Comparison of the Frictional Properties of Several Popular Arborist Blocks

"Commercial arborists spend much of the workday managing friction. In some places, friction is needed, but in others it can be a hindrance; the arborist block is one place friction is not wanted. This device is attached to the tree and supports a rope used to lower wood during pruning or removal operations. When a short section of rope is led from the wood to the block, then a much longer section from the block to the ground, friction will cause the force in the short leg to be larger. This short leg of rope, with limited rope fiber, is required to absorb more energy than the corresponding longer leg. In the extreme case, this may lead to failure of the rope, and hence motivates the desire to quantify the friction that may be present in this device. Three blocks were tested for the coefficient of static friction during raising and lowering. The friction coefficient was nonlinear with the load being managed, and ranged from 0.049 to 0.99 over all the loads and among the 3 blocks."