Determining the optimal angle of traction force application of a "walking sledge" skidding device
Authors: Mahura Bohdan , Bakay Borys , Bilous Oleksiy , Karatnyk Ihor , Kiy Volodymyr 
Published: October 2023

Problem. Rounwood skidding is one of the most important operations during a timber harvesting. Often, especially during the shelterwood and improvement felling, it is necessary to use small-sized means of mechanization, including horse traction. For the effective use of horse traction, it is advisable to use special means that would facilitate the work of animals and allow to achieve appropriate labor productivity on   skidding operation. The most famous and numerous auxiliary devices for horse timber skidding are various carriages whose design is constantly being improved. However, the carriages have proven themselves well on soils with high bearing capacity. On moistened and overmoistened soils, during the movement of such carriages with load, significant resistance to the rolling (movement) of the carriage’s wheels occurs, due to the significant wheels’ subsidence in the soil and the appearance of soil prisms in front of the wheels in the direction of movement. Even greater complications arise, when an obstacle appears - a stone, stump, etc. Then the movement of the wheel, depending on the obstacle, is impossible or requires a significant increase in the traction force. Therefore, the development of environmentally safe and energy-saving technologies and equipment for timber logging in complicated, particularly swampy, forest usage conditions is an important task for forestry scientists. Goal. The purpose of the research is to confirm the effectiveness of the skidding device "walking sledge" (obtained theoretically), namely to determine the optimal angle of traction force application for moving the device in the presence of obstacles. Methodology. Experimental studies were carried out with the use of a small-sized skidding device "walking sledge" in laboratory conditions with three different weights of the wood package (load), on surfaces with different sliding resistance coefficients, namely on a surface with a low coefficient of movement resistance (chipboard), on a surface with a high coefficient of movement resistance (concrete) and snow cover, which simulates the real conditions of the  skidding device usage. The movement of the skidding carriage was carried out with and without an obstacle. Results. As a result of the conducted experimental studies, the optimal angle of traction force application for moving the skidding device "walking sledge" during its movement in a cutting area in the presence of obstacles has been determined, which lies in the range of 15°-19°. Originality. The small-sized skidding device "walking sledge" has been developed at the Ukrainian National Forestry University, which combines the advantages of both a sliding-type mover and a wheeled-type mover [1]. Such device is intended for use in a complicated conditions of forest usage, namely on swampy cutting areas. The carriage mover, when it meets with an obstacle or when it is “immersed” in the swamp, scrolls and makes a step. The proposed device received a utility model patent № 109011 [2]. Practical value. The proposed skidding devise "walking sledge" has shown its effectiveness when used in conditions closed to real ones and is recommended for usage during logging operations in moistened and waterlogged plots of forest cutting areas.