AbstractŠpokas L., Adamčuk V., Bulgakov V., Nozdrovický L. (2016): The experimental research of combine harvesters. Res. Agr. Eng., 62: 106-112.The paper presents results of the experimental research of a middle-size combine harvester when used for harvest of winter wheat and spring barley in heavy harvest conditions. Based on the results obtained, it was possible to determine the effect of field conditions on the crop mass flow in combine harvester, grain losses, fuel consumption, and combine harvester field performance. It was found that grain moisture content and conditions of the crop stand have a significant effect on the work indicators of the combine harvester when compared with its technological parameters and crop mass flow.Кeywords: grain losses; fuel consumption; combine harvester field performance As stated by Kutzbach and Quick (1999) the main processes in a modern harvester are gathering and cutting, threshing, separating, cleaning, and material handling. Currently, designers of the combine harvesters pay more attention to the improvement of the quality of control process, its automatic control, improve the trafficability of the chassis and the environment protection. They argue that an increase in engine power increases the throughput of the combine harvester. Engine power of the combine harvesters equipped with the classic straw walkers already exceeded 295k W/400 HP, and hybrid and axial -closer to 440 kW/600 HP (Srivastava et al. 2006). But the throughput of the combine harvester is associated not only with the power of the engine, and it is more closely connected with the separation deck area, straw walker and cleaning mechanism capacity.According to the FAO Report (FAO 2014) in Ukraine, the 2014 aggregate cereal production is estimated at about 61.9 million tonnes marginally below 2013 year's record level and around 25% above the five-year average. This output reflects near-record yields, following favourable weather conditions during the cropping season, which more than offset a slight contraction in the planted area compared to 106

The exact knowledge of olive suckers and branches cutting behaviour is one of the main parameters for optimizing the design of cutting elements in pruning machines. In this study, the cutting properties of five different varieties of the table olive, namely Halhali, Gullaki, Mavis, Belloti and Zoncuk respectively, were determined. The cutting properties were measured at three moisture content levels (17.05, 34.44, and 39.47 %) and four cross-sectional areas (12.56, 28.27, 50.26 and 78.54 mm2). The results showed that the cutting force and cutting energy requirement of olive suckers decreased with increasing moisture content in all of the olive varieties. However, these properties increased with increasing cross-sectional area. The maximum cutting force, cutting strength, cutting energy requirement and specific cutting energy of olive sucker were obtained at the Halhali variety as 869.15 N, 18.66 MPa, 4.29 J and 0.0875 J.mm-2, respectively, while the minimum cutting values were obtained at the Zoncuk variety as 619.19 N, 14.75 MPa, 2.44 J and 0.0531 J.mm-2, respectively. As a result, the data obtained from cutting tests of the olive sucker can be used in a new design and development of an experimental prototype of olive branch cutting and pruning machine.

The harvest and transport of sugar beet leaves during harvesting can be considered a current task in the area of sugar beet growing system development. A rotary sugar beet leaf cutting mechanism is used for achieving the significant increase in the harvester forward speed during harvest. This leads to intensive vibrations of the topping mechanism in the longitudinal vertical plane causing the decrease of harvest quality. Therefore, it is necessary to analytically determine the effect of kinematic and design parameters of the sugar beet topping mechanism front-mounted on the tractor and to discover the value of the amplitude of oscillations in the longitudinal vertical plane of its sugar beet topping mechanism. We have constructed a mathematical model of the estimated motion of this machine by means of dynamics equations in Lagrange II-kind form. A system consisting of two non-linear differential equations was obtained by developing the equivalent scheme of selected generalized coordinates and by performing the necessary mathematical transformations. This system describes the vibrations of the sugar beet topping mechanism in the longitudinal vertical plane. The optimal design and kinematic parameters of the sugar beet topper mechanism front-mounted on the tractor were determined by means of our own software and numerical solution of the differential equation system, which allows the reduction of mentioned vibrations.

: Wide span tractors have a wide transversal bar, on which different implements can be mounted, while the supporting wheels follow the set traffic-lanes. The stability of wide span tractor movement is influenced by unbroken small angular deviations and transversal displacements of the machine due to several factors. These deflections from the set trajectories affect the working implements, especially the peripheral ones, which can cut the plants if wide span tractors are used to manage row crops. In this context, it needs to consider a safeguard zone that allows to reduce the probability of contact between working implements and plants. The aim of this paper was to determine the quantitative effect of transverse displacements of the working implements and the suitable size of the aforesaid safeguard zone. The magnitude of the inner and outer displacements of the working implements depends significantly on their location in relation to the center of the wide span tractor. For working implements located outside the center of the tractor, the outer safeguard zone should be larger than the inner zone. The probability of crop damage by working implements can be reduced by automated control of wide span tractor movement.

Acta Technologica Agriculturae 1/2015 Miroslav MACÁK et al.Increasing concerns about climate change mitigation and rising oil prices are creating an unprecedented interest in the development of economical and convenient renewable energy fuels. Recent advances in biomass feedstock development and conversion technologies have created new opportunities for using agricultural land as a means of producing these renewable fuels in larger quantities than relying on wood and agricultural residues alone. Dedicated agricultural feedstocks such as wheat straw, maize stover, rape stover, switch grass, miscanthus, etc. and short rotation willow can abate with high quality petroleum running out in the next 50 years. World governments and the petrochemical industry alike are looking at biomass as a substitute refinery feedstock for liquid fuels and other bulk chemicals. New large plantations are being established in many countries, mostly in the tropics, but also in China, North America, Northern and Central Europe, and also in Russia (Samson et al., 2000). From a total energy use standpoint, however, biomass provides a relatively small percentage of the world's current energy needs. Most of the total energy use is found in more developed countries, not in regions with large populations. Biomass has the potential to provide a much greater share of the world's energy, particularly in the USA. Renewable biomass removes CO 2 from the atmosphere for biomass production and then releases this CO 2 back into the atmosphere when burned.There are different methods of biomass processing for energy purposes. In last years, the pelleting of biomass has become the most used technology for processing of biomass. There are different systems of pellets manufacturing, but the efficiency of biomass using depends upon the type of biomass. Pellets are usually made of lucerne, miscanthus, maize stover, wheat straw, and prickly lettuce.Lucerne pellets have been known to generate dust and fines because of repeated handling and transport. During transport, this product loses or gains moisture, which may affect its quality. Therefore, there is a need to manufacture pellets that are not prone to breakage but still can be palatable to animals. Tabil (1996) conducted an experiment to determine the effect of chop quality, process and machine variables on the quality of lucerne pellets. Three different qualities of lucerne chops, namely low, intermediate and high quality, were used in the experiment.An experiment was conducted by Mani et al. (2004), where maize stover was compacted in a piston cylinder with three pressures, i.e. 5, 10, and 15 MPa, at three moisture content levels, i.e. 5, 10, and 15 % (wb), to produce briquettes. The total energy requirement to compress and extrude briquette was in the range of 12-30 MJ.t -1 . The briquette density was in the range of 650-950 kg.m -3 , increasing with pressure and biomass moisture. Moisture content and pressure had a significant effect on briquette density, durability and stability. Maize stover produced h...

Abstract:The risk rate of sugar beet growing was analyzed by using the algorithm for modelling and generating the random numbers based on the conditions determined in advance and the statistical distribution of sugar beets yield, the total costs, earnings and gross profit. on the bases of results of the analysis of economic risks of sugar beet production in years 1995-2009, it follows that the sugar beet growing in all regions is highly risky in the czech republic. The subsidy SAPS and ToP-UP per 1 hectare of sugar beet have a positive impact on its economics though not sufficient enough. in practice, it means that it is highly probable that the break-even point will not be achieved and thereby it is highly probable that the fixed costs are not covered and the update of machines is significantly limited. This happens mainly in the marginal regions. if the agricultural companies count on the separate sugar payment, the sugar beet growing is in all regions of the czech republic with acceptable risk.

Recently, rapid development of controlled traffic farming convincingly demonstrates the broad prospects of using the wide span tractor-based field machines throughout the world. The issue at hand lies in the fact that having a wide span tractor-based machine with steering-wheel system moving along the tracks of a constant technological track is not a rational option. According to the concept of bridge and rutting agriculture, it is advisable to subordinate the automated means of mechanization to the principles of the functioning of the coordinate transport system in which machines can move only in two mutually perpendicular directions and for implementation of which the field must have strictly defined dimensions. Therefore, a method of power steering similar to a crawler tractor (track-type tractor) can be more efficient in the automatic driving of bridge means of mechanization within the coordinate-transport system than a kinematic control. Furthermore, methodology utilized for selection of design schemes, parameters and operating modes of machine-tractor aggregates can not be used for study of dynamics of the wide span tractor-based field machine. Theoretical study is based on theoretical mechanics, theory of mobile energy facilities, statistical dynamics and theory of automatic control of linear dynamical systems with reproduction of statistically random control and disturbing input effects. Purpose of the research lies in development of a dynamic model of plane parallel motion in the horizontal plane of a wide span tractor-based field machine unit using a power (onboard) method of control, which would allow investigation of impacts of the control parameters and disturbing influences on the controllability and stability of its motion. Mathematical models have been developed and new regularities of the straightforward parallel movement of the wide span tractor-based field machine unit for controlled traffic farming have been obtained. The results obtained allow the validation of new schemes, design parameters and modes of operation with acceptable controllability and stability of movement in the horizontal plane with a power control method of the chassis.

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.