Findings of investigation of vibration loading of a motor cultivator are given. The cultivator was tested as a part of transport and soil cultivating aggregates on artificial track, concrete road and fertilized soil. Level of vibration on operator seat and on steering wheel in dependence on different tire types, different inner air pressure in the tires and speeds was compared to standards.

Off-road performance improvement remains one of the main problems in designing wheeled dragging and forestry tractors. Improvement of off-road performance of the dragging and forestry tractors is closely related to the general problem of wheeled vehicles’ off-road performance, however it features a number of specific aspects which require specialized research to be made. During tree skidding by a wheeled tractor, vertical load on a double-reduction axle greatly changes that is linked to additional load by a roundwood bundle and redistributed in-motion load. The above in-motion redistribution of load and driving moments along the axles greatly affects the vehicle’s off-road performance. While skidding, the increased load on a wheel leads to increased specific pressure, track depth and rolling resistance. This work employs simplified tire calculation model used as a base to determine relationship between load and deformation. Calculation is made successively for each elementary tire section that allows for finding diagram of pressure distribution in the contact longitudinal plane and researching rolling resistance related to rutting and hysteresis losses in the tire material. Further experimental research of the driving wheel and wheel system motion allowed for elaborated theoretical analysis and helped to justify parameters the forestry tractor wheels. The following tasks were set during this work: 1. To make efforts to elaborate approximated method for estimating relative elongation of the rolling resistance depending on wheel parameters, vertical load and air pressure. The method is based on calculation of contact pressure distribution on the basis of simplified tire model 2. To conduct experimental research of rolling resistance for one wheel and wheel set of a tractor in the leading movement mode with due regard to tire tangential deformation. 3. To study aspects of a process of rolling resistance of a forestry tractor during tree skidding in summer time. To run comparative draw tests of a forestry tractor equipped with tires of variable size. 4. To find out possibilities to reduce rolling resistance basing on theoretical and experimental researches.

Results of the theoretical investigation dealing with the choose of optimal structure and parameters of vibration protection system for transport unit of a motor cultivator are given. Engineering design of adjustable seat suspension with fitted parameters is suggested.

The problems of creating tractors, self-propelled chassis, forestry and agricultural machines of special designs for the mechanization of crop production, land reclamation and construction in hard-to-reach conditions of forest, agricultural and mountain lands are considered in the work. A comparative analysis of design solutions that have found application in domestic and foreign tractors used in the performance of technological and transport operations on sloping lands and badlands in agriculture and forestry is given. It is noted that a number of models of universal row-crop tractors provide for the possibility of increasing stability by turning the housings of the remote final drives relative to the rear axle housing. For tractors, at the same time, the wheelbase increases and the ground clearance (ground clearance) decreases. It is indicated that the analysis of the features of the operation of wheeled tractors on the slopes made it possible to substantiate the methods and means that improve their main indicators: differential lock; lowering the center of gravity; the use of tires with high lugs, additional steel wheels, lugs, expanders; the use of half-tracks and wheeled tractors with a 4K4 wheel arrangement. The advantages and disadvantages of using tracked and wheeled tractors as the base machine have been established. Slope preference for tractors with front drive axle. Such tractors, equipped with the previously listed devices, have better traction properties, maneuverability and controllability, approaching caterpillar tractors in these indicators. Recommendations for the implementation on slopes, forest and agricultural lands of all-wheel drive low-clearance wheeled tractors are given in the work. In conclusion, it is indicated that, despite the considered features, when creating tractors for working on small-contour plots located on slopes up to 25 °, preference is given to wheeled low-clearance tractors, which is caused by a cheap design due to minor design changes compared to the basic models.

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