| Abstract [eng] |
The literature review and analysis of this paper delves into the types of motorcycle suspensions, their advantages and disadvantages, and the most commonly used suspensions types in modern motorcycles. The elements used in suspensions, their connection types and production materials are reviewed with explanation on why the mentioned elements are used in the exact cases. Shock absorbers are analyzed along with their structure, types and their advantages and disadvantages, where certain types are most often used. Physical phenomena occurring in shock absorbers, their influence and how to avoid them are briefly reviewed. It is theoretically analyzed how the characteristics of the damper's resistance to travel change when the viscosity of the oil or the dimensions and arrangement of the adjustment plates changes. In the practical part of the work, the change in the force dependence of the resistance to the movement of the rear shock absorber of an off-road motorcycle is investigated by changing the oil viscosity and the set of internal adjustment plates. The research begins by conducting an oil viscosity study of different manufacturers, where we find out that the difference between the most liquid (420.67 mPas) and the most viscous (844.67 mPas) oils is twofold. After the oil viscosities have been tested, the damping forces of the vibration damper depending on the stroke are studied on a dynamometer bench in the laboratory with each test filling the damper with oil of different viscosity and setting three different adjustment positions of the damper. After conducting the latter study, we found that no clear difference was observed between the different oils at the piston excitation frequencies of 2, 3 and 4 Hz that we investigated. The second test cycle was conducted using a single viscosity oil, but with three different modifications to the internal piston adjustment plates. During laboratory tests, while studying the modifications of the plate set, we found out that the first change reduces the damping forces on average by 10-20%, the second modification increases the resistance forces for compression by 27-52%, for extraction it increases up to 10%, and finally the third change in the set of plates increases the damping forces for compression by 20- 44%, for extraction up to 7%. In order to find out the real change, a natural test was carried out with measuring equipment that measures the travel of the suspension and impacts to the motorcycle frame. During the last study, it was found that during the smallest stroke of the damper (43 mm), the damper absorbed the shock using the third modification and with the regulators in the stiffest position, but with these settings, a fairly significant impact acceleration (0.89 G) was transmitted to the motorcycle frame. Taking into account the shocks transmitted to the motorcycle frame, the conclusion was made that the most effective modification of the damper is the original one, with the regulators in the stiffest position, because during this test the damper reached the maximum travel of 46 mm and the maximum acceleration of the impact to the frame 0.76 G. Finally, the paper presents conclusions and recommendations for vibration for adjusting the damper according to the obtained results. |
