During dynamic testing of vehicle air springs, work is required for loading the springs. This work is partially returned by the spring to the driving system during the release phase. Testing is energy-efficient when at least a portion of the returned work can be utilised. This was taken into account in the design of the new inovative test rig for the simultaneous testing of four air springs. There is a phase shift between the phases of loading individual air springs; thus, the work returned to the drive system by a spring during its release is also used for loading another spring. The test rig was constructed and operates in the laboratory of an air spring manufacturer. We developed a computer program to analyse the energy situation in the test rig. The program calculates the work required for loading the springs, power and friction for different sizes of springs and test conditions. In this paper, computational algorithms are deduced and the results of the calculation for the treated spring are presented. The energy situation in the test rig during start-up and operation is discussed, taking into account the energy loss due to the hysteresis of springs and friction losses. The friction losses are evaluated for different implementations of critical elements. The influence of a flywheel on conditions during the start-up and operation of the test rig is analysed.

In recent years we have conducted research of new gears with a progressively curved path of contact as illustrated in Figure 1 below. We also tried to prove features anticipated for these gears. Thus our research focused on durability of this type of gears regarding to pitting and scuffing. We compared them to the involute gears of the same dimensions. We discovered a higher load capacity of tooth flanks of the new gears compared to the involute gears in case of scuffing. Both types of gears showed approximately the same load capacity against pitting if a transverse operating angle was the same in both cases. It has been proved that the new gears had better efficiency and considerable lower wear. We tested gear pairs made of through hardened steel and those nitrided after machining. Our paper will discuss some results of the research work on the new type of gears for which we believe they will find their way to the practice.

To determine the life of air springs, a new test rig enabling dynamic sinusoidal loading of air springs has been developed. The test rig enables the adjustment of air spring deformation and load frequency, as well as the adjustment of its geometry to different sizes of air springs. Four air springs are tested simultaneously. Between the phases of loading the air spring some time delay occurs, which is why the work that the air spring returns into the drive system during its unloading is consumed as well. The concept of the test rig and the possibilities of adjustments are presented. In order to carry out a dynamic analysis of the drive and determine the load on test rig elements, a computer program has been developed that enables the calculation of the forces, torques, and power of the driving motor for different sizes of air springs and various testing conditions. The algorithms that the program is based on and the characteristic results of the calculations are presented. Also, a comparison of energy consumption for the test of one, two, and four air springs is shown. The advantages of the new test rig as compared to other test rigs are discussed, too.

In practical use, most gears have an involute shape of tooth flanks. However, external involute gears have some drawbacks, such as unfavourable kinematic conditions at the beginning and end of meshing, a limited minimum number of teeth, and the highly loaded convex-convex (i.e., non-conformal) contact. Researchers have developed and analysed various non-involute forms of tooth flanks, but they have not been widely accepted. The main reasons are higher manufacturing costs and sensitivity to manufacturing and assembly errors. Analyses of non-involute forms of teeth are mostly theoretical (analytical and numerical), while there is a lack of experimental confirmations of theoretical assumptions. This paper reviews external non-involute shapes, their operating characteristics and possibilities of use compared to involute gears. Established criteria, such as Hertzian pressure, oil film thickness, bending stress at the root of the tooth, contact temperature, and gear noise, were used for assessment. The results of analytical studies and experimental research on S-gears are presented in more detail. S-gears have a higher surface durability and a lower heat load when compared to involute gears. The usability of non-involute gears is increasing with the development of new technologies and materials. However, the advantages of non-involute shapes are not so significant that they could easily displace involute gears, which are cheaper to manufacture.

The influence of the working load on the dynamic loading of the bolt was investigated in our study for two cases of flange joints. The analytical calculation according to the Verein Deutscher Ingenieure (VDI) 2230 recommendation and the numerical analysis using the finite element method (FEM) were performed for a model of a four-bolt joint. To verify the FEM analysis, the forces in the bolts were measured during preloading and during the application of the working load on the test rig. Based on the analytical and numerical results, the influence of the working load application point on the bolt load and its fatigue life was analysed for different cases. Comparison of the results shows that the analytical method overestimates the additional bolt stresses at low working load, mainly due to the extremely large fraction of bending stress. As the working load increases, the differences between the two methods decrease, but only for the reason that the analytical method can only linearly scale the overestimated results at lower working load, and FEM analysis, on the other hand, shows a progressive increase of the additional stress in the bolt at higher working loads due to the spreading of the flange. It is also shown that a high washer significantly increases the fatigue life of the bolt for two reasons: (i) a high washer reduces the additional stress in the bolt, and (ii) the high washer shifts the critical fatigue point from the thread area to the transition of the bolt shank to the head.