Karabiner gates and foreseeable error

Sorry if that last post didn’t make much sense – and no, don’t worry, I’m not turning into a grouchy old man, just my thoughts – and they don’t always have to make sense… 😉

I was thinking about karabiner locking mechanisms before, prompted by a video posted on Facebook that shows an Locksafe Ultra O rolling out as it the locking mechanism is pushed against and past a limb. This failure mechanism is not specific to one brand, but rather inherent to the lift, turn and push type triple-action gate.

Essentially the limb in the video is doing exactly what you would have to do to unlock and open the gate. This phenomenon is known as roll-out. Statham and Roebuck wrote a report, Karabiner Safety In The Arboriculture Industry, for the UK Health and Safety Executive a couple of years ago, in which – amongst other things – they describe some roll out testing they performed on a range of connectors  commonly used in tree care and how they all struggled with the test set-up shown below.


The locking mechanisms that did best out of the lot was the Petzl Ball Lock, then still the plastic version with the thumb print on it. In my eyes though, it would be a bit hasty to start crying foul and accusing manufacturers of making bad quality gates. Essentially, this is not a design flaw, but rather it is operator error: In a cluttered environment it is up to the operator to ensure that the locking mechanism shall not come into contact with the structure and inadvertently be pushed open. Look at any user instructions and somewhere in there you will find a pictogram or text warning against this exact case, as in screen shot of the Petzl Carabiner Experience PDF shown below…

This is actually talking about something different, which is the danger of cross loads and lever action across the gate, but the fact remains: It is a clear warning against loads on the gate and once again emphasizes the importance for visual inspection, especially in an environment, like in tree climbing, where the connector is frequently being loaded and unloaded, making a cross load on the gate more likely.

What is clear though is that there is not one type of locking mechanism that addresses all issues. The Ball Lock type mechanism mentioned above may solve roll-out type problems, but especially the old plastic version had a low tolerance to outside loading of the gate. So, it is really up to the operator to consider what type of environment he or she intends to use the connector in, obviously the requirements you make of a karabiner is not the same when climbing large, open-canopy trees or when cone picking in the forest – and to choose an appropriate type karabiner. Depending on the situation, this may have a triple-action or a screw gate – or yet another type.

For more info, here is a link to the Go Configure article that Chris wrote a couple of years ago for ISA’s Arborist News.

The video below illustrates a different case:

Here a light tap on the outside of the gate is sufficient to push it open. This is a different matter alltogether: From a design point of view this sort of load is a foreseeable error. Whilst superficially the Skylotec Pinchlock karabiner has similarities with the Magnetron by Black Diamond, the failure mechanism in question is specific to this karabiner as the rods that locate into the slot on the nose have a round profile, rather than the square ones on the Mangetrons, that on top of it don’t only rely on springs to locate the rods, but also use a magnet to ensure correct closure. In an outside-loading situation the round rods on the Pinchlock are simply pushed up and out of the slot, a tap against the side of the hand being sufficient to do so.

Again, this is not a value judgement, it is merely an observation, as for all I know there may be an application where this type gate is spot on, but certainly a busy, cluttered environment such as a tree canopy is probably not one of them.

V-Rig rocks!

Working on a mixed species alley along a road here in Basel on the way out to Alschwil consisting of Sopphora japonica, Cladastris lutea and  Robinia pseudoaccacia. 

Especially the Sopphoras are really quite big trees – well, not exactly monsters, height-wise, maybe 22m, but just ridiculously wide with limbs taking off in the direction of the horizon. Looking at some of the structures you can’t help but think that trees have a sense of humor (ok, dreadful piece of anthropomorphizing there, I realise!) or are daring each other to grow further and further out.

Be that as it may…

Frankly, on jobs like this I am just so grateful for having the V-Rig technique in my mental tool box. In my opinion this is the most functional way of working with two anchor points for a number of reasons:

  • low friction
  • load is equalized between the two anchor points
  • mechanical advantage when returning up the limb
  • low lateral forces on the anchor points (unless you are level with and suspended between them)

This technique is known by a number of names, like the M-Rig, as some credit it to Mark Chisholm or the V-Rig, makes more sense to me, as that describes the line of the rope between the two anchor points. The first time I saw this technique demonstrated was by John Hartil in 2002 or thereabouts. Sometimes it’s hard to put a specific name to a technique, the truth being that it’s shown by one person and someone else adopts it, takes it and evolves it further. I am, however a great believer in crediting ideas, as it puts them in a context, it’s not just something that popped up out of the ether, all nicely configured, but rather something that evolved over time with names and stories attached to it.

There came a moment on the job this morning, where I found myself almost horizontal to the two anchor points, waaaaay out in the canopy– over the road – using my lanyard as an extra tie in point. Using one point this would have been a nigh impossible point to reach. Apart from spreading the load to two anchor points, I also find it helpful to be able to balance between two anchor points, as this is inherently more stable than just the one and returning off a long flat limb like this is just so much easier with the mechanical advantage integrated into the system.

V-Rig permitting easy movement back and forth, here to install a bracing system

Key to using this technique (or any technique, come to that), is to have the gear handy. If it’s a major hassle to organise it all, you won’t do it, and believe me, that’s me speaking from experience. On trees like this I will have a compact, adjustable thimble saver stowed on my harness, then all I have to do is to lanyard in, release the swivel on the rope bridge that I have secured to one side with a short sling with a Revolver karabiner on it, install the saver, sling through top hole of the Hitch Climber pulley, catch the high line with the Revolver, attach the whole combo onto the swivel and I’m all set to go. I’m not saying, do it like this, but suggesting that you develop a sequence in which you install gear and rig techniques and they will automatically get easier to use and therefor the decision to employ them so also becomes easier.

For trees like this, I would be stuck without having been introduced to the V-Rig all those years ago, so thanks to John, Mark and whoever else thought this one up. And spread the word, it certainly beats the old karabiner in a sling redirect technique hands down, that much is for sure!

Rigging Hubs

Rigging Hubs resulted out of discussions I described in the Tripple Whammy post the other day.

The aim was to come up with a device that could act an easy interface between metal connectors and textile elements, such as slings or rigging lines. It should provide the possibility of direct attachment with connectors, as well as directly knotting onto it – also it should be possible for the device to accommodate running ropes. As such it needed to have rope friendly radii and surfaces, be tolerant of funky loading and intuitive in use. The result was the two sizes of Rigging Hubs…

The uses we foresaw were initially 2D uses, i.e. in an up/ down and left/ right orientation, whether this is in a rigging application, drifting masses between two anchor points, as a base anchor or as a floating climbing anchor point.

On the way we also came up with some off-beat applications, sure there’s plenty more you can come up with 😉

Increasingly though we had questions regarding 3D use, i.e. horizontal orientation and loading of the Rigging Hubs. Initially we were not able to answer this question, as it had not been tested in that orientation. However, we requested DMM to do the additional tests which demonstrated that the Hubs have an ample breaking strain in that orientation and consequently ended up with even more uses.

This process resulted in a super-strong, super-versatile piece of kit that has many uses and, looking back, I wish I had had for a number of technical rigging jobs, as it makes your life so much easier when inter-connecting hardware and textiles.

Article on testing of damage to synthetic fibres

At the Climbers’ Forum in Augsburg Angela Sipos from Teufelberger presented some preliminary results of on-going testing that they are doing regarding various types of damage to synthetic fibres, such as abrasion, heat, exposure to various chemicals, UV exposure etc.

Rope failure due to overload
Rope failure due to overload

Here is a summary of the findings that she and her colleague presented.

Obviously, it’s in German, but Angela will be attending the NZ arb conference in Rotorua in October and will be presenting these results there.

As I understand it, these tests were intended to establish a baseline in quite general terms, the plan is to continue these tests and taylor the types of damage to be more specific to what might be encountered in tree care.

Final day of testing

Today concludes a week of rigging testing in the Highlands – and what a week it was!

As I wrote earlier this week, it’s much to early to even consider communicating any conclusions or wisdom in regards to what we were testing, however these days have certainly given us much to think about and discuss – not to mention 120GB of video and photo footage.

I would like to use this opportunity to mention how thoroughly annoying GoPros can be. Not just because of the weeks worth of wobbly, uncut helmet cam footage (that always makes me feel rather nauseous and bores me  to tears after about fifteen seconds) we are bombarded with via Youtube  and the likes, but mainly because they are soooo temperamental, which is not ideal if you have four cams dotted around the site fifteen meters up trees. Still, minimum one was working all the time.

We feel strongly that it is essential to continue building on the insights gained through research such as the HSE and Forestry Commission Rigging Research, or work done by people such as Andreas Detter or Peter Donzelli to increase our understanding  in regards to the ways in which we work and techniques that we employ, and where possible to identify ways in which we can make them safer, more ergonomic and/ or more efficient. Hopefully in the future weeks and days such as this past one will contribute something towards these goals.

We had the privilege of having a fantastic team working with us, as that is always the thing that makes or breaks this kind of enterprise. So big thanks to Jon Turnbull, Henk Morgans and Georg Schwenteck for helping to work through a really very demanding schedule – and of course to Chris for making this all happen in the first place.

Day three of testing

Day three, what can I say?

Fantastic weather and big forces sums it up. Best explained with some pictures…

Things get heavy

Wow! That was an interesting day yesterday. And it was only day two of the week, wonder what more is going to come to light.

Don’t expect any quick statements regarding the testing. The temptation of course is to rush out to share snippets of information, but the truth is when it comes to rigging, caution may be advisable when attempting to express generic guide lines. Rigging is complex. Many factors come into play, that will influence the way the machine you have built into the tree behaves – and that is one of the things we are trying to improve our understanding on.

So the next steps will be mulling over the data, evaluating all of the video and photographic footage and trying to formulate coherent conclusions that are of use in the field. The problem is not lack of data, but the sheer volume of it, and this will only increase by the end of the week.

Bit of rain over night, cleared now, so it looks like we’re good for today, which is fantastic as it means we can press on…

Caledonian Give It Some Depth

A while back I wrote a post about giving it some depth, reflecting upon the need to beef up opinions with fact it they are to be meaningful. So here we are, in the Highlands, with a load of rigging gear, attempting to do just that.

Arrived on site on Sun and was blown away by the amount of work that Chris has put into this. The site was super-well organized and well set-up, more or less ready to get going on Mon. We had a day of drops yesterday and regardless of what comes out of all of this by the end of the week, just watching rigging systems under high dynamic loads teaches me lots every time: Seeing the impact, hearing the equipment being loaded, and seeing the damage that these kind of forces can cause.

Food for thought indeed. I’ll be very interested to see how the week progresses.

So maybe this is the other side of the coin of what I wrote about the other day, about just going out there and doing some testing yourself if you have questions you want to find more out about.

Testing doesn’t come free.

You have to invest time and effort. The degree of which depends upon how ambitious the scope of the foreseen testing is, so to a degree you can influence that. The aim has to be for the methodology to be sound and for it to be replicable, i.e. the test set-up to be clearly defined.

One of the exciting things about going into a process like this is that you don’t know what’s going to come out the other end… some profound insight, a confirmation of something you already knew (but can now put figures to or can back up) – or profound puzzlement, because the outcome was not at all what you had anticipated. But that’s ok, then it’s really down to discussion to find out where the variables are that influenced the outcome, was it a mistake in set up, were you thinking down the wrong lines… or was is something else that’ll take some more work to understand?

So, big thanks to Chris for making this all happen, with this kind of preparation things go more smoothly, even if unforeseen events occur. As is often the case… especially when chucking big lumps of wood overhead into rigging systems.

Make your life easier

Yesterday during a break we were discussing how sometimes it’s all very well to decide to do something in a certain way, but if the correct tool to do it with is missing – you won’t do it… until the right tool comes along.

A classic example for me to illustrate this is the throw line on a spool or in an old paint bucket. You won’t use it, because the line off the spool is all twisted and really annoying to wind on and off and the paint bucket is just not handy… along comes the folding cube, and hey presto, suddenly your life gets much easier, you use the throw line more – and become more proficient by doing so. Well, most of the time anyways, unless you happen to be having a throw line meltdown day.

Another use of a throw line
Another use of a throw line

The example we were discussing yesterday was securing the load on the back of the vans.

The authorities in Switzerland have become much more restrictive in this matter over the last couple of years – probably rightly so. When we first got a net to cover the brush we got wide mesh nets, with the result that they were really annoying to use as the branches would always get stuck in them, it was hard to install and to remove. The result? Often as not they were not used. Then we found very fine-meshed material – I think that originally the fabric is used to shade green houses – , really tough but still easy to handle. One person can easily cover the load area on the back of a van with it and it’s easy to remove as the branches don’t pass through the mesh.

So, because it’s easy to do so, it gets used.

This got me thinking about lanyards: I think lanyards are a fantastic tool right there on our harness that can be used in many versatile ways. I find it frustrating to see people thinking no further than side D-ring to side D-ring. But often as not, this is because in people’s perception a lanyard is something that’s inconvenient and burdensome.

So, I say, let’s make it easy.

For instance, you might consider how you stow the lanyard. I dislike nothing more than returning from a limb walk to find my feet tangling in the lanyard hanging down behind the adjuster… this will provoke very un-Zen like states in my mind! So you could use a shorter lanyard to prevent this from happening, which seems a pity as you lose versatility – or stow it in multiple loops, so that when you’re not using it, it’s out of the way – and when you do need some extra length, it’s there for taking.

Over the years we used different ways to do this, small prusic loops of accessory cord, short bits of hose – but all of these methods didn’t feed very well.

Gabriele Dovier from Formazione3t in Italy came up with a very elegant solution: Scuba clips. These are used for scuba diving to hold the air hoses. They have two or three open clips that will take a line from 10 to about 11.5mm. If you give the line a tug it’ll pull out, if you pull it steadily, it’ll feed nicely.

Scuba clip
Scuba clip

So, you just attach it below you lanyard adjuster, stow the lanyard in two loops – and you’re sorted. Most models even have an integrated swivel, which is handy.

With this simple, compact and light solution, that’ll cost you maybe a couple of Euros, you have uncluttered your harness and tidied up your lanyard and by doing so made your life easier. This means you don’t have to focus on messing around with your lanyard, but can rather focus on the climb. Which is a good thing.