gear

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.

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.

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 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.

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…