2023 Volume 38 Issue 2 Article ID: 38.99
In this study, the tension in the skyline and guyline as well as the load under the hook and that on the tires and outriggers of a medium-range tower yarder during uphill yarding was measured. Furthermore, we evaluated the safety and estimated the working capacity of the machine. After analyzing 16 cycles, for which the load under the hook was measured, results indicated that the maximum load volume based on the safety factor of the mainline and skyline was 1.51 and 1.74 m3, respectively. Thus, 1.51 m3 was estimated to be the load volume limit of the machine used in this study. The highest loading volume per cycle was 1.55 m3, and yarding was generally performed safely during the test. However, during lateral yarding, the tension in the loaded mainline was equivalent to the maximum pulling force regardless of the loading volume. Therefore, the guyline tension and outrigger load were within the safety limits, but the increase in tension of the guyline against the tension in the skyline was low because the guyline was stretched nearly horizontally in this case. When the elevation angle of the antechamber is approximately 45°, the safety factor may become less than 4, and the load on the road surface at that time was approximately 1.7 times greater than when the antechamber was horizontal. Therefore, the greater the elevation angle of the antechamber, the greater the load on the antechamber and road surface.