The parts required for heavy-duty bearing selection are essentially the same as those for high-rigidity bearings. Heavy-duty bearings must be considered in conjunction with their operating characteristics. Heavy-duty bearings often operate under high loads, and bearings are highly sensitive to these loads. Bearings designed for these applications strive to minimize their loads, and reducing these loads significantly extends bearing life.
For example, in a high-load machine, if the axial position allows, the original single bearing at a certain fulcrum can be doubled to two to bear the radial load. Despite the impact of uneven load, under the same workpiece conditions, the life of the two bearings at the fulcrum can be expected to be more than doubled compared to the original single bearing. In fact, heavy-duty machines often use multiple bearings or multi-row bearings at a single fulcrum to bear radial loads.
1) The fit, clearance, and lubrication of heavy-loaded bearings must be considered together. To reduce stress in heavy-loaded bearings, a thicker lubricant film is desirable. Therefore, a higher-viscosity lubricant or a grease with a higher-viscosity base oil is preferred. At the same time, while ensuring good lubrication, the friction torque caused by the lubricant’s viscosity should be kept low.
2) The interference fit of the rotating ring of a heavy-loaded bearing is larger than normal, which has an adverse effect on raceway deformation and even bearing life. Therefore, if possible, it is hoped that the interference fit will be appropriately reduced. This requires reducing the roughness of the mating surface while maintaining normal lubrication. Because if the lubrication fails, the excessive friction torque on the raceway surface under heavy load will increase the creep tendency of the mating surface and even cause slippage. Although these phenomena mostly occur on the outer ring, they are also inevitable on the inner ring in severe cases.
The actual fit of the outer ring should be careful not to allow excessive clearance to form, as this prevents grease from penetrating the surface, causing slippage, and easily deforming the ring, reducing the bearing’s load-bearing area.
3) Only after careful and effective measures are implemented can the interference fit of heavy-duty bearings be appropriately reduced. Although this slight reduction in interference fit significantly improves the bearing’s stress state, the benefits of thickening the oil film are even greater. Due to the large contact area of the rolling surfaces of heavy-loaded bearings, the tight fit and greater ring proximity and deformation, so the bearing clearance is generally also greater.
4) Improve the use conditions of bearings from the perspective of main engine design. All transmission shafts in the main engine’s transmission chain should have a relatively high speed until the transmission reaches the main shaft, and then reduce the speed to the operating speed. The mounting parts reserved for the main shaft bearings should also be larger to facilitate the selection of larger bearings. All these are very beneficial to the bearings.
