Researching impact of pressure re-distribution along the length of the track ground contacting area on resistance of the timber-hauling vehicles' travel over snow

摘要

The tracked timber-hauling vehicles which operate in the cutting areas having highly deforming soil, virgin snow in particular, feature significantly reduced performance due to rutting and caused frontal resistance. Most logging enterprises harvest bulk timber in I and IV quarters of the year. However, deep snow during the second half of winter significantly reduces performance of the dragging tractors. Snow mostly affects performance of the feller-skidders and feller-bunchers which need to move from tree to tree to collect load while frequently crossing deep virgin snow. Snow 0.4-0.6 m deep slightly resists to movement. However, when virgin snow is 0.7 m and deeper, the resistance rises sharply. The tracked vehicle capacity to cross virgin snow can be improved in two ways: by improving friction properties and by reducing motion resistance. As is evident, more even distribution of track pressure and lack of pressure concentration under individual rollers will improve vehicle's hauling power by reducing frontal resistance. But as researcher M.G. Bekker stated, despite the fact that pressure distribution was considered one of the most important factors determining vehicle's performance, the theoretical research and assessment of the problem was frequently neglected. Today designers while designing new tracked dragging vehicles and assessing their performance refer to the researches made for industrial and agricultural tractors. This can be explained by few works dedicated to researching performance of the forest tracked vehicles. The design and operating conditions of the forest and non-forest vehicles are much different so that the results of research made for one type of vehicles cannot be applied to other types of vehicles. That is why it is necessary to research the process of tracks' impact on snow and pressure re-distribution due to snow reaction to justify parameters of the tracked undercarriage of the forest vehicles, provide optimized location of the gravity center and reduce motion resistance. Our work is aimed to develop a method to estimate pressure distribution along the length of the track ground contacting area, test the method with experiment and provide recommendations to designers on improving oversnow performance of the forest tracked vehicles.