Assessments - 1, GPA: 5
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Facilidade de uso
Contact at the upperportion of the tip of the guide bar can cause the chain to dig into the object and stop the chain for an instant. The result is a lightning fast, reverse reaction which kicks the guide bar up and back toward the operator. If the saw chain is pinched along the top of the guide bar, the guide bar can be driven rapidly back toward the operator. Either of these reactions can cause loss of saw control which can result in serious injury. __ 2. UNDERSTANDING REACTTVE FORCES Pinch-kickback and Pull-In occur when the chain is suddenly stopped by being pinched, caught, or by contacting a foreign object in the wood. This stopping of the chain results in a reversal of the chain force used to cut wood and causes the saw to move in the opposite direction of chain rotation. Either reaction can result in loss of control and serious injury. • Pinch-Kickback— — occurs when the chain on top of the bar is suddenly stopped. — rapidly drives the saw back toward the operator. "•.-Pull-In— — occurs when the chain on the bottom of the bar is suddenly stopped. — pulls the saw rapidly forward. 3. PROCEDURE Practice cutting a few small logs using the following technique to get the “feel” of using your saw before you begin a major sawing operation, a. Accelerate engine to full throttle before entering cut by squeezing the throttle trigger, b- Begin cutting with the saw frame or spur against the log. Figure 16. c. Keep the engine at full throttle the entire time you are cutting. d. Allow the chain to cut for you; exert only light downward pressure. If you force the cut, damage to the bar, chain, or engine can result. e. Release the throttle trigger as soon as the cut is completed, allowing the engine to idle. If you run the saw at full throttle without a cutting load, unnecessary wear can occur to the chain, bar, and engine. f. To avoid losing control when cut is complete, do not put pressure on saw at end of cut. g. Stop the engine before setting the saw down after cutting. B. TREE FELLING TECHNIQUES 1. CAREFULLY PLAN YOUR SAWING OPERATION IN ADVANCE a. Clear the work area. You need a clear area all around the tree where you can have secure footing. b. Study the natural conditions that can cause the tree to fall in a particular direction. 1.) The WIND direction and speed. 2.) The LEAN of the tree. 3.) WEIGHTED with BRANCHES on one side. 4.) Surrounding TREES and OBSTACLES. -11- c. Look for decay and rot. If the trunk is rotted, it can snap and fall toward the operator. d. Check for broken or dead branches which can fell on you while cutting. e. Make sure there is enough room for the tree to fall* Maintain a distance of 2 1/2 tree lengths from the nearest person or other objects. Engine noise can drown out a warning call. f. Remove dirt, stones, loose bark, nails, staples, and wire from the tree where cuts are to be made. g. Plan to stand on the up-hill side when cut-ting on a slope. Figure 17. h. Plan a clear retreat path to the rear and diagonal to the line of fail. Figure 18. 2. FEllJNG SMALL TREES—LESS THAN 6” IN DIAMETER a. If you know the direction of fall: 1.) Make a single felling cut on the side away from the direction of fall. 2.) Cut all the way through. 3.) Stop the saw, put it down, and get away quickly on your planned retreat path. b. If you are not sure which way the tree will fall, use _the notch method described for felling large trees. DO NOT CTO AWARNING —near electrical wires or buildings. —if you do not know the direction of tree fall. —at night since you will not be able to see well. —’during bad weather — rain, snow, strong wind, etc. 3. FELLING LARGE TREES—6” Dim Or More The notch method is used to cut large trees. A notch is cut on the side of the tree in the desired direction of fall. After a felling cut is made on the opposite side of the tree, the tree will tend to fall into the notch. NOTE: If the tree has large buttress roots, remove them before making the notch. Cut into the buttresses vertically, then horizontally. Figure 17 . a. Make the notch cut. Figure 19. 1.) Cut the bottom of the notch first, through 1/3 of the diameter of the tree. 2.) Complete the notch by making the slant cut. 3.) Remove the notch of wood Make felling cut on the opposite side of the notch about 2” higher than the bottom of the notch. Leave enough uncut wood between the felling cut and the notch to form a hinge. Figure 20. b. c. AWARNING Stay on the uphill side of the terrain to avoid injury from the tree rolling or sliding downhill after it is felled. Figure 17. NOTE: Before the felling cut is complete, use wedges to open the cut when necessaiy to control the direction of fall. Use wood or plastic wedges, hutnev-er steel or iron, to avoid kickback and chain damage. Figure 17 Figure 18 Direction « hi Of Fall Notch Figure 19 Opening Of Felling Cut Direction O f Fall Closing Of Notch Hinge Holds Tree On Stump And Controls Fall Figure 20 d. Be alert to sig...
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