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The analysis of the factors that show decisive influence on the tractors stability and the possible overturning, should preventively indicate the possible improvements of the tractor construction, in order to increase the tractor's and operator's safety. The purpose of this paper is to check the static angles of the longitudinal and lateral tractor stability, using the different methods that check the tractor stability up to the to the turnover limit. The process is based on the tractor longitudinal and lateral tilting and measurement of the reference values of the wheels heights with respect to the base. The same angles can be obtained by various analytical and numerical methods based on the Theoretical mechanics. This paper suggests on the importance of empirical data, because they are the basis for further stability analysis of the tractors, other self-propelled agricultural machines.

Modern agricultural engineering involves the wide application of hydraulic and pneumatic systems for the transmission of power (energy) and control signals. This paper presents the most commonly used types of valves in hydraulic systems. In the literature, more classification of hydraulic valves is reported, according to their construction, purposes, etc., which, even within the same classification criteria, sometimes strongly differ one from the another. Therefore, this presentation is organized by principled valve assignment into four basic groups based on purpose, although there are other divisions according to the purpose of the valve. Other classifications, although present in the available literature, have not been commented in detail, due to space constraints. In this manuscript, the basic elements of the construction of the most important types of valves are described and analyzed, their most important characteristics are described, the base functional principles and technical limitations described, and the given guidelines and recommendations for their optimal application.

The paper presents and analyzes the hydrostatic transmission of power and motion. The most important elements of this group of systems and the possibilities of their application in agricultural technology are given. Particular attention is paid to the positive-displacement pumps that have the widest application in agricultural machinery: gear pumps with external and internal gears, vane pumps, piston-axial pumps with inclined swash plate and piston-axial pumps with inclined cylinder block. Two hydrostatic power transmission and control systems are also presented. The first is a very simple mechanical- hydraulic system of automatic leveling of self-propelled berry fruits harvester. In contrast, the other hydrostatic system is very sophisticated. It is implemented as a very complex combination of hydrostatic and mechanical power transmission subsystems, with the accompanying control digital electronic system, and is intended for the wheat harvester propulsion and steering.

Among others, an airborne dust particles concentration is a crucial microclimate quality parameter of each livestock building. Increasing the concentration of dust particles affects the indoor air quality and health of employed workers and breeding animals. In order to enrich the existing data base and improve the understanding of mechanisms of controlling the microclimate conditions in livestock buildings, the influence of operational air flow rate of under-roof axial fans on airborne dust particles distribution crossover the tied cows barn has been analysed in present study. Six different air flow rates of both installed fans have been tested: 0 m3·h-1 (only natural ventilation), 23750 m3·h-1, 30750 m3·h-1, 37300 m3·h-1, 39900 m3·h-1 and 48000 m3·h-1. Measurements have been performed at four typical height levels (0,5 m; 1,0 m; 1,5 m and 2,0 m), cross-over the three lateral and four longitudinal characteristic building sections. Consequently, 48 measuring points were appropriately selected, in order to cover the whole indoor space in adequate way. Comparative analysis of air flow velocities and dust concentrations showed that this fan setup can provide satisfactory results under adequate operational regime. Certain working regimes were recommended for use, and the first fan rate step, generating the airflow of 23750 m3·h-1, or indoor air exchange level of approximately 16 1·h-1, has been found as the most suitable. .

The structure of land is one of their most important characteristics. Substantially influence the structure of the many features and processes in the soil is generally accepted. Soil aggregates are strongly influenced by human activities, including land use, tillage, application of manure and growing crops. Size of aggregates and their stability are interconnected to describe soil structure. Size distribution and aggregate stability after the break, are used to calculate quantitative stability index. In the classical approach to statistical analysis of soil structure are used: Gaussian normal function, and log-normal, Rosin-Rammler and Gaudin's-Schuhmann's functions. In addition to these distribution models recently introduced models are based on a dimensionless statistical moments and the log-hyperbolic distribution. .