8.14: Pivot Bearings
In mechanical systems, bearings are crucial in facilitating relative motion between two components while minimizing friction and wear. They help distribute various loads (radial, axial or a combination of both loads) across machinery parts, ensuring smooth and efficient operation.
A pivot bearing is a specialized type of bearing designed to support axial loads on a rotating shaft. The bearing surface, or the pivot, is positioned at the end of a shaft to support the axial thrust. The pivot may feature a flat, conical, or truncated surface depending on the application.
In a flat pivot bearing, when subjected to an axial load, the uniform pressure exerted on the bearing can be calculated as the ratio of the load to the bearing area. This pressure distribution helps minimize friction and wear on the bearing surface, contributing to more efficient operation and longer service life.
To further analyze the forces acting on a flat pivot bearing, we can examine an infinitesimal ring within the bearing area, with a radius r and thickness dr. The load transmitted to this ring can be estimated based on the pressure distribution across the bearing surface.
As the shaft rotates, frictional forces resist the sliding of the ring and act tangentially at the radius r. By calculating the moment of the ring and integrating it within the radial limits, the moment of the shaft can be determined as follows:
This calculation provides valuable insights into the performance and efficiency of the bearing under varying load conditions.
Pivot bearings are utilized in a diverse array of industries and mechanical systems due to their unique ability to support axial loads on rotating shafts. These versatile components can be found in rotating machinery such as turbines, generators, pumps and automotive components like steering systems and transmission assemblies. Additionally, pivot bearings, including landing gear and flight control surfaces, are crucial in aerospace applications. Industrial equipment, such as cranes, winches, and conveyors, also rely on pivot bearings for efficient operation and reliable performance. As a result, the widespread use of pivot bearings across various sectors highlights their importance in maintaining smooth and effective mechanical systems.
