Surface smoothness of journal and bushing has significant influence on properties of sliding bearings. Relevant literature contains a number of theoretical works connected with the subject of surface roughness pattern and height. Calculations based on various models indicate that the structure of sliding surface influences bearing's hydrodynamic properties. One of the main conclusions is that roughness transversal to the sliding direction can increase hydrodynamic capacity of a bearing (H. Christensen and K. Tonder, 1973, Journal of Lubrication Technology, Vol. 4, pp 166–172). In bearings lubricated by a low-viscosity liquid such as water, the influence of roughness is of particular importance. This is due to low hydrodynamic film thickness and the resulting limited hydrodynamic capacity of these types of bearings. In fact, these are the reasons for deciding to conduct experimental research aimed at verifying the influence of roughness pattern on bearing properties. Research conducted for a selected group of polymer materials demonstrates strong influence of roughness height on movement resistance and working properties of bearings. No significant influence of roughness pattern on working parameters was observed. Furthermore, the running-in process for this type of bearing material is rapid. The sliding surface becomes smoothed out in just a few hours of work, significantly reducing all of the coefficients of friction.

Influence of main design parameters of ship propeller shaft water-lubricated bearings on their properties: In recent years more and more frequently can be met ships in which propeller shaft water-lubricated polymer bearings have been applied. It results from their simplicity and associated relatively low initial and operational cost as compared with the complex classical sealed system based on oil-lubricated bearings. It is worth mentioning that the water-lubricated bearings are also environmentally friendly as no risk of pollution with lubricating oil used in classical systems, is involved. Design procedure of bearings in question based on materials made available by producers is relatively simple. However it turns out that choice of an appropriate sliding material, clearance value and optimum arrangement of lubricating grooves may greatly influence bearing's properties. As results from the performed research investigations, bearing of the kind is a highly sensitive unit. Problems of choosing a suitable bearing clearance, designing an optimum bush geometry, selecting a proper bush material are crucial for life time of the bearing. In particular the problem is in forming hydrodynamical properties of bearing as owing to its operation in the fluid friction regime durability of bearings, the very responsible units of propulsion transmission system, can be greatly extended.