THE UNIVERSITY OF MICHIGAN COLLEGE OF ENGINEERING Department of Mechanical Engineering Final Report THE FLEXIBLE ENGINE E. T. Vincent ORA Project 05847 under contract with: U. S. ARMY DETROIT PROCUREMENT DISTRICT CONTRACT NO. DA-20-018-AMC-0729-T DETROIT, MICHIGAN administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR May 1964

TABLE OF CONTENTS Page LIST OF TABLES v LIST OF FIGURES vii ABSTRACT ix I. OBJECT 1 II. INTRODUCTION 3 III. DEFINITIONS5 IV. GENERAL 7 V. M-151 MODEL 1/4 TON 4x4 UTILITY TRUCK 9 VI. STANDARD VEHICLE SYSTEM PERFORMANCE 19 VII. FLEXIBLE VEHICLE SYSTEM 31 VIII. COMPARISON OF STANDARD AND FLEXIBLE SYSTEMS 35 IX. TRANSMISSION 49 X. FIVE-TON VEHICLE WITH COMPRESSION IGNITION ENGINE 51 XI. SYSTEM COMPARISON 68 XII. TRANSMISSION REQUIREMENTS FOR COMPRESSION-IGNITION ENGINE 73 XIII. DISADVANTAGES OF FLEXIBLE SYSTEM 77 XIV. FUTURE INVESTIGATIONS 79 XV. CONCLUSIONS 81 REFERENCES 83 iii

LIST OF TABLES Table Page I. Vehicle Resistance in Pounds for Various Surfaces 19 II. Ground Horsepower Requirements 20 III. Ground Horsepower Required With Five Percent Slip 20 IV. Brake Horsepower Required in the Different Gears 22 V. Road and Engine Speeds in the Different Gears 25 VI, Standard System Performance at Four Road Resistances 27 VII. Flexible Engine Performance 33 VIII. Standard System Requirements for Battlefield Day 37 IX. Flexible System Performance at Four Road Resistances 39 X. Flexible System Requirements for Battlefield Day 40 XI. Fuel Requirements for 48-Hour Battlefield Day for Standard and Flexible Systems for Increased Cross Country Time 44 XII. Fuel Requirements for Battlefield Day for Heavy Soil Resistance in Cross Country Operation 45 XIII. Ranges of Operation for Standard and Flexible Systems 47 XIV. GM6-71E Engine Performance 56 XV. Extended Performance at all Loads and Speeds of the GM6-71E Engine 57 XVI. Standard System Performance at Four Road Resistances for Five-Ton Vehicle 62 XVIIo Flexible System Performance at Four Road Resistances 66 XVIII. Minimum Fuel Flow Flexible Engine Requirements 67 v

LIST OF TABLES (Concluded) Table Page XIX. Standard System Battlefield Day Requirements for Five-Ton Vehicle 69 XX. Flexible System Battlefield Day Requirements for Five-Ton Vehicle 70 XXI. Comparison of Standard and Flexible Systems for FiveTon Vehicle 71 XXII. Comparison of Transmission System Requirements 74 XXIII. Power Available for Acceleration M-151 Vehicle 77 vi

LIST OF FIGURES Figure Page 1. M-151 engine performance test results at full load. 10 2. M-151 engine performance after 52-1/2 hours of endurance testing. 11 3. M-151 engine performance test results at part load. 12 4. M-151 vehicle rolling resistance on pavement. 13 5. Rolling resistance for various types of soils. 14 6. Brake horsepower vs. revolutions per minute relationship for engine. 15 7. Percent load vs. fuel flow relation. 16 8. Fuel flow vs. revolutions per minute at various percent loads. 17 9. Fuel flow vs. brake horsepower at different revolutions per minute. 18 10. M-151 combined vehicle and engine performance. 23 11. Fuel flow vs. miles per hour at four road resistances. 29 12. Flexible engine performance. 32 13. Fuel flow flexible system. 41 14. Road resistance of five-ton vehicle. 52 15. Percentage indicated horsepower vs. fuel flowo 53 16. Final brake horsepower and specific fuel consumption curves for engine. 54 17. Brake horsepower vs. fuel flow map for GM6-71E engine. 55 18. Combined vehicle and engine performance chart. 59 19. Flexible engine performance. 61 vii

ABSTRACT The report covers an analysis of an engine and transmission system in which the latter is capable of adjusting the ratio between vehicle and engine speed in such a manner that the fuel flow is always at the minimum possible quantity for the ground horsepower requirements of the vehicle at that timeo No new engine concepts are involved except that a wider usable speed range of the engine is required, the extension of range being necessary at the low-speed end of the scale but not at the top-speed end. The results of this analysis indicate that a 50% reduction in fuel flow is possible (alternatively, a corresponding increase in range of operation), if the required conditions can be fulfilled over the typical 48-hour Battlefield Day examined. This Battlefield Day involved operation at all vehicle speeds from 0-70 mph over all types of terrain. The above gain in economy applied equally to both spark-ignition and compression-ignition engines systems. The main penalty to be paid for this improved economy is reduced acceleration. However, a suitable gear set could be made available that would give the present acceleration and still achieve a 40-45% improvement in fuel economy for the conditions examined. ix

I. OBJECT The object of this investigation is to examine the widely varying conditions under which the internal combustion engine in a vehicle has to function, with a view to achieving maximum economy at all times under all conditions of vehicle performance. 1

II. INTRODUCTION The best overall combination of engine and transmission required to achieve this objective will be termed "flexible" since, to secure the desired results, it will be found that engine operation must occur over a much wider combination of speed and load range than that normally employed when coupled to existing types of transmission. To achieve the desired maximum in performance and economy, the transmission itself must also be capable of a wider range of operating conditions than is normally demanded. It must be admitted that neither the engine or transmission exists today that will completely achieve the desired results under all conditions of vehicle operation. This investigation is an examination of the conditions that would have to be met if such an economical system is to be obtained. When these necessary conditions are known, it will then be possible to see what can be done, if anything, to combine them into a practical working mechanism. 5

III. DEFINITIONS In order to have a common basis for study of the operation, the following definitions set forth what is to be understood as a flexible system. A. ENGINE The engine, be it of the spark-ignition or compression-ignition type, is assumed to be sufficiently flexible as regards speed of rotation, power output, etc., that it can at all times perform satisfactorily at its point of maximum fuel economy for the road conditions being imposed. B. TRANSMISSION The attached transmission will be of such'a type that it will, if necessary, be infinitely variable; that is, capable of accommodating any combination of vehicle and engine speed as necessary to achieve maximum fuel economy at all times. It is true that neither of these conditions represents practical available mechanisms at the present time. The results to be obtained will indicate, however, whether such a combination is of any value, if it could be achieved. Some idea of what is to be gained will then be available on which to base a judgment as to the value of achieving even part of the objective. In what follows it will therefore be assumed that any combination of engine power and speed is a possibility at any vehicle condition, permitting a comparison to be made with operation under present engine and transmission combinations. 5

IV. GENERAL The Army Tank-Automotive Center has great interest in both spark-ignition and compression ignition engines. The former is, in general, employed in engines of the lower horsepower ranges, while the latter is in the heavy vehicles involving 200 hp and up. The M-151, 1/4 ton 4x4 Utility Truck (the modern jeep) represents one of the smaller vehicles employed in large numbers. It is of recent design and thus represents one vehicle type consuming relatively large quantities of gasoline in total. This unit is to be employed as a typical example of the spark-ignition engine for this investigation. Fairly complete data on both vehicle and engine performance, in its presently designed condition, are available on which to base the comparison. The compression-ignition engine selected for the study was a General Motors 6-71 E Diesel engine of 200 hp net (approximately 2000 rpm) fitted to a hypothetical medium truck of 5-ton gross vehicle weight. This vehicle was employed since reasonably reliable data could be predicted for its road resistance etc., plus the fact that some engine performance data at various speeds and loads were also available. These two examples do not give anywhere near a complete coverage of the whole subject, but it is believed the results will indicate if there is any necessity to continue the analysis beyond this first analysis point. 7

V. M-151 MODEL 1/4 TON 4x4 UTILITY TRUCK As mentioned earlier, this unit represents a typical small vehicle fitted with a spark-ignition gasoline engine. All the data employed for this socalled standard or conventional system were obtained from material supplied by the Army Tank-Automotive Center on the standard "Transport Vehicle Engineering Data Sheets" plus engine performance test data recorded by the manufacturer on endurance runs. The engine performance curves are represented in Fig. 1, the full-load data; Fig. 2, full-load data after 52-1/2 hours of endurance running; and Fig. 3, the part-load performance of the engine. The rolling resistance of the vehicle on pavement at 2550 lb weight is recorded in Fig. 4; an effective rolling radius of 14.2 in. was employed. Utilizing the above data, Fig. 5 was first produced showing the vehicle resistance for off-the-road conditions for soils giving 1.5, 2.0, and 3.0 times pavement rolling resistance. The engine data at various percentage loads were then plotted on a base of rpm as in Fig. 6, from which a reasonable prediction of performance at speeds below 1000 rpm could be obtained. This was followed by Fig. 7 showing the percentage of BHP from Fig. 3 at each speed and the fuel flow in lb/hr. These curves were extrapolated to zero BHP to obtain the idle fuel flow. With the aid of the frictional horsepower from Fig. 1, these results were converted to, and then plotted on, an IHP basis as a check of the extrapolations. A satisfactory agreement was shown. To obtain a further correction on the fuel flows, these corrected data were replotted as in Fig. 8, showing fuel flow in lb/hr on a base of rpm for the various percentage loads. In this diagram the idle values from Fig. 7 were included to again mean out the extrapolation. This diagram then permitted the addition to Fig. 7 of the 500 rpm fuel flow line shown there. It is now possible to plot Fig. 9, showing fuel flow versus BHP at various speeds. By the use of these diagrams the combined vehicle performance can be obtained for all engine operating conditions. 9

70 NET OUTPUT --- Includes Air Cleaner, Generator, Fan and Exhaust System NET B. H. P. _~~60 0 GROSS B.H.P. 60 / / 130 50 1- / 20 / ^/^" -/ "-^^^^^ ^- 110_ 1.1 -// 100 a. / // TORQUE GROSS 90g 1.0 - 40 0 / TORQUE NET 80 1.0 ~ 40 80 r //N 70.0.9 -- / 0. 9 0.8 30 / FUEL CONSUMPTION F.H.P.g 20 d/ I I/ AFTER 52 1/4 HOURS,.7,, | // // ENDURANCE TESTING L 1 0.6 20 /V 10 c ^ ^> ^'^NET S. F. C 0.5 - 57 — 5 L 10 - - ~AUX. LOSSES, FAN, ETC. GROSS S.F.C. 500 1000 1500 2000 2500 3000 3500 4000 R. P. M. 10

BRAKE TORQUE 110 CORRECTED TORQUE t, 100 0L 90 OBSERVED TORQUE CY io 80 70 BRAKE HORSEPOWER 60 CORRECTED HORSEgo ~ POWER 50 40 30 20 1110 I r~ BRAKE SPECIFIC FUEL CONSUMPTION 05 1000 1800 2600 3400 4200 ENGINE SPEED, R. P.M. Fig. 2. M-i1i engine performance after 52-1/2 hours of endurance testing. 11

)I OBSERVED BRAKE TORQUE t 80 4- 7575%o FULL LOAD..,60 20 OBSERVED BRAKE HORSEPOWER L 40 75% FULL LOAD /-50%o FULL LOAD — 10 20 a 25% FULL LOAD 2 1.3 BRAKE SPECIFIC FUEL CONSUMPTION 7. m ~ 7525% FULL LOAD::).9 =3 0 - sJ^ ^-^ -50% FULL LOAD V) 7 — 75% FULL LOAD.3 1000 1800 2600 3400 4200 ENGINE SPEED, R. P.M. Fig. 3. M-151 engine performance test results at part load. 12

200 180/ 160/ 140LU. 0 120 (/) LJ I /,,,100 / ogO.Z 60 = 80 — 60 40 0 10 20 30 40 50 M. P. H. Fig. 4. M-151 vehicle rolling resistance on pavement. 13

240 220 3.0 2.0 1.5 PAVEMENT 200 180 160 140,) C, 120 C 100 80 60 AO 20 0 10 20 30 40 50 60 70 M. P. H. Fig. 5. Rolling resistance for various types of soils. 14

_~~~~60 IOO%100OA.W LOAD 5550- 45% LOAD 45 40 35- I / / 50% LOAD c 30252025% LOAD 15 10 5O0 1000 2000 3000 4000 R. P.M. Fig. 6. Brake horsepower vs. revolutions per minute relationship for engine. 15

40.0 202600 30.0- 2200 3800 ~I R.1 P.M.~1400 A^ 25.0 C " 1000 2600 i- 20.0 U15.0 10.0 -2 5.0 0 10 20 30 40 50 60 70 80 90 100 PERCENT B. H. P. Fig. 7. Percent load. vs. fuel flow relation.

40 35 100% B. H. P. 30 25 ~: / / 95% 20 | 1 / 50% 15 / 2 5% 10 -- 0 500 1000 1500 2000 2500 3000 3500 4000 Fig. 8. Fuel flow vs. revolutions per minute at various percent loads. 17

40.0 35.0 30.0 - =t 25.0 o,-20.0 co Li 15.0 _~-~ ~ ~ ---- " 500R.P.M. 4200 ~~~~10.0~-, 3400 3000 -R.P.M. 1400 " 2600 5.~ 1000 2200 500 1 1800 250 0 5 10 15 20 25 30 35 40 45 50 55 60 B. H. P. Fig. 9. Fuel flow vs. brake horsepower at different revolutions per minute.

VI. STANDARD VEHICLE SYSTEM PERFORMANCE It is proposed to determine first the operating conditions, fuel consumption, etc., of the M-151 as at present constituted. This has a fourcylinder liquid-cooled OHV engine of 3.875 in. diam by 3.0 in. stroke developing 61 BHP net approx. at 3600 rpm, fitting to a Selective-Synchro-Mesh transmission with four forward speeds and one reverse with ratios as follows: lst-5.712:1; 2nd-3.179:1; 3rd-1.674:1; 4th-1.0:1.0; Rev.-7.497:l. The rear axle had a gear ratio of 4.86:1, giving overall drive ratios, indicated by the symbol DRo, as follows: lst-27.72:1; 2nd-15.44:1; 3rd8.12:1; 4th —4.86:1; Rev. —36.4:1. With the aid of the appropriate diagrams, the data of Tables I-III can be calculated. The above ground-resistance data provide the material for the calculation of the horsepower to be applied at the wheels, as is shown in Table II. If a ground slip of 5% is assumed, then Table III gives the horsepower to be supplied to the wheels by the transmission. The horsepowers of Table III remain constant for each of the vehicle speeds and ground resistances irrespective of transmission and engine characteristics, but this power can-be supplied to the wheels in a variety of ways, depending upon the gear ratio employed. TABLE I VEHICLE RESISTANCE IN POUNDS FOR VARIOUS SURFACES Pavement Resistance, lb mph x 1.0 x.5 x 2.0 x 3.0 0 12.0 18.0 24.0 36.0 10 30.0 45.0 60.0 90.0 20 55.0 82.5 110.0 165.0 30 89.0 133.5 178.0 267.0 4o 135.0 202.5 270.0 405.0 50 200.0 300.0 400.0 6oo.o 60 265.0 397.5 530.0 795.0 70 340.0 510.0 680.0 1020.0 19

TABLE II GROUND HORSEPOWER REQUIREMENTS Ground Horsepower at Pavement Resistances mph mph 1.0 1.5 2.0 3.0 0 0 0 0 0 10 o.8 1.2 1.6 2.4 20 2.93 4.39 5.76 8.79 30 7.11 10.66 14.22 21.35 40 14.4 21.6 28.8 43.2 50 26.7 40.1 53.4 80.1 60 42.4 63.6 84.8 127.2 70 63.4 95.2 126.8 190.0 TABLE III GROUND HORSEPOWER REQUIRED WITH FIVE PERCENT SLIP Horsepower to be Supplied to Wheels, mph 5% Slip 1.0 1.5 2.0 3.0 0 0 0 0 0 10 o.84 1.26 1.68 2.51 20 3.o8 4.61 6.05 9.24 30 7.47 11.2 14.95 22.4 40 15.13 22.7 30.5 45.4 50 28.02 42.1 56.1 84.2 60 44.5 66.8 89.0 133.6 70 66.6 100.0 133.2 199.5 Due to the varying number of tooth contacts in the different gear trains, the efficiency of transmission, from the engine to the wheels, will vary. In order to arrive at the required engine horsepower, these efficiencies must be known or assumed. The values given below for transmission and rear axle respectively were employed in these calculations. Transmission Efficiency 1st gear 2nd gear 3rd gear 4th gear Rear axle 92% 94% 96% 98% 95% 20

Overall Transmission Efficiency Gear 1st 2nd 3rd 4th %o 87.3 89.3 91.2 93.1 By employing the above values, the data of Table III can be transposed into engine horsepower in the different gear ratios. These data are shown in Table IV. The corresponding rpm of the engine, with an effective rolling radius of 14.2 in. together with a 5% slip, is given by Eq. (1). rpm of engine = mph x 12 x DRo x 5280 irD x 60 x 0.95 = 12.46 x DRo x mph (1) where DRo = overall drive ratio from engine to rear wheels. It is thus possible to obtain the engine speed for each road speed when using the different gear ratios as shown by Table V. The horspower, engine speed, fuel flow/hr, vehicle speed in mph, and road resistance can now be plotted on one diagram as in Fig. 10, where in the left hand portion of the plot is shown a construction for engine rpm with 5% slip against vehicle speed in mph for any overall drive ratios from 2 to 35:1. Those ratios of particular interest, i.e., 1st, 2nd, 3rd, and 4th gears, are shown by the heavy lines drawn on the chart. To obtain a line for any other gear ratio, join the origin to the point corresponding to that ratio plotted on the left-hand vertical axis and along the 60.0 BHP line at the top of the chart. In this same plot are given the engine horsepower curves for the relative resistances of 1.0 to 3.0 times pavement resistance when the vehicle is in 1st gear, which has the assumed overall efficiency of 87.3%. Thus the relationship between road speed, engine speed, and engine horsepower is available for all gear ratios at an efficiency of 87.3%. In order to obtain the fuel flow at the different overall efficiencies corresponding to the other gears, the righ-hand portion of the graph contains four diagonal lines of relative efficiencies of 87.3, 89.3, 91.2, and 93.1%, representing the four gears. In the right-hand quadrant, fuel flow is 21

TABLE IV BRAKE HORSEPOWER REQUIRED IN THE DIFFERENT GEARS mph Engine Horsepower at Pavement Resistances mph Engine Horsepower at Pavement Resistances _.o.5. 2.0 3.0 1.0 1.5 2.0 3.0 First Gear Third Gear 0 0 0 0 0 0 0 0 0 0 10 0.96 1.44 1.93 2.87 10 0.92 1.38 1.84 2.75 20 3.53 5.28 6.93 10.58 20 3.38 5.05 6.64 10.14 30 8.56 12.84 17.12 25.7 30 8.19 12.28 16.4 24.6 40 17.3 26.0 34.9 52.0 40 16.58 24.9 33.4 49 8 50 32.1 48.2 64.2 96.4 50 30.7 46.2 61.5 92.4 60 51.0 76.5 102.0 153.0 60 48.8 7302 97.6 146.5 70 76.2 114.5 152.5 228.5 70 73.0 109.6 141.0 219.0 ro ro Second Gear Fourth Gear 0 0 0 0 0 0 0 0 0 0 10 0.94 1.41 1.88 2.81 10 0.90 1.35 1.81 2,70 20 3.45 5 16 6.77 10.35 20 3.31 4.95 6.5 9.9 30 8.36 12.53 16.75 25.1 30 8.02 12.02 16.1 24.1 40 16.94 25.4 34.1 50.8 40 16.25 24.4 32.7 48.7 50 31.4 47.1 62.8 94.3 50 30.1 45.2 60.2 90.4 60 49.8 74.8 99.6 149.5 6o 47.8 71.9 95.6 14 5. 70 74.5 112.0 149 0 223.2 70 71.5 107.5 143.0 214.0. _ _. =.. _..... 71 5_ 07.

TABLE V ROAD AND ENGINE SPEEDS IN THE DIFFERENT GEARS Engine Speeds in the Different Gears mph mph 1st 2nd 3rd 4th 0 0 0 0 0 5 1726 961 507 503 10 3455 1921 1014 605 15 5180 2880 1520 908 20 - 3840 2028 1211 30 -- 5760 3040 1817 40 - 4060 2422 50 -- - 5070 3025 60 - -- -- 3630 70 - - - 4240 plotted along the horizontal axis against the BHP for various constant engine speeds from 250 to 4200 rpm. The use of the chart can be illustrated by an example of two: (1) At a vehicle speed of 45 mph in 4th gear on pavement what hp, engine speed, and fuel flow occur? Follow the vertical line at 45 mph to its intersection with the pavement hp curve at "A" and read the hp in 1st gear on the vertical axis at "B,' result 24 hp; proceed to the right to the intersection with 1st gear efficiency line of 87.53% at T"C" then vertically downward to the 4th gear efficiency line of 93.1% at "D" and read power required on axis at "E," viz. 22.4 hp. Now proceed vertically from "A" to "G," the intersection with the 4th gear ratio line of 4.86:1, and read engine speed at 2730 rpm. Finally move horizontally from "D" to "F" at constant hp until the intersection with the fuel line at a speed of 2730 rpm is made and read the fuel flow from the horizontal scale at 14.2 lb/hr. Results: rpm = 2730; BHP = 22.4; fuel flow = 14.2 lb/hr. (2) For the same vehicle speed and using 3rd gear, obtain the performance on ground having three times the resistance of pavement. Start as before and obtain the intersection"H" with the load curve of 3 times pavement and find the horsepower of 48.5 in 1st gear, correct as before for efficiency of 3rd gear as shown by dotted lines and read 46.2 as the required horsepower. 25

The intersection "J" with the 3rd gear ratio line of 8.12:1 in the left-hand plot gives the engine speed of 4560 rpm. Projecting the horsepower of 46.2 to the fuel line for a speed of 4560 rpm gives an estimated fuel flow of 28.8 lb/hr. Results: rpm = 4560; hp = 46.2; fuel flow = 28.8 lb/hr. It will be observed that in this last example the diagram says that the results are outside the present rating of the engine since the speed is high and this final point "K" is not inside the fuel flow map. Thus the performance given here is an estimated one. Proceeding in the above manner, the engine performance lines for 1st, 2nd, 3rd, and 4th gears have been determined for operation on hard pavement and are drawn in on the fuel flow map of Fig. 10. Repeating this process for all four gear ratios at the four road resistances employed produced the data of Table VI and Fig. 11. 26

TABLE VI STANDARD SYSTEM PERFORMANCE AT FOUR ROAD RESISTANCES First Gear Second Gear Third Gear Fourth Gear mph ePM Fue Fuel Flow, mph BHP RPM Fuel Flow, BHP RPM Ful Flow, BHP RPM Fuel Flow, BHP RPM F Flow, Blb/hr lb/hr lb/hr lb/h (a) Pavement 5 0.3 1710 6.9 0.25 950 4.6 0.2 500 2.6 0.2 300 1.7 10 0.8 3420 10.7 0.75 1910 7.4 0.6 1000 4.9 0.6 600 3.2 15 1.9 5170 14.6 1.8 2860 10.2 1.7 1510 6.5 1.6 900 4.5 20 3.5 3830 11.9 3.4 2020 8.3 3.2 1210 5.8 25 5.9 4790 15.2 5.7 2520 10.0 5.5 1510 7.1 30 8.5 3030 11.8 8.3 1820 8.7 35 12.0 3540 13.3 11.6 2110 10.0 40 16.6 4050 15.7 16.2 2420 12.0 _o 45 23.0 4560 19.4 22.9 2730 14.2 50 30.0 3030 17.1 ~~~~~~~55 5~~~~38.8 3330 21.6 60 48.0 3630 27.4 (b) Secondary Roads-1.5 x Pavement 5 0.6 1710 7.0 0.35 950 4.7 0.5 500 2.7 0.4 300 1.7 10 1.4 3420 10.9 1.5 1900 7.6 1.4 1000 5.0 1.3 600 3.3 15 3.1 5170 14.9 2.9 2860 10.3 2.8 1500 6.8 2.7 900 4.8 20 5.0 3830 12.4 4.9 2020 8.7 4.7 1210 6.2 25 8.0 4790 15.7 7.8 2530 10.4 7.5 1510 7.4 30 11.8 3030 12.4 11.6 1820 9.3 5540 14.4 17.2 2120 14.4 11.2 40 24.7 4050 17.7 24.0 2420 13.7 45 33.0 4560 23.2 32.2 2730 17.0 50 43.0 3030 22.2 55 56.4 3330 31.4 60 -- 3630

TABLE VI (Concluded) First Gear Second Gear Third Gear Fourth Gear mph BHFP RPM Fuel Flow, BHP RPM Fuel l BFlow, BP RPM FuelFlow, lb/hr lb/hr lb/hr lb/hr (c) Cross Country-2.0 x Pavement 5 0.8 1710 7.1 0.70 950 4.8 0.7 500 2.75 o.6 300 1.8 10 2.0 3420 11.0 1.9 1900 7.7 1.9 1000 5.1 1.8 600 3.4 15 4.0 5170 15.0 3.8 2860 10.5 3.7 1500 6.9 3.5 900 5.0 20 6.8 3830 12.8 6.6 2020 8.9 6.4 1210 6.5 25 11.0 4790 16.5 10.8 2530 10.9 10.5 1510 7.9 30 16.2 3030 14.4 15.9 1820 10.3 35 23.0 3540 16.7 22.5 2120 12.5 40 33.3 4050 20.5 32.4 2420 16.4 45 46.2 4560 28.8 45.0 2730 22.5 oo 50 -- -- 59.6 3030 -- 55 -- - -- -- 3330 60 - - -- -- 3630 (d) Cross Country-3.0 x Pavement 5 1.1 1710 7.2 1.2 950 4.9 1.0 500 2.8 1.0 300 1.9 10 2.9 3420 11.2 2.9 1910 7.8 2.6 1000 5.2 2.7 600 3.5 15 5.6 5170 15.9 5.6 2860 10.8 5.5 1510 7.1 5.2 900 5.2 20 9.0 3830 13.2 9.8 2020 9.4 9.6 1210 7.0 25 17.0 4790 18.3 16.5 2520 12.4 16.1 1510 9.5 30 26.0 3030 16.0 25.3 1820 13.0 35 35.5 3540 19.8 35.5 2120 17.2 40 49.0 4050 28.4 49.0 2420

(a) 1st GEAR 1st GEAR (c) 2nd,, I 2nd, 30 3rd 30 3- I- rd, - II- I I 4th 4th 0 10 20 30 40 50 60 10 20 30 40 50 60 10 0 1 M.MP.H. M.P.H. (b) (d) 1st GEAR 1St GEAR 2id 2nd GEA 20/ /m -o 0 10 20 30 40 50 60 0 10 20 30 40 50 60 M. P. H. M. P. H. Fig. 11. Fuel flow vs. miles per hour at four road resistances.

VII. FLEXIBLE VEHICLE SYSTEM The present problem of obtaining the absolute minimum fuel flow for any given condition can be solved simultaneously on this same diagram. The fuel map records all possible engine operating conditions; thus the required horsepower conditions of Example (1), viz. 22.4 BHP to give 45 mph on pavement, can be obtained theoretically at any point along the 22.4 hp line where it crosses any speed line of the fuel map, provided that the transmission can permit the appropriate engine speed that corresponds to the fuel flow selected. It follows that the minimum fuel flow is at that speed where the horsepower line crosses the first fuel line at the slowest speed. The dotted line of Fig. 10 showing the envelope in the left side of the fuel map represents the minimum fuel flow over the total BHP range of the existing engine. It follows that the minimum possible fuel flow in Example (1) would be at point "11 where the engine operated at 22.4 BHP at 1400 rpm, the flow being 11.4 lb/hr in place of the 14.2 lb when in conventional 4th gear. Proceeding in this manner, the minimum fuel flow given in Table VII can be determined irrespective of the practicability of engine operation under such conditions. The results so obtained do represent the absolute minimum fuel consumption for the particular engine and vehicle combination being considered. The plot of minimum fuel flow, rpm, and horsepower is given in Fig. 12. The data presented in Fig. 12 show the BHP of the engine irrespective of the gear ratio employed; it is a plot of BHP versus fuel flow and speed of the engine at minimum consumption for each power. It is only when tied in with the left-hand portion of Fig. 10 that the engine horsepower is that for 1st gear. Figure 12 thus shows BHP, fuel flow, and revolutions of the engine under minimum economy conditions for each BHP. The points of the fuel-flow curve are seen to be relatively smooth. Near zero horsepower it was assumed that no matter what horsepower was required, the revolutions would not go below 250, hence the flat portion of the dotted rpm curve. It is also seen that at other speeds more than one horsepower can be obtained at minimum fuel flow for one given engine speed. This is due to the speed curve and enveloping minimum fuel-flow curve lying on top of one another for a range of powers at such points. The finally accepted rpm curve in Fig. 12 was the full-line outer envelope of the dotted curve of the plotted observation; this is on the conservative side since more speed and power capabilities exist along such a curve than the stepped dotted one. 31

40- 4000 I') 30- 3000 C) -5......... _ 20- 2000D) LU /L LL 10 1000 O- 0 0 10 20 30 40 50 60 ENGINE B.H.P Fig. 12. Flexible engine performance.

TABLE VII FLEXIBLE ENGINE PERFORMANCE rpm BHP Fuel Flow, rpm BHP b/hr _lb/hr 250 1.0 1.6 250 2.0 1.8 250 3.0 2.4 350 4.0 3.2 500 5.0 3.6 500 6.0 4.2 750 8.0 5.5 800 10.0 6.4 1350 15.0 8.5 1400 20.0 10.5 1500 25.0 12.5 2200 30.0 14.7 2200 35.0 16.9 2600 40.0 19.3 2600 45.0 22.2 2900 50.0 25.7 3100 55.0 30.3 3 600 6.0 36.5 The curves of Fig. 12 assume that the transmission is of such an infinitely variable variety that the engine speed demanded for minimum fuel for any road speed and horsepower combination can be met at all times. This condition is necessary if the proposed scheme is to be employed. For example, 40 mph on pavement requires 17.4 hp at 87.53% transmission efficiency from the engine to provide the required traction; the transmission must then adjust itself to give an engine speed of 1440 rpm with a fuel flow of 10 lb/hr — the minimum fuel for 17.4 hp from the engine at any operating speed. This means an overall drive ratio of 2.89:1 is required with a 5% wheel slip. At the 25 mph and 6 BHP combination, a fuel flow of 4.3 lb/hr can be obtained if an engine speed of 630 rpm can be achieved resulting in an overall drive ratio of 2.05. Assuming for. the time being that such difficult conditions can be met, it is now possible to examine what gains in economy can be made. Would the development of such a transmission be justified? 33

VIII. COMPARISON OF STANDARD AND FLEXIBLE SYSTEMS In order to obtain a standard of comparison between the two systems, some typical operating schedule must be employed. In evaluating this problem the following schedule of operation was employed in all cases. A. OPERATING SCHEDULE The 48-hour Battlefield Day is to consist of the following: Fraction Road Surface Operation Vehicle Resistance 1/3 Hard Surface Pavement Resistance Curve Provided by ATAC 1/3 Secondary Road 1.5 x Pavement Resistance Curve Provided by ATAC 1/3 Cross Country 2.0 x Pavement Resistance Curve Provided by ATAC Speed Schedule mph Operating Time Percent Hour Idle 10 4.8 0-10 21 10.08 10-20 37 17.76 20-30 21 10.08 30-40 10 4.80 50-60 1 0.48 Total Hours 48.00 In addition to the time schedule, the question of the gear ratio to be employed is involved when establishing the performance of the standard engine and transmission. It will be assumed that the engine will be operated on the gears given in the table below at all times. 35

mph Road Gear 0-10 Pavement 2nd 0-10 Secondary- 2nd 0-10 Cross Country 1st 10-20 Pavement 3rd 10-20 Secondary 3rd 10-20 Cross Country 2nd 20-60 Pavement 4th 20-60 Secondary 4th 20-30 Cross Country 3rd 30-60 Cross Country 4th This schedule employs first gear as a starting aid only: this would be true, probably, except for steep hills. B. STANDARD SYSTEM FUEL REQUIREMENTS During the above-defined 48-hour Battlefield Day, the standard engine and transmission will require fuel flows as given in Table VIII (based upon the road surface) and the time schedule set out above. In this connection, the 50-60 mph group for cross country operation seems to be impossible to achieve, first because of the power requirements reaching or exceeding the limits of the engine, second because over rough ground such speeds would produce excessive bouncing, requiring all personnel and equipment to be adequately belted down. (And even then the motion could be tolerated only for short periods.) There is possibly some cross)country terrain over which high speed could be achieved, but it is believed to be a rather exceptional circumstance. However, for comparative purposes, the highest possible speeds are included in the tables. If the percentages of times on various types of roads are changed to 25% pavement, 355 secondary roads, and 40% cross country, then the fuel requirement becomes: Total fuel for 48-hour BFD with above distribution = 372.9 lb of roads From the data of Table VIII any desired combination of road speeds, etc., can be employed and the total fuel requirements determined for the standard vehicle. 56

TABLE VIII STANDARD SYSTEM REQUIREMENTS FOR BATTLEFIELD DAY Fuel Flow Surface mph Hours Gear rpm lb/hr Total, lb Idle 1.6 - 500 2.6 4.16 0-10 3.36 2nd 500-1910 4.2 17.5 10-20 5.92 3rd 1000-2020 6.6 39.1 Hard Pavement Hard Pavement 20-30 3.36 4th 1210-1820 7.3 24.5 30-40 1.6 4th 1820-2420 10.3 16.5 50-60 0.16 4th 3030-3630 21.3 3.4 Total Hours = 16 Total Fuel Flow = 106.16 Idle 1.6 - 500 2,6 4.16 0-10 3.36 2nd 500-1910 4.5 15.1 Secondary 10-20 5.92 3rd 1000-2020 6.8 40.2 Roads 20-30 3.36 4th 1210-1820 7.6 25.5 30-40 1.6 4th 1820-2420 11.4 18.3 50-56 0.16 4th 3030-3400 3400 4.0 Total Hours = 16 Total Fuel Flow = 107.26 Idle 1.6 -- 500 2.6 4.16 0-10 3.36 1st 500-3420 6.8 23.9 Cross Country 10-20 5.92 2nd 1910-3830 10.5 62.2 Roads 20-30 3.36 3rd 2020-3030 11.2 37.6 30-40 1.60 4th 1820-2420 12.8 20.5 40-45 oo16 4th 2420-2730 19-7 3.2 Total Hours = 16 Total Fuel Flow = 151.56 Total fuel for 48-hr BFD including pavement, secondary roads, and cross country with standand engine and transmission = 363.98 lb 37

C. FLEXIBLE SYSTEM Figure 10 is also employed to determine the absolute minimum fuel flow for any combination of traction resistances. It should be remembered that there is now only one engine speed possible —that giving minimum fuel flowfor any given horsepower output as shown by Table VII and Fig. 12. It follows that Fig. 12 can be employed with greater ease than Fig. 10. The engine horsepower will depend upon the efficiency of the imaginary variable-ratio transmission. Since nothing is yet known about how the variability is to be obtained, assumptions must be made. Variability instinctively indicates more complexity, and complexity generally indicates greater losses. It follows that some loss in efficiency of transmission is to be expected. It will be assumed that this special duty gearbox will have an efficiency equal to that of the standard one when in 1st gear, viz. 87.3o. It follows that the engine horsepower requirements are those given by the left-hand portion of Fig. 10. Using this efficiency the horsepower values of Fig. 10 for any ground surface enables the engine speed, gear ratio, and fuel flow required for minimum fuel flow to be obtained, since, Overall gear ratio rpm (engine) (2) (with 5% slip) 12.46 x mph Proceeding in this manner, Table IX is constructed. From the data of Table IX Fig. 13 has been plotted and a comparison can now be made with the results shown for the standard engine and transmission of Table VI. The results obtained from Table IX for the same schedule employed for the standard system are given in Table X. D. COMPARISON OF FUEL REQUIREMENTS Comparing the Battlefield Day with standard and flexible systems, the results show a fuel requirement of 364 lb for the former and 193 for the latter-almost a 2:1 reduction in favor of the flexible assembly. To obtain such a gain by other means (supercharging, compression ratio, fuel rating, etc.) is not to be thought of, due to the involvement of some difficult factors which enter such engine developments. To achieve the indicated results a new type of transmission may be required, a development of no mean undertaking, if the results aimed for were to be in complete adherence to the principles employed in the above calculations. It would be possible to sacrifice quite a percentage of the unlimited flexibility assumed, and still come up with a fuel reduction of considerable magnitude compared with that to be obtained by other means. 58

TABLE IX FLEXIBLE SYSTEM PERFORMANCE AT FOUR ROAD RESISTANCES Overall OveiaZ Fuel Flow, OveralFuel Flow, Overall MPH BHP RPM Ib/hr Drive Ratio MPH BHP RPM Ib/hr Drive Ratio lb/hrRequired lhrRequired (a) Pavement Idle - 250 1.6 -- 20.0 5.6 450 5.1 1.805 2.0 0.1 250 1.6 10.4 25.0 6.1 640 6.1 2.03 4.0 0.2 250 1.6 5.2 50.0 9.0 840 9.0 2.25 6.0 0.4 250 1.6 5.5 55.0 12.5 1090 12.5 2.50 8.o0 0.6 250 1.6 2.5 40.0 17.4 1450 17.4 2.87 10.0 0.8 250 1.6 2.01 45.0 24.0 1850 24.0 5.29 12.0 1.2 260 1.7 1.74 50.0 52.1 2500 52.1 5.69 14.0 1.7 500 2.0 1.72 55.0 41.5 2670 41.5 5.90 16.0 2.2 550 2.5 1.755 60.0 51.5 2960 51.5 5.96 ^1 ~ 18.0 2.9 400 2.7 1.782 (b) Secondary Roads-1.5 x Pavement (c) Cross Country —2.O x Pavement Idle - 250 1.6 -- Idle - 250 1.6 2.5 0.5 250 1.6 8.02 2.5 0.55 250 1.6 8.02 5.0 0.62 250 1.6 4.01 5.0 0.80 250 1.6 4.01 7.5 1.1 270 1.7 2.89 7.5 1.40 280 1.8 2.99 10.0 1.6 500 2.0 2.41 10.0 2.1 540 2.2 2.75 12.5 2.5 550 2.5 2.245 12.5 2.9 400 2.7 2.565 15.0 5.1 410 2.8 2.19 15.0 4.0 470 5.2 2.512 17.5 4.1 480 5.5 2.20 17.5 5.5 580 4.0 2.6 20.0 5.5 570 4.0 2.29 20.0 7.0 700 4.8 2.81 25.0 8.5 790 5.5 2.55 25.0 11.5 1000 6.9 5.2 50.0 12.5 1090 7.5 2.91 50.0 17.0 1400 9.4 5.74 55.0 18.4 1500 9.9 5.45 55.0 24.1 1860 12.1 4.26 40.0 25.8 1960 12.8 5.95 40.0 34.6 2410 16.7 4.85 45.0 54.5 2410 16.6 4.29 45.0 48.5 2840 24.4 5.06 50.0 45.9 2770 22.8 4.44 55.0 60.1 5670 59.0 5.55 6o.O

TABLE X FLEXIBLE SYSTEM REQUIREMENTS FOR BATTLEFIELD DAY ^j-Gear pFuel Flow Gear Surface mph Hours Ratio rpm lb/hr Total, lb Idle 1.6 - 250 1.6 2.56 0-10 3.36 2.0-10.0 250 1.6 5.37 10-20 5.92 2.0- 1.7 250- 450 2.3 13.64 Hard Paveme20-30 3.36 1.8- 2.2 450- 840 4.4 14.8 30-40 1.6 2.2- 2.9 840-1430 7.6 12.16 50-60 0.16 3.7- 4.0 2300-2960 20.8 3.33 Total Hours = 16 Total Fuel Flow = 51.9 Idle 1.6 -- 250 1.6 2.56 0-10 3.36 10.0-2.4 250- 300 1.7 5.72 Secondary 10-20 5.92 2.4-2.3 300- 570 2.9 17.2 Roads 20-30 3.36 2.3-2.9 570-1090 5.7 19.2 30-40 1.6 2.9-3.9 1090-1960 10.1 16.2 50-55 0.16 4.4-5.4 2770-3670 30.6 4.9 Total Hours = 16 Total Fuel Flow = 65.8 Idle 1.6 -- 250 1.6 256 0-10 3.36 10.0-2.7 250- 340 1.8 5.72 Cross Country 10-20 5.92 2.7-2.8 340- 700 3.4 20.2 Roads 20-30 3.36 2.8-3.7 700-1400 7.0 23.5 30-40 1.6 3.7-4.8 1400-2410 12.7 20.3 40-45 0.16 4.8-5.0 2410-2830 20.6 3.3 Total Hours = 16 Total Fuel Flow =75.6 Total fuel for 48-hr BFD including pavement, secondary roads, and cross country with flexible engine and transmission 195.5 lb 40

-220 / 200 / I / co -180 B. H. P. 3 x PAVEMENT " 2x " / / ".5 -- / /x 1. x / 160' / I / / 120 / / / / 90 / / / 100 / / 80 / / 80 I 70 / 60/ / 260-/ / / 0- / 1.0 x 2 /4 / /0 410 0 10 20 30 40 50 60 70 M. P. H.

In comparing these sets of results it must be kept in mind that the standard system has a higher transmission efficiency in all gear ratios, other than 1st, compared to that employed for the flexible assembly. The manner in which this affects the results can be seen when the engine load becomes great, such as 50-56 mph on secondary roads and 40-45 mph cross country. In these cases, it is seen that the fuel flow for the flexible engine exceeds that of the standard system. This is due to the BHP required for the flexible engine being some 4-5 hp greater than the standard, resulting from the reduced transmission efficiency. At these conditions the engine performance is entering the zone of fuel enrichment for maximum power, thus fuel consumption suffers a rapid increase for relatively small power increase. (This can be seen by the shape of the fuel curves from 45-60 BHP for both standard and flexible engines.) It should also be pointed out that the 2:1 reduction of fuel is not achieved by some large gain at a particular local point. It is almost equally distributed over all speeds and types of terrain surfaces investigated in about the same proportion. Looking at this performance comparison on a miles per gallon (mpg) basis at a constant speed of 35 mph the following data emerge:' Standard Vehicle Fuel Tank Capacity = 102 lb Assumed Usable Capacity = 90 lb Cruising Speed = 35 mph Fuel Flow at 35 mph = 10.3 lb/hr (on pavement) Assume that one tenth of travel time is with engine idling at stop lights, or other causes then: Fuel/hr of Travel = 0.9 x 10.3+0.1 x 1.6 = 9.43 lb/hr Time to Consume 90 lb of Fuel = 90/9.43 = 9.54 hr Time Actually Travelling at 35 mph = 0.9 x 9.54 = 8.58 hr 42

Distance Travelled = 35 x 8.58 = 300 miles Fuel Mileage (gasoline at 6.3 lb/gal) = 300 x 6.3/90.0 = 21.0 mpg Fuel for 300 Miles = 14.30 gal Vehicle With Flexible Power Train The available tank capacity will be kept constant at 90 lb, as well as the cruising speed of 35 mph. Then: Fuel Flow with Flexible Engine = 7.6 lb/hr (on pavement) Fuel per Hour of Travel = 0.9 x 7.6+0.1 x 1.6 = 6.84+0.16 = 7.00 lb/hr Time to Consume 90 lb = 90/7 = 12.9 hr Time Travelling at 355 mph = 0.9 x 12.9 = 11.61 hr Distance Travelled = 35 x 11.61 = 407 miles Fuel Mileage = 407 x 6.3/90 = 28.5 mpg Fuel for 300 Miles = 10.5 gal In the above results no allowance for the excess fuel used by the accelerating pump in the carburetor, for the energy required for acceleration, for that lost by braking, or for the fact that on normal roads there will be some up and down gradients; the calculations assumed a perfectly constant speed on a level road. The effects of the above factors, under good driving methods, could change the ideal mpg from 21.0 to about 18.0 mpg and under 43

adverse conditions possibly as low as 17 mpg, with the standard system and 25-26 mpg for the flexible system. This compares with the roughly 1:2 ratio when the whole BFD schedule is employed. If the distribution of time over the various types of terrain is changed from that assumed to that shown below, then the comparative fuel figures for the two cases become as shown in Table XI. Road Surface Vehicle Resistance 25% Pavement Hard Surface 35% Secondary 1.5 x Hard Surface 40% Cross Country 2.0 x Hard Surface The results for this case indicate little change in the relative saving to be made; 170 lb of fuel for first case, and 174 lb for the second. TABLE XI FUEL REQUIREMENTS FOR 48-HOUR BATTLEFiIELD DAY FOR STANDARD AND FLEXIBLE SYSTEMS FOR INCREASED CROSS COUNTRY TIME Fuel Flow, Total, Surface Hours lb lb Ib Ib Standard Engine and Transmission Pavement 12 78.8 Secondary 16.8 112.6 Cross Country 19.2 181.7 373.1 Flexible Engine and Variable Transmission Pavement 12 38.9 Secondary 16.8 69.1 Cross Country 19.2 90.8 198.8 44

If a third case is examined (terrain in which the cross country resistance amounted to three times that of pavement), then the data of Table XII are obtained. TABLE XII FUEL REQUIREMENTS FOR BATTLEFIELD DAY FOR HEAVY SOIL RESISTANCE IN CROSS COUNTRY OPERATION Gear and Fuel Flow Surface mph Hours Gear rpm Ib/hr Total, Ratio lb Standard Engine and Transmission Idle 1.6 - 500 2.6 4.16 0-10 3.36 1st 250-3430 6.8 22.8 Cross Country 10-20 5.92 2nd 1900-3830 10.8 63.8 3 x Pavement 20-30 3.36 3rd 2020-3030 12.5 42.0 30-40 1.6 4th 1820-2420 18.5 29.6 40- 0.16 4th 2420- 26.4 4.2 Total Hours = 16 Total Fuel Flow = 166.56 Flexible Engine and Variable Transmission Idle 1.6 - 250 1.6 2.56 0-10 3.36 10.0 -2.7 250- 370 1.8 6.06 Cross Country 10-20 5.92 2.97-3.8 370- 950 4.4 26.1 3 x Pavement 20-30 3.36 3.8 -4.4 950-1650 9.8 32.9 30-40 1.6 4.4 -6.02 1650-3000 19.6 31.3 40- 0.16 7.4 - 3700- 36.5 5.84 Total Hours = 16 Total Fuel Flow = 104.76 The comparison between the two types of power systems (for the duty assumed in this case) thus becomes: Standard System Fuel = 379 lb/48-hr BFD Flexible System Fuel = 222 lb/48-hr BFD This again emphasis that the ratio between the two systems varies but little over the operating ranges of values examined. 45

The above data can be converted to a basis of distance travelled for a given fuel supply. It will be assumed that the fuel supply for the standard vehicle will be available to both power train systems (573.1 lb of fuel for 48 hr) that the schedule of operations is that already outlined for the calculation of Table XI, viz., 25% pavement, 35% secondary roads, and 40% cross country; then we have Table XIII. It follows that the distance travelled for the same fuel supply is almost doubled when using the flexible combination. One other point of interest here is that the bulk of the fuel is burnt in the 15-25 mph range of vehicle velocities. It will be observed that the sum of the fuel used for the 10-20 and 20-30 mph condition exceeds that for all other speeds put together. This of course is partly a time factor, there are 9.28 hr of operation at these speeds compared with 6.72 of the rest speed of the schedule. The high-speed operation consumes a negligible fuel quantity for the schedule assumed. 46

TABLE XIII RANGES OF OPERATION FOR STANDARD AND FLEXIBLE SYSTEMS (Hours of operation = 48.0) Total Average, Time, Distance, - Tot Surface Fuel mph hr miles Miles lb Standard Vehicle System 0 1.2 0 5 2.52 12.60 15 4.44 66.50 Hard Pavement 5. 65.00 25 2.52 63.00 55 1.2 42.00 55 0.12 6.60 190.70 78.8 0 1.68 0 5 3.53 17.65 Secondary 15 6.21 93.15 Roads 25 3.53 88.25 55 1.68 58.80 553 0.17 9.02 266.87 112.6 0 1.92 0 5 4.05 20.15 Cross Country 15 7.108 106.22 Roads 25 4.03 100.75 35 1.92 67.20 42 0.192 8.16 302.88 181.7 Total distance for 373.1 lb of fuel (= 59.2 gal) in 48 hr 760.45 Flexible Vehicle System 0 1.2 0 5 2.52 12.60 15 4.44 66.50 Hard Pavement 5. 65.o 25 2.52 63.00 35 1.2 42.00 55 0.12 6.60 190.72 38.9 0 1.68 0 5 3.53 17.65 Secondary 15 6.21 93.15 Roads 25 3.53 88.25 35 1.68 58.80 52.5 0.17 8.93 266.78 69.1 0 1.92 0 5 4.03 20.15 Cross Country 15 7.108 106.62 Roads 25 4.03 100.75 35 1.92 67.20 42.5 0.192 8.16 302.88 90.8 Total distance for 373.1 lb of fuel (= 59.2 gal) in 48 hr 1430 47

IX. TRANSMISSION The object of this analysis was to examine economy as to fuel quantities, which has been carried out. However, in the process sufficient data regarding the overall drive reduction ratio have been accumulated to allow some observations regarding the transmission to be made. Looking at the data of Tables IX and X it is seen that an overall drive ratio of the flexible system for the various types of terrain considered varies from a maximum of 8.02:1 to a low of 2.5:1 for cross country operation; from 8.02 to 2.20:1 for secondary roads; and from 10.4 to 1.72:1 for pavement. Of the above, the 10.4:1 is for pavement at a vehicle speed of only 2 mph while at 4 mph the DRo required has already dropped to 5.2:1. The 8.02:1 for the other two cases also applies to about the same vehicle speed. If this lowspeed e-nd of the operation is allowed to be off the minimum fuel-flow curve, it is seen that a variable ratio of from 2.0 to about 5.0:1 would achieve the great majority of the gains already outlined, since the fuel for such low speed operation is small anyway. The overall drive ratio includes the rear axle as well as the transmission ratio. The axle ratios usually employed for this type of vehicle are 3.5 up to 5.0 approx. It follows that to achieve a DRo = 2.0, this could be made up of a 2:1 rear axle and a 1:1 transmission, while the other required ratios could be achieved by a variable unit capable of gradual variation through the range of 1:1 to 2.5:1. The effect of a 2.0:1 rear axle would be that of increased torque with the need for increased load carrying gears etc., but due to the low speeds of rotation under these conditions the size increase could be minor. Going one step further, a variable DRo of 2.0 to 3.0, in place of 2.0 to 5.0, would enable all but the 2-3 mph and speeds in excess of 45.0 mph on pavement, 33 mph on secondary roads and 25 mph cross country to be achieved at minimum consumption. It is believed that the exclusion of the above speed ranges would be satisfactory in the great majority of cases under normal operating schedules. Performance at these excluded ranges could still be possible by some special provisions involving some small increase in fuel flow, with the result that the overall conditions would still result in a very satisfactory fuel saving. There would still be the problem of a satisfactory start from rest on soft ground or a steep hill. This could be handled by the equivalent of a 1st gear giving high engine speed for the initial motion from rest. Examination of the required power curve for 1st gear in Fig. 10 reveals how little 49

horsepower is demanded when in this gear ratio, but, of course, there is considerable torque applied to the wheels due to the reduction ration employed. If the idea of a variable transmission is discarded for the moment and the gear ratios of Table IX examined, it is seen that the 2:1 axle plus a three speed transmission of, say, 2.5, 1.50, and 1:1 would provide overall drive ratios of 5, 3, and 2:1, which would bracket the group desired for economy operation in a fairly satisfactory manner. It will be observed that a 5:1 ratio exists compared with the 4.86:1 of the present 4th gear; thus highway travel would be little if any different, while cross country travel on relatively level terrain would be almost identical except for the improved fuel consumption. The great difficulty would arise in the cases of high gradients on the roads or cross country. The suggested 1st gear ratio for starting would take care of the very steep grades but intermediate ones could only be negotiated at slow speeds in that gear to avoid overspeeding of the engine, or some other gear must be added. An alternative could be the use of the present transmission with an overdrive added, the overdrive being about 2.2:1, then there would be gear ratios of: 2.21, 3.69, 4.86, 7.02, i.12, 12.6, 15.44, and 27.7. Normal driving over pavement and fairly level country would be possible in the first 3 or 4 gears with considerable fuel savings, while the higher ratios would be used for hill climbing, etc. An overdrive added to a 3-speed in place of a 4-speed box would provide all that is available in the standard system. The above represents one method of attacking the problem of economy. A second and better solution would be the combination of a variable step in the transmission as discussed earlier. What this unit would be like it is not ventured to guess at this point; it would be a project of no mean size to effect such a unit. Whether the expense of such a development is justified depends upon the value to be placed upon a fuel saving of about 2:1 maximum, with (say) about 1.5:1 for some simplified transmission system which approached the conditions over a major portion of the schedule. 50

X. FIVE-TON VEHICLE WITH COMPRESSION IGNITION ENGINE In order to examine the possible fuel economies to be achieved when employing the compression-ignition principle, a hypothetical 5-ton vehicle powered by a GM 6-71E engine was examined. The data employed in this instance had, in general, to be predicted. The road resistance was made up as shown in Fig. 14, and 1.5, 2.0, and 3 times this employed in the calculations as before, while the engine-performance curves were derived from "GM Diesel's Additional Engines" by K. L. Hulsing and C. E. Ervin, SAE Transactions, Vol. 67, 1959, pp. 596-617 in the following manner: (1) From data in the above publication a frictional horsepower curve and blower-power cruve were constructed. (2) With the aid of (1), IHP curves for full load were plotted and extrapolated as required, and percent IHP versus fuel flow obtained as in Fig. 15 in conjunction with such part-load performance data as were given in the reference. Some extrapolation of the results were necessary at this point, and these are best done on an IHP basis. (3) Using the results from the plotted and extrapolated curves of Fig. 15, the data were again reduced to a BHP basis at engine speeds of 500, 1000, 1400, 1800, 2100, 2400, and 2700 rpm and plotted on an rpm base in Fig. 16, which also includes the SFC data; the performance from this map for this investigation was obtained. The basic data obtained from the reference work are given in Table XIV. Plotting of the data of Table XIV led to the estimated BHP performance and fuel data referred to and shown in Table XV and Fig. 17 over the extended speed range required for the analysis. The specifications of the vehicle that will be employed with the engine data of Table XV are: 51

110 100 90 80 ROAD LOAD H. P. - 70 160 LU uj I^~ ~~~~ / I ^"~RESISTANCE 40 m20 - / ROLLING 0 10 20 30 40 50 60 70 80 M. P. H. Fig. 14. Road resistance of five-ton vehicle. 52

110 100 R.P.M. 2700 2400 90 2100 1800 1400 80 1000 \/ 500 70 I 60 0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 I.H.P. IN PERCENTAGE Fig. 15. Percentage indicated horsepo'wer vs. fuel flow. 5040 30 10 0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 I.H.P. IN PERCENTAGE Fig. 15. Percentage indicated horsepower vs. fuel flow.

250 200 150 100 - 0.4 =c 0.6 ^ 50 0 S. F. C. - 0.4 L250 500 750 1000 1250 1500 1750 2000 2250 2500 2700 R. P. M. Fig. 16. Final brake horsepower and specific fuel consumption curves for engine.

240 220 - 200 180 - 160 140 120z Lu 100 - R. P. M. 250 80~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I ~~~~80 -~ ~ ~/ 500 1000 1400 1800 50 - 2100 2400 2700 40 20 0 10 20 30 40 50 60 70 80 90 100 FUEL FLOW LBS/HR Fig. 17. Brake horsepower vs. fuel flow map for GM6-71E engine. 55~

TABLE XIV GM6-71E ENGINE PERFORMANCE RPM BHP BSFC Fuel Flow, Blower, Friction, IHP Percent ISFC RPMI P lb/BHP/hr lb/hr h p h Lp IHP lb/IHP/hr Part-Load Performance 210 0.41 86.2 14.0 40 264 100 0.326 180 0.40 72.1 14.0 40 234 88.6 0.309 150 0.408 61.3 14.0 40 204 77.4 0.300 2100 120 0.430 41.7 14.0 40 174 66.0 0.297 90 0.478 43.1 14.0 40 144 54.5 0.299 70 0.535 37.5 14.0 40 124 47.0 0.302 6o 0.574 32.9 14.0 40 114 43.2 0.289 152 0.402 6o 0 5 30 187 100 03.26 130 0.392 51.1 5 30 165 87 0.310 110 0.390 43.0 5 30 145 76.4 0.297 1400 90 0.400 36.0 5 30 125 65.8 0.288 70 0.420 29.4 5 30 105 55.3 0.280 60 0.438 26.4 5 30 95 50.0 0.278 50 0.454 22.7 5 30 85 44.6 0.268 Full-Load Performance 2700 240 0.457 110.0 315.0 100 0.349 2400 228 0.430 98.0 290.0 100 0.338 2100 210 0.41 86.2 264.0 100 0.326 2000 203 o.405 82.2 253.8 100 0.324 18oo 190 0.40 76.0 235.5 100 0.323 1600 172 0.395 68.o 212.5 100 0.320 1400 152 0.402 61.0 187.0 100 0,326 1200 130 0.409 53.2 160.5 100 05331 1000 109 0.421 45.9 134.5 100 0.341 500 57.5 0.438 25.2 70.0 100 0.560

TABLE XV EXTENDED PERFORMANCE AT ALL LOADS AND SPEEDS OF THE GM6-71E ENGINE Fuel Flow, BSFC Blower plus _____RPE_________M BHP lb/hr lb/BHP/hr Friction, hp 240 110.0 0.457 177 82.0 0.463 2700 114 61.0 0.535 75.0 51 40.5 0.793 19.5 30.5 1.56 228 98.0 0.43 170 73.5 0.432 2400 112 54.5 0.486 62.0 54 36.2 0.67 25 27.2 1.09 210 86.0 0.410 184 74.0 0.402 157 63.8 0.406 131 55.5 0.424 54 104 47.5 0.456 78 39.5 o.506 52 32.0 0.616 25 24.0 0.962 190.5 77.0 0.404 166.5 65.5 0.393 143.5 56.5 0.394 119.5 47.8 0.400 45 96.5 40.5 0.420 72.5 33.8 0.466 49.5 27.0 0.545 25.5 20.0 0.79 152.0 63.0 0.414 143.0 56.5 0.374 114.0 45.3 0.397 1400 96.0 38.0 0.396 77.0 32.0 o.46 55 58.0 26.5 0.456 40.0 21.1 0.528 21.0 15.6 0.744 110.5 47.8 0.432 96.5 40.4 0.419 83.5 33.4 0.400 1000 69.5 27.6 0.397 56.o 22.6 0.4025.5 42.5 18.6 o.436 29.0 15.0 0.510 15.5 11.5 0.741 57.5 25.2 o.438 50.4 20.5 o.407 43.5 16.7 0.384 36.5 13.6 0.372 500 29.5 11.40.586 12.5 22.4 9.5 0.424 15.5 7.5 0.484 8.5 5.6 0.658 57

Gross vehicle weight: 10,000 lb Vehicle height: 7 ft-0 in. Vehicle width: 6 ft-0 in. Tire size: 11 x 22 in. Assumed rolling radius: 21.2 in. Rear axle ratio: 4.75:1 1st 2nd 3rd 4th Transmission ratios: 5.90 2.95 1.97 1.0 Transmission efficiencies, %: 85.0 88.0 91.0 94.0 DRo: 28.0 14.49 93.8 4.75 The above gear ratios and efficiencies are hypothetical; 4th gear ratio was selected to give a vehicle speed of 60 mph at an engine speed of 2400 rpm. Employing the data shown, Fig. 18 can be constructed, as for the M-151 vehicle, and comparisons can now be made as before. Using a slip factor of 5%, the engine speed for any road speed is given by Eq. (3). Engine rpm = 8.42 x DRo x mph. () There is one difference between Figs. 10 and 18; the latter has various transmission-efficiency curves plotted on it from 100 down to 80%. This permits selection of any desired efficiency rather than the fixed values of Fig. 10. The use of the chart changes slightly as a result, the horsepower value is taken to the right to the intersection of the desired efficiency curve. This point of intersection is then taken vertically to the 100% line then back horizontally to the BHP axis for the engine horsepower. The performance with the assumed engine and transmission, employed in a conventional manner, is read out of Fig. 18 and recorded in Table XVI for all the various terrain surfaces and gear ratios available. Repeating the process for the engine and variable transmission giving minimum fuel consumption, the data of Table XVII are obtained, of which Table XVIII and Fig, 19 give engine performance only.

2600 / 2400 - 2200 / 2000 / 1800 / // 1600 R. P.M. 1400 1200 - looo loo / 1000 - 100 // 800- 80 600 60 // UEL FLOW LBS/HR 400 40 / 200 / 20 0 20 40 60 80 100 120 140 160 180 200 220 240 B. H. P. Fig. 19. Flexible engine performance. 61

TABLE XVI STANDARD SYSTEM PERFORMANCE AT FOUR ROAD RESISTANCES FOR FIVE-TON VEHICLE (a) Pavement First Gear Second Gear Third Gear Fourth Gear mph BHP RPM Fuel Flow, BP R Fuel Flow, BH RM FuelFlow, FuelFlow, BHP RPM BHP RPM BHP RPM BeP RPM lb/ lb hr lb/hr Ib/hr Ib/hr 2 0.35 470 3.0- --- - 4 0.80 940 6.6- --- -- 5 1.2 590 4.5 1.1 395 2.8 1.0 200 1.6 6 1.5 1420 9.5 -- -- - -- - 8 2.5 1880 13.8- -- - - 10 3.5 2360 20.3 4.0 1180 8.8 3.8 790 6.8 3.7 400 3.6 12 4.9 2830 27.4- -- o\ 15 6.1 1770 13.6 7.2 1190 10.1 7.0 600 6.0 20 10.7 2360 23.0 10.0 1590 13.2 9.9 800 8.0 25 13.8 2950 32.6 14.5 1990 18.8 13.5 1000 10.5 30 18.5 2380 25.5 17.8 1200 12.9 35 23.0 2790 33.5 22.0 1400 15.0 40 29.0 1600 19.0 45 38.5 1800 22.9 50 49.8 2000 29.5 55 63.5 2200 36.5 60 78.0 2400 44.0 65 94.5 2600 52.8 70 110.0 2800 62.0

TABLE XVI (Continued) (b) Secondary Roads-1.5 x Pavement First Gear Second Gear Third Gear Fourth Gear mph BHP RPM Fuel Flow, BHP RPM Fuel Flow, BH RPM Fu B R el Flow, Fl BHP RPM lb/hr BHP RPM BP lb/hr BHP RPM lb/hr -Ib/hr Ib/hr Ib/ hr Ib/hr 2.5 1.0 560 4.0 - - 5 2.1 1170 8.5 2.0 590 4.6 1.9 395 2.9 1.9 200 1.9 7.5 4.0 1740 13.0 - - 10 5.5 2360 20.8 5.4 1180 9.5 5.2 790 6.9 4.7 400 4.0 12.5 8.0 2950 31.0 -- - - 15 10.1 1770 14.2 9.8 go1190 10.6 8.5 600 6.5 20 15.1 2360 23.9 14.8 1590 14.6 14.0 800 9.2 25 20.8 2950 35.0 20.2 1990 20.2 19.0 1000 12.0 30 26.4 2380 27.2 24.8 1200 15. 355 34.2 2790 37.0 32.1 1400 18.5 40 42.4 1600 22.5 45 53.2 1800 27.2 50 71.5 2000 36.3 55 89.4 2200 44.5 60 111.5 2400 54.3 65 135.2 2600 64.5 70 161.0 2800 78.5

TABLE XVI (Continued) (c) Cross Country-2.0 x Pavement First Gear Second Gear Third Gear Fourth Gear mph BHP RPM FuelFlow, BHP RPM Fuel Flow, Fuel Flow, BHP RPM l BHP RPM BHP RPM Fw BHP RPM Ib/hr lb/ hrIb/hrIb/hr 2.5 1.5 560 4.2 - -- -- -- -- -_ -_ 5 3.4 1170 9.0 3.3 590 5.0 3.1 395 3.0 3.0 200 2.0 7.5 5.4 1740 13.0 - -- -- -- -- -- - - 10 8.2 2360 20.6 8.1 1180 10.2 8.0 790 7.8 7.9 400 4.8 12.5 11.3 2950 31.8 -- - - - - - -- -- 15 13.5 1770 15.2 13.2 1190 11.7 13.0 600 7.3 20 20.8 2360 25.8 20.5 1590 16.3 19.4 800 10.5 25 27.3 2950 37.8 27.2 1990 22.8 27.0 1000 14.1 30 36.0 2380 30.5 34.0 1200 17.8 35 46.5 2790 40.8 43.0 1400 21.8 1~~~40~~~~o~~~~~~~~ ~57.0 1600 27.2 45 73.5 1800 33.2 50 96.7 2000 43.8 55 122.2 2200 54.2 60 152.0 2400 67.0 65 182.8 2600 81.5 70 216.0 2800 96.6

TABLE XVI (Concluded) (d) Cross Country —3.0 x Pavement First Gear Second Gear Third Gear Fourth Gear mph BHP RPM Fuel Flow, BHP RPM Fuel Flow BHP RPM Fuel Flow BHP RPM low _______lIb/hr l____Ib/hr la _Ib/hr l_____Ib/hr 2.5 2.3 560 4.6 - -- -- -- 5 5.0 1170 9.5 4.7 590 5.8 4.5 395 3.9 4.4 200 2.5 7.5 8.4 1740 14.0 -- -- -- -- -- -- -- -- 10 12.2 2360 22.6 11.5 1180 11.1 12.1 790 8.9 11.0 400 5.5 12.5 15.8 2950 32.5 — -- - 15 20.6 1770 17.5 20.3 1190 13.6 19.0 600 9.0 20 31.4 2360 28.8 30.3 1590 19.0 82.0 800 13.1 25 42.7 2950 41.0 39.0 1990 24.7 38.8 1000 17.5 30 52.7 2380 30.2 50.0 1200 22.4 CO, 35 68.5 2790 47.8 64.6 1400 28.4 Un 40 84.5 1600 34.8 45 110.0 1800 44.8 50 144.0 2000 58.2 55 183.8 2200 75.5 60 229.0 2400 98.8 65 -- 2600 - 70 -- 2800

TABLE XVII FLEXIBLE SYSTEM PERFORMANCE AT FOUR ROAD RESISTANCES Fuel Flow, Overall Fuel Flow, Overall MPH BHP RPM Drive Ratio BHP RPM lb/hr Drive Rati Required Required (a) Pavement (c) Cross Country-2.0 x Pavement Idle - 250 1.8 - - 2501.8 2.5 0.5 250 1.825 11.90 5.0 1.4 250 1.9 5.94 3.0 250 2.3 5.94 7.5 2.4 250 2.2 3.96 4.9 250 2.8 3.96 10.0 3.9 250 2.62.97 8.3 50.9 2.97 12.5 5.3 250 3.0 2.38 11.1 300 4.5 2.85 15.0 7.3 250 3.6 1.98 13.7 350 5.6 2.77 20.0 9.2 250 4.2 1.49 20.7 400 8.4 2.37 25.0 13.8 300 5.6 1.43 27.5 500 102.38 30.0 18.0 400 7.6 1.58 36.3 550 13.8 2.18 35.0 23.0 450 9.0 1.53 46.5 650 17.6 2.20 40.0 30.0 500 111.49 6.5 800 23.2 2.37 45.0 39.8 600 15.0 1.58 78.5 1050 30.9 2.77 50.0 51.2 700 19.5 1.66 101.5 1350 39.6 3.20 0h1\ 55.0 65.3 950 25.5 2.05 130.0 1430 50.8 3.08 60.0 80.0 1000 31.8 1.98 161. 175062.6 3.46 65.0 98.0 1350 38.0 2.47 194.0 1900 76.8 3.47 70.0 114.0 1400 44.5 2.38 228.0 2400 94.8 4.06 (b) Secondary Roads-1.5 x Pavement (d) Cross Country-3.0 x Pavement Idle - 250 1.8 - - 250 1.8 2.5 1.0 250 1.9 11.90 2.1 250 2.1 11.90 5.0 2.3 250 2.1 5.94 4.8 250 2.8 5.94 7.5 3.2 250 2.4 3.95 8.3 250 3.8 3.96 10.0 5.5 250 3.0 2.97 11.8 300 4.3 3.57 12.5 8.4 250 3.8 2.38 15.5 350 6.1 3.33 15.0 10.0 250 4.2 1.98 20.0 400 7.8 3.16 20.0 15.2 350 6.2 2.08 29.0 550 11.5 3.26 25.0 20.7 450 8.2 2.14 41.5 600 15.7 2.85 30.0 26.4 500 10.0 1.98 51.0 700 19.3 2.77 35.0 34.0 600 12.9 2.04 68.o 1100 26.4 3.73 40.0 45.0 750 17.0 2.23 89.0 1200 34.8 3.56 45.0 59.5 850 22.8 2.24 115.5 1400 45.0 3.69 50.0 76.0 1000 30.0 2.37 152.2 1750 59.2 4.15 55.0 87.5 1100 34.5 2.38 196.5 2150 70.8 4.64 60.0 116.7 1400 45.5 2.77 65.0 143.7 1500 55.8 2.74 70.0 170.8 1950 66.5 3.30

TABLE XVIII MINIMUM FUEL FLOW FLEXIBLE ENGINE REQUIREMENTS RPM BHP lb/hr.............. lb/hr Idle 0.0 1.8 250 2.0 2.0 250 4.0 2.6 250 6.0 3.2 250 8.0 3.8 250 10.0 4.5 250 14.0 5.8 375 26.0 10.0 500 37.0 14.0 750 57.0 22.0 1000 74.5 29.5 1200 100.0 39.0 1400 123.0 48.o 1600 143.0 55.5 1800 160.0 63.0 2100 203.0 81.2 2400 228.0 94.5 2700 238.0 103.0 The data of these tables have been obtained using an overall efficiency of the transmission of 90%. The dotted line of Fig. 19 is seen to follow the trend of the engine rpm quite closely; the error by using this straight line relationship would be of negligible mangitude. 67

XI. SYSTEM COMPARISON The information contained in these performance tables permits comparing the Battlefield Day requirements for the two compression-ignition systems. In order to do so, the operating schedules (Section VIII-A) will again be employed and the necessary data are collected together in Tables XIX, XX, and XXI. Repeating this tabulation for the flexible system the data of Tables XX and XXI are obtained. Examination of the data of Table XXI again shows that at minimum consumption the flexible engine consumes almost one-half the fuel of a conventional engine and transmission even when a compression-ignition engine of the General Motors type is used, which for light loads at high speeds is paralized somewhat by high blower plus friction horsepower losses. Actual vehicles fitted with the compression-ignition engine and conventional transmission have demonstrated on many occasions two-to-one increase in miles per gallon over that of the spark-ignition type when fitted to the same vehicle. The calculations covered by this report indicate the possibility of almost a four-to-one increase in miles per gallon when using a flexible compression-ignition engine system in place of a conventional sparkignition unit coupled to a standard transmission. 68

TABLE XIX STANDARD SYSTEM BATTLEFIELD DAY REQUIREMENTS FOR FIVE-TON VEHICLE Fuel Flow Surface MPH Hours Gear RPM lb/hr Total, lb Idle 1.6 - 350 2.6 4.16 0-10 3.36 2nd 350-1180 5.4 18.15 10-20 5.92 3rd 790-1590 10.1 59.80 Hard Pavement 20-30 3.36 4th 800-1200 10.5 35.30 30-40 1.6 4th 1200-2400 15.6 25.0 50-60 0.16 4th 2000-2400 36.7 5.9 Total Hours = 16 Total Fuel Flow = 148.31 Idle 1.6 - 350 2.6 4.16 0-10 3.36 2nd 350-1180 5.6 18.80 Secondary 10-20 5.92 3rd 790-1590 10.7 63.30 Roads 20-30 3.36 4th 800-1200 12.1 40.60 30-40 1.6 4th 1200-1600 18.7 29.90 50-60 0.16 4th 2000-2400 45.1 7.21 Total Hours = 16 Total Fuel Flow = 163.97 Idle 1.6 - 350 2.6 4.16 0-10 3.36 1st 250-2360 9.9 33.20 Cross Country 10-20 5.92 2nd 1180-2360 17.1 101.50 2 x Pavement 20-30 3.36 3rd 1590-2380 23.2 77.80 30-40 1.6 4th 1200-1600 22.3 35.70 50-60 0.16 4th 2000-2400 55.0 8.80 Total Hours = 16 Total Fuel Flow = 261.16 Idle 1.6 - 350 2.6 4.16 0-10 3.36 1st 350-2360 10.66 35.80 Cross Country 10-20 5.92 2nd 1180-2360 19.10 113.20 3 x Pavement 20-30 3.36 3rd 1590-2380 24.60 82.50 30-40 1.6 4th 1200-1600 28.50 45.60 50-60 0.16 4th 2000-2400 77.50 12.41 Total Hours = 16 Total Fuel Flow = 293.67 Total fuel for 48-hr BFD, 1/3 pavement, 1/3 secondary, and 1/3 cross country (2 x pavement) = 573.5 lb Total fuel for 48-hr BFD, 1/3 pavement, 1/3 secondary, and 1/3 cross country (3 x pavement) = 606.0 lb 69

TABLE XX FLEXIBLE SYSTEM BATTLEFIELD DAY REQUIREMENTS FOR FIVE-TON VEHICLE Fuel Flow Gear Surface MPH Hours Ratio RPM lb/hr Total, lb Idle 1.6 -- 250 1.80 2.88 0-10 3.36 14.5 -2.97 250 2.1 7.05 10-20 5.92 2.97-1.49 250 3.5 20,70 Hard Pavem20-30 336 1.49-1.59 250- 400 5.8 19.48 30-40 1.60 1.59-1.48 400- 500 9,4 15.05 50-60 0.16 1.66-1.98 700-1000 25.6 4.10 Total Hours = 16 Total Fuel Flow = 69.26 Idle 1.6 -- 250 1.80 2.88 0-10 3.36 14.5 -2.97 250 2.25 7.56 Secondary 10-20 5.92 2.97-2.08 250- 350 4.50 26,60 Roads 20-30 3.36 2.08-1.98 350- 500 8.10 27.20 30-40 1.60 1.98-2.23 500- 750 13530 21.30 50-60 0.16 2,37-2.77 1000-1400 36,70 5.88 Total Hours = 16 Total Fuel Flow = 91.24 Idle 1.6 -- 250 1.80 2.88 0-10 3.6 14.5 -2.97 250 2.6 8.74 Cross Country 10-20 5.92 2.97-2,37 250- 400 5.6 33510 2 x pavement 20-30 3.36 2.37-2.18 400- 550 10.9 36.60 30-40 1.60 2.18-2.37 550- 800 18.2 29.10 50-60 0.16 3.21-3.46 1350-1750 51.0 8.16 Total Hours = 16 Total Fuel Flow = 118,58 Idle 1.6 250 1.80 2.88 0-10 3.36 14.5 -3.56 250- 300 2,96 9.94 Cross Country 10-20 5.92 3.56-3.27 300- 550 7.87 46.50 3 x pavement 20-30 3.36 3.27-2,77 550- 700 15.50 52.00 30-40 1.60 2.77-3.56 700-1200 26.80 42.90 50-55 0.16 4.16-4.63 1750-2150 65o00 10o40 Total Hours 16 Total Fuel Flow = 164.62 70

TABLE XXI COMPARISON OF STANDARD AND FLEXIBLE SYSTEMS FOR FIVE-TON VEHICLE (Fuel requirements for 48-hr power plant-GM6-71E) Schedule Engine and Transmission System, lb Conventional Flexible 33-1/3% Pavement 33-1/35 Secondary Roads 573.5 280.0 33-1/35 Cross Country (2 x Pavement) 33-1/35 Pavement 33-1/35 Secondary Roads 33-1/3% Cross Country (3 x Pavement) 25% Pavement 35% Secondary Roads 40% Cross Country 597.0 290.6 (2 x Pavement) 25% Pavement 355 Secondary Roads 635.6 345.8 40% Cross Country (3 x Pavement) 71

XII. TRANSMISSION REQUIREMENTS FOR COMPRESSION-IGNITION ENGINE In order to achieve the economies predicted for the flexible engine system, the only important element changed is the transmission. The engine is identical for each system, developing the same power at the same speed for the same fuel consumption. The fuel saved comes from the reduction in engine speed that is possible for a given power output. To reduce engine speed relative to vehicle speed, a lower overall drive ratio between engine and wheels must be employed. Looking at the requirements for the two power systems examined for the 5-ton vehicle, the data of Table XXII are obtained for speeds up to 70 mph. It is seen that the conventional system in 1st gear on pavement can only employ up to a maximum of about 1/70 full power output at full engine speed. In such a case the frictional losses are about twenty times the useful power being generated, i.e., for every pound of useful fuel 20 lb are wasted in friction. It is not until 4th gear is employed, and even then high road speed is also necessary, that a reasonably good relationship between useful fuel and friction fuel is obtained. If cross country operation is examined, it is seen that the engine is now working up near its capacity at high speed and the proportional fuel flow is improved. It follows that the savings to be made are reduced as the engine load increases. These observations are not new; it has been well known for a long time that high speed and economy cannot be achieved simultaneously. In these calculations the actual sacrifice made to achieve high speed has been brought into the open for perhaps the first time for those not intimately connected to vehicle development. The engine and transmission are designed to meet certain top-speed conditions, conditions which in the schedule of operations employed in this analysis are only existant for a total of 1% of the 48-hour BFD. The transmission is then totally unsuited for operation over about 80% of the total time period. The flexible engine concept reduces engine speed, and thus frictional losses to a minimum. As a result the fuel savings over the above 80% period are considerable and at the same time there is but a small loss in the maximum performance viz., 55 mph maximum speed with flexibility against 60 mph for the conventional system when operating on level ground of three times pavement resistance. There is no loss in maximum speed at any of the other 73

TABLE XXII COMPARISON OF TRANSMISSION SYSTEM REQUIREMENTS Engine Requirements Sysm Gear Pavement Secondary Roads Cross Country System and 2 x Pavement 3 x Pavement Ratio Vehicle, Engine, Vehicle, Engine, Vehicle, Engine, Vehicle, Engine, mph rpm mph rpm mph rpm mph rpm 1st 2-10 470-2360 0- 3.5 2-10 470-2360 0- 5.5 2-10 470-2360 0- 8.2 2-10 470-2360 0- 12.2 28.0:1.0 C.I. Engine 2nd 5-20 590-2360 0- 10.7 5-20 590-2360 0- 15.1 5-20 590-2360 0- 20.8 5-20 590-2560 0- 1.4 and 14.49:1.0 Conventional Transmission 3rd 5-30 395-2580 0- 18.5 5-30 395-2380 0- 26.4 5-30 395-2380 0- 36.0 5-30 395-2380 0- 52.7 9.38:1.0 4th 5-70 200-2800 0-110.0 5-70 200-2800 0-161.0 5-70 200-2800 0-216.0 5-60 200-2400 0-229.0* 4.75:1.0 1.5:12.0 0-70 250-1400 0-114.0 Flexible C.I. Engine 1.98:12.0 0-70 250-1950 0-171.0 and Variable Transmission 2.2:12.0 070 250-2400 0-228.0 2.7:12.0 55 250-2150 0-196.5** *At 3 times Pavement resistance maximum speed limited to 60 mph. **At 3 times Pavement resistance maximum speed limited to 55 mph.

ground conditions examined. This sacrifice is minor and the question can be raised as to whether any sacrifice is made anyway since it can be asked "Where and under what conditions could 70 mph be maintained over rought terrain cross country?" By looking at Table XX it is seen that the flexible engine requires overall gear ratios of 14.5 to 1.5 (approximately) for complete conformity with the calculations. Now as in the case of the spark-ignition engine previously considered, it is probable that some high gear ratio would be required for starting from rest, particularly on hills. If such was provided, say for speeds from 0-5 mph, and then from about 5 mph on up the flexible system came into operation, the range of overall ratios would be reduced to about 6.0 to 1.5:1.0, with the great majority of the operation being within the range of 4.5 to 1.5 for all the various ground conditions considered. If the three-to-one ground data were eliminated, the range could be cut to 3.5 to 1.5. It is possible that such a range could be handled with a first gear conventional reduction plus a form of hydrostatic transmission. In such a case it is true that the full savings would not be achieved, but it is possible, today, that a worthwhile saving of fuel could be made by using the system in the most favorable combination that could be worked out. It seems that a new look at transmissions in the light of this investigation would be justified on the following basic principles (1) Economy of Fuel (2) Logistic Problem (3) Range of Operation (4) Reduced Repair and Maintenance of Power Plant 75

XIII. DISADVANTAGES OF FLEXIBLE SYSTEM This proposed system of operation, as is common to most changes, does not present a completely clear-cut decision to be made. To achieve the objective of fuel economy, etc., some sacrifices must be made in other directions. In this case the major sacrifice would be in the field of the vehicles acceleration. The maximum speed would be unaffected, but the time to reach that speed would be increased considerably. This would be of considerably consequence to most drivers of today's passenger cars on the freeways. How this would affect military convoys only those with such experience could judge. In order to illustrate this point the data of Table XXIII are provided for the M-151 vehicle. This table records, for both conventional and flexible systems, the operating horsepower for each engine speed, i.e., the point at which the vehicle would be performing under the contemplated idealized conditions, together with the maximum BHP that would be available if the throttle were suddenly opened wide at that same speed. The difference in power then represents that available for accelerating the vehicle. TABLE XXIII POWER AVAILABLE FOR ACCELERATION M-151 VEHICLE Engine, Conventional System, BHP Flexible System, BHP rpm Min Max A Min Max A 250 0.1 3.4 3.3 2.8 3.4 0.6 500 0.3 7.1 6.8 5.7 7.1 1.4 1000 2.5 17.0 14.5 12.0 17.0 5.0 1400 4.6 28.5 23.9 20.0 28.5 8.5 1800 8.0 36.5 28.5 29.0 36.5 7.5 2200 12.3 45.5 33.2 35.0 35.5 10.5 2600 19.5 51.5 32.0 43.5 51.5 8.0 3000 29.5 55.5 26.0 53.0 55.5 2.5 3400 39.3 59.2 19.9 54.5 59.2 3.7 3800 52.0 60.0 8.0 60.0 6. 0.0 0 4200 61.0 61.0 0.0 61.0 61.0 0.0 77

Comparing the two sets of data, it is seen that the difference in these accelerating powers for the two cases is in the order of about 3 or 4:1 on the average. It follows that the fuel-consumption increase shown for the M-151 unit between the two systems (174.0 lb/48 hr), represents the penalty to be paid for a 3:1 increase in vehicle acceleration. By reducing this saving in fuel, increase in acceleration is possible. Also as is well known, by further increasing maximum BHP, additional increase in acceleration of the standard unit is possible, at the expense of further increase in fuel, over and above that of the existing vehicle. The selection of the best operating combination can only be made by those closely connected with the actual overall vehicle operational requirements, the problem of fuel supply, and the effects that the range of operation has on the general problems encountered in the field. It is considered that the present trend of the automotive industry in vehicle development, both passenger car and trucks (i.e., high speeds and higher accelerations with transmissions to suit these conditions) may not be the best basis for the design of military vehicles to meet their average operating schedule. Lack of rapid acceleration seems to be the outstanding disadvantage of the flexible system. Its importance versus savings must be judged by competent authorities. It is, of course, quite probable that some other problems may exist, increased costs, complexity, etc.-these cannot be evaluated until the transmission problem has been examined and a proposed design prepared. It is believed that Figs. 10 and 18, can be added to in such a way that the instantaneous acceleration resulting from wide open throttle conditions could be added without much difficulty. In addition, the time of acceleration from x to y mph could also be added to the same chart if necessary. Alternatively, these acceleration values could be given separately if thought desirable. No reason is seen why the fuel flow during acceleration and deceleration could not also be plotted without complicating the problem to an impossible extent. With such data a fairly exact prediction of actual vehicle operation should be possible. 78

XIV. FUTURE INVESTIGATIONS It is believed that this analysis should be continued by working out an example of an engine coupled to an automatic transmission of the torqueconverter type giving the position of that combination relative to those already examined. 79

XV. CONCLUSIONS It can be concluded from the data presented in this report that a typical modern vehicle fitted with an internal combustion engine (and also a gas turbine, it is believed, though this has not been investigated) and connected to a typical modern transmission of either the conventional stick shift or automatic variety produces a combination which is conducive to excessive fuel consumption compared to the minimum that could be obtained given the most efficient combination of units. The various conclusions, both for and against, are as follows: (1) The ideal flexible system could be designed to use about one half the present fuel quantities in a 48-hour day. (2) In order to achieve the savings indicated, a new approach to the transmission problem must be made. (3) Existing engines were employed in the analysis. Nothing in the way of new engine concepts are involved in the reduction of fuel flow. (4) To achieve the reduced flow the present type of engine would need some improvements in the direction of satisfactory slow-speed operation without stalling, and with smoothness of operation. (5) It is probable that some new development in controls may be necessary; this will depend upon the transmission design, when worked out. (6) A distinct sacrifice in acceleration would be involved to achieve the indicated economy. (7) Some sacrifice in the maximum available economies shown here can be made which would be reflected in improved acceleration, and still leave a major fuel saving available. (8) The fuel economy indicated of about 50% is an overall one taking into consideration all the various conditions encountered in a BFD of 48-hours. It is not the economy at any one isolated point. (9) The general engine operating conditions will be improved and should result in increased life and reduced maintenance. 81

(10) By suitable design, with some sacrifice in the maximum fuel saving possible, the range of variability of the transmission could be reduced greatly with perhaps considerable simplification of the unit. (11) The design of a suitable overdrive unit attached to a two or three speed transmission and special rear axle probably could achieve a large percentage of the possible gains for the M-151 vehicle. (12) There is a distinct possibility that the successful solution of the low-speed engine operation, which would be necessary to achieve the objective, would involve some increase in the rotating weights to eliminate torque reversal on the transmission. (13) The sacrifice of say 15% in maximum vehicle speed (for the two cases examined) would reduce considerably the range of variability of the transmission without loss in the gains to be expected; in fact some improvement seems possible. (14) If the "flexible" concept is compared with the "responsive" one of Refs. 1 and 3, it is seen that where fuel economy is of major consideration the flexible system will do much more than the responsive one. (15) The "responsive engine" needs considerable development in order to be a practicable power plant. It does not reduce fuel quantities, but it does eliminate some, and in an ideal case all, of the transmission problems. It provides torque multiplation as engine speed reduces. (16) The "flexible system" employs existing engines with little or no change (slower speed operation being the major requirement). This system, however, adopts the engine fuel-flow characteristics to the vehicle requirements in the most efficient manner, via the use of a transmission of special design or by a conventional gearbox plus overdrive. If some sacrifice in maximum fuel savings is accepted, probably a 40% saving in place of 50% (approx.) could be achieved relatively easily. (17) An engine developed specifically for economy of operation coupled to the flexible system would not achieve any additional major gains, since the engine operation over the majority of the operating schedule is at a point of maximum economy anyway. Some small gains could be made at the high-speed, high-load conditions only. 82

REFERENCES 1. E. T. Vincent, Flexible Versus Responsive Engines, The University of Michigan, ORA Report 04612-3-F, August 1962. 2. K. L. Hulsing and C. E. Ervin, "G.M. Diesel's Additional Engines," SAE Transactions, 67, 1959, pp. 596-617. 3. E. T. Vincent and N. Tokuda, Vehicle Performance Employing Minimum Responsiveness With an Existi Transmission, The University of Michigan, ORA Report 05847-2-T, January 1964. 85

UNIVERSITY OF MICHIGAN 3 9015 03527 2460