Cycloidal drives belong to the group of planetary gear drives. The article presents the process of modelling a cycloidal gear. The full profile of the planetary gear is determined from the following parameters: ratio of the drive, eccentricity value, the equidistant (ring gear roller radius), epicycloid reduction ratio, roller placement diameter in the ring gear. Joong-Ho Shin's and Soon-Man Kwon's article (Shin and Know, 2006) was used to determine the profile outline of the cycloidal planetary gear lobes. The result was a scatter chart with smooth lines and markers, presenting the full outline of the cycloidal gear.
The paper presents selected results of tribological tests on ball bearings. The elements for tests were obtained from their manufacturer. Two groups of ball bearings were evaluated: 134-781TNG-2RS and CBK 441TNG. Tribological tests were conducted with SMT-1 device in two-stage cycle. The first stage involved tests based on the authors’ own method. In the second stage the tests were conducted according to the manufacturer’s recommendations (methodology). The obtained results indicate varied tribological characteristics of the tested ball bearings, both in reference to the parameters of the external function and the applied test method.
The article analyses the process of friction in the needle bearing as the function of the alterations of geometrical parameters, namely the diameter of the shaft – D, the needle – d and the bearing clearance. The change in the relation between the diameters D and d results in the change of the contact area of the friction pair; in the case of two shafts with parallel axes (the needle of the bearing and the shaft pin) the contact area, if compared with the analogical process in the ball bearing, alters significantly and leads to resistance in motion. There are two types of friction in the needle bearing: the rolling friction and the sliding friction; the analysis of the movement of the bearing elements enabled the estimation of the extent to which the sliding friction matters in the overall balance of motion resistance. The article also defines the type of wear as the function of initial clearance.
On the basis of the experiment, the changes in the moment of friction in the double-row ball bearing were estimated. The experimental data indicated the presence of significant differences between the average values of the moment of friction in the whole spectrum of the rotational speeds that were examined. At the same time it was observed that there exist certain characteristic rotational speeds at which the given bearing is informed by a greater working resistance. It may indicate the presence of both optimal and unfavourable working conditions for these bearings; the conditions during which there occur minimal or, respectively, maximal resistances (in a given situation). The results of the examination were analyzed statistically; the after-examination samples were closely observed and this further visual scrutiny proved that during the work of the bearing, the lubricant was displaced.
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