TECHNICAL REPORT NO. 3-808 EVALUATION OF THE PERFORMANCE OF THE XM759 LOGISTICAL CARRIER B. 6. Schreiner A A Rula January 196& Sponsored by U. S. Army Materiel Command Conducted by u. S. Army Engineer Waterways Experiment Station CORPS OF ENGINEERS Vicksburg, Mississippi This document is subject to special export controls and each transmittal to foreign governments or foreign nationals may be made only with prior approval of U. S. Army Materiel Command. TECHNICAL REPORT NO. 3-808 j~y-,;v( J EVALUATION OF THE PERFORMANCE OF THE XM759 ~O~~S!~iL..~aBB.lg~j' by B. G. Schreiner A. A. Rula January 1968 Sponsored by " i U. S. Army Mat:eriel Command \ \ -",----: '- ~,,---- Conducted by U. S. Army Engineer Wat:erways Experiment: St:at:ion CORPS OF ENGINEERS )." . ,/ Vicksburg, Mississippi ARMY-MRC VICKSBURQ. MISS. rThis document is subject to special export controls and each transmittal to foreign governments or foreign nationals may be made only with prior approval of U. S. Army Materiel Command. THE CONTENTS OF THIS REPORT ARE NOT TO BE USED FOR ADVERTISING, PlffiLICATION, OR PROMOTIONAL PURPOSES. CITATION OF TRADE NAMES DOES NOT CONSTITUTE AN OFFICIAL EN­ DORSEMENT OR APPROVAL OF THE USE OF SUCH COMMERCIAL PRODUCTS. iii FOREWORD A development program for the XM759, 1-1/2-ton Logistical Carrier, Amphibious, was requested by the Commandant of the U. S. Marine Corps (USMC) in February 1965, and the U. S. Army Materiel Command (AMC) was designated as monitoring agency. AMC subsequently designated the U. S. Army-Tank Automotive Command (ATACOM) as the action agency. The study reported herein was a part of the development program and was conducted as a joint effort by ATACOM, the General Equipment Test Activity (GETA), and the U. S. Army Engineer Waterways Experiment Station (WES). The study was conducted during the period from(October 1966 to July 1967: Acknowledgments are made to MAJ S. G. Tribe and MAJ L. J. Trembley, USMC Headquarters, who participated in numerous planning meetings and observed the field test programs; to Mr. James Carr, AMC project manager for his coordinating efforts and general guidance; to ATACOM personnel, particularly Messrs. J. Tannenbaum, R. E. Nette, and V. J. Kowachek, for assistance and guidance in programming; and to GETA personnel, partic­ ularly Messrs. S. DeStefano and G. B. Penn, for their support and co­ operation in conduct of the field program. WES participation in the study was under the general direction of Messrs. W. J. Turnbull, Technical Assistant for Soils and Environmental Engineering, W. G. Shockley, Chief, Mobility and Environmental (M&E) Division, S. J. Knight, Assistant Chief, M&E Division, and A. A. Rula, Chief, Vehicle Studies Branch. Field tests and data analyses were con­ ducted by personnel of the Soil-Vehicle Studies Section under the direc­ tion of Mr. E. S. Rush, Chief, and Mr. Penn, GETA. Field tests were under the direct supervision of Mr. B. G. Schreiner, Soil-Vehicle Studies Section, and Mr. Duncan, GETA. This report was prepared by Messrs. Schreiner and Rula. Appendix C was written by v Mr. W. K. Dornbusch, Jr., Geology Branch, WES. Director of the WES during the conduct of this study and preparation of this report was COL John R. Oswalt, Jr., CEo Technical Director was Mr. J. B. Tiffany. vi CONTENTS FOREWORD ..•... v CONVERSION FACTORS, BRITISH TO MErRIC UNITS OF MEASUREMENT. ix SUMMARY ...... xi PART I: INTRODUCTION 1 Background 1 Purpose. 2 Scope. .. 2 Previous Studies of Pneumatic Track Vehicles 3 Definitions. .. 3 PART II: TEST VEHICLES .......• 9 Pertinent Vehicle Characteristics. 9 XM759 Propulsion System. 9 PART III: TEST PROGRAM .•...•.• 12 Selection, Location, and Description of Test Sites 12 Test Procedures and Data Collected 24 PART IV: ANALYSIS OF DATA. • 30 Trafficability Tests . 30 Mobility Tests •..••••• 42 Notes and Observations . 47 PART V: EVALUATION OF PERFORMANCE OF VEHICLES. 50 Comparison of Trafficability Test Results. 50 Comparison of Mobility Test Results.... 56 PART VI: SUMMARY OF TEST RESULTS .AND REr;OMMENDATIONS .• 57 Summary of Test Results. 57 Recommendations .•... 59 TABLES 1-11 PLATES 1-24 vii APPENDIX A: DETERMINATION OF VEHICLE CONE INDEXES FOR TRACKED VEHICLES. Al Fine-Grained Soils . Al Organic Soils ••• A3 TABLE Al APPENDIX B: EFF:EDTS OF SOFT SOIL BOOYANCY ON VEHICLE CONE INDEX DETERMINATION .....••• •• •.• •. Bl Introduction •...•••.•.•.• Bl Volume and Weight Computations ••.•. B2 Buoyancy Effects on VCI Determination. B5 PLATES Bl and B2 APPENDIX C: COMPARISON OF TERRAIN TYPES. Cl Background ••••••.•••. Cl Terrain Factors..•••.••.••• c4 Development of Analog Criterion. ••••.• C7 Comparison of Mekong Delta and Mississippi River Delta Terrain Types. ....................... c8 Comparison of Mekong Delta and Mobility Test Course Terrain Types. .. ................... c8 TABLES Cl and C2 viii CONVERSION FACTORS, BRITISH TO MErRIC UNITS OF MEASUREMENT British units of measurement used in this report can be converted to metric units as follows: Multiply By To Obtain inches 2.54 centimeters square inches 6.4516 square centimeters feet 0.3048 meters cubic feet 0.0283168 cubic meters pounds 0.45359237 kilograms pounds per square inch 0.070307 kilograms per square centimeter pounds per cubic foot 16.0185 kilograms per cubic meter tons 907.185 kilograms miles 1.609344 kilometers miles per hour 1.609344 kilometers per hour square miles 2.58999 square kilometers ix SUMMARY The XM759, 1-1/2-ton Logistical Carrier, Amphibious, was tested at five sites in Virginia and eight in Louisiana on a wide range of terrain conditions analogous to those of the Mekong Delta of South Vietnam. The off-road performance of the XM759 was compared with that of an Ml16, 1-1/2-ton Cargo Carrier, Amphibious, on the same test sites. The purpose of the test program was to (a) identify terrain conditions commonly found in the Mekong Delta and to locate analogous terrain in the United states that could be used for vehicle tests; (b) determine the.o.f.f.-...... rQ§W~it~rILance of the XM759 and the ..!11J,Q. on a wide range of terrain con- "ditions occur!i;g in wet, deltaic marshlands; (c) describe in d@iall the terrain on which vehicle tests were conducted; and (d) evaluate the com­ parative performances of the XM759 and Ml16 on similar terrains., Trafficability tests were conducted on level terrain to determine (a) the minimum soil strength, in terms of rating cone index (RCI), re­ (VCI~) quired for the vehicles to complete one pass and 50 passes (VCI sO ); (b) drawbar pull-slip relations for a range of sOlI strength condition~ and vegetal covers; (c) drawbar pull-strength relations on a variety of surface vegetation; (d) the effect of soil strength and vegetal cover on vehicle turning radius and speed; and (e) the maximum step height negoti­ able in exiting from bodies of water. Mobility tests were conducted to determine the average maximum safe speed while traversing straight-line test courses that included more than one type of terrain in each traverse. Tests were conducted with empty vehicles and with vehicles loaded to 100% and 200% pay loads in 47 types of terrain. Of the 44 mobility test course terrain types used in the development of analog criterion, 16 were highly analogous to one or more terrain types identified in the Mekong Delta, 14 were analogous, 12 were moderately analo­ gous, and 2 were slightly analogous. For the six soft-soil areas selected in the Mekong Delta, it is estimated that the XM759 with 100% pay load can traverse 100% of the areas for 50 passes, whereas the Ml16 with the same pay load can traverse only 89% of these areas for one pass and only 61% for 50 passes. The XM759 with 100% and 200% pay loads completed 50 passes on a soil strength as low as 2 RCI. The Ml16 with 100% pay load completed one pass on a soil strength of 7 RCI and 50 passes on 14 RCI. The experimental VCII at 100% pay load for the XM759 was considered to be zero. The pneumatic xi tires and sponson of the XM759 provide buoyancy when they are immersed in soft, viscous soils, thereby reducing the effective weight of the vehicle. Closer agreement between experimental and computed VCI's can be achieved by considering the effect of buoyancy. r;he maximum draWb~~ull of both vehicles at 100% pay load was limited because of lnsu~ci~~t power to develop sufficient force to shear the soi~ On an RCI of about 75, the XM759 developed a maximum traction coefficlent (TC) of 0.64 when empty and 0.49 with 100% pay load. On the same RCI, the Ml16 developed a maximum TC of 0.89 when empty and 0.75 with 100% pay load. On an RCI of about 7, the XM759 developed a maximum TC of 0.27 with 100% pay load. On the same RCI, the empty Ml16 was barely able to propel itself. For all vehicle weights tested, the motion resistance coefficient for the XM759 was 0.18 and 0.07 at RCI's of 4 and 75, respectively. For the same RCI's, the Ml16 developed a motion resistance coefficient of 0.34 and 0.14, respectively. Maneuver test results were not as definite as results of other per­ formance tests; however, general trends indicate that the XM759 at 100% pay load was capable of negotiating turns of slightly shorter radii than the Ml16 on RCI's between 40 and 8. On RCI's less than 8, the Ml16 could not negotiate turns; the XM759 negotiated turns on RCI's between 8 and 2 with a great increase in turning radius for a small decrease in soil strength. Data indicate that the 0059 can negotiate tighter turns on soil strengths between an RCI of 12 and 40 than it can on pavement.