Tripple Whammy

I was thinking yesterday about how your mental focus evolves over time and about how you collect mental cornerstones on the way that you construct a foundation around, that you then base your thoughts and assumptions on. Sometimes these aspects of focus may be expressed in key words or terms.

It’s one of the things that always strikes me when watching an Arbormaster presentation, is how this is something that they are really good at, clearly identifying key words and then hammering them home. As a spectator this makes it easy for me to follow the red thread of a presentation and it also gives me a nugget of information that I may choose to take home with me.

For us, when we were launching into what was to become treemagineers, configuration was such a key word. A lot of the issues that Chris and I would discuss during work revolved around how we use PPE (Personal Protective Equipment) components and how we assemble them into systems. Our impression was that if we could ensure correct configuration, the rest would follow. Configuration became a key word that we would use to communicate our point, to identify issues, i.e. misconfigurations, but also the solution, i.e. correct configuration. The friction hitch based work positioning system built around the Hitch Climber pulley was the result out of this process.

Hitch Climber pulley
Hitch Climber pulley

It incorporated a number of novel concepts, such as:

  • system split into two karabiners, one on top of the Hitch Climber to attach the splice into, the other on the bottom to attach the eye to eye sling onto. This set up reduces the amount of sit-back when ascending and also eliminates three-way loading when work positioning on large stems, …
  • correct alignment of connectors: All connectors are loaded along the major axis, as they were designed to be. Also the points of loading are close to the 12mm pins used in the certification process. This ensures performance in line with the MBS indicated by the manufacturer, and finally…
  • rope friendly interfaces: the chosen manufacturing process, hot forging, allowed the Hitch Climber to be designed with flowing, rounded surfaces that are inherently rope-friendly.

These points, in our opinion, encourage and aid the end user to consider correct configuration of his or her equipment.

In time though we came to realise there was another, important point to be taken into consideration, compatibility. It is important not just to ensure that components are well configured, but also that neighboring elements are mutually compatible with each other. These discussions  led to a series of tests a couple of years ago examining the compatibility between ascenders, ropes and lanyards. Compatibility issues can be very complex and challenging to resolve if no guidance is provided by the manufacturers. One output out of these discussions was the presentation Good Choices, Poor Choices – Discrete performance loss, accumulated performance loss and assembling fall protection systems with confidence.

Ascender configuration comparison
Ascender configuration comparison

The third term that forms this tripple whammy is resilience. Here is what the Oxford Dictionary of English has to say on the topic:

resilience
Pronunciation: /rɪˈzɪlɪəns /
NOUN

The ability of a substance or object to spring back into shape; elasticity

This is obviously the missing element when considering system design: You want your system to have the ability to return to its original form after having been loaded, regardless of whether it is a karabiner, a harness, a rigging or a climbing system. In a past blog post I described the high cycle testing we did some years back. Essentially that was assessing the resilience of the material used to manufacture the eye to eye slings under low load and high cycles. Or the testing we did last week in Dunkeld, which was – amongst other things – to take a closer look at the resilience of rigging systems used in tree care.

Resilience can be the result of design, materials or the manufacturing process – or a combination of the above, however it is not something superficial or something that can be added on as an afterthought: Resilience ought to be a key consideration and objective that runs through and permeates the whole design and manufacturing process – pretty styling of a fragile assembly or system is not an acceptable substitute for resilience.

So if you asked me today what I feel key requirements are that we should be making of our PPE assemblies and systems, I would answer you that they shall be well configured, mutually compatible and resilient. If these three points are taken into account I believe that we are on a viable path towards ensuring good system design.