Document zzDqL4J68OB5jmmkZrXjBaRB0

PLAINTIFF'S EXHIBIT FD-6J8 FRICTION AND WEPtR. OF PPfFER TYPE WET FRICTION {ELEMENTS * SCF-FORD-OOll 8002 i9fr0 PRODUCED BY FORD FRICTION AND WEAR OF PAPER TYPE WET FRICTION ELEMENTS A. E. Anderson Fold Motor Company, Scientific Research Staff ABSTRACT A simple model of the engagement process has been conceived for paper friction materials, consisting of squeeze film, squash film, and adhesive contact phases. In support of the model, laboratory test results are presented of paper clutch squeeze and squash film behavior in a nev laboratory test fixture. Also SEM photographs, profllometer data, and clutch inertia dynamometer friction and vear results are dis cussed in the context of the nev engagement model. 8002 1901 PRODUCED BY FORD 1 FRICTION AND VEAR OF PAPER TYPE VET FRICTION ELEMENTS INTRODUCTION Paper-type friction materials have been used in automatic transmissions for over 10 years and presently are specified for all OEM passenger car and light truck automatic transmission plates. However a plausible mechanism of the friction and wear process for these materials has not been reported. Most published research appears to have been directed towards measuring the effects of different fluids and test conditions on the frictional behavior of vet clutches. In these studies, complete automatic transmissions, constant velocity test machines, and clutch inertia dynamometers have been employed. Complete transmissions are used extensively in development and dura- . bility testing since the behavior of clutch elements and transmission fluids in actual service is the final determinant of acceptability. But automatic transmissions are ill-suited for clutch research investigations. For this reason investigators generally use production and experimental clutch elements and fluids in special laboratory test fixtures. For example, studies of single clutch plates and full clutch packs have been performed at 6teady-state sliding conditions over a vide range of rubbing speeds vith the. SAE No. 1 Friction Test FixtureTo obtain conditions more closely resembling actual clutch engagements, later versions of this machine and the SAE No. 2 Friction Text Fixture operate as inertia dyna- mometers for the transient testing of clutches('2' 3)'. Static and low-speed dynamic friction of small specimens of clutch materials and fluids has been studied at quasi-equilibrium conditions by several investigators using 6002 -1^02 * PRODUCED BY FORD 2 the Low Velocity Friction Apparatus (LVFA)^ and modified 4-ball testers^. While each of these test machines has undoubtedly provided valuable test results, there has been rather poor agreement of friction data among the different test machines, even for the same material combinations, the same test fluid, and nominally the same test conditions^. Despite thiB, each test machine has yielded results vhich vere reported to correlate with actual transmission operation. This apparent inconsistency may be resolved through examination of the vet dutch friction and vear processes. The purpose of this paper is to present a simple model of the engagement process for vet friction materials in general, and for dutches vith porous paper-type facing6 in particular. . ENGAGEMENT MODEL A simple concept of vet clutch engagement vas developed to aid in research and diagnostic investigations. This model employs three phases: 1. Squeeze Film Phase - vhere oil flows over and through the porous paper material, preventing physical contact of the friction surfaces, and providing torque through viscous shear of the fluid film; 2. Squash Film Riase - vhere intermittent rubbing contact of the dutch asperities produces some adhesive and hysteresis friction and "squashes" oil from within the porous paper material; ! 3. Adhesive Contact Phase - vhere hydrodynamic and elasto- l hydrodynamic effects are minimal and adhesive effects are dominant. 8002 1903 PRODUCED BY FORD 3 BQUEEiE FILM PHASE - In this phase the hydrodynamic forces predom inate such that the friction elements are separated fey a continuous film of oil. In the development of this model an analytical investigation of the squeeze film phase vas conducted. This vork has been published /> separately . Portions of the analysis describe squeeze films vitb porous annular platesand porous rectangular plates^. The annular plate model applies directly to an ungrooved clutch plate. A grooved clutch plate may be vieved as an array of rectangular plates in those instances uhere the pressure in the grooves-is negligible. The effect of sliding velocity on the squeeze film is only partially known. If an ungrooved porous flat plate is pressed against a similar non-porous plate, the effect of rotation is to reduce the oil film thickness ^ . But actual paper plates are usually grooved and their surfaces may be non parallel. No analytical solution of this case has been found as yet, but these factors can be expected to provide positive hydrodynamic action. Extensions of the squeeze film analysis for flat ungrooved porous plates has led to the simulation of a complete clutch application. Including the calculation of clutch torque, oil film thickness, and film temperature /g\ rise '. From this analysis it was found that only near the end of the squeeze film phase does the calculated friction reach levels normally associated with paper plates. The early portion provides an apparent time lag between pressure application and torque generation. In this early portion of the squeeze film, the oil between the plates flows predominantly over the clutch surfaces, rapidly closing the initial gap to about 600 microlnches. As the plate separation diminishes, thi6 flow rapidly eooE w* . * PRODUCED BY FORD 4 decreases and the resultant flow 'becomes largely Into the porous clutch material. The oil vithin the paper plates probably is slowly exchanged by this means. While the power density and energy absorbed by viscous 6hear in the squeeze film phase i6 relatively small for paper plates, this time-dependent phase is important to: 1. supply "fresh" oil into the porous paper facings; 2. assure uniform convergence of the clutch plates, ' thereby preventing cocking and uneven plate loading; 3. provide a smooth torque buildup for the initial engagement. SQUASH FILM PHASE - With a porous friction element, the squeeze film thickness does not asymptotically approach zero. Instead there is a finite closing velocity, 6lnce oil can flow into and through the porous material. The squash film phase begins and the squeeze film phase ends when mechanical contact is made. Initial contact is to the highest surface asperities of the resilient paper plate, producing elastic deflections which release oil from within the surrounding porous material. The oil flow provides localized cooling for the contact zone and helps generate hydro dynamic support around the asperity. This unique self-protection of asperity contacts appears to be essential for durability of paper-type clutches. With the passage of time the proportion of hydrodynamic support generally will decrease and the extent of mechanical action will increase. This mechanical action results in adhesive and hysteresis friction which complements the friction due to viscous shear. The phenomena of the squash film phase are both time and speed dependent and are not readily amenable either to mathematical analysis or controlled eOC2 1905 PRODUCED BY FORD experimental investigations. This is unfortunate, since the hulk of the engagement energy absorption appears to occur in this phase. If this phenomenon vene fully understood it vould be possible to optimize paper density, permeability, and resilience. However, it is probable that present paper materials are nearly at their optimal form, as the result of years of intensive evolutionary development. ADHESIVE FRICTION PHASE - When the sliding velocity is low and sufficient time has elapsed for the hydrodynamic squeeze and squash films to vanish, the adhesive friction predominates. According to the theory of adhesion this friction is sensitive to the paper compliance, flow pressure, surface geometries, and surface energy of adhesion. With an ATF present, the physical and chemical properties of the adsorbed and chemical reaction surface films must also be considered. These are both temperature and ' prior-history sensitive. With typical friction elements and transmission fluids, the unknown factors become 60 overwhelming that experimental studies must be used almost exclusively. ' Investigations of wet clutch friction U6ing the LVFA and modified four-ball testers have revealed phenomenological effects of changing fluids, additives and temperatures. These steady-state studies can help provide understanding of vet clutch engagement phenomena for the final phase of clutch engagement where adhesive effects predominate. Tests of this type show that when physical adsorption governs, the adhesive friction will decrease with increased sliding velocity. This is the characteristic of Type F transmission fluids. Dexron transmission fluids appear to depend on chem ical action to provide a positive friction dope with sliding velocity. 8002 1906 PRODUCED BY FORD 6 PATCR FRICTION MATERIALS This class of materials is made from celluloslc and often chrysotile asbestos fibers, using a liquid phenolic-type resin as a binder. Filler materials may be used, the most apparent of vhich is graphite. The tvo prime vendors of these materials appear to differ primarily in the finishing of the paper surface. One vendor obtains the final finish directly from a hot-pressing operation in vhich the paper material is bonded to the steel core plates. This results in a relatively smooth and flat surface, but vith some density and permeability variations over the plate. These variations presumably result from small irregularities in the paper stock. Furthermore, with this process the paper surface may have a lover permeability than the interior material. The second vendor grinds the surface of the paper after bonding to provide a more uniform structure, but vith substantially greater surface roughness and vaviness. Vith this process the paper surface may retain substantial amounts of the grinding debri6. Both types of paper materials have performed veil in automotive service. Typical profilometer* traces for nev samples of these materials are shovn in Figure 1. The differences between pressed and ground surfaces should be readily apparent from the SEM (Scanning Electron Microscope) photographs of Figures 2 and 3* A partially opened asbestos fiber bundle and some manu facturing debris can be seen in Figure 2b. The smoother sections of .* All profile and roughness measurements were made using a Brush-Clevite 150 system. Surface damage and attendant profile error during measurement was avoided by limiting the profilometer stylus pressure to 200 mg. P002 1967 PRODUCED BY FORD ]7 i A tbe corresponding profiledeter trace result from local flat areas such as appear la this photograph. The corresponding photograph of the ground sample (Pig. 3b) reveals tbe effects of grinding; Obscured fiber structure. Irregular plastic flew zones and substantially greater surface debris. These plastic flew zones provide 6ome of the smooth-curved portions of the corresponding profilometer trace. SQUEEZE FILM TESTS The complete clutch pack was Judged Impractical for direct squeeze film measurements. For this reason a small, constant force fixture was designed which could accept most passenger car clutch plates and permit precise transient measurements of the oil film thickness for constant force, non-rotating applications (Fig. 4). The apply force is set by adjusting air pressure to the Bellofram actuator with a precision regulator. A 6ingle clutch plate, located in a pool of oil, is supported by low rate springs (not 6bown) to provide a known initial oil film thickness. Individual clutch faces also may be tested by bonding clutch plates directly to the base. When the release lever Is tripped, the voltage signal from the displacement sensor triggers a storage oscilloscope which records the variation of displacement with time. The squeeze film fixture was tested with precision ground steel plates to compare experimental oil film thickness-time te6t results with analytical values. The test and analytical thickness-time curves were coincident down to 70 microinches. Below 70 microinches the results were somewhat erratic, presumably due to a randomly occurring, very slight cocking of the plate. Above this film thickness the test results were repeatable within an indicated 10 microinches. 8002 190B J PRODUCED BY FORD B New paper plates vere found to require up to 100 applications to achieve repeatable behavior. This vas believed to be the result of air removal from the Interior of the paper structure. When new plates vere vacuum Impregnated with the test oil, the oscilloscope traces vere Immediately repeatable, vithln 15 mlcrolnches, over the entire trace. Test results then matched veil with calculations from the squeeze film analysis for porous facings when the transient vibrations vere filtered (Fig. 5)* The initial contact occurred at roughly 200 mlcrolnches, apparently due to a slight cocking of the plate. 1Mb squeeze film apparatus has served as a means to measure conveniently and rapidly the average permeability of complete dutch facings and the elastic response of the paper. As might be suspected, both the squeeze film and elastic deflections differ between hot-pressed and ground paper plates of Bimilar paper structure (Figs. 6,7). These differences nearly vanished after both plates vere ground In an identical manner, cleaned, vacuum impregnated and retested (Figs. 6,9)* The horizontal lines on the right of the traces denote the equilibrium deflection for each load. FLUID EFFECTS - Continued squeeze film cycling on this fixture with an ATF using a high molecular weight Viscosity Index (VI) improver resulted In an apparent loss of paper permeability after about 1000 cycles. No such effect was noted when a similar fluid vlth a low molecular velght VI Improver vas used. Furthermore, the squeeze film behavior could be restored by pentane extraction of the fluid within the paper plate and re Impregnating with fresh oil. Some used plates which exhibited abnormally low friction levels in service similarly vere found to provide near-normal friction after a solvent extraction and re Impregnation. The squeeze film behavior of 8002 P909 PRODUCED BY FORD 9 these plates also recovered normal properties by this process. The extract from these used plates vas analyzed and found to be high in oxidized oil and acrylates, compared vith fresh factory-fill oil. Ibis suggests that one possible cause of clutch failure Is the selective accumulation of thickened oil onto and Into the paper plates, causing a thicker oil film, lover friction, and an extended, higher energy shift. Presumably, this added energy and resultant higher temperatures would precipitate the thermal degradation of the cellulosic fibers and their binder resin. ` PARTICIE EFFECTS - Independent of fluid effects, production samples of paper plates sometimes exhibited small variations of squeeze-squash behavior with cycle time. Small particles were found In the oil after cycling which looked like the debris pictured In the SEM photographs. Micro scopic examination of these cycled plates revealed the paper pore structure to be substantially cleared of debris, apparently from the alternating oil flow of the squeeze and 6quash film action. A lesser quantity of these particles were found upon cycling pressed paper plates than with ground plates. The possibility that the debris from ground paper clutch plates might Influence clutch engagement behavior was then Investigated. For this study a production paper clutch plate was tested which was known to exhibit a drop in dynamic friction after the first few engagements, then 6lowly recover over the next few hundred engagements. This paper was graphited, so lamellar vear particles from the graphite possibly could foliate on the paper surface during the squeeze film phase. From the model it vas hypothe sized that during breakin the combination of surface debris and the graphite vear particles might "clog" the pore6 of the paper surface, effectively 8082 1910 PRODUCED BY FORD 10 reducing its permeability and thereby providing a thicker oil film and a lower dynamic friction. With repeated use, the flake6 of graphite and other debris could slovly erode away, restoring the normal frictional characteristics. A clutch plate of this type was tested on the SAE No. 2 clutch test fixture and found to have low friction after 18 application cycles. This plate was then tested on the squeeze film fixture, cleaned, reimpregnated with fresh ATP, and retested. An apparent increase in permeability was noted after cleaning. Substantial amounts of debris, high in graphite flake content, were released' during the initial squeeze film tests, although little was visible following subsequent squeeze film tests 'which were performed after cleaning. Further clutch machine tests initially showed normal friction, but a small dip in friction occurred with added application cycles. This minor drop was presumed to have resulted from the generation of additional wear debris with the added testing. SAE HO. 2 CLUTCH FIXTURE TESTS Tests of single plates and complete clutch packs were performed on the SAE Ho. 2 machine to further evaluate .the engagement model. From tests on the squeeze film apparatus, it appeared that the wear of the paper material should be insignificant for a few tenths of a second, since most of the engagement energy in this period would be dissipated in viscous shear. To test this notion, ungrooved single plates were carefully measured, then tested with an apply time of 0.2 seconds. Measurements were taken periodically until equilibrium conditions were reached. This required about 400 applications. The samples wore rapidly for the first several applications, then gradually tapered off such that no additional wear was detectable after 200 applications. When the apply time was increased to 0.4 seconds, apparently the samples both wore and swelled. 800? 19J1 PRODUCED BY FORD After additional testing, surface examination of some samples shoved greater contact areas, hut vith an increased average paper thickness. Indirect measurements of the vear then had to he employed, such as profile mapping several areas of the clutch plate and noting changes in the peak-to-valley height distributions vith added testing. These calculations shoved an equilibrium vear rate for the 0.4 second apply time of 0.1 x 10'9 cu. in/ft .lb. The apply time vas extended further in increments until a complete engagement vas made at 2.2 seconds. The volume of paper material vorn, per unit of vork, vas found generally to increase and at an increasing rate as the engagement time increased. Ifce specific vear rate vas 1.6 x 10 cu.in./ft.lb. for the full engagement. Hovever, the vear sometimes vas confined to one area of one side of a plate. The cause of this had not been determined, but it appears that the paper material vears in a manner 6uch as to produce a constant contact pressure. With some localized svelling, the paper vear presumably also becomes bigily localized until the paper material becomes stabilized dimensionally. Despite the non-uniformity of vear, the vear rate per unit of vork done vas found to increase dramatically as the engagement time increased and the sliding t velocity decreased. After this vear testing, paper clutch plates of both the pressed type and the ground type may be quite similar in visual appearance, profilcoeter traces, and squeeze film behavior. SEM photographs of a ground , paper plate after 4000 clutch applications are shown in Figure 10. Note the similarity of this used, ground paper sample vith the nev, pressed paper sample of Figure 2. The relative absence of particulates vithin the 8002 m.2 f' PRODUCED BY FORD 12 paper structure should he apparent in Figure 10b. Representative profilometer traces of this and other clutch surfaces are ehown In Figure 11. Note the change of 6cale from Figure 1, particularly the horizontal scale. This vas done to provide a better visualization of surface flatness. The sample vlth 8000 cycles vas tested under more severe conditions, resulting in a slightly vavy surface. This seems to cause a slightly lower dynamic friction at the higher sliding velocities, presumably due to the more favorable hydrodynamic action of a vavy surface. Two glazed appearing plates were included in Figure 11 to illustrate the fact that "glazing" does not necessarily produce substantial friction changes. The sample with the low friction vas found to have near-normal friction after a solvent extraction of the retained oil and reimpregnation with fresh oil. Both samples exhibited a smeared, almost scaled surface appearance under the SEM, with periodic pores of a few thousandths diameter. These surface scales could be expected to greatly reduce the permeability of the surface layer and possibly produce a lover friction level in the squeeze and squash film phases. However, when examined under an optical microscope, it vas found that the "scales" open readily as the paper surface is loaded in com pression by a flat glass plate. Apparently the "scales" are relatively free to move, making them influence friction only in the relatively short squeeze film period. WEAR OF A CLUTCH PACK A pack of four new paper plates vas measured at . several locations on each face and tested for 2000 cycles on the SAE No. 2 clutch machine. Plates vere periodically removed during the test for wear measurements and squeeze film testing,then reinstalled in the same order and orientation. The wear of the paper plates vas uneven at first, being R002 1913 PRODUCED BY FORD *i 13 < "5 ;#* greatest toward the plate CD and at circumferential locations where the total pack thickness was greatest. Thus, in some plates the wear was not a maximum at the point of maximum plate thickness. These findings were expected, since the largest mechanical contact pressure should occur at the thickest section of the pack and he biased toward the OD due to mechanical deflections of the end plate. After about 500 cycles the CD bias diminished rapidly. The paper wear from 1000 to 2000 cycles was essentially uniform from CD to ID, but was cot yet uniform circumferentially. The wear of the facing closest to the apply piston was greatest, with wear generally decreasing for more remote positions (Fig. 12). This may be attributed to the effect of spline friction, since displacement of the clutch and separator plates is required to maintain torque in the squeeze and squash film phases. The plates nearest the piston then have a larger average apply pressure and a slightly longer apply time. Since the wear occurs primarily st the end of the engagement, these relatively small differences of load and time can pro duce significant differences of paper wear rate. The steel separator plates exhibited a similar trend (Figure 13). Steel plate wear was variant with angular position, also tending to reduce the total separator pack thickness variations. The.greatest wear on each plate occurred at the same angular location. Some minor scoring was observed in these tests which appeared to have resulted from abrasive inclusions in the asbestos. 4 II EFFECT OF FATTY ACIDS In an attempt to determine experimentally the j extent of mechanical contact, a clutch plate was cycled under closely * * 4 II \ % 9002 19H PRODUCED BY FORD 14 controlled conditions on the SAE No. 2 machine until 6teady state frictional behavior vas reached. Several successive torque-velocity traces vere recorded using a Type F fluid. At the end of one of these engagements a syringe vas used to inject 0.1$ oleic acid into the fluid chamber of the test machine. While this concentration does little to alter the fluid flov and viscous shear behavior, it is more than adequate to lover the adhesive forces greatly. The change of torque vas immediately apparent on the next clutch application and vas repeatable thereafter. The shaded area of Figure 14 should be indicative of the relative amount of mechanical contact during the clutch application, 6ince this is the result of a change primarily to the adhesive component of friction. SUMMARY AND CONCLUSIONS A simple model of the engagement process has bee* conceived for vet friction materials, especially those vith porous paper surfaces. The model consists of three phases: a time-dependent hydrodynamic squeeze film phase vhere no mechanical contact is made and torque i6 generated through viscous shear alone; a time and velocity dependent squash film phase vhere intermittent rubbing of asperities generates some adhesive frletlon, produces additional hydrodynamic action, and provides local coding; an adhesive contact phase vhere hydrodynamic effects are minimal andtoere physical and chemical reaction surface films largely control the friction. In support of the model, laboratory test results vere presented of .papea clutch squeeze/squash film behavior in a nev laboratory test fixture. AlsoSEK photographs, profilometer data, and clutch Inertia dynamometer friction and vear results vere discussed in the context of the nev engagement modd. 8602 1915 . : 1 PRODUCED BY FORD 15 * K Vblle no Incontrovertible conclusions may be reached at this time about the validity of the model, it has proven to be useful in under standing inconsistencies of test results from different test machines. Both the model and the squeeze film fixture have aided in diagnostic investigations. 8002 1916 9 PRODUCED BY FORD References: 1. 0. R. Stoith, V. J. Jandasek, S. R. Sprague, R. B. Springer,- "A Hew Concept of Measuring Frictional Characteristics", Preprint 363A . SAE Midyear Meeting, June 1961. 2. G. R. Smith, V. D. Ross, p. L Silbert, W. B. Herndon, "Putting Auto matic Transmission Clutch Friction Researchers on Speaking Terms", Preprint 670051, SAE Annual Meeting, January 1967. 3. E. D. Davidson, "A New Bench Test for Evaluating Clutch Plate Lubrication", Preprint 642A, SAE Annual Meeting, January 1963. 4. J. J. Rodgers and M. L. Haviland, "Friction of Transmission Clutch Jteterials as Affected by Fluids, Additives and Oxidation", Preprint 194A, SAE Midyear Meeting, June i960. .' 5. S. R. Sprague and R. G. Cunningham, "Chemical Additives Control Friction Characteristics of Lubricants", Industrial and Engineering Chemistry, Vol. 51, Ho. 9, September 1959, pages 1047-1050. 6. Hai Wu, "Squeeze Film Behavior for Porous Annular Disks", Jour, of Lubrication Technology, October 1970. 7. Hal Vu, "An Analysis of the Squeeze Film Between Porous Rectangular Plates", ASME Paper No. 71 Lub-2, presented at ASIE-ASME Joint Lubrication Conference, Pittsburgh, Pa., October 1971 8. Hai Vu, "The Squeeze Film Between Rotating Porous Annular Disks" Wear, Vol. 18 (1971) pages 461-470. . 9. Hai Vu, "An Analysis of the Engagement of Un-Grooved Wet Clutch Plates", Private Communication, M*y 26, 1971 10. C. E. Albertson and H. S. Okubo, "Influence of Lubricant Breakdown on Frictional Performance" Preprint 642C, SAE Annual Meeting, January 1963- PC02 1917 ; PRODUCED BY FORD Figure Captions: Figure 1 Profllometer traces of typical unused paper materials. Figure 2 (a and to) Figure 3 (a and to) Figure 4 SEM photographs of a typical pressed paper material. SEM photographs of a typical ground paper material. Schematic of squeeze film fixture. Figure 5 Comparison of squeeze film results. Figure 6 Squeeze film traces for a new pressed paper plate. Figure 7 Squeeze film traces for a new ground paper plate. Figure 8 Squeeze film traces for a ground pressed plate. Figure 9 Squeeze film traces for a reground paper plate. Figure 10 (a and to) Figure 11 SEM photographs of a typical ground paper plate after 4000 applications. ' Comparison of new and used paper surface profiles. Figure 12 Paper plate wear as a function of pack position. Figure 13 Separator plate wear as a function of pack position. Figure 14 Effect of a fatty acid on clutch torque. 8002 1918 PRODUCED BY FORD PRODUCED BY FORD T'~1 v* v u.wi.'j'vrvu'UJ'uftNW 8002 1920 PRODUCED BY FORD  ..//'VAv ^ 1-- 'Ma * ' ** r..i .?** r ` >,J . '-.7'A*s,' =? i*1 . io *i. ,.cvj IJ - -- v-y v ' *> \x v :imiM tXi>: 7 V -**. g : `HwrgK 8608 *921 PRODUCED BY FORD r 4 l l I iii i I ** -V **' r\ / / f ki.' . V. . i I j i I 4^ 4 M>% % to *. I I I I *008 1922 PRODUCED BY FORD * 8002 1923 PRODUCED BY FORD RELEASE LEVER RE6ULATED AIR PRESSURE BELL OPRAPI ACTUATOR DISPLACEMENT TRANSDUCER CLUTCH SAMPLE 0/L RESERVOIR 8008 1924- PRODUCED BY FORD 8062 1925 PRODUCED BY FORD - 2 5 0 0 OIL FILM THICKNESS-MICRO INCHES 250 500 750 1000 t im e cmn> /! ifiRSoffirff'1'0 soo* v*6 PRODUCED BY 75F TYPE F ATF GROUND PAPER PLATE t H SS3NM0IH1 mid 110 BftOE 1927 PRODUCED BY FORD 75F GROUND PRESSED PLATE TYPE F ATF V CO QUIUI /ni I Ul SS3NX01HJL Wild HO 8062 1^28 PRODUCED BY FORD 75F REGROUND PAPER PLATE TYPE F ATF >- in Quuj "Si III in in / ni i iu cc SS3NX0IH1 mid 110 8002 1929 PRODUCED BY FORD w NEW PRESSED 'f"fwV^v'v T HOitfM .001" NEW GROUND 8502 1930 PRODUCED BY FORD SAE #2 MACHINE to cvi 2000 ENG. CYCLES P= PISTON FACE R=REVERSE FACE Q CM PLATE 1 AT PISTON m to R PAPER WEAR 1 0 * IN. IO 12 34 CLUTCH PLATE POSITION 8002 1931 PRODUCED BY FORD SAE # 2 MACHINE 2 0 0 0 ENG. CYCLES P = PISTON FACE SEPARATOR PLATE POSITION OLlI 2 til CO cc < LlI LlI LU h* <(T trii 0. rsr to K) 0J ICE - .... ....... efe irfr rb o 'Nl gOI HV3M 3331S 9002 1932 PRODUCED BY FORD S A E WZ M ACHINE 6902 {933 PRODUCED BY FORD / Comments and Questions (1) ^ince the objective (one and only) of the study was to assess the capabilities of the testing procedures, the specific observations from individual tests are of interest, not the general conclusions on material character snd expected performance. Since we have no idea of the application, I think we would be taking quite a chance imx if we were to go so far into making predictions, and there is no reason that we should. * (2) for the reasons in point (1), the material in Appendix B and some of the material in Appendixes A and C are really the important parts, and therefore they must be in the text, rather than in the Appendix. (?) If point (?) is followed, then it would be easier to retain the figure order selected by combining Exptl. Proc. and Exptl. Results. Hence I tried to do this; I may not like it when I look it over a few days hence. (4) Ihe'YrerspegMve in *ig. 1 does not seem very good to me; in particular, [pay linee>/or\^ark^tfmpig8 w^tcfi\l beilev^ sjioul< be rad Lai do not look radial aV'drawn. 1 Bands on Fa6t tests; how obtained? nab clear to me. rxi+M. .oi i/^ Viijti In 'ig.j4p(-- Graphite area --.How obtained? Not, cc lear to me. the Bibliography references are so incomplete that I cannot loct most of them; I am Darticularly puzzled by reference 7, which apparently is addressed to me but, to the best of my knowledge I have never received, and reference 10, in which only the authors are given. Some of the otner reference descriptions are also incomplete, but not es bad. (Asisjita A^.Ku ARL. "Si ft (Z L TVr' Z-C *^ ^ r*;> ,'Cc (jl. \ n.j'-VcA'Nf"- ^r'- *1 ` < \ 8002 1934 PRODUCED BY FORD