Friction Torque of Ball Bearings in Vacuum with Seven Polytetrafluoroethylene-Composition Retainer Materials.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
Pagination or Media Count:
Self lubricating retainer materials containing various weight percentages of poly- tetrafluoroethylene PTFE, glass fibers, molybdenum disulfide Mos2, and bronze were evaluated in 20-millimeter-bore ball bearings operating in a vacuum of 106 torr 1. 33X10 4 Nm2. The lubricating capability of the retainer materials was evaluated by measurement of the bearing friction torque. The test bearings were run at 3600 rpm with axial loads from 35 to 100 pounds 156 to 445 N for periods of approximately 1 hour. Although all retainer materials lubricated the bearings reasonably well, the best lubrication, as measured by the lowest average friction torque, was obtained with a bearing equipped with a retainer of 70 percent PTFE, 15 percent glass fibers, and 15 percent MoS2. In an initial run at a load of 50 pounds 222 N with this material, the bearing torque was high and erratic in the next three consecutive runs, however, the torque remained at a low, constant level. This behavior indicated that a run-in period was required before good lubrication of the bearing could be achieved. In the following three consecutive runs, the bearing registered low, steady torque upon re- start and thereby demonstrated good restart capability. During the time intervals of 24 hours or more between the runs, the bearing soaked in the vacuum chamber. The good performance with this retainer was partly attributed to a fabricating process that produced a homogeneous mixture of PTFE, glass fibers, and MoS2 in the material.
- Laminates and Composite Materials
- Machinery and Tools