If you are just starting out, you are going to need to know a lot of basic terminology. This will be a good starting point, and I will continue to update it as need be.
a. Rigging – use of ropes to lower and control sections of tree to the ground.
b. Rigging System – interaction of all elements used for rigging including points in the tree, slings, hardware, rope, force angles, etc.
c. Piece – the section of tree being rigged.
d. Small Rigging – piece can be carried or dragged by one or two people once on the ground.
e. Big Rigging – pieces that are too heavy for two people to carry, must be cut up once on the ground.
f. Positive/Overhead Rigging – rigging point is above the piece, used whenever possible.
g. Negative Rigging – rigging point is below the piece, used in the absence of other options, always involves shock loading.
h. Shock Loading – mass coming to a short, sudden stop. Can multiply peak forces by 10X or more.
i. Tension wood – fibers are being pulled apart.
j. Compression wood – fibers are being squeezed together.
k. Leverage – bending force being exerted at a distance from a fulcrum.
a. Tensile strength / Minimum Breaking Strength (MBS): the average breaking strength of a piece of equipment when pulled to failure under controlled conditions. Tensile strength is usually quoted in kN.
b. Kilonewton (kN): approximately 225 lb.
c. Minimum strength: as defined by safety legislation and regulations, life safety gear is required to have a tensile strength of at least 5000 lb (usually rounded up to 23 kN).
d. Working Load Limit (WLL): expressed as a fraction of the tensile strength, this is the maximum load that the equipment is rated for over a large number of cycles. Standards are rigging gear 5:1, climbing gear 10:1. For example, if a rigging line is rated for 5000 lb and the working load limit is 5:1, that means you can consistently load it with 1/5 of its tensile strength (i.e. 1000 lb). For a climbing line rated at 5000 lb, you can consistently load it with 1/10 of its tensile strength (i.e. 500 lb).
e. Cycles to Failure: Ropes and slings can only be exposed to heavy loads so many times before they eventually fail. Adherence to WLL guidelines will ensure long life for your equipment, this is why it is so important to know the history of your gear.
f. Static Rope: very low stretch (0.5-1.5% range). Rarely used in rigging.
g. Semi-static Rope: low stretch (1.5-4% range). This is standard arborist rope used for climbing and rigging.
h. Dynamic Rope: very high stretch (5-20% range). Used in mountain climbing to catch a lead climber during a fall to minimize injury.
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