Rigging @ Arborfest

Here is a live feed of the session I did earlier today with Nick Bonner at the Arborfest in Asheville, NC on his micro rigging set-up. This is as concept I had seen Bernhard Schütte of the Munich School in Germany use before, but not something I have ever had the opportunity to try, so I enjoyed this opportunity to have a play, thanks, Nick.

Mark Bridge Micro Rigging Lab Demo

Mark Bridge, a Treemagineer and co-inventor of the TreeMotion harness, demonstrates some rigging theory at the TreeStuff Micro Rigging Lab at ArborFest Expo. #AFX

Posted by TreeStuff.com on Thursday, 21 March 2019

This is shaping up to be quite an event, if you have nothing planned for the weekend and have the possibility to stop by, why not come and join us. I am seriously impressed by the amount of energy, creativity and effort the Sherrill Tree/ Treestuff crew have invested into making this happen…

Replace wear parts

Quite a few years back we did an inspection on a nineteenth century chimney that was part of an old brewery here in Basel. The chimney had rather disconcertingly started spitting bricks and its condition was… questionable. I will spare you the gory details of the story, but put it this way, it was quite an adventure getting up there and moving around the chimney.

What struck me, as is often the case with old buildings, is how sometimes they only seem to be holding together out of habit. In this case the mortar between the bricks was being washed out, climbing up the inside of the chimney you could see chinks of light in many places where there was simply no mortar left. Give me a tree any day!

The parallel that struck me was to the wear you can sometimes find when inspecting equipment. Friction hitch cordage, for instance. Oftentimes you will look at the eye to eye sling, think it looks a bit weary but otherwise fine, for the mantle to then fall apart soon after. What is going on here? Well, in the Ocean Polyester eye to eye slings, for instance, the mantle is braided, made up of Aramid and Polyester, the core is braided Polyester (PES). You cannot die Aramid, so that is the yellow-ish part of the mantle, the PES is the green.

I have written this before, but what seems to give you the ability to dose the exact degree of friction in friction hitch cordage is the PES. High-modulus cordage on the other hand tends to be much more on/ off and less easy to dose. The reason for having Aramid in a friction hitch cord is heat resistance. The combination of PES and Aramid gives you the characteristics you are looking for, responsive handling as well as heat-resistance. By and by in use, the PES part of the mantel will be melted away, leaving you with Aramid, at which point in time the hitch starts to run less nicely on the line, you start to lose function – whilst still retaining the full strength of the core!

The link to the chimney above is how cordage can also apparently be intact, but that once you start plucking apart the mantle of a friction hitch cord which seems well-used but otherwise ok, the whole thing will simply disintegrate. This shows how Aramid – besides all its strengths – is a brittle fibre, which that has the tendency break when bent frequently. Yet that is acceptable in a wear part that will be replaced on a regular basis, the same is true of its low UV tolerance. Before this becomes an issue the hitch will be due to be replaced. Conversely, the same cannot be said of a device or assembly with a longer intended life-span, such as a lanyard or a false crotch.

Then there was the bridge below, which I came across during a gear inspection of a treeMOTION, it had been in use about one and a half years. I take every opportunity I get to pull apart old bridges to try to gain a better understanding of the variables which are in play when it comes to how they age. In this instance, the mantle was quite worn and distinctly flattened. The intermediate cover also showed quite a bit of wear, though no material was lost on either of them. The core showed similar wear.

I would suggest that this is quite a long time to wait before replacing a bridge, yet was positively surprised by the condition of the cordage.

When it comes to assessing wear parts in your PPE, I would strongly encourage you to identify and understand them, to heed manufacturer recommendations, inspect and maintain them diligently – and to replace them sooner rather than later – after all, the cost of the replacement parts is not that high, especially considering the potential risks that not doing so could entail.

Do not use as an indicator the fact that a component looks ok to draw the conclusion that it is ok. Do not be shy to dig a bit deeper and to look closer.

Glass half-empty, glass half-full?

On crane removals always use the same crane company, usually the same type of crane, the MK80, and the same operator. This has proven to be a good combination, meaning you do not have to redefine procedures every time before you can get started. This was also the crane we used for the removal of the beech beginning of February I wrote about a couple of days ago.

I was concerned last week to read in the newspaper that there had been an accident on Friday with that very crane. The Liebherr MKs are great once set up, but the whole way they folds up is intricate, to say the very least. I am always struck how the operator is able to pivot the whole length of the boom round by hand during set-up – that is how precisely the whole construction is balanced – yet it turns out that the down side of that is that during set-up the construction does not handle wind at all well…

Friday there were intermittent gusts of wind of quite variable strength, one of these caught the MK at precisely the wrong moment, almost shearing the boom off. In view of the fact that the crane was set up right next to the motorway and the boom was now hanging over traffic, this led to the busy motorway having to be closed for the whole of Friday afternoon. Far from ideal.

I am not quite sure what the take-away lesson from this is. Well, obviously, that cranes and wind do not mix well. But to be fair these were tricky conditions, it was not as though there was continuous gusts, they were few and fairly spaced out – but when they came they were strong. I also suspect that what happened here was a perfect storm in the sense that a strong gust caught the crane at exactly the wrong moment.

The main thing I take away from seeing a tool I am familiar with looking so very broken is that thinking positive is all very well, yet sometimes it can be a good idea to consider situations from a glass half empty point of view, not assuming everything will go as well as possible or as planned.

Interestingly I had cancelled a job the day before due to the weather forecast: a very large London plane right in the centre of town that is due for a canopy reduction, removal of dead wood etc. The canopy is very wide, spanning a road, two tramlines with overhead power lines, a busy pedestrian area and the entrance and exit to a public underground parking space. For organisational reasons we were really committed to do this last Thursday, as that was the day after the carnival ended here and the bicycle parking spaces below the tree would be clear, which would be convenient. The forecast for Thursday remained obstinately bad during the whole week, strong winds and rain from mid-morning onwards. The client for this job is the council, they had their crew lined up, also a security person for the public transport company to supervise the work around the power lines and the trams, so quite a bit of organisation had gone into the job already.

The closer the date came the uneasier I became, working scenarios back and forth in my head. Then I realised I was applying glass half full-type planning optimism. Ok, it will be a bit wet, but we will bosh it out, everything will go perfectly and we’ll be fine.

This kind of thinking has to be a red flag. The tree in question is a good thirty meters tall, fine to climb when dry, less easy in the wet, add wind into the mix and things start to look more than just a bit sketchy. I realised that my assessment of the situation was being biased due to trying to accommodate a date dictated by (justified) organisational concerns of the council. Taking a step back though brought back to the front of my mind the facts that this is challenging climbing in a challenging environment – and that therefore from a risk-assessment point of view I could not justify performing this kind work in adverse conditions. When weighing up operational versus organisational considerations, the safety aspect of the operational angle trumps the organisational one of having to shuffle dates.

I am not saying any of the considerations above are relevant to the crane accident, yet it brought home to me how easy it is to get fixated on a target, especially if you are already invested in it and you “only” need to do this or that to achieve it. This is the moment to take a deep breath, maybe get a second opinion on it, consider alternatives or options – and most certainly not to cut corners. In this case, the responsible people in the council were very understanding when I explained what the issue was, so we have rescheduled the work on the tree for in two weeks, hopefully in better conditions – this makes it more fun, and safer.

Fun in the sun – and a mishap

We removed a Sycamore last week. Nothing huge, yet it presented some interesting rigging challenges due to the length of some of the limbs and the targets below. We ended up balancing and/ or winching a number of picks, as well as moving anchor points around and using multiple rigging anchor points, allowing us to load them in compression, something I like to do when diameters are not huge.

Those first climbs after winter when the sun starts to regain some warmth have a magical quality, not being bundled up in thermals makes them feel effortless and easy – this was one such instance. Roll on spring!

I enjoy balancing loads, as it is an activity which gives you a very immediate feedback as to whether you got it right or not, no shades of grey there. Enough of those in other instances!

Did I mention some of the limbs were quite leggy? 😊

I managed to make a real rookie mistake at the start of the day whilst removing one of the lower limbs. As there was a clear drop zone below, I simply dropped the lower two limbs in a couple of sections. When I put in a face and made the back cut in the last of these pieces, which was maybe four meters long with a diameter of 40cm, I missed the fact that it was banana-shaped, with the far end facing downwards – so when this hit the ground the butt pushed back and tonked me on the arm – hard. In the first moment I thought the arm was broken, all numb and tingly, but luckily it merely turned out to be thoroughly bruised.

This is an issue I would normally be really wary of, exerting considerable caution when dropping pieces that are longer than my distance from the ground, for exactly this reason. Yet in this instance it somehow slipped below my radar, maybe due to the unusual shape or my being focused on the more complex picks to come? Who knows. Just goes to show once again how the fact of being aware of an issue is not a sure-fire protection against stuffing up regardless – and that no one is above making mistakes. I was lucky that I had free space to swing back into and that the section in question was not larger.

This might hurt a bit…

Despite this slight mishap, the rest of the day really smoothly, we had a lot of fun – and I enjoyed the sunshine, to boot.

Crane work

Cracking video by Vito Cordasco documenting a crane removal we did a couple of weeks ago.

It shows the removal of a really large beech tree, sadly one stem of which had severe die-back over a period of a number of years, as well as the base being absolutely full of fungus. The sum of these defects consequently lead to the decision to remove it. Due to restricted access and the amount of wood to be removed we chose the crane removal option, with thirty seven picks this was a long day – and we removed four skip-loads of wood! Conditions on the day were beautiful, chilly but clear, allowing for great drone footage.

I thought the sequences showing balanced loads were especially interesting – this was indeed the challenge for this removal: very long pieces with not a lot of space to deposit them into. The individual picks were not very heavy, around one tonne, but larger pieces simply would not have made sense from a handling point of view. Also, the crane, a Liebherr MK80 could take around 1.9 tonnes at the furthest point out at 51 meters, so it did not make sense to go overboard on size.

The pic below gives you an impression of just how tight we were for space… the processing zone being just above the crane. All the loads were lifted between the two buildings. The space below the crane was not used as this had to remain open for vehicle to get in and out and also due to street light electricity cables.

A further interesting sequence is the one where Vito did a time lapse sequence of the space we were depositing the limbs into. I was struck by how this space was constantly being cleared, right down to being raked and swept between picks. This makes sense, in all likelihood the highest risk on a site like this is that someone slips or trips while handling a load during tidy-up.

A big thank you goes out to all involved in this project: Serge, obviously, for his diligent organisation of all the aspects of the job, the crew from Team Vertical, Christian and Patrick from Welti Furrer – and of course Vito for the great footage and editing the video.

Coming up #1

Coming up in the next couple of weeks is the Arborfest Expo from 22 to 24 March in Asheville, NC, hosted by Sherrill Tree. Chris and I will be there, kicking around the DMM and Teufelberger booths, as well as presenting on a number of topics.

Should you live in that general area and happen to be at a loose end that weekend, why not join us, we are always keen to chat about gear, as well as getting your feedback.