Abstract
The research revealed that rolling of wheels of misaligned semi-trailers axles is identical to rolling of slip wheels under the influence of lateral forces, which leads to a discrepancy between the rotation and rolling planes of the wheel. As a result, there are additional lateral and longitudinal forces and increased rolling losses, and as a consequence, the tractor-trailer truck performance, in particular, fuel efficiency, deteriorates. Note that even with the same technical condition of the running gear of the truck tractor and the semi-trailer during their manufacture, different degrees of wear of tires, suspension elements of axles of the truck tractor and the semi-trailer can be revealed after a certain period of operation, as the wear rate depends on axle angles, wheel load, lateral forces, tangential forces (traction and braking) and air pressure in tires. In quantitative terms, these factors are not identical for each axle of the tractor-trailer truck. So, if there are different axle angles and different wear rates of the tread, it is possible to speak about changes in the rolling resistance and fuel consumption of the tractor-trailer truck. Thus, in case of misalignment of one semi-trailer axle by 0.57 degrees, the rolling resistance coefficient increases by 12 %; by 1.25 degrees – 17.8 %; by 2.11 degrees – 26.2 %. An increase in the rolling resistance coefficient leads to the growth of fuel consumption. As an example, it was shown that in the highway driving cycle of the tractor-trailer truck, an increase in the rolling resistance coefficient is doubled from 0.01 to 0.02, fuel consumption in the cycle increases by 43 %, and under the three-time change from 0.01 to 0.03 – by 95 %. This necessitates the design and research works aimed at reducing the axle misalignment of semi-trailers and tractors in the process of manufacture and operation
Highlights
The long operating practice of vehicles proves that tractor-trailer trucks have significant advantages over singleunit trucks
Value 4 × 2 where Ma is the gross vehicle weight, kg; f0 is the coefficient of rolling resistance at low speeds; Kf is the coefficient cons idering changes in the rolling resistance coefficient at increasing speed; KВ is the drag coefficient, Н∙s2/m4; F is the frontal area, m2; Аі, Bі, Cі are the approximation coefficients of the circular force equation: Ai
The results of the research will find their application in the analysis of operational properties of tractor-trailer trucks, in particular, fuel efficiency, in order to ensure the correct adjustment of their running gears
Summary
The long operating practice of vehicles proves that tractor-trailer trucks have significant advantages over singleunit trucks. As the wear rate depends on axle angles, wheel load, lateral forces, tangential forces (traction and braking) and air pressure in tires In quantitative terms, these factors are not identical for each axle of the tractor-trailer truck. A large number of tractor-trailer trucks are operated with running gears having different technical conditions and, accor dingly, different properties. In this case, a question arises about the fuel efficiency and motion stability of the tractor-trailer truck with different technical conditions of the running gear. The search for methods of assessing the tractor-trailer truck performance, in particular, fuel efficiency, taking into account the semi-trailer axle angles, is an urgent problem for further improvement of performance and technical level of tractor-trailer trucks
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