:,Vf ,'. '; i:-'.-\ ■■■■ *!':■■< : iibamry Inf». Servic PREPRINT: Subject to revision. Per­ mission to publish this paper, in full or in part, after its presentation and with credit to the author and the Society may be ob­ tained upon request. The Society is not re­ sponsible for statements or opinions advanced in pa­ pers or discussions at its Meetings. #716 ■rf SCo3of FRICTION MATERIALS FOR AUTOMATIC TRANSMISSIONS By J. F. JOHNSON E. P. STEFL Raybestos-Manhattan, Inc. Written discussion of this paper will be accepted at SAE Headquarters until April 16, 1956. Three double-spaced copies would be appreciated. For presentation at the SAE PASSENGER CAR BODY & MATERIALS MEETING Hotel Statler, Detroit, Michigan March 6-8, 1956 [SOCIETY of AUTOMOTIVE ENGINEERS, Inc., 29 West 39th Street, New York 18, N. Y. Downloaded from SAE International by North Carolina State Univ, Tuesday, September 18, 2018FRICTION MATERIALS FOR AUTOMATIC TRANSMISSIONS ****** * * * * ABSTRACT Friction materials for use in oil applications have been classi­ fied into five types by nature of their composition and charac­ teristics. These types are: Resilient, Woven, Semi-Metallic, Rigid Molded and Sintered Metallic. Specific application of the various types of friction material for band and plate applications in automatic transmissions is presented. The effect of grooving patterns on the frictional characteristics of various materials is discussed. Various use factors to be considered in the selection of a friction material for use in oil are outlined. These are: Frictional Value, Operating Temperatures, Engagement Characteristics, Durability, Conformability, Formability, Release Aids, Unit Pressures and Price. * ********* I - INTRODUCTION As part of a symposium on new developments related to automatic transmis­ sions the writers of this paper were placed in a quandry by the assignment. This condition was not because of lack of new developments but because a new development does not become truly such until its successful adoption and application in the field. Many new developments are in progress as the result of joint efforts between customers and ourselvesj however, most of these, as could be expected, are of a serai- confidential nature until final approval. In this presentation we have elected to avoid this development sphere and confine the data to a presentation of types of friction material from which new de­ velopments must arise with some thoughts on trends toward new developments. II - TYPES OF FRICTION MATERIALS By nature of composition and characteristics, friction materials for oil can be divided into five general classifications. These are; Resilient Woven Semi-Metallic Rigid Molded Full Sintered Metallic RESILIENT Resilience can be defined as the ability of a material to resume normal shape after removal of a deforming force. This sponginess makes for a slower Downloaded from SAE International by North Carolina State Univ, Tuesday, September 18, 2018_ 2 - build-up in applied pressures with a built-in dampening effect that tends to elimi­ nate chatter and makes for a smooth engagement„ After release of pressure this fam­ ily of materials spring back to their original shape. Principal ingredients of the resilient materials are binder, cork, cellulose and asbestos. The most popular re­ silient to date is a composite dual faced assembly comprised of alternately opposed rings of cork and cellulose. Resilient materials are low gravity, somewhat porous and have low tensile strength. They fall into a high range of friction compared to other types, this range is nominally ,07i> to .13, Advantages of the resilient types in addition to the high friction are the good engagement characteristics by virtue of their compressibility and their natural dampening characteristics which tend to prevent chatter. Still another virtue of major importance is that as a family they are lower in price than