#558 # 550121 CLUTCH PLATE FRICTION MATERIALS FOR AUTOMATIC TRANSMISSIONS By J. F. JOHNSON Raybestos Division Raybestos-Manhattan, Inc. For presentation at the SAE GOLDEN ANNIVERSARY SUMMER MEETING Chalfonte-Haddon Hall, Atlantic City, N. J. June 12-17, 1955 Written discussion of this paper will be accepted at SAE Headquarters until August 1, 1955. Three double-spaced copies would be appreciated. PREPRINT: Subject to revision. Permission to publish this paper, in full or in part, after its presentation and with credit to the author and the Society may be obtained upon request. The Society is not responsible for statements or opinions advanced in papers or discussions at its Meetings. SOCIETY of AUTOMOTIVE ENGINEERS, Inc., 29 West 39th Street, New York 18, N. Y. Downloaded from SAE International by University of Leeds, Monday, September 24, 2018CLUTCH PLATE FRICTION MATERIALS FOR AUTOMATIC TRANSMISSIONS The subject assigned to us for this paper limits us to a brief history of friction material in oil operations, a description of the types of materials in use, some of the factors which would influence the choice of a particular material, and something of their individual characteristics. The entire history of automotive development is unique in that again and again we find instances of car builders touching lightly on some phase of engineer­ ing design only to abandon that approach in favor of another, and then, years later, bring forth a distant relative of the original idea raised to an undreamed of high level. Friction material use in transmissions has been no exception. Certainly, today's automatic transmissions with their use of oil clutches have some relation­ ship to the original leather clutches soaked in Neatsfoot oil, the cork friction face running in an oil bath and the Ford Model T Planetary transmission bands run­ ning in oil. All of these were early attempts to obtain sufficient friction and engine torque holding ability, while providing for what was then considered optimum driving comfort. The next step touching on present practice was a multiple disc clutch used both from engineering reasons and customer appeal. Today's automatic transmissions bring back the multiple disc clutch and bands running in oil. The automotive use of friction material in relation to oil lay almost dormant until about 1938. Two developments at that time brought pressure to bear on the friction material manufacturers which they were only able to cope with, at first, in an almost primative manner. Military needs suddenly became very pressing, the aeronautical industry, with its oil clutch supercharger drives, made heavy de­ mands for engineering information and for new products. There was no correct frictional data in regard to the use of friction material in oil. The then novel concept of spiral grooving and precision machin­ ing placed severe requirements on our industry. New materials were conceived, evaluated, and developed. Problems of manufacturing thin sections of friction material, bonding to steel cores, and meeting centrifugal strength requirements of as high as 12000 rpm were among the many others that made the early stages of pro­ duction hectic, to state the case mildly. To be in a position to meet the demand of the aircraft industry for de­ sign information dealing with such factors as, engagement characteristics and in­ stantaneous frictions, it was necessary to construct a dynamometer designed to test friction material in oil. This was the first known dynamometer to be con­ structed for oil friction exploration. Although this machine did not lend itself too well to the obtaining of data for other uses, it did educate us in the behavior of friction material in oil and enable us to obtain aircraft orders. On the heels of aircraft came the automotive industry with its requirements for oil friction data for automatic transmissions. It was by interpretation of data from hundreds of