More force testing on 5:1 systems

This post follows up on some initial testing done on 5:1 mechanical advantage systems used to tension tyrolean crossings done a few months ago. I suggest anyone who has not read that report catch up with it here before reading on as I don’t explain everything again here.

For this batch of testing I used the same site but rigged things using metal strops instead of rope loops. This would act more like the solid bolt anchors used underground and would nearly eliminate false readings from knots tightening.

I used 2 types of readily available Type A rope

  • 11mm Mammut Performance semi-static
  • 10mm Beal Antipodes / Industrie

The tests were repeated with 3 different progress capture devices

  • Brand new Petzl Stop (rigged both fully and half threaded)
  • 10 year old worn Petzl Stop fully rigged
  • Brand new Petzl RIG

I created a 5:1 system on 10m section of rope using a Petzl Ascension jammer, Petzl Tandem pulley and a Petzl Partner pulley. These are all items that would likely be used by leaders underground or of similar type. No big rescue pulleys or prussics.
I pulled all of the tests on my own with un-gloved hands. I weight approx. 90kg and pulled as hard as I could using just hand grip.
The final tension in the line was estimated by hanging off it and the force on the jammer ascertained using a Rock Exotica Enforcer load cell measuring in kN.

11mm rope

New Petzl Stop – fully rigged
New Petzl Stop – half rigged
Old Petzl Stop – fully rigged
Petzl RIG – belay mode

10mm Rope

New Petzl Stop – fully rigged
New Petzl Stop – half rigged
Old Petzl Stop – fully rigged
Petzl RIG – belay mode

There clearly was a drop off in force required to tension a 10mm system over the 11mm system, although only small. The fully rigged Petzl Stops required the highest force to tension although the old Stop in the 10mm test oddly required more than the new one (*see foot note).

I took the highest force generating configuration and added some more people to the pulling end.

11mm rope with a fully threaded brand new Petzl Stop

2 smaller adults pulling

2 small adults & myself pulling

I think it is entirely possible to exceed the 4kN figure if 3 large and/or strong adults were to be pulling on a 5:1 tensioning system. Both ropes used were clean and supple, with a dusty rope friction would again increase and coupled with some less efficient pulleys might tip the force higher still. I think that it is still appropriate to give out the advice that no more than 2 people are used to tension 5:1 systems, perhaps 3 if using youths or very small adults but certainly no more. The force required to damage a rope at the teeth of the jammer is rather large, especially on 11mm rope, but repeated tensioning on the same spot in the rope may, over time, lead to degredation of the rope.

The best advice I can give is to echo what is already taught at LCMLA and CIC:

  • Keep your pulling ratios at 5:1 or lower and don’t exceed 10 men equivalent pulling power. i.e. 3:1 with 3 pulling or 5:1 with 2 pulling.
  • Keep ropes clean and supple.
  • Use only Type A ropes compatible with your choice of progress capture device.
  • Thick ropes are stronger and stretch less but require more force to initially tension.
  • Thinner ropes are strong enough but stretch a little more and require less force to initially tension.
  • Where very high tension systems are required consider doubling up on ropes and using a non-toothed rope clamp like a prussic or Petzl Shunt / Rescuecender.
A final thought. It is only a short period that the tension is applied to the rope via the teeth of a jammer in these set ups. It is the resultant tension and forces in use that are just as, if not more important to keep an eye on. Tensions in tyroleans can easily exceed 2.00kN, the maximum load Petzl advise for a Stop descender. Consider all components carefully and practice safely before using for real.
* Having given this some thought I believe that I can explain the added friction for this configuration. Over its life, the older Stop has been used for many miles of 10mm rope, wearing the alloy bobbin into a matching profile. Now there is a larger contact area between the alloy and the rope when compared to the brand new Stop. The larger contact area requires more friction to overcome and hence the greater force required to pull the rope through.
2 Stops

Loads on a 5:1 Tensioning System

Tyroleans have been a bit of hot topic with me recently. I’ve developed some sites to use in my woodland near Whaley Bridge and been involved in some testing with BCA Trainer Assessors for the LCMLA scheme. We’ve measured the actual forces held by the anchors in a number of tyroleans but a really interesting questions was yet to be answered definitively:

In using a high mechanical advantage tensioning system, how much force is being applied to the rope via the teeth of the jammer and could we be at risk of damaging the rope?

To explain, when using a 3:1 or 5:1 system as is common with tyrolean set-ups, a toothed jammer is most commonly used to create the attachment point on the rope to build the mechanical advantage system. The force applied by whomever is hauling in is multiplied in a mechanical advantage system, which is kind of the point, and all this force is transmitted to the rope via the toothed jammer. The picture below shows a 5:1 set up with a Rock Exotica Enforcer load cell.

5to1 load test (1)

If you omit the load cell from this set up you have a standard 5:1. As you can see it is the toothed cam on the Petzl Ascension device that is the contact point with the rope. This device, like many of the Petzl rope clamps, is approved for use with 8 to 13mm ropes but comes with the warning that the toothed cam can damage or cut the rope at forces around 4kN for smaller diameters and 6.5kN for the largest. As it is hard to compare one rope to another, even of the same diameter, most rope professionals simply take the 4kN figure as that which must never be achieved in use.

5to1 load test (3)

Using 2 people to tension the 5:1 system, the Enforcer gave a max force of 2.88kN through the jammer. Had we been on more solid ground (and my partner not been a positively tiny 5’2″ & 50kg) I think we could have gone higher.

Inspecting the rope (Gleistein 9mm Type A) after moving the jammer showed a flat spot and gaps in the sheath where the teeth had opened up the weave. There was some furring but it was impossible to say if this is new or was already present on this rope.

5to1 load test (5) 5to1 load test (6) 5to1 load test (7)

A repeat test on a different section of rope produced a force of 2.66kN and a similar flat spot and sheath opening.

We then set up a standard 3:1 ‘z-rig’ and repeated the test.

3to1 load test (1)3to1 load test (3)3to1 load test (2)

This test gave us a force of only 1.84kN using the same 2 person team with a less pronounced, but still visible, opening of the rope sheath bundles and overall flattening.

I think these observations uphold the understanding that the tensioning in tyrolean systems must be done with great care and by using the least amount of tensioning required for the crossing. I will conduct a further observational test at a real underground site with 10mm or above diametre rope for a comparison but the force figures will not be too dissimilar. It would be interesting to find the 2 heaviest/strongest volunteers I can and use them on a 5:1 system to see if it is possible to creep further toward the 4kN limit.

In conclusion, you can get close to, or potentially exceed, the 4kN safe load on a toothed-cam jammer when using tensioning systems in tyroleans. Tyroleans really are an element of verticality that you need to understand well and get training for to know how to be safe. Go and do a CIC/MIA/UKMR or other course or get in touch with me for a chat.

I’ll be investigating this further at some point but it might be worth looking at employing the use of a non-toothed rope grab like the Petzl Shunt or even an appropriate prussic knot as a way of limiting damage to ropes in high mechanical advantage systems.

NB – The current Petzl literature for the current Croll and Basic do not show a load at which the ascenders may damage the rope. These devices are sold as personal ascenders and are only labelled to take up to 140kg of user weight.

Woodland Tyrolean Development

Recently I headed out to our private woodland site to have a play with my new Rock Exotica Enforcer. We have recently developed a tyrolean crossing here along with calculations of anticipated loads and safety factors. Using the Enforcer on this tyrolean would give a real world check of my calculated figures as well as giving me a relatively safe and controlled location to experiment.

The tyrolean spans a 20m gully and is rigged using large trees slung with Lyon steel strops and the tensioning is done on the lower end using a 3:1 system through a Petzl RIG clutch. In this testing I purposely tried to over tighten things to see how much tension, and hence force at the anchors, it was possible for 1 person to produce.
I used a 5:1 pulley system and installed the Enforcer between the anchor and the RIG so it gave a reading on the total tension force being held by the lower anchor strop.

The calculations I had done previously were based on an average weight of participant of 100Kg. The span was measured and the sag was estimated at 10% as in practice we’ve found it impossible to achieve less than that with semi-static rope (usually more like 15-20%). The load on each anchor (so x2 for the rope itself) was calculated using a number of methods, some involving scary trigonometry, but the simplest equation was:

Tension = (Load × Span) / (4 × Sag)
Tension = (100kg × 20m) / (4 × 2m)
Tension = 250kg (roughly translated to 2.5kN)

The WLL (working load limit, or safe working load) of each component was calculated at a fairly standard ratio of 5:1, that is a fifth of its MBS (minimum breaking strength). Using this ratio the lowest figure was 4.8kN for a Petzl OK Oval karabiner. Technically the Petzl RIG is weaker but as it will slip before it’s WLL is reached then it can be discounted*.

*providing the RIG is not locked off and the rope is dogged back into the rigging so a running slip could not result in a complete slackening of the system.

So the maths with a 10% sag gave me 2.5kN tension force on each end of the tyrolean.

The tension force graph is downloaded off the Enforcer to iPhone and then edited in Microsoft Excel looks like this, with Time on the x and Force in kN on the y axis. Click to expand:

Little T 5to1 Graph

The graph starts with me applying tension to the system and having a few test bounces. The main force peak near 2m20s is me hanging suspended and pulling myself to the centre of the crossing and bouncing. I then pull up to the higher end, take a breather, and run back off, giving the last spike.

Little T 5to1 Graph top end

The second graph was me installing the Enforcer at the high end of the tyrolean crossing and tensioning it back up again with the 5:1 system. The tension at the top anchor was a little less than before on the lower anchor but the peak tension (me doing a running jump crossing) was similar to the previous graph.

Some interesting observations from the day:

  • At no point was it possible to install more than 1.5kN of pre tension in the rope prior to crossing. This was tested up to 9:1 and on 2 different tyroleans.
  • Tension in the line always dropped after the first crossing and remained at or below 1kN. Probably after the knots tightened up.
  • Tension could then be raised back up with additional hauling but the force remained below 1.5kN. Do not keep re-tensioning in real use as the increase in tension for each loading may cumulate to break a rope. See BMC technical reports.
  • The peak force was close to our 2.5kN calculation. This is predicated on having at least 10% sag in the system. A set of specifications for mechanical advantage systems and number of people pulling should be set by a company to limit over tensioning.
  • Whatever the tensioning method, we could not achieve less than 10% sag on a tyrolean in use with a correctly installed clutch.
  • Even on a 9:1 tensioning system the peak force created was only 2.8kN, probably because the Petzl RIG slipped at that point.

The 2.8kN high figure was achieved on a 50m tyrolean set up later that day. Here I was using a 10mm Beal rope today with a MBS of 24kN and 5:1 WLL of 4.8kN. The 5:1 safety factor is acheived with this rope. The rope I have on order for this when it is done with the public is a Mammut 11mm, the same as we use on the 20m line. It has a MBS of 35kN and hence a 5:1 WLL of 7kN, far above the expected loads in use.

Why all this effort? I like to know that the real world forces are actually near to how we calculate things, especially in tyrolean systems. Vector forces are scary and you just need to watch YouTube clips of slackliners breaking rated kit to see that. I can sleep well knowing all our research and calculations are backed up by real world testing and I can be confident that we are delivering as safe a service as we can.

Thanks for reading and remember, I can be hired to come to your site and test your rigging with the Enforcer too. Contact me direct for a quote and a chat.

Can you cut rope with a household jet washer?

After the last blog post where I tried to compare washing a caving rope in a washing machine to jet washing I thought I’d try to see how much damage I could do to a rope with a jet washer.

This photo was from the previous test where I exposed the rope to a full power, fine jet for approximately 30 seconds.OLYMPUS DIGITAL CAMERAI could not see any evidence to say that the rope had been damaged by the jet wash exclusively. The longer fibres shown here could have been the result of the already cut fibres in the sheath (short cut sections showing) being forced out from under another braid. Of course, the damage may be down to the jet wash alone. I think the only real way to progress with this test is to take a piece of brand new rope and jet wash it. I don’t have any laying about right now so I did some more testing with the leftover Beal Antipodes 9mm from the previous testing.

I split the rope down into various grades, from single bundles to cotton size filaments.Anatomy of a ropeI hypothesis that the worst case scenario is a rope being jet washed up against a solid surface whilst under moderate tension. The tension would keep the rope in the jet longer and the solid backing would provide a surface for the fibres to be crushed against or even abraded. It had occurred to me the damage could come from the power of the jet rubbing the rope against a course material.
The backing for this test was a piece of porcelain tile, almost completely smooth to the touch. The tile sat between the rope fibre and the wood in the test device I knocked up.Test assembly v1I tested each size of bundle on both full power and the normal setting that I use for washing. Both jet setting were fired at point blank range into the fibres for 60 seconds. This test was repeated at least twice for each sample after it was checked close up.
This sample had been washed on high power/very tight jet for 120 seconds. The jet was directed at the same area of the sample for all the test time. For scale, the fibre here is about size of that very tough cotton used for stitching canvas and kit bags together.One strand

The fibre bundles became so small that I could easily break them in my hands. This one was no bigger than a piece of cotton.Cotton thinkI figured that if my jet wash could not cut through a piece of sample that was thin enough to break easily with my hands then I did not need to progress onto smaller samples.


As before, I need to state that this back garden test does not give a statistically sound result and as such only serves to show what occurred in this one instance of testing.

I could not get my jet washer to cut any size of sample on this test. In both high power/confined and low power/wide spread modes, I saw no damage to the rope fibres. No doubt individual filaments of the fibres may well cut very easily but they break with the slightest of effort in the hands anyway so I doubt the value of that observation. The cotton size sample was the smallest test size and even that could be broken by hand with little effort.
It is also worth noting that this experiment was done on a 7 year old rope that had seen high use in very abrasive environments over its life.


I’d really like for other cavers to go out and try this experiment for themselves. Take a small piece of old or new semi-static caving rope and split it down to various sample sizes. Use a domestic jet washer / pressure washer on it’s highest setting and see if you can cut or damage the sample. For consistency, do it in 60 second, point blank range bursts.
Let me know via the contact address on my website or via the thread on UKCaving what happens. Failures to cut are just as important as actual cuts, so let me know either way.

Thoughts on jet washing caving ropes

I thought I’d ponder a little bit about the ‘myth’ of jet washers and caving ropes. I say myth because it appears that there is no real test data out there in the caving community. Recent caving forum discussions about jet washing happened to coincide with an associate company requesting we don’t use jet washers on their kit earlier this week and the two events spurred me to type something up.

Disclaimer – This is not a scientific, empirical experiment and you should always follow the care instructions of the equipment manufacturer.

I have used all sorts of methods for washing ropes over the years and most of my older ropes have been subjected to each at one time or another. Some times a rope may simply get dunked in the stream by the cave, other times I see fit to pull it through my home made rope washer but, more often than not, I get the jet wash on them.
The jet wash is always set to its lowest power and widest spray pattern. I’ve caused real damage to wood and clothing before by using the jet wash on full power so I am cautious. Some site this as the reason you should never use a jet wash on ropes. I agree. If you don’t know how to wash with a jet wash don’t do it. That, and if you don’t know how to operate your washing machine and it ends up on a boil wash, you probably shouldn’t put your ropes in there either.
This Beal 9mm got a super fine jet of water for about 30 seconds at point blank range in a test today. Damaged Rope

Apart from being incredibly clean for a 7 year old rope, you can clearly see the elongated sheath fibres. I’m not convinced the jet wash cut any fibres, more that it simply forced the already cut and abraded fibres out from under the other braids. The core was not exposed. I’d not want to do this to my ropes ever but I would call it far from ‘cut’ or ‘shredded’ as some anecdotal tales from the web recall.

Moving on. The rope I chose to retire was a Beal Antipodes 9mm semi-static that I purchased in 2007. The rope was one of my main users for 3 years as a 40m before being cut into 2 shorter lengths for cave leading handlines and general Italian Hitch duties. For the last 2 years it has languished unloved in the shed and has been the subject of much abuse in non life-critical applications. It’s probably not been washed for a year but before that it saw regular jet washing and stream dunking.

I cut the length in half and removed a control sample from either piece. The two 1m control sections came from the very end of the rope, where it was marked, and roughly half way along the 20m length respectively. I single daisy-chained one 10m length and double daisy-chained the other.

Test rope setup

The 2 longer lengths were soaked in cold water for 10 minutes as a pre-treatment.

As this was happening I cut open the 2 control lengths for a comparison.

End of rope section:Mid rope inner sheathEnd reel control Mid rope section: OLYMPUS DIGITAL CAMERAMid rope inner

The 2 samples looked very similar and I’m happy to say, despite years of being jet washed, were relatively clean and un-abraded inside. The fluffing you see was caused by the cut into the rope.

I dropped one of the test lengths in the washing machine. I set it to ‘delicate’ on a cold wash with no spin after first running a rinse cycle to clear any detergent. It had a 62 minute wash time.
While this was going on I jet washed the other test length in the same manner I do all my ropes. The process took approximately 5 minutes and once complete the rope was allowed to drip dry until the washing machine had completed it’s cycle.

After washing After washing

In both photos the washing machine cleaned rope is at the top and the jet washed one at the bottom.
I think it’s clear to see from the photos, and certainly was in real life, that the jet washed rope was far cleaner than the machine washed rope. It also had a much suppler feel and was more knotable over all. Remember the ropes have been identically treated until this very last wash in this test.ComparissonThe rope on the left is the machine washed and the one on the right has been jet washed.

It is hard to draw conclusions from the comparison here as this is only one wash cycle. The jet wash seemed to get the better results in terms of appearance and suppleness but the internals of the ropes looked very similar.
The one thing that I do take from this test is that despite the differences in the test washing, all the samples from this rope did not show any appreciable abrading of internal fibres from grit ingress. The anti jet wash argument is that the force of the water pushes grit into the core, causing damage. What I observe here is that this is an incorrect assumption as the 4 sections of visible inner on this very old, well used and heavily jet washed rope show no signs of damage by internal abrasion.

My theory is that the jet washing forces the grit and mud through the core and out the other side of the rope, as opposed to moving it into the core and it magically stopping there. I always clean my ropes after each trip. Perhaps they simply do not stay dirty long enough for the grit that does enter the core to be damaging. The outer sheath shows far more wear and damage than any of the internal structures of the rope.

I continue to believe that regular low-power jet washing does no harm to my ropes. I do know that some manufactures do not suggest using a jet wash on ropes and you should make your own choice with reference to the manufacturer’s guidelines. I will continue to cut open ropes as they are retired and will update this blog should my opinions or observations change. Meanwhile, if there is anyone out there prepared to take this subject up for a dissertation or just for interest then get in touch!

Gleistein GeoStatic NE 9mm rope – 18 months use

It’s now March 2014, about a year and a half after I bought my first length of the Gleistein Geostatic 9mm rope.
The 31m length I bought was soaked at home and measured to 32m, no doubt down to Shaun at Hitch N Hike’s generous measuring style!
I labelled it up as a 30m and went about using it.
I re-measured it today and it came in just over 29m, a shrink of 3m since initial cutting, approx. 9%. So it seems, just like any other rope, once it’s cut you still need to factor in about 10% for shrinkage over the life of the rope. I’m still happy because there was no noticeable shrinkage after cutting and soaking when first purchased in Sept 2012.

I have a 21m length bought about a year ago that has just re-measured to 19m. This length has had a hard life already, it is my traveling rope on cave leading work and has been dragged through numerous Italian hitches whist being covered in grit and the particularly abrasive mud in Peak Cavern’s trade routes. It has done a good job at sawing through my alloy krabs but the rope itself is still in excellent condition. There is some light fluffing on the sheath comparable with some of my far less used ropes and the colour, like the 29m length, has faded into a more pastel orange. It still handles extremely well, clearly not as supple as when new but a massive improvement over the 2-3 yr old Mammut 9mm I have, which is more akin to wire cable now.

My cleaning regime for all my semi-static ropes is simple and it gets done after every trip. For clean trips it is just a spray with the hose or a dunk in clean water to remove particles from the surface. More often than not it gets a low power jet wash (controversial I know!). Never force dried, only hung in a spare room or over the bath.

I’ve got 3 lengths now, each bought about 6 months apart and will continue to purchase this rope as my current ones approach retirement.
In another year and a half, when this rope is no longer in service I’ll do a final post mortem report. I’d also like to send a few samples to be tested by the BCA and Bob Mehew to see what toll the hard life has taken on it.

Gleistein is still available at Hitch N Hike as cut lengths or entire reels:

The initial blog post is here:

2013 Petzl Croll & Basic review

I’m a self confessed gear junky. I love to play with shiny things and we all love a rope trick or two. I also like looking good when I work, image is important as a first impression can be the difference between a days work and no work. All vanities aside, I think that a professional instructor should be equipped with the most up to date equipment available and of course the knowledge of how to use it! You can imagine how excited I was to read that Petzl were planning a re-release of the Croll and Basic early 2013. I was also mildly worried as historically there had been little change to the design of what was arguably an already excellently functional pair of products.
I managed to get my hands on one of the new Croll ascenders as they hit the shelves and have just acquired a new Basic literally as Hitch N Hike unpacked their shipment from Lyon.
I’ll start with a look at the Croll.

2013 Petzl Croll


Like the Basic, the last major design change in the Croll was when they went over to plastic safety catches from the metal ones. Since then we’ve only seen some small cosmetic tweaks. As you can see above the the 2013 Croll (right) is a complete redesign on the previous model. It looks as though Petzl have done a ground up redesign with a completely new set of parts and with an eye on size and weight.

The previous versions of the Croll weighed in at 130g, the 2013 is a featherweight 90g.
Usefully, the 2013 Croll is small enough to stir your coffee with if you are unable to find a spoon nearby.


The safety catch although small is easy to operate, one handed installation and removal from the rope is just as easy and smooth as prior versions. With the cam being smaller a shorter action is required to disengage the safety catch making the process faster but in no way less secure.
The attachment holes are well sited and allow the Croll to sit flat. I have used mine with a Torse chest harness and found they make a perfect combination, as I’d expect from 2 products from the same manufacturer. I’d recently had issues with an Anthron AC-30 chest ascender as the use of a Torse interfered with the clean running of the rope.
The main change apart from size is the addition of a stainless steel plate inside the rope groove. Although it does not cover the entire rope contact surface it shields the frontal portion where most heavy wear is generated as the user leans back on ascent. The stainless steel insert should improve the lifetime of the 2013 Croll, especially for cavers operating in digs or where there are a lot of fixed, gritty ropes.

I had a test of the Croll down Oxlow Mine recently and we used a mix of rope types and diameters, some very supple and some stiff and fat. After the initial bit of step and pull, the rope runs as smoothly through the Croll as it ever did, with no twisting or feeding issues.

In summary then, in producing the 2013 Croll, Petzl has taken a much loved and hugely popular item of equipment and completely redesigned it. A bold step but one that appears to have completely paid off. Petzl’s updated documentation for the Croll can be found here.

2013 Petzl Basic

The 2013 Basic is the newest piece of kit to hit the shelves from Petzl. Just like the 2013 Croll it has had a complete redesign. I will probably sound a bit like a parrot here repeating lost of stuff from the Croll comparison but I’ll be as brief as possible.

Again the Basic has been on a diet, dropping from 135g to a skinny 90g. If you were to make the switch from the previous jammer versions to the 2013 ones you’d save a total of 85g, that’s the equivalent of a 3rd jammer in your pocket. You could even stop your New Year diet 0.19lbs early or not feel guilty about bringing that extra bag of Haribo underground.

Just like the 2013 Croll, the Basic has shrunk. Perhaps not to the same degree as the Croll but the unit feels noticeably more compact in the hand, not to mention comfortable.


The upper section of the Basic is now fitted with a gentle curve and a matching section of plastic. These changes fit my hand like a glove, feeling comfortable with a left or right handed grip. I may however find it a little harder now they are so easy to hold to coach efficient technique with out over reliance on arm strength.
Another big change is the loss of the double hole at the top. In the past we have been able to build pulley-jammers or mechanical advantage SRT systems by placing a karabiner through the top holes and capturing the rope. This is no longer possible on the 2013 version but have no fear, Petzl have thought of that and given us the solution.
The new lower attachment point is double size, allowing 2 karabiners to be clipped in.

The previous version of the Basic allowed us to clip into the top attachment holes for use in tyroleans, pulley systems and rescue:


The 2013 version allows us the same versatility but with a simpler, single attachment point:


The only use that the Petzl documentation indicates for the top attachment hole is to add weight to help reset a z-rig hauling system. You should probably read Petzl’s documentation if you don’t understand that.

The final big change to the use of the Basic is involving pulley-jammer setups, the kind of hauling and rescue technique that an instructor first learns. The new advised method is arguably simpler to arrange and easier to learn. It does however require an extra krab over the previous method.


I intend to spend some time hauling weights on this arrangement but I really expect no loss in function over previous techniques.

Although it may take users a little while to adjust to the new method of use, I think that the 2013 Basic is a good addition to the Petzl family and combines nicely with the Croll to shrink both the size and weight of the average SRT kit. I think that I could remove my new Basic and 8mm footloop assembly and put it in my pocket between pitches.

One moan (well it can’t be all singing Petzl’s praises), bring back the bright colours! I love my new Basic but I know that one day I’ll drop it in a puddle or sump whilst I’m sorting my harness out and because of its stealth colour I’ll not be able to find it again. Give us a choice of tactical colour for the bandit runs and military users but lets have some red, purple, orange or lime greens for the people who don’t wish to blend in!

Final Thoughts

Interestingly, neither the 2013 Croll or Basic are listed as having a breaking strength or working load limit. The closest we get is the advice that for industrial users Petzl do not recommend the use by anyone over 100kg.
I think this reflects the attitude where the jammers are not placed in situations that require them to hold more than a person’s weight and high load scenarios like traverses and rescue have specialist rigging kit. The issue we may have with this is in a spare rope rescue scenario where we pick off a caver from one rope and accompany them to the floor on another rope attached via a Basic or Ascension jammer. Petzl has an online tool to advise people over 100kg how to use the equipment and that appears to show that correct use of a Croll (i.e. no fall factors!) will be fine with larger loads. For an Ascension it suggests increasing the shock absorbency of the attachment point, i.e. using a dynamic safety link or a cowstail as is widespread in Europe.
I’d still like to see some figures from Petzl for 9mm and 10mm rope to confirm that we can continue to use the Basic in the above way. I don’t expect any loss of strength but it would be comforting to know for sure.

Finally, with all this lovely new lightweight and compact kit coming to our shores, when can I expect a nice redesigned Stop descender?

New Bolts at Pindale Farm

Recently I have been spending a lot of time swinging about on the surface, either through testing knots or coaching SRT skills. For all of this I’ve been using the excellent tower facility up at Pindale Farm near Castleton.
The SRT platform offers scaffolding bar belays and back-ups and the surrounding walls of the old mining buildings are equipped with many 8mm anchor sleeves (Spits) and a few alloy Troll hangers. You can rig just about any permutation of SRT pitch your brain could possibly come up with.
Using the tower over the past few years I’d noticed the deterioration in some of the anchors and as I was such a frequent user I thought some of the replacement anchors should be paid for out of my pocket.

Yesterday (19th March 2013) I managed to procure both equipment and assistance.
Jez Parr CIC (contact) was kind enough to loan me his SDS drill and all the bits for the job.
Nigel Ball CIC (Website) donated half of the anchors and 90% of the expertise in the operation.

We placed 4 new Petzl P38 Longlife anchors on the main wall of the facility; a line of 3 forming a traverse and pitch head which then drops to a rebelay or deviation on the 4th anchor.
We also lubricated and cleaned out all of the 8mm sleeves with a threaded tap to give them a new lease of life.

The tower is now a mix of anchors and can be used with or without hanger plates. Please bare in mind that the tower is equipped by volunteers/individuals and is on private land so booking is essential. Users are reminded to check the anchors they use are safe before commiting their life to them as they would underground and that anchors should never be used alone but as part of a safety chain.
All bolts will fail at some point.

Pindale Farm is an excellent place to stay in the Peak for caving or any other reason. They have camping and bunkhouses on their site as well as the excellent SRT tower.

New bolts circled:Pindale Tower

Conclusions on the use of the BotB

So, the footage has circulated, tests have been done and reports and statements have been published. Where are we on BotBs?

I echo the BCA advice that the BotB is safe to use provided that a cowstail is always clipped into both loops. I will continue to use the knot in my range of personal and professional tools. I think that the knowledge of this method of failure has been there since the BotB came into use, I do think that a number of people were shocked as to the extent of the failure when they saw it. This knee-jerk away from the BotB has calmed down as people have looked into the evidence and scenarios of failure.
Hopefully enough information is out there now to allow cavers to make their own choices on knot application.

A concern may crop up for some riggers where they are leading less experienced cavers or those who simply do no know about the single loop issue. The rigger may descend the pitch and those following could inadvertently clip a single loop placing them at risk of this failure. This scenario perhaps would benefit from the use of a knot that won’t fail if a caver clips a single loop – However the advice to clip both loops does not change.

What if you don’t want to use BotBs?

Well, a number of suggestions have been put forward.
The Fig 8 ‘Bunny Ears’ / Double Fig 8 on the Bight is the most common knot but lacks the ease of adjustment and untying that the BotB has.
The Fusion (Karash) Knot is simple enought to tie but is a struggle to dress on stiff rope and has zero history in UK caving prior to a few months ago.
Alpine Butterflys or Caver’s Butterflys can provide a good Y-hang but an overhand knot would need to be introduced to one of the loops to give a central rescue point.
The Double Bowline on the Bight is one extra twist from the BotB. It adjusts, ties, unties and looks like a BotB, meaning it is easier to use and spot mistakes for existing BotB users.

The choice is down to the individual rigger. The evidence is out there for you to see.

Warning – correct use of Bowline on the Bight Knots

BCA’s Training and Equipment & Techniques Committees would like to highlight the importance of ALWAYS clipping a cowstail through BOTH loops of a Bowline on the Bight knot. Although this has been taught for years by BCA instructors, it appears
that many cavers are not aware of the importance.

The problem is that in a fall the knot can slip in such a way that the rope going down the pitch can actually run all the way back through the knot. This means that a caver falling
at a pitch head with their cowstail clipped into only ONE of the two loops could
potentially plummet all the way to the bottom of the pitch. This cannot happen
if they are clipped into BOTH loops.

A useful tip is for the rigger to leave an HMS karabiner clipped between the two loops to make it easier for the rest of the party to clip in and it is always worth remembering that two cowstails are preferable to one.

From here:

The report from drop tests at BPC on the 30th Jan 2013 is here:

UKCaving discussion here:;topicseen#new

2nd round of testing on the Bowline-on-the-Bight knot

Thinking that 2 heads were better than one I set out today with a good friend and colleague, Jez Parr. Jez in another CIC holder with many years of experience. He was also my mentor through the CIC scheme and the ideal person to bounce ideas off.

Our first stop was local gear shop and purveyor of lovely shiny things, Hitch N Hike. We purchased 5 metre lengths of all the most commonly used semi-static rope they had, in both 9 & 10mm.

The test was set up identically to the ones done previously on the 8th Jan. We had a mock Y-hang arrangement that allowed us to position the test ropes at varying heights and angles as well as a solid bar from which to rig a secure dynamic safety back-up for ourselves.
The aim of the first testing done previously was to identify the main contributing factors that caused the failure in the Bowline-on-the-Bight, or BotB. This was achieved and we could generate failures almost 100% of the time. This test is written up in the last blog post.
Today’s testing was all about trying to get a failure in a normal use environment with normal conditions. All the tests we did were on knots that has been tied, dressed and set as we would and have done thousands of times underground. We were not wanting to tie sloppy knots, we wanted to see if it would fail when it was done well.


For every test of every rope in every combination of orientations we tried, so long as the cowstail was attached through both loops of the knot there were no failures. This was as expected and ties in with the best practice advice that has been taught for years with the use of the BotB – ALWAYS CLIP BOTH LOOPS.

For tests carried out where we dropped onto a single loop – the one formed from the traverse line or stopper knot, we could also generate no failures. However this is outside the intended use of the knot so little time was spent investigating that scenario.

When connected to the Bowline-on-the-Bight with a cowstail attached to the single loop formed by the pitch rope we were able to generate failures in knots that were tied and dressed correctly that had been hand tightened or on occasion body weight tightened.

Below are a pair of images showing slip through the knot. Note the blue mark.
BotB test 3

BotB test 4

A second set of test images:


For a YouTube film of 3 of today’s tests see here:

For the previous test film see here:


The Bowline-on-the-Bight can fail when you are clipped into a single loop and the knot is dressed correctly and tightened. The failures we generated included ones where we both agreed that we had tied a perfectly acceptable BotB before testing.
Although we can identify many modes in which we could not get a failure to occur, the fact that one can occur in normal* use is very worrying.

* normal use if you only use one loop to attach your cowstails as is against the best advice – always clip through both loops!

So now what?

Cavers should draw their own conclusions from these tests or indeed conduct their own perhaps.
I believe that it is still appropriate to teach the Bowline-on-the-Bight as one of the standard knots for caving alongside the information about how to use it safely and the consequence of misuse.
I will copy this information to the British Caving Association for review. It is not my place to advise on caving policy for the UK.

I have been offered the chance to use a rope tester to look at potential replacements for the BotB. The test will give us a chance to see how a replacement compares with the existing methods in terms of strength and durability.
The French’s preferred option – the Fusion Knot, which has also been called the Karash Knot, is high on the list of contenders but I feel that a similar knot to the BotB would be more easily absorbed by the caving community. Both myself and Jez think a closer look at the Double-Bowline tied on the Bight may give a very good alternative. We’re calling it a D-BoB, or Double Bowline-on-the-Bight, until we can establish its correct name.