Effect of Transmission Type on Wheel Slip under Overload – Presented on the Example of the AGT 835 T Tractors

• Published in: Croatian journal of forest engineering Vol. 35; no. 2; pp. 221 - 231
• Main Author: Jurij Marenče
• Format: Journal Article
• Language: English
• Published: University of Zagreb, Faculty of Forestry 01-09-2014
• EISSN: 1848-9672
• ISSN: 1845-5719

During their occasional work on small forest holdings, forest owners often use tractors that are, as a rule, not intended for professional forest purposes. Due to their small size, these tractors are appropriate for cultivating smaller agricultural areas and, with additional forestry equipment, also for forestry operations. This paper analyses their performance at the capacity limits, since this type of use is possible but very limited due to their low technical characteristics. Here, a comparison is made between two AGT 835 T tractors produced in Slovenia, with the same basic characteristics but different types of the engine power transmission to the forest ground (comparison between a machine with a standard mechanical transmission system and a machine with a newer version of a hydro-mechanical transmission system). The analysis focuses on the wheel slip – this time only in the last meters of skidding when the slip reaches its peak and the tractors stop because of excessively demanding working conditions. Both tractors were used for skidding timber in the same working conditions – the same skid trail and the same load size. On the steepest section with a 27% longitudinal incline and under the load of 1 m, both tractors stopped due to excessively demanding working conditions. However, there was a fundamental difference between the two machines in the final section of skidding. The mechanical transmission system enabled rotation of tractor wheels, which led to a multi-fold increase in slip values (remarkable 80% in the last metre of movement). Contrary to that, the system with hydro-mechanical power transmission resulted in a substantially lower wheel slip (no more than 31%). In the latter case the tractor stopped due to excessively demanding working conditions but the hydro-mechanical steering system reduced the wheel slip. It is important to know that the selected transmission system can significantly influence the efficiency of transmitting power to the ground surface – with a smaller slip, which is also important for the forest ground and the environment.