400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 SAE TECHNICAL PAPER SERIES 1999-01-3612 Traction Behavior Under Extreme Conditions P.A. Willermet and D.G. McWatt Ford Motor Co. L.D. Wedeven Wedeven Associates International Fall Fuels and Lubricants Meeting and Exposition Toronto, Ontario, Canada October 25-28, 1999Downloaded from SAE International by Univ of California Berkeley, Friday, July 27, 2018The appearance of this ISSN code at the bottom of this page indicates SAE’s consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition,however, that the copier pay a $7.00 per article copy fee through the Copyright Clearance Center, Inc.Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sec-tions 107 or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such ascopying for general distribution, for advertising or promotional purposes, for creating new collective works,or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Sales and Satisfaction Department. Quantity reprint rates can be obtained from the Customer Sales and Satisfaction Department.To request permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior wr it t e n permission of the publisher. ISSN 0148-7191 Copyright 1999 Society of Automotive Engineers, Inc. Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is p ublished in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Group. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 3 00 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USAAll SAE papers, standards, and selected books are abstracted and indexed in theGlobal Mobility DatabaseDownloaded from SAE International by Univ of California Berkeley, Friday, July 27, 20181 1999-01-3612 Traction Behavior Under Extreme Conditions P.A. Willermet and D.G. McWatt Ford Motor Co. L.D. Wedeven Wedeven Associates Copyright © 1999 Society of Automotive Engineers, Inc. ABSTRACT Traction drive continuously variable transmissions (TCVTs) are under active investigation by a number ofOEMs and suppliers. Along with advances in control sys-tems and metallurgy, improved traction fluids will be keyto successful implementation of this technology. Tractionfluids will need to function over a wide range of tempera-tures and contact pressures. Contact pressures mayreach as high as 4 GPa, while temperatures may rangefrom about - 40 C to about 140 C. It is widely recognizedthat low temperature fluidity at start-up is an issue, sincefluids which give high traction coefficients and adequateviscosity under normal operating temperatures generallyexhibit high viscosity at low temperatures. However, fepublished data are available on traction behavior at tem-peratures below about 20 C and at contact pressuresabove about 2 GPa. Since published data are an inade-quate guide to traction behavior under extreme condi-tions, we have extended our traction measurements tocontact pressures as high as 3.7 GPa and to tempera-tures as low as - 20 C, using point contact tractionmachines. The results show that traction can drop dra-matically at temperatures below about 20 C, indicatingpotential operating problems at low temperatures. Thiseffect needs t