. I imagine threading rope through a 540 in addition to a rack would be painful to cavers. Whatever is used to perform the safety function will have to be easy to thread, light, and relatively cheap (although what would you pay to save your life?).

Or we could just put sensors in our boot heels and attach an airbag to our arses! ;D

Actually that has me thinking again. A small cartridge actuated device (tiny explosive that creates rapidly expanding gas) could be used to drive a curved block or wedge etc into position to slow or stop an out of control rappel. Combined with the tiny accelerometer it would be small and light enough for cavers to actually use. If this package could be produced to simply replace the top bar of most racks it could be a decent way to accomplish what we want to do. The device would be a totally sealed one time use only and a souvenir after wards to keep people from being able to mess with the actuator. The battery to run the accelerometer should be the only replaceable part. I envision it to look like a fat hyperbar (that you could use for just that purpose). The hyperbar end sticking out beyond the rack would house the battery, accelerometer, and actuator device. The actuator would drive a small piston that pushes a shaped end from the center of the device (where the rope passes through unaffected in normal use) to cause the rope to have to go around a sharp bend thus increasing friction dramatically. This should happen well before the caver can attain so much speed that it would stress the rope too much or not be enough to slow or stop the caver .

Oh Yes - how do you keep it from going off in your pack when you drop it? Good question! There would be a gate built in that you must have open to place the rope through and a latch (sliding or hinged) to encapsulate the rope. The latch - once locked in place - turns on the device and arms the actuator. An LED lets you know it is ready for action (good battery, armed, etc). Now I feel better!

[MessedUpMike]

www.cmcrescue.com/product.php?CatalogID=1&dept_id=20705&rootNode=0&pid=20312

This is almost the optimal device. at 73.00 it's in line with the pirces of a lot of racks, and less expensive than most bobbin or stop type devices. It's mechanically operated, so you don't have to worry about batteries, loss of power, or other gizmo's to wipe out. the shortcoming seem to be the fact that you have to have the line already threaded, which would stop you from being able to do change overs, and the fact it's made for 7-9mm rope, whcih would be to small for most cavers use.

[Rick Brinkman]

1. Ability to disengage/re-engage quickly while on rope.

I'm thinking about those TIGHT drops where you have one arm below you controlling the rope and the the other has to be fully extended straight up...just to fit through.

2. Can be used with many different devices. (Racks, Bobbins, 8s, ATC's, etc.)

[Brian Roebuck]

rickbrinkman said:

1. Ability to disengage/re-engage quickly while on rope.

I'm thinking about those TIGHT drops where you have one arm below you controlling the rope and the the other has to be fully extended straight up...just to fit through.

2. Can be used with many different devices. (Racks, Bobbins, 8s, ATC's, etc.)

Good points to consider Rick. If that were the case the device would have to be a seperate piece of gear entirely. I consider having more stuff attached to the rope (with straps etc attached to the harness) tougher to manage - especially in tight spaces so it would have to be small and used without any extra thought or action required. What rappelers really need for safety is a way to prevent them from ever going fast enough to hurt themselves. It would be a rappel speed limiter. Then even if you let go, passed out, got rocked, slipped when not ready , didn't know what you were doing, or otherwise you would not get injured (at least badly anyhow). There would be no need to control it or any need to do anything but "thread the rope through it" to make it work. It would not affect a normal rappel except to limit vertical speed. Theoretically you could use it alone to rappel hands off and survive - but you would want some control especially at the top and bottom so normal rappel devices should be used in conjunction with it.

[Rick Brinkman]

Little off topic.....

I've been wondering if a 'chinese finger trap' type device might work as a rappel device/auto lock. I know it's a kinda wacky idea ....but I'm trying to think of something that hasn't been tried before.

No idea what material it would be made out of or if it would even work. One thing...if it COULD be made to work, you could travel down a loaded rope too.

[tncaveres]

rickbrinkman said:

Little off topic.....

I've been wondering if a 'chinese finger trap' type device might work as a rappel device/auto lock. I know it's a kinda wacky idea ....but I'm trying to think of something that hasn't been tried before.

No idea what material it would be made out of or if it would even work. One thing...if it COULD be made to work, you could travel down a loaded rope too.

It almost sounds like a prusik.

[Brian Roebuck]

The big issue for me is controlling the thing. Having something that would keep you out of trouble automatically with no interaction is the ideal thing. That leaves you to rappel normally and worry about what you are doing. Prusiks and grabbers may work but how do you control when they engage (or disengage). It's a tough design problem - otherwise somebody would have figured it out already!

[tncaveres]

That is why you will see me with my micro rack .

[NZcaver]

rickbrinkman said:

Little off topic.....

I've been wondering if a 'chinese finger trap' type device might work as a rappel device/auto lock. I know it's a kinda wacky idea ....but I'm trying to think of something that hasn't been tried before.

What you describe - if constructed with rope/cord - sounds like a Dog and Tails (aka Cross Lashed Strap, aka Basket Weave).



You can descend a taught rope on this as well, but from experience it's a rather long hitch to manipulate. A more effective shorter version of this is the Valdotain Tresse (VT), aka Machard Tresse. (There is some discrepancy in correct nomenclature vs hitch design here, but this is what I mean:)




As far as regular rappel safties go, the so-called French Wrap seems to be a favorite flavor for many cavers these days.

Personally I prefer something integral with the descender itself, which is probably why my device of choice is a usually a Stop descender.

[Rick Brinkman]

I guess I wasn't quite clear....

I mean a completely new device made out of.....aluminum, titanium, teflon, plastic, etc...that the design is inspired by the 'prusik type' knots. Something that when compressed would slide down the rope. As I said before....just 'off the wall' thinking.

[NZcaver]

I understood what you meant... and I don't think it's too far "off the wall."

I was just referencing some examples of the same idea in rope/cord to help the flex the brain a little. In the past, I've used stainless steel mesh "basket weave" attachments to secure the ends of cables for suspended crossings - they basically work on the same principal. I can't see why some other strong/flexible/springy material like that wouldn't work in a rappel safety application, assuming it does what you want it to do and doesn't shred your rope in the process.

[treenail]

There are a couple of good articles on friction hitches in the "Articles" section of my website. I'm not sure if you'll have to register to read them or not.

Arborists spend all of their time while climbing hanging on the rope, ascending or descending. Friends of mine in Switzerland were working in the drippy, cold rain and a fellow stopped on the sidewalk to watch. After they got the tree down using lots of rigging and lowering techniques the fellow introduced himself. It was Franz Bachmann of the eponymous hitch fame. They all struck up an immediate friendship. FB was very impressed with how my friends used friction hitches to move up and down the rope effortlessly.

Here's the link:

www.treebuzz.com/articles.php

Tom

[Brad Tipton]

How about a good bottom belayer? Wouldn't effectively work on big, deep drops, but how many people are rappelling 200 plus footers every weekend? I believe the best rappel safety available is common sense.

[Cave Rat]

If you already have it on hand, take a Gibbs Ascender and construct yourself a Speleo Shunt.

Takes a little practice, but it makes a great back-up safety.

Unless you are lucky enough, find yourself a new one at the bottom of a pit, like a friend of mine did, on the last trip I did with him.

I use the French Wrap myself and it works. I have the webbing loops, to attach it, sewn to both my harnesses.