Abstract:In this paper, a design of testing stands for the durability tests of hydrostatic pumps of agricultural tractors is presented. The designed testing stands will be used for the laboratory verification of the influence of biodegradable oils on the durability of tractor hydrostatic pumps. The designed testing stands were built and tried out. On the basis of the results achieved in the system function tests, we can say that the testing stands are suitable for the durability tests of hydrostatic pumps. -by a strong dirty fluid -hydraulic fluid with a higher content of contamination has a greater influence on the durability of the hydrostatic pump, -by increased operating pressure, -by acceleration of the operating cycle. Laboratory tests by the acceleration of the operating cycleThe testing stand for these tests uses the selected characteristic of the cyclic pressure loading for the loading of the hydrostatic pump tested. The working principles of most frequently used types of testing stands are shown in Figure 1a and Figure 2.The tests of hydrostatic pumps can be realised by the testing stand according to Figure 1a (Radhakrishnan 2003). The characteristic of the cyclic pressure loading is given Figure 1b. This characteristic is created by the solenoid valve EHTV which is part of the circuit, Figure 1a. The solenoid valve is supplied by the voltage signal which creates the required pressure loading according to Figure 1b.The pressure loading can be realised by a flywheel which is connected to the circuit of the testing stand according to Figure 2. The loading of the hydrostatic pump is realised by flywheel Z which is mechanically connected by coupling to the hydrostatic motor HM. Three-position, four-port valve R realises a change in the rotation direction of hydrostatic motor HM. It causes the increase or decrease of pressure in compliance with the characteristic of the cyclic pressure loading Tkáč et al. 2004). MATERIAL AND METHODS Design of testing standsThe demands for the design of the testing stands issue from the parameters of hypothetically tested hydrostatic pumps and the loading process of the hydrostatic pump during the durability test (STN 11 9287 1988). The function of the suggested stands will be checked by the system function test. During the system function test and durability test, mineral oil MOL Traktol Ultra SAE 80W, API GL-4, will be used. The temperature will be 50°C ± 2%. Demands on cyclic pressure loading according to standard STN 11 9287The demands according to the standard STN 11 9287 (1988) are stated as follows: "Technical durability must be minimum 10 6 cycles under cyclic pressure loading from zero to the nominal pressure within frequency 0.5-1.25 Hz during velocity of pressure increasing 100-350 MPa/s and in nominal parameters. It this case decreasing of the volumetric Figure 3. The testing stand must be designed so that the running of the durability test corresponds to the standard STN 11 9287 (1988) Hydrostatic Gear Pumps and Hydro-motors in which the dynamic loading of...

Three filtration systems using the tractor hydraulic circuit were proposed and verified during the tractors operation. Using the tractor-implement hydraulic system and filter body with accessories the universally useful filtration systems were designed. The designed filtration systems are the second stage of universal oil filtration whereas the first stage is the standard tractor filter. The decrease in the content of iron reached the values 25.53 %, 32.95 % and 41.55 % and the average decrease in oil contamination characterized by average value of decrease in content of iron, copper and silicium reached values 24.3 %, 24.7 % and 35.53 % in dependence on the filtration system and an oil contamination level. The decrease in contamination level verified the ability of designed filtration systems for agricultural tractors.

Majdan R., Kosiba J., Tulík J., Kročková D., Šinský V., 2011. The comparison of biodegradable hydraulic fluid with mineral oil on the basis of selected parameters. Res. Agr. Eng., 57 (Special Issue): S43-S49.The paper presents a comparison of two fluids quality. The first one was mineral oil type UTTO which is commonly used in the transmission and hydraulic systems of agricultural tractors. The second one tested was biodegradable hydraulic fluid type ERTTO which could replace the toxic mineral oil. Both fluids were tested under the same test conditions using a special test device. The selected parameters of the hydrostatic pump were evaluated. The tests were evaluated according to the parameters describing the technical state of the hydrostatic pump as follows: flow efficiency, decrease of flow efficiency and cleanliness level of the fluid tested. This additional measurement verifies the test results. On the basis of the results achieved, we can state that the biodegradable hydraulic fluid exerts no harmful influence on the technical state of the hydrostatic pump. Therefore, the biodegradable fluid tested can be applied to the agricultural tractor. Has been demonstrated that the selected parameters are suitable for the evaluation of hydraulic fluid during its working performance. Therefore, these parameters will be used in the next examination of the fluid under operational conditions of an agricultural tractor.

MÁCHAL PAVEL, MAJDAN RADOSLAV, TKÁČ ZDENKO, STANČÍK BOHUSLAV, ABRAHÁM RUDOLF, ŠTULAJTER IVAN, ŠEVČÍK PETER, RÁŠO MILAN: Design and verifi cation of additional fi ltration for the application of ecological transmission and hydraulic fl uids in tractorc.Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 5, pp. 1305-1311 This contribution presents the design and function verifi cation of additional fi ltration. It is intended for the common transmission and hydraulic oil fi lling of tractors. The main role of this fi ltration concept is to ensure a high level of oil cleanness as a condition for the application of ecologic fl uids in tractors. The next one is to decrease the wear of lubricated tractor components, the degradation of oil and eventually to extend the interval of oil change. The designed additional fi ltering is characterized by ease installation through the use of quick couplings and hoses to the external hydraulic circuit. Therefore, the fi ltration is suitable for various tractor types. Filter element has been designed with the fi lter ability 1micron and the ability to separate to 0.5 dm 3 of water from oil. Function of additional fi ltration was verifi ed during the 150 engine hours of tractor operation. During this time period the oil contamination was evaluated on the basis of chemical elements content such as Fe, Cu, Si, Al, Ni, Mo and Cr. The additive concentration was evaluated on the basis of chemical elements content such as Ca, P and Zn. During the test operation of tractor the concentration decrease of chemical elements reached the values 25.53 % (Fe), 23.53 % (Si), 25 % (Al) and 5.5 % (Cu). The decrease of additive concentration reached only medium level (6.6 %). Therefore, the designed additional fi ltration doesn't remove additives from oil. Based on the evaluation of the content of chemical elements (that representing contamination and additives), we can say that the designed fi ltering method is suitable for use in agricultural tractors. oil contamination, additives, biodegradable oil, spectroscopy, environmental protection Fluids that are used in common transmission and hydraulic systems of tractors are exposed to specifi c conditions characteristic for agricultural production. These oils must perform all requires functions in the transmission and hydraulic system of tractor and they also must be resistant to oxidation and thermal degradation. Agricultural tractors o en operate in dusty and humid environment which eff ects oil fi ll contamination. In addition, the oil fi lls are polluted by the amount of wear particles mainly from the transmission system, which carries the full power of the engine to the wheels of the tractor.

Tkáč Z., Majdan R., Drabant Š., Jablonický J., Abrahám R., Cvíčela P., 2010. The accelerated laboratory test of biodegradable fluid type "ertto". Res. Agr. Eng., 56: 18-25.The accelerated laboratory tests can evaluate the properties of new biodegradable fluids under relatively short time. These test results are the ground for the continuity of the tests under operation conditions in machine. The paper presents the test of new biodegradable hydraulic fluid type "Environmentally responsible tractor transmission oil" by designed special test device. The test evaluation was realized by technical state of concrete hydrostatic pump UD 25 which is used in tractors Zetor Forterra. This pump was loaded by cyclic pressure loading during the test with tested fluid. The evaluated parameter was flow efficiency of hydrostatic pump which reached the value 7.3% after the test. The reached value hints a high quality of the tested fluid (the limit value per standard is the flow efficiency decrease -20%).