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Tree Machine · 30th August 2007, 11:08 PM

Goodness!

Dr Attaway, welcome to Treeworld, Let me introduce you to Ekka, he's our grand Poobah. Also, meet Dr Gary Storrick, owner of the most extensive collection of aerial devices in the world, as well as being a dedicated caver and and an exceptionally cool dude. Dr Gary, like yourself, has answered our call and stepped in to contribute to our conversation. Dr. Gary's collection and expertise are the 'shoulders' upon which this topic stands. The topic revolves around the control of friction, and friction is an area you clearly have a very thorough handle on.

THE TOPIC: Just to summate what this thread is about. It is about friction control in the professional world of tree climbing, namely tree care or Arboriculture.

Friction has historically been accomplished through rope-on-rope friction using friction hitches, rope fashioned around itself in a constricting manner to apply a firm and adjustable pressure to the rope. The advantage is the setup can be used to both ascend and descend the rope. Form a pure climbing standpoint, that is where the benefits stop. Economically, it can be very economical, requiring no gear other than the rope itself. This system was devised long before ascenders or even modern, synthetic ropes. The system has been a number of varying setups, each improvment trying to overcome the inherent disadvantages one must accept when using a friction hitch system. The main disadvantage is that it is a full-time 2:1 mechanical advantage system. The other is managing slack in the rope. Friction is created at the point of the friction hitch, but also overhead where the rope passes over top of a limb before coming back down and anchoring to the climber.

Descent is OK on a 2:1 system, but ascending is anything but joy. Friction in two places and only getting one unit of altitude gain for every two units of rope pulled through those two points of friction. Unavoidable slop in the system diminishes efficiency further. Tending slack also means pulling double the length of rope over top and then through the hitch just to keep the climbing line tensioned. Tending slack is a continuous process and must be maintained for safety.

These 2:1 friction hitch systems are used worldwide by Arborists and have been since the earliest of times. History has passed this working knowledge from treeman to treeman as that is generally how professional tree climbing is taught; by experienced treeclimbers who have learned from treeclimbers before them.

Mechanical devices have been slow to impact our industry. The friction hitch is unique to modern climbing disciplines and by pure convention has continued on.

Ascenders have been gaining popularity, but often are subbed in for the friction hitch on the ascent, removing one of the two sites of friction. Slings with rings can be installed up high in the tree canopy and the rope passed through this to diminish friction further and create a more 'predictable' friction element. This is called a friction saver, or often called a cambium saver as the rope is no longer passing over a natural limb or crotch, but rather through an aluminum ring.

Improvements in tending slack have been made through hitch configurations incorporating a micropulley. Arborists call it a 'self-tending' configuration. It is an improvement over the more basic hitch setups.

The current cutting-edge tree climbers use modern-day hitch setups and friction savers. The way cutting-edge dudes use access lines to support their climbing lines. The access line is an SRT line, up which the climber may ascend with a single handled ascender, a 1:1 ascent with near zero friction. Once to the top, a backed-up single ascender holds a pulley through which passes the climbing line, configured in traditional 2:1 style, minus the normal friction encountered as the rope passes over the tie-in point. This setup overcomes more friction and now just about 100% of the friction is concentrated in the hitch. In this 2:1 setup, the climber's weight is supported equally on each of the two legs of the system, meaning the side that the friction hitch is on handles half the climber's weight. This is what allows the friction hitch to be effective, that it only need control 50% of the climber's weight, but at the expense of twice the amount of rope being pulled through per amount of gain in altitude.

2:1 descent is OK, a few disadvantages, but with gravity as your constant companion, it helps overcome some inefficiencies inherent in the system. As long as you're moving laterally or down, the friction hitch system is OK, though heat is created in the hitch, frictional wear eats away and changes the performance characteristics of the hitch over time. The hitch needs to be re-tuned in accordance with the wear and changes when the rope gets wet or when you change the diameter size of your climbing line.

The variables affecting the performance of the climbing hitch are many, and without going into all of them, it is accurate to say that the learning curve on using a hitch is long and slow. I would guess to say that when a novice climber finally comes upon something that he or she is 'comfortable' with, thay may never move beyond that, fearing complexity and a new, long, slow learning curve to again be faced, new techique, new style, new setup, but still a 2:1 mechanical advantage arrangement. This keeps a lot of guys from moving beyond their 'comfort zone', and this is what gets taught to the next guy on down the line.

30th August 2007, 11:08 PM	#187 (permalink)
Tree Machine Over mature heritage tree Join Date: Mar 2007 Location: Indianapolis Posts: 714	Goodness! Dr Attaway, welcome to Treeworld, Let me introduce you to Ekka, he's our grand Poobah. Also, meet Dr Gary Storrick, owner of the most extensive collection of aerial devices in the world, as well as being a dedicated caver and and an exceptionally cool dude. Dr Gary, like yourself, has answered our call and stepped in to contribute to our conversation. Dr. Gary's collection and expertise are the 'shoulders' upon which this topic stands. The topic revolves around the control of friction, and friction is an area you clearly have a very thorough handle on. THE TOPIC: Just to summate what this thread is about. It is about friction control in the professional world of tree climbing, namely tree care or Arboriculture. Friction has historically been accomplished through rope-on-rope friction using friction hitches, rope fashioned around itself in a constricting manner to apply a firm and adjustable pressure to the rope. The advantage is the setup can be used to both ascend and descend the rope. Form a pure climbing standpoint, that is where the benefits stop. Economically, it can be very economical, requiring no gear other than the rope itself. This system was devised long before ascenders or even modern, synthetic ropes. The system has been a number of varying setups, each improvment trying to overcome the inherent disadvantages one must accept when using a friction hitch system. The main disadvantage is that it is a full-time 2:1 mechanical advantage system. The other is managing slack in the rope. Friction is created at the point of the friction hitch, but also overhead where the rope passes over top of a limb before coming back down and anchoring to the climber. Descent is OK on a 2:1 system, but ascending is anything but joy. Friction in two places and only getting one unit of altitude gain for every two units of rope pulled through those two points of friction. Unavoidable slop in the system diminishes efficiency further. Tending slack also means pulling double the length of rope over top and then through the hitch just to keep the climbing line tensioned. Tending slack is a continuous process and must be maintained for safety. These 2:1 friction hitch systems are used worldwide by Arborists and have been since the earliest of times. History has passed this working knowledge from treeman to treeman as that is generally how professional tree climbing is taught; by experienced treeclimbers who have learned from treeclimbers before them. Mechanical devices have been slow to impact our industry. The friction hitch is unique to modern climbing disciplines and by pure convention has continued on. Ascenders have been gaining popularity, but often are subbed in for the friction hitch on the ascent, removing one of the two sites of friction. Slings with rings can be installed up high in the tree canopy and the rope passed through this to diminish friction further and create a more 'predictable' friction element. This is called a friction saver, or often called a cambium saver as the rope is no longer passing over a natural limb or crotch, but rather through an aluminum ring. Improvements in tending slack have been made through hitch configurations incorporating a micropulley. Arborists call it a 'self-tending' configuration. It is an improvement over the more basic hitch setups. The current cutting-edge tree climbers use modern-day hitch setups and friction savers. The way cutting-edge dudes use access lines to support their climbing lines. The access line is an SRT line, up which the climber may ascend with a single handled ascender, a 1:1 ascent with near zero friction. Once to the top, a backed-up single ascender holds a pulley through which passes the climbing line, configured in traditional 2:1 style, minus the normal friction encountered as the rope passes over the tie-in point. This setup overcomes more friction and now just about 100% of the friction is concentrated in the hitch. In this 2:1 setup, the climber's weight is supported equally on each of the two legs of the system, meaning the side that the friction hitch is on handles half the climber's weight. This is what allows the friction hitch to be effective, that it only need control 50% of the climber's weight, but at the expense of twice the amount of rope being pulled through per amount of gain in altitude. 2:1 descent is OK, a few disadvantages, but with gravity as your constant companion, it helps overcome some inefficiencies inherent in the system. As long as you're moving laterally or down, the friction hitch system is OK, though heat is created in the hitch, frictional wear eats away and changes the performance characteristics of the hitch over time. The hitch needs to be re-tuned in accordance with the wear and changes when the rope gets wet or when you change the diameter size of your climbing line. The variables affecting the performance of the climbing hitch are many, and without going into all of them, it is accurate to say that the learning curve on using a hitch is long and slow. I would guess to say that when a novice climber finally comes upon something that he or she is 'comfortable' with, thay may never move beyond that, fearing complexity and a new, long, slow learning curve to again be faced, new techique, new style, new setup, but still a 2:1 mechanical advantage arrangement. This keeps a lot of guys from moving beyond their 'comfort zone', and this is what gets taught to the next guy on down the line.