The necessity of increasing the efficiency of logging road trains by reducing the transport costs spent on hauling timber in existing road and climatic conditions is substantiated. A review of scientific research by foreign scientists is presented, which made it possible to identify the most significant factors influencing transportation costs. A promising design of a recuperative pneumohydraulic fifth wheel coupling device has been proposed, which makes it possible to reduce transportation costs by reducing the amount of fuel used by a road train, to increase the reliability of a logging road train by reducing the dynamic loads that occur between its links when driving over uneven surfaces of a logging road. The mathematical model of the movement of a timber tractor with a semi-trailer equipped with the proposed coupling device, under conditions of frequent accelerations and decelerations, over the unevenness of the logging road has been improved, which makes it possible to perform a preliminary assessment of the energy recovery by the proposed device in various modes of transient processes, as well as to investigate the influence of the main parameters of the recuperative pneumohydraulic fifth wheel coupling device for performance indicators. Two computer programs have been developed to study the performance indicators of a recuperative pneumohydraulic fifth wheel coupling under various transient modes of movement of a logging road train with given parameters of roughness of a logging road. It has been established that the use of the proposed coupling device in a logging road train makes it possible, when driving with randomly repeated decelerations and accelerations, to regenerate power up to 6.5 kW, and also to achieve a value of longitudinal acceleration of the semi-trailer relative to the tractor of 0.72 m/s2. Computer modeling made it possible to establish the value of the optimal diameter of the hydraulic cylinder, which provides the highest value of recuperated power at the lowest value of the acceleration of the semi-trailer relative to the tractor.
The importance of using timber road transport in the technological process of harvesting and hauling timber has been substantiated. The influence of the design flaws of fifth-wheel couplings on the safety indicators of the road train, its stability, productivity, and fuel consumption, which are manifested during the operation of timber tractors with semitrailers, has been revealed. The work of foreign authors aimed at improving the efficiency of using fifth-wheel couplings used in the designs of tractors with saddle trailer has been considered. The advantages of using the proposed recuperative spring-hydraulic fifth-wheel coupling device in a timber lorry train have been described. They consist in ensuring a simultaneous increase in the reliability of road train, recuperating energy of the working fluid, reducing the magnitude of dynamic loads, as well as ensuring favorable working conditions for the driver. On the basis of the developed mathematical and simulation functioning models of a timber tractor with a saddle trailer equipped with the proposed design of a recuperative spring-hydraulic fifth wheel coupling, computer experiments have been carried out, which made it possible to obtain the dependence of the influence of the inner diameter of the hydraulic cylinder, the stiffness of the springs used in the recuperative spring-hydraulic fifth wheel coupling on the longitudinal acceleration of the semitrailer and the average value of the recovered power. It was revealed that the optimal spring stiffness of the recuperative spring-hydraulic fifth wheel coupling, which is in the range from 150 to 200 kN/m, makes it possible to achieve the value of the average recovered power in the range from 7 to 8.4 kW
The main advantages of using timber tractors with semitrailers in comparison with single timber trucks and timber trucks with trailers are listed. The analysis of the results of scientific works of foreign authors engaged in increasing the efficiency of timber haulers with semi-trailers in the process of hauling timber is carried out. The existing conditions for the transportation of timber in the Russian Federation by timber haulers with semitrailers are considered. Described are the negative consequences that are manifested in the process of movement on forest roads, limiting the efficiency of using timber tractors with semi-trailers. Among them, the most significant one is highlighted, which consists in the occurrence of significant efforts when braking a timber tractor with a semitrailer in a fifth wheel coupling, accompanied by the appearance of cracks in the elements of the supporting system, breakdowns in the coupling device, as well as folding of the timber road train. The schemes of forces acting on a timber tractor with a semitrailer during braking are presented. The dependences of the change in the braking forces of the axles of a timber tractor with a semitrailer are given, taking into account the non-simultaneous operation of their braking mechanisms, as well as the change in the force in the fifth wheel coupling of a timber tractor with a semitrailer during braking. In order to increase the efficiency of a logging tractor with a semitrailer, a promising design of a recuperative fifth wheel coupling has been proposed.
The advantages of timber road transport over other types of timber transport used by logging enterprises for hauling timber are described. An urgent scientific task aimed at improving the designs of their coupling devices was determined on the basis of the identified drawback inherent in a timber-carrying road train when driving on an insufficiently equipped timber road. The perspective recuperative coupling devices developed earlier by the authors are considered, their advantages and general principle of operation are described. The tasks for the practical implementation of the proposed designs of recuperative coupling devices are formulated.
The relevance of increasing the efficiency of timber transportation by forest transport vehicles through development of a promising hydropneumatic suspension scheme has been substantiated. A diagram of the proposed modular design suspension and logging vehicle equipped with this type of suspension has been presented. The results of its simulation have been also showed. A mathematical model of the movement of a six-wheeled timber truck in three-dimensional space has been developed to evaluate the use of such hydropneumatic suspensions in a forest car. The design scheme for constructing a timber truck dynamic model has been presented. The sequence of numerical integration at each time step has been described. It includes seven stages, repeated many times during the computer experiment. A computer program has been developed. It enables to investigate the coordinated operation of hydropneumatic suspensions and the influence of their parameters on the smooth running of a timber truck. Computer experiments have been carried out to overcome bumps and obstacles with given parameters at different speeds. The time dependences of the volume of the pneumatic cavity of the hydropneumatic suspension, pressure and gas temperature in it have been obtained. The influence of the average height of irregularities, the number of obstacles per unit length, the speed of timber truck on the maximum vertical acceleration of timber truck, the maximum pressure and temperature difference in the pneumatic cavity of the suspension under study has been revealed
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