The Use of Metal-Polyfluoroethylene Bearings in Heavily Loaded Friction Components,

Study of the possibilities of constructing helicopter rotor hinges using dry friction bearings capable of operating either with or without lubrication is reported to achieve sufficient wear resistance and to create by their natural friction the necessary damping in the hinges. One satisfactory material which has been developed consists of a steel base, bronze-polyfluoroethylene and fluoroethylene layers. The steel base gives the material high structural strength, the bronze framework, consisting of small bronze particles mixed in the resin, carries the load, transfers the head away from the friction surface and acts as a reservoir for solid lubricant, which flows from the pores of the bronze during operation and thus is delivered to the area of contact between the bronze and the other part of the friction couple, reducing the coefficient of friction. Results of strength and wear tests of the material are presented. Since the coefficient of friction increases with increasing friction speed, multilayer thrust bearings can be used to decrease friction. The tests have indicated that the material is satisfactory for all oscillating friction couples in the lifting system of a helicopter. Author, modified-PL