A new design of a two-stage cycloidal speed reducer is presented in this paper. A traditional two-stage cycloidal speed reducer is obtained by the simple combination of single-stage cycloidal speed reducers. A single-stage reducer engages two identical cycloid discs in order to balance dynamical loads and to obtain uniform load distribution. Consequently, the traditional two-stage reducer has four cycloid discs, in total. The newly designed two-stage cycloidal speed reducer, presented in this paper, has one cycloid disc for each stage, that is, two cycloid discs in total, which means that it is rather compact. Due to its specific concept, this reducer is characterized by good load distribution and dynamic balance, and this is described in the paper. Stress state analysis of cycloidal speed reducer elements was also realized, using the finite elements method (FEM), for the most critical cases of conjugate gear action (one, two, or three pairs of teeth in contact). The results showed that cycloid discs are rather uniformly loaded, justifying the design solution presented here. Experimental analysis of the stress state for cycloid discs was realized, using the strain gauges method. It is easy to conclude, based on the obtained results, that even for the most critical case (one pair of teeth in contact) stresses on cycloid discs are in the allowed limits, thus providing normal functioning of the reducer for its anticipated lifetime.

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This paper describes validation process of numerical model of combined collision kinetic energy absorber of rail vehicles based on results of experimental investigations. Combined absorber works on the principle of extrusionsplitting the seamless tube. With the aim to choose the most appropriate tube geometry, the tubes of the different geometry of cross section were made and tested. Key geometry parts have the shape and length of the grooves along the inner tube wall. During the second phase of deformation comes to controlled splitting of the tube wall along these grooves. Experimental and numerical investigations were realized on the scaled samples. Using this type of absorber energy absorption occurs by friction between absorption elements and elastic-plastic deformation of the tube.Combining of two deformation processes gives a higher absorption power as well as compact dimensions of absorber which can be installed in a very limited space in the front part of the vehicle structure. Creating of the numerical model and numerical simulations of extrusion-splitting processes were realized using SolidWorks and ANSYS LS Dyna software packages. Results of experimental investigations and numerical simulations show very good agreement which verifies developed numerical model for use in further investigations in this field.

The problem of internal forces that occur on the cycloid disc during the cycloid speed reducer operation so far has not been considered in a way that reflects its actual workloads and stresses in the cycloid disc itself. This paper presents a dynamic analysis of the stress-strain state of a cycloid disc by using experimental and numerical methods. The following cases of meshing are presented in the paper: a single-tooth, double-tooth, and triple-tooth meshing of the cycloid disc and the ring gear. The cycloid disc was chosen for this study because it is one of the main elements and the most critical element of the cycloid speed reducer. An experimental physical model of the cycloid disc and the meshing elements of the cycloid speed reducer was made based on a previously performed 3D CAD model. The numerical analysis of the stress-strain state of the cycloid disc was performed with the identically defined external load using the transient stress method. The paper presents a comparative analysis of the experimental and numerical results, which gives a solid insight into what is happening in the cycloid disc during the cycloid speed reducer operation. The experimental and simulation results both give the results with a deviation between 3% and 15%. After the detailed analyses, it is shown that the most critical element of cycloid speed reducer are output rollers, which need further study.