400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2002-01-2820 USCAR Traction Test Methodology for Traction-CVT Fluids L. D. Wedeven, G. G. Wedeven and S. H. Kratz Wedeven Associates, Inc. T. E. King DaimlerChrysler Corporation J. L. Linden and F. Caracciolo General Motors Res earch and Development D. G. McWatt Ford Research Laboratory Powertrain & Fluid Systems Conference & Exhibition San Diego, California USA October 21-24, 2002Downloaded from SAE International by University of Michigan, Tuesday, July 31, 2018All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: [email protected]: 724-772-4028Tel: 724-772-4891 For multiple print copies contact: SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: Customer [email protected] ISSN 0148-7191Copyright © 2002 SAE International 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 pap er if it is publishe d in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send themanuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by University of Michigan, Tuesday, July 31, 20182002-01-2820 USCAR Traction Test Methodology for Traction-CVT Fluids L. D. Wedeven, G. G. Wedeven and S. H. Kratz Wedeven Associates, Inc. T. E. King DaimlerChrysler Corporation J. L. Linden and F. Caracciolo General Motors Research and Development D. G. McWatt Ford Research Laboratory Copyright © 2002 SAE International ABSTRACT A traction test machine, developed for evaluation of traction-CVT fluids for the automotive consortium, USCAR, provides precision traction measurements to stresses up to 4 GPa. The high stress machine, WAM hs, provides an elliptical contact between AISI 52100 steel roller and disc specimens. Machine stiffness and positioning technology offer precision control of linear slip, sideslip and spin. A USCAR traction test methodology includes entrainment velocities from 2 to 10 m/sec and temperatures from -20°C to 140°C. The purpose of the USCAR machine and test methodology is to encourage traction fluid development and to establish a common testing approach for fluid qualification. The machine utilizes custom software, which provides flexibility to conduct comprehensive traction fluid evaluations. The traction characterization of three reference fluids covering a matrix of 90 test conditions shows the sensitivity of traction coefficient to stress, temperature, surface speed, spin and fluid type. The database with the three reference fluids provides a benchmark for future fluid development. INTRODUCTION Continuously variable transmissions (CVTs) offer improved fuel economy and reduced emissions. The desi gn and performance of “traction” continuously variable transmissions are a direct function of the traction characteristics of the fluid media transmitting power between highly stressed contacting surfaces. While traction testing has been conducted for many years with disc machines and various types of roller or ball contact configurations, there is no commercially available test machine or recommended test procedure that covers the range of test conditions required for advanced automotive traction-CVT systems. This need, along