For more than 30 years, Arbor Age magazine has been covering new and innovative products, services, technology and research vital to tree care companies, municipal arborists and utility right-of-way maintenance companies
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TRAINING & EDUCA Rigging TRAINING & EDUCATION Intro to Or to paraphrase Cypress Hill — when the top goes down, you better be ready By Michael "House" Tain Rigging in tree care is a subject that can be either complex enough to fill an entire book, as it often has, or as simple as to be easily discussed and decided over the first cup of coffee in the morning right beneath the tree in question.However, in both sim- ple and complex rigging, some basic knowledge and understanding is necessary to avoid situations involving insurance companies, friends who do roofing and gutters, or, worst case scenario, the emergency room of the local hospital.A good basic understanding of the terms, equipment, and forces involved in rigging in tree care 200 lbs. 2 to 1 Force Factor at 180 degrees 100 lbs. will pay huge dividends in getting large, woody debris on the ground and into the chipper safely, easily and efficiently. Terms and definitions Breaking or tensile strength: The amount of force that will break or distort the particular rope or component. This should either be stamped on the particular component (block, pulley, etc.) or part of the literature that came with it. Putting a rope or component with an unknown breaking strength into a rigging system is a very bad idea. Safety factor: The ratio used to determine the safe working load (SWL) or working load limit (WLL) of a particular component. For example, with a ratio of 10:1 the tensile strength would then be divided by 10 to arrive at a safe working load. This factor is often generated by the manufacturer of a piece of gear,but can also be used by tree crews to decide how far they wish to push their rigging system components.Typically, the lower the safety factor, the less use prior to breaking the component will provide as each use weakens the component slightly; and greater loads will weaken it more quickly, bringing it closer and closer to failure. Safe working load, or working load limit: This amount of 100 lb. piece 100 lbs. 8 Arbor Age / October 2011 An example of a basic 2:1 force factor at the rigging point, which, with the addition of just a slight drop, will magnify in force greatly. All photos and illustrations courtesy of Michael "House" Tain force, arrived at by using the safety factor and tensile strength of the component, gives the user a load limit that he or she can use the component at safely for an extended period of time.As mentioned previously, low safety factors will lessen the life of the component, while high safety factors should extend it, but also limit the size of the load put on the component. Cycles to failure: The process by which repeated loading weakens a component in the rigging system. Ropes, connecting links, and other components are losing strength all the time through use. Loading them near their tensile strength will speed up this weakening process.This can be likened to the simple process or breaking a wire coat hanger, each bend weakens it more and www.arborage.com