The article presents research results of a machine-tractor unit that performs two technological operations simultaneously: (i) chopping plant residues (sunflower stubble); (ii) covering the chopped stubble with the soil. The first operation is carried out with a front-mounted plant residues chopper, and the second one is carried out with a rear-mounted plough. The chopper’s working devices are rotated by the tractor’s front power take-off (PTO), which has two operating modes: 540 and 1000 rpm. It was determined that to reduce the dynamic load in the drive of the chopper’s plant residues working devices, to chop these residues qualitatively, and then to cover them with the soil, the tractor’s front PTO should be adjusted to a speed of 1000 rpm. With this mode of the chopper’s working device’s rotation, the difference in its vertical vibrations’ dispersion and the tractor front axle’s oscillations is insignificant. The variance of the plowing depth vibrations (1.44 cm2), changing aperiodically in the frequency range of 0–2.5 Hz, is not accidentally less than the variance of irregularities vibrations of the longitudinal field profile (2.75 cm2). The plough draft resistant oscillations of the plow-chopping unit had the least impaction at the plowing depth oscillations. The proof of this is the small value of the cross correlation function; for such oscillating processes as ‘plough draft resistance—plowing depth’, it was equal to 0.22, which is 3.4 times less than for oscillating processes ‘surface’s longitudinal profile—plowing depth’. The number of chopped particles less than 15 cm in length increased by 1.5 times, and the number of particles longer than 30 cm decreased by 3 times. With the complete incorporation of plant residues into the soil, their non-chopped part did not exceed 1%.

The versatility of tractors can be increased by using them as a part of a modular draft device (MDD). MDD consists of energetic (EM) and technological (TM) modules. EM is a high-energy tractor with a 2WD or 4WD wheel arrangement and a traction force of 14-16 kN. TM is an additional axle with an active drive of its wheels. By connecting TM to the rear hitch linkage (RHL) of EM, the tractive effort of the entire MDD, which has a 4WD or 6WD wheel arrangement, increases to 32-36 kN. MDD can function as a road-rail vehicle. Depending on the traction resistance, MDD can be used both as part of an EM+TM or as a single EM. According to the research results, it was found that the maximum traction efficiency (TE) of MDD with a 6WD wheel arrangement is about 10% higher than that of MDD with a 4WD wheel arrangement. The TE value of MDD increases with an increase in the inclination of EM rear hitch linkage top link. The increase in MDD’s tractive efficiency is facilitated by an increase in the coefficient of kinematic discrepancy in the drive of the EM and TM wheels from 1.00 to 1.05.

This paper is dedicated to Tekrone composite material utilization in agricultural machinery. In terms of its technical properties, tekrone is very similar to steel 60 that is used for production of plough mouldboards and landsides. However, Tekrone shows more preferable characteristics, because its friction coefficient (kf) is 2.6 times lower in contrast to steel 60. This fact indicates that the draft resistance can be decreased by replacing the plough mouldboards and landsides made of steel 60 with their counterparts made of Tekrone. This science hypothesis was confirmed by experimental investigation results. Analyses showed that utilization of plough with Tekrone mouldboards and landsides instead of steel ones significantly reduces their sticking to the wet soil. This results in a “soil moves over plough mouldboard surface” process instead of a “soil moves over soil” process. The plough draft resistance was decreased by 13.6% after replacement of the steel equipment with Tekrone one. Simultaneously, the performance of new tractor-plough aggregate was increased by 12.6%, the specific fuel consumption was reduced by 11.8%, and the preserving probability of the agrotechnological ploughing depth tolerance (±2 cm) was increased from 88% to 93%.

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The paper is focused on the issues of controllability of machine-tractor units based on wheel-type tractors during their non-straight driving on the soil surface, which is positioned at an angle to the horizon. There were obtained analytical expressions for the determination of the actual indicator of control l d , including both the power and the design parameters of the machine-tractor unit, which affect the abovementioned indicator in the longitudinal vertical plane. These expressions are obtained for the tractor driving on both road and also driving during field operation. In addition, the paper discusses the conditions under which there may occur the cross-slip of the tractor steering wheels in the transversal horizontal plane. As a result of this review, there were obtained the analytical expressions for determining the required indicator of the controllability l d of machine-tractor unit in the horizontal plane, excluding the possibility of lateral sliding of the unit by turning its steering wheels at a certain angle. These expressions are obtained for the two modes of the machine-tractor unit: for driving during transport on the road and during the operation in the field. The machine-tractor unit based on the wheel-type tractor with rear mounted 3-mouldboard plough was analytically investigated. By means of computer calculations, there was observed the fact that when moving in non-straight direction on the soil surface, inclined to the horizon at an angle of 12°, the machine-tractor unit is controllable only when the angles of the steering wheel of the given tractor do not exceed 9°. During the working movement (ploughing) of the given machine-tractor unit on an inclined field surface, its controllability will be preserved on condition that the angle of the tractor steering wheels does not exceed 11°. According to obtained results, it can be stated that the controllability of the machine-tractor unit is determined by the indicator of controllability, taking into account the value of the vertical load acting on the tractor steering wheels, the possibility of their turning in the horizontal plane, as well as the withdrawal of the machine-tractor unit from rectilinear motion and its movement on the field surface, inclined at an angle to the horizon.