Pulley jammer warning

mikem

Well-known member
Not surre why this hasn't made it onto forum already:
http://british-caving.org.uk/wiki3/lib/exe/fetch.php?media=notice_re_toothed_jammers.pdf
 

Speleotron

Member
I always thought that anything which might involve falling onto a jammer is dodgy; why you wouldn't just use an italian hitch?
 

JoshW

Well-known member
Speleotron said:
I always thought that anything which might involve falling onto a jammer is dodgy; why you wouldn't just use an italian hitch?

hauling on a loaded italian hitch is near on impossible.

but agreed on the life lining on a jammer being dodgy for me.
 

Speleotron

Member
Yes I meant for belaying/lifelining not z-rigging or hauling etc. And you can make the italian hitch auto-locking as well https://andy-kirkpatrick.com/cragmanship/view/locking_munter
 

JoshW

Well-known member
Speleotron said:
Yes I meant for belaying/lifelining not z-rigging or hauling etc. And you can make the italian hitch auto-locking as well https://andy-kirkpatrick.com/cragmanship/view/locking_munter

I guessed you meant for belaying/lifelining, but sometimes they can turn to needing to haul somebody
 

Bob Mehew

Well-known member
The report of the work on which the notice was based can be downloaded from https://drive.google.com/file/d/1XLZyRdMzNjlnUar5LA0r_rVk-nqfLu2F/view?usp=sharing .  No doubt, BCA's E&T, QMC and Training committees will issue minutes in due course covering their deliberations.

Two asides: I would observe that the terms belaying / lifelining / progress capture / hauling etc seem to me to be splitting hairs and fundamentally are covering the same task with the same potential fault scenarios; and that a person falling even short distances on low stretch (SRT / semi static) rope can be seriously hurt.
 

JoshW

Well-known member
Bob Mehew said:
The report of the work on which the notice was based can be downloaded from https://drive.google.com/file/d/1XLZyRdMzNjlnUar5LA0r_rVk-nqfLu2F/view?usp=sharing .  No doubt, BCA's E&T, QMC and Training committees will issue minutes in due course covering their deliberations.

Two asides: I would observe that the terms belaying / lifelining / progress capture / hauling etc seem to me to be splitting hairs and fundamentally are covering the same task with the same potential fault scenarios; and that a person falling even short distances on low stretch (SRT / semi static) rope can be seriously hurt.

from my perspective the difference between hauling and the other three is that hauling has 0 potential (outside of gear failure) for a distance to fall. the other three introduce the chance of a shock loading.
 

Badlad

Administrator
Staff member
This is a very old technique which hopefully is finally being committed to history.  There are many other methods and devices which can achieve the same thing in a much safer way - and are recommended by the manufacturer for that purpose.

Regardless of the deformed equipment, the force on the body or the potential damage to the rope the greatest danger with this method is not being able to release it under load.  Any lifelining, capture or whatever you wish to call it should be releasable under load with the ability to lower back to safety in a controlled manner.  The fatality on Giants pitch a few years ago springs to mind where those lifelining with a cammed device were unable to release the exhausted climber and he died stuck on the pitch under a waterfall.

I am very surprised this fact alone wasn't good reason enough to stamp out the practice.
 

Speleotron

Member
droid said:
Was that Garlands? 15 foot pitch, usually taken far too lightly. Gets VERY wet.

Agreed. I couldnt remember all the reasons why I dont like this method but you've just reminded me. I find setups which are hard or impossible to realease to be a bit scarey when you think about what might happen.
 

mikem

Well-known member
The only question I have is where was the load cell located? As force on climber will not be the same as force on pulley (the easiest place to locate the cell).
 

Bob Mehew

Well-known member
mikem said:
The only question I have is where was the load cell located? As force on climber will not be the same as force on pulley (the easiest place to locate the cell).
The location of the load cell does not influence the force seen by it, see page 6 in http://www.roperesearch.co.uk/pdfs/the%20rig%20v2.PDF . It only affects the timing of when the force is seen.  (http://www.roperesearch.co.uk/index.html provides more detailed information on the rig.)

The report of the work shows the location of the pulley or jammer for all bar two of the drops is at the top of the rig.  The load cell is immediately above that point.  (The set up was device / crab / shackle / load cell whose black end protrudes through the horizontal beam.)  The only cases where it was not, were drops 34 & 35 BPC 40 where the set up is shown in diagram 8 in the report.
 

Antwan

Member
If you do have to haul with that specific equipment the jammer should be on the other side  :spank:

If it rises when you haul hang some krabs on it.
 

mikem

Well-known member
But even if you assume that there is zero extension in the low stretch rope, the 6.7kN recorded by the load cell has also been dissipated into bending the pulley and stripping the rope, so won't be equal to that experienced by the climber...

Climbing walls are now using semi-static ropes for top roping, but they will always have at least the full length of the climb between the belayer & climber (so still a reasonable amount of rope to minimise the fall factor), whilst a caver slipping at the top of the pitch will have hardly any rope between them - should we still be advocating dynamic rope, or is the effective distance so short that it will make hardly any difference?

Antwan said:
If you do have to haul with that specific equipment the jammer should be on the other side  :spank:
In which case the full load will go onto the jammer, so the effective force on the climber will be higher (you're probably better off damaging the pulley!)

Presumably the climber or rope in Giants got caught somewhere, so couldn't be pulled up that little bit to release the jammer, which would be the same whichever side of the pulley it was.
 

Bob Mehew

Well-known member
mikem said:
But even if you assume that there is zero extension in the low stretch rope, the 6.7kN recorded by the load cell has also been dissipated into bending the pulley and stripping the rope, so won't be equal to that experienced by the climber...
What is your evidence for this statement?  It is not force that is dissipated, it is energy. 
mikem said:
Climbing walls are now using semi-static ropes for top roping, but they will always have at least the full length of the climb between the belayer & climber (so still a reasonable amount of rope to minimise the fall factor), whilst a caver slipping at the top of the pitch will have hardly any rope between them - should we still be advocating dynamic rope, or is the effective distance so short that it will make hardly any difference?
The point you miss is that the belayer will have a bigger effect in reducing the peak forces seen by the system since their body is not as resilient as the steel.  (The report touches on this point.)  The feature of the system we are discussing (pulley and toothed jammer) is that there is no equivalent human body, just steel.  If you look at the detail you will see that the peak force in the simpler set up of just a toothed jammer is higher (10 BPC 40) than for pulley and toothed jammer (12 or 20 BPC 40). 

Unfortunately we don't have three load cells to do the experiment to show that the force is the same along the whole length of a multi component system. 
 

andrewmcleod

Well-known member
The rule is simple.

Don't belay with your teeth, or anyone or anything else's.

Use one of the thousands of safe belaying systems used by climbers for generations, ranging from body belaying (properly done), chucking the rope around a (suitably smooth) rock, Italian hitches, Fig 8s, belay plates, guide mode belay plates, Stops, grigris, Rigs, ID's, all the way up to hanging an autobelay at the top of the pitch if you feel the need. Just don't use anything with teeth...

PS some of the above systems are a lot better than others!
 

Roger W

Well-known member
andrewmc said:
The rule is simple.

Don't belay with your teeth, or anyone or anything else's.

Beagle-puppy-gnawing-on-rope-with-his-teeth-using-it-like-a-chew-toy.jpg
 

mikem

Well-known member
I'm not suggesting using a pulley jammer, but trying to get my head around whether the force on the climber will be the same as the force on the pulley (which is what was recorded).

Energy = Force x distance, so if energy is lost in the deformation of the pulley, but distance remains the same, the force must surely also reduce...

& I'm not missing the effect of the belayer, just hadn't mentioned it as my question was whether belaying at the top required a dynamic rope (as many cavers are switching to semi-static without realising the difference from top roping, where it is now common practice).

Also the document referred to by Bob suggests a Stop is not suitable for belaying when only threaded around one bobbin.
 

andrewmcleod

Well-known member
mikem said:
Energy = Force x distance, so if energy is lost in the deformation of the pulley, but distance remains the same, the force must surely also reduce...

As an (ex) physicist, it's complicated, because people fail to properly include the effect of time dependence in that (simplified) equation.
 
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