Tree rigging is the use of lines, pulleys and lowering instruments to dismantle a tree. According to the Executive Tree Services website, the practice has grown in recent decades out of a need for the removal of large trees near residential areas. Rigging can be quite dangerous without the proper people, training and tools. Over the years, riggers have developed several techniques to undertake this job. Although these workers still use pulleys and ropes, in recent years they have also started to employ heavy lifting cranes.
Tip Tie and Lift
The tip tie and lift method involves lifting a limb to a vertical position before lowering it. The Arbor Master website advises that to avoid complications such as limbs swinging beyond control, the rigger should set their rigging point directly over the cut. They should make a face notch and a back cut, causing the limb to be nearly vertical before breaking. A precise cut allows time for the climber or bucket operator to clear the immediate area of the fall, increasing the chances of a safe operation.
Slide lining, according to the Arbor Master website, is a method of attaching limbs or logs with rigging tools, such as pulleys or slings, to a line high in a tree on one end, and low on another tree or anchor point far away from the tree the rigger is preparing for removal. A ground worker controls one end of the tree so as to land the piece after cutting it. It slides diagonally down the slide line to the ground. The purpose is to remove sections while avoiding obstacles below the tree while moving the sections closer to the truck or chipper.
This technique utilizes spurs and lanyards. The climber uses a lanyard to scale a large tree, such as a cedar or a redwood. As tree experts Susan Jenkins, Ian Barlow and Bob Beckley point out, this method has its advantages in wilderness and back country projects because the equipment involved is lightweight, making packing easy. This makes the work more efficient as it radically reduces the preparation time, according to Jenkins et. al.
High Lead Systems Technique
The high lead systems technique, according to Jenkins et. al., uses at least two hoists on opposite ends of the system. Lines run from the hoists through blocks suspended from the spars and towers to each end of the load in question. This process enables the lead rigger to communicate with the hoist operators, instructing them to tighten their load or to slacken it.
The use of a tripod, a three-legged steel stand, facilitates rigging in areas where spurs are sparse. The worker mounts a block beneath the device. A skyline connects the hoist through the block to the next tripod or spar. As Jenkins et. al. suggest, tripods make work possible after a rain because their footings are strong enough to hold up on water or otherwise unstable ground.
The multiple block technique entails the construction of several pulleys to handle a group of loads simultaneously. According to tree expert and climber Mark Chisholm, this system allows even weight distribution among multiple points on a tree. This helps a rigger to relocate a drop zone if he needs to do so for safety reasons. Also, he can adjust his rope angles at any time by guiding the forces of gravity along a vertical axis of the tree. This enables him to increase his work load limit. Moreover, since tree branches' attachments are stronger on the underside than at the top, the worker can arrange individual sections of the pulleys to exploit such strengths.
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