Tribological characteristics of needle bearings

Abstract

A Needle Bearing Test Rig has been constructed which allows the measurement of frictional torque, axial thrust, needle axial skew angle, and needle complement velocity for an applied radial load of up to 3500 N and a speed of up to 7000 rpm. Either shaft rotation or cup rotation can be accommodated. Preliminary data indicate that frictional torque is greater for full-complement bearings than caged bearings, that torque is higher for cup rotation than shaft rotation, and that torque is minimized when the needles (full-complement) are axially aligned with the shaft in the load zone. A correlation was found between needle skew angle and axial thrust. Less than one degree change of needle skew is required to go from no thrust to the maximum thrust developed (about 5% of the radial load). Full complement bearings tend to operate with a preferred needle skew direction and attending thrust direction with occasional spontaneous reversals. Operation without thrust and needle skew is not stable.