Now bring it all together.
Mechanical Advantage -
This describes the process of using additional ropes, fiddle blocks and/or pulleys to multiply an input force (i.e., your muscle) into a greater output force. This process is often useful in pulling over trees in felling applications, adding tension to slide lines or lifting pieces within various rigging systems/scenarios. Examples are fiddle blocks or the tree pulling kit.
Natural Crotch Rigging -
This is a rigging technique that uses the branch attachment points or crotches of the tree itself as rigging points to lower limbs or wood safely to the ground. Natural crotch rigging requires little equipment other than an appropriate rigging line, and is quite simple to set up and use. However, due to its use of the tree's structure as rigging points, friction will vary considerably from tree to tree, and can cause serious long term damage to both ropes and the tree's living tissue.
False Crotch -
A careful approach to tree care
A false crotch or manufactured rigging point is simply the creation of an anchor point within the tree without using the branches, crotches, or branch attachments of the tree itself. The use of various rope tools such as eye slings, whoopies, or loopies with arborist blocks or pulleys allows the placement of anchor points for rigging anywhere within the tree’s canopy. The appropriate rope tool is simply attached to the branch or trunk of the tree with a block or pulley correctly attached, and almost friction free lowering is yours to enjoy. You're happy, your ropes are less worn and happy, and most important of all, the tree is undamaged and happy.
Port-a-wrap -
Amazingly simple and strong
This simple device is an excellent tool for lowering large loads safely and efficiently. With the addition of a fiddle block set or the tree pulling kit, the Port-a-wrap can also be used to lift loads, move them laterally in a drift line system, or to tension a slide line. The barrel of the Port-a-wrap is used to generate friction. The more wraps around it, the more friction generated. It should be attached to the anchor point with an appropriate sling, typically an eye or whoopie sling. Avoid connecting the Port-a-wrap to the sling with a carabiner or screw link, these pieces of hardware can easily be cross loaded and compromised in a dynamic rigging situation.
Dynamic Spar Rigging -
This involves dropping pieces into a rigging point below the wood being removed. Due to the extreme forces created in dynamic rigging situations, care should be taken to ensure that all components of the system have safe working load limits sufficient to the forces experienced. In addition, the use of some type of lowering device to gradually decelerate the piece, instead of bringing it to a sudden stop, will lessen the forces experienced at the rigging point. This system may be used in conjunction with another, such as a slide or drift line, once the dynamic load has been brought to a stop. The Rigging Software 1.0 program is an excellent educational tool to learn what types of forces may be generated in dynamic spar rigging, and will help arborists make appropriate equipment choices.
Limb Lifting -
This system, one which experiences primarily static loads when used properly, is used when a limb needs to be lifted vertically, then lowered, or perhaps transferred with another rigging system such as a slide or drift line. The limb is typically 'tip tied' and lifted by a rigging line through a block or pulley directly above the area of the chain saw cut. The use of a GRCS or other lifting/lowering device is recommended for use with this system.
Knotless Rigging -
This system is used to quickly and efficiently lower multiple branches or other light pieces. Knotless rigging's requirement for an appropriate connecting link means that it should only be used with static loads, due to the possibility of the connecting link being cross or side loaded in dynamic situations. However, in the proper situation, the ability to quickly attach multiple branches to a rigging line without having to tie knots, simply attaching the connecting link to loop runners or other slings, makes this system the safe and efficient choice.
Spider Leg Balancer -
This balancing system may be used when the limb or piece being removed needs to maintain its same position or orientation after being cut free. Spider leg balancers form a climbing hitch around the rigging line, providing adjustability to balance the load, while the other end of the balancer is secured to the limb. Spider legs may be used singly or in multiples, depending on the balance needs of the piece to be removed. The use of a rigging point centered directly above the piece being removed will lessen the likelihood of uncontrolled swings or movement when the piece is cut free. This system may also be used with some of the transfer systems such as slide or drift lines, where the balanced piece then needs to be moved away from the tree.
Drift Line -
Use this system when an obstacle beneath the tree prevents the piece from being lowered directly down, or the piece needs to be transferred over an obstacle such as a fence or stone wall. Using a drift line requires a second tree to be used as a rigging point, and works most efficiently when lowering/lifting devices are employed at both ends. Drift lines may also be used in conjunction with some of the other systems such as spider leg balancers or dynamic spar rigging once the piece has been brought to a stop.
Slide Line -
This system, though very gear intensive, can be quite useful and efficient to transfer brush and wood fairly long distances over obstacles. Slide lines should never be dynamically loaded due to the likelihood of creating a serious bending moment. The rope used as the slide line should remain slack, then be put under tension once the load to be moved is attached to it through the use of an appropriate traveler. In addition, each load should be attached to a line through a lowering device to control the speed of its descent on the slide line. Slide lines may also be used in conjunction with other systems such as spider leg balancers or dynamic spar rigging once the piece has been brought to a stop. Setting up the slide line so tension can be released from it while under load will assist in placing the load exactly where required. |
