Arboriculture & Urban Forestry 35(6): November 2009 Damage Inflicted on Climbing Ropes by Handsaws Arboriculture & Urban Forestry 2009. 35(6): 305–310 Brian Kane, Mac Cloyes, Mollie Freilicher, and H. Dennis Ryan Abstract. Arborists frequently use handsaws while climbing, and a recent accident highlighted the danger of cutting one’s rope with a handsaw. There do not appear to be any robust tests describing the ability of handsaws to cut ropes. The following study attached handsaw blades to a pendulum, which swung into a rope, bringing the blade and rope, which was under tension, into contact. The percent of the rope’s diameter cut by the blade was measured, as well as the percent loss in the rope’s strength after it was cut. Type of blade was a more important factor than type of rope with respect to the percent cut and percent strength loss, and there was a nearly one-to-one relationship between those response variables. The results of this study are discussed in the context of a climber’s safety. Key Words. Handsaw; Rope. Arborists frequently use handsaws while pruning trees. When- ever they work aloft using ropes, there is a risk of the hand- saw coming into contact with the rope. This is also true of chainsaws, and while the Z.133 Standard (Anonymous 2006a) clearly states that arborists shall be tied-in twice whenever they use a chainsaw, there is no such requirement when us- ing a handsaw. It is required to use a lanyard as a second tie- in point during the work climb and Masters’ Challenge events of the International Tree Climbing Championship (ISA 2008). A recent injury highlighted the risk posed when a climber cuts his or her rope with a handsaw. In this accident, the climber com- pletely cut his rope, fell out of the tree, and broke his neck (Geor- gia Arborist Association 2009). In light of this recent accident, which left the climber, who was not a novice, a quadriplegic, it became obvious that controlled testing of this type of accident was required. The objectives of this study were to determine the ease with which a climber could cut him- or herself out of the tree using a handsaw and whether a particular blade or rope (or combination thereof) was more likely to lead to rope failure. METHODS The study tested several common climbing lines and handsaw blades (Table 1, Figure 1). Ropes differed with respect to diam- eter and construction; blades differed by curvature, length, and teeth per millimeter. The study also tested one used blade and one new blade (each with conventional teeth), but did not include them in any statistical analysis because of the limited sample size. Initially, each author attempted to cut several ropes using the F3 blade, which was attached to a pole saw head. Each in- dividual held the saw with two hands and made a single, quick pull along the rope, which was hung from a beam and loaded with a 41 kg (90 lbm) mass. The mass represents the maximum rope tension when a climber of mass 82 kg (180 lbm) is tied- in, situated with the rope running over a branch, around the trunk, and back to the saddle. Each author easily cut each rope. Since there are many scenarios in which a climber’s hand- saw or pole saw might contact their climbing line or lanyard, and 305 Figure 1. Blades (left to right): used (manufacturer unknown), new standard tooth (Gilmour), IB, ZU, F1, F3, F2 (abbreviations are in Table 1). since it was also clear that a handsaw could easily cut through a climbing rope, an experimental protocol was developed to main- tain a consistent interaction of rope and blade, with respect to impact force. Each rope was hung from the beam, as described above, and on the same beam was attached a pendulum (Figure 2), which held each blade (Figure 3) parallel to the ground when the long axis of the pendulum was perpendicular to the ground. The pendulum was raised 45° from perpendicular to the ground and released, delivering an impact force of approximately 440 N (100 lbf) at the point of contact, just before the pendulum re- turned to its initial position. Before cutting any ropes, the impact force was measured with a dynamometer (Dillon EDExtreme, Weigh-Tronix, Fairmont, MN) connected to the pendulum by a rope anchored to a wall. After releasing the pendulum from 45°, the rope stopped the pendulum as it reached its initial posi- tion and the dynamometer measured tension in the rope at the point of impact. The impact force of the pendulum was equiva- lent to the mean force (n = 10) measured when the second and ©2009 International Society of Arboriculture
November 2009
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