VEHICLE PARAMETER MEASUREMENTS OF AN LAV WITH 90 mm. CANNON. Final Report. Contract No. ~ A A ~ ~ - ~ C.B.

Transcription

1 VEHICLE PARAMETER MEASUREMENTS OF AN LAV WITH 90 mm. CANNON Final Report Contract No. ~ A A ~ ~ - ~ C.B. Winkler July 1983

2 1. R.rrt No. 1. h - t Accossirn No. Tubaicol R~port Documentatik Pqe 3. Rocipimt'r Cotalog No. 4. Titlo mnd Subti110 VEH lcle PARAMETER MEASUREMENTS OF AN LAV WITH 90 mm. CANNON 6. P~fomrng Orgonitorion Cod. I C. B. Winkler 8. Pw(omrng Orgm~zmtron Report Mo. 9. Pukmng Orwirstion Mmo md Address 10. Wed Untt No. The University of Michigan Transportat ion Research lnst i tute 11. Contrmct or trmt NO Baxter Road ~~~~07-83-C-R068 Ann Arbor. Michiqan TYP of R m and Poimd brorod 12. Spassorrng A-Y MI. md A*~~OSS Final US Army Tank- Automotive Command Warren, Michigan Vehicle parameter measurements were made on a Light Armored Vehicle. Measurements of inertial, suspension, and tire properties were made. Techniques are briefly described and results presented. 17. Key Wads c.g. position, moments of inertia, suspension properties, tire spring rate, cornering stiffness 19. S.curity Clmosil. (of his m) X). b i t y Clmssif. (of kis p-1 I I 18. Diskitmtion Stmianrt 11. Ma. of Popes 22 Price C

3 VEHICLE PARAMETER MEASUREMENTS OF AN LAV WITH 90rnm. CANNON Inertial Properties The LAV was separated into i ts two component parts (viz. the "vehicle" less the turret, and the "turi-et" equipped with a 90mm. cannon) for inertial testing. For each of these two parts, weight, center of gravity position in the vertical, lateral and longitudinal directions, and the roll, pitch and yaw moments of inertia about the c.g. were measured. Weight, plus center of gravity position in the pitch plane and the pitch moment of inertia of the vehicle, were all measured using the UPITRI heavy vehicle pitch plane inertial test facility. Roll moment of inertia was measured using a similar compound pe!ndulum device. The vehicle's yaw moment of inertia was measured by oscillating the vehicle in yaw against a coil spring of known rate, while the vehicle was supported vertically on "zero-friction," hydrostatic bearings. The turret was weighed using a straingauge load cell. Its center of gravity position was determined by suspending the entire assembly from an overhead crane and determining the plumb line from the suspension point with a precision transit. Repeating this procedure using several points of suspension identifies the center of gravity as the single point in the body at which a11 plumb lines intersect. Roll and pitch moments of inertia of the turret were determined using the compound pendulum device used to measure roll moment of the vehicle. Yaw moment of inertia of the turret was measured using a multi-filar (torsional) pendulum dev i ce. Results of the inertial measurements are presented in the following two tables.

4 Vehicle Inertial Properties?: Weight 22,178 lbs. Center of Gravity Position Longitudinal (aft of front axle center) 62.1 i nches Vertical (above lower face of belly 17.0 inches plate at fore/aft c.g. position) (above ground in test condition) 39.9 inches Lateral (right of center) 2.0 inches Moments of Inertia about c.g. Yaw Pitch 294,990 in- 1 b-sec 2 294,690 i n- 1 b-sec 2 Roll 94,130 in-lb-sec 2 *Less turret; inclusive of unsprung masses in static ride height position; fully loaded ammo rack; fuel tank full. Weight Center of Gravity Position Turret Inertial Yroperties~~ 4689 Ibs. Vertical (above plane of lower face of 3.88 inches turret drive gear) Longitudinal (forward of lateral center inches 1 ine of turret drive gear) Lateral (right of longitudinal center- 1 ine of turret drive gear) 0.75 inches Moments of inertia about c.g. Yaw 14,250 in- 1 b-sec 2 Pi tch 15,280 in-lb-sec 2 Rol in-lb-sec 2 racks. *With 90mm. cannoq horizontal, eight dummy rounds in storage

5 Ti re Properties A variety of properties of the L/1V ti re were measured using the UMTRl Flat Bed Tire Tester. Tire properties measured were: o o o o standing tire vertical spring rate standing tire lateral spring rate ti re s i desorce response to s 1 i p ang 1 e peak friction of the standing tire on a concrete surface in the longitudinal and lateral directions As original ly proposed, these properties would have been measured for two tires, each at two inflation pressures and three vertical load conditions, thus providing a matrix of 12 test conditions (two tires x two pressures x three loads). By agreement with M. Ricketts, the test matrix was altered such that the tire properties of interest were measured for one ti re removed f rom the L.AV. Each property was determined under conditions of 0, 45, and 65 psi. inflation pressure and at 1500, 3500, 5500, and 7500 lbs. vertical load. This matrix also provided for 12 test conditions (one ti re x three pressures x four loads), and, therefore, an equivalent volume of ti re data as original ly proposed. The results of the tire tests are contained in the series of graphs which follow. Note that the friction coefficient of the standing tire was measured on new concrete which was prepared with both "smooth" and "rough" surface sections. Moderate differences are seen in the resulting data. Side force data for the uninflated tire is also of interest. Note that the tire behaves remarkably well at low levels of slip angle, but above four degrees of slip, the side wall apparently becomes unstable and side force 1 i teral ly "goes away." (The ti re is very erratic in its behavior under these conditions such that the data sampl i ng and averaging routines employed may not be appropriate. Accordingly, data in the unstable regime should be considered to be qua1 itative only.) Drivers should be aware that, with flat tires (particularly at the rear), the vehicle [nay handle reasonably well at low maneuvering levels (possibly providing a false sense of security) but may rapidly become unstable at moderate levels of maneuvering severity.

6 Suspension Properties The suspension properties requested by the reference sol ici tat ion were measured using UMTRl's heavy vehicle suspension test facility. The vehicle's rearmost axle was chosen as t:he "rear" axle for test, while the second axle from the front was chosein as the "front" axle for test. Ti res and wheels were removed from the t:est axles and replaced with "rigid" surrogates. Thus, the properties measured are those of the suspension only, and do not include the influences of tire compliances. Test resul ts are presented in the several graphs which fol low. Vertical rate is shown over the full suspension travel, with bump stop effects clearly evident. Coulomb friction is relatively low in both vertical and roll rate data. The rear suspension shows virtually no roll steer and little aligning moment ccmpliance steer as would be expected from this stout, "pure" trailing arm suspension. Front suspen sion roll steer is significant, however, and front suspension aligning moment steer reveals a substantial steering system compliance. As is typically the case, the front aligning moment compliance steer data also reveal steering system lash (i.e., the more vertical, central portions of the data) but there is a somewhat large level of Coulomb friction (evidenced by the horizontal spacing of the hysteresis loops) also apparent in the data. In addition to the data presented graphically, roll center height of both suspensions was determined. As predicted by theory, the roll center of the trai 1 ing arm rear suspension was found to be at the ground plane. For the front suspension measured, roll center heights were found to be as fol lows: Total Axle Load (pounds) Suspension Roll Center Height 1 / / ( i nches below reference*). *Vertical reference is the sharp, outer body edge at the longitudinal position of the axle.

7 Ti re Properties Graphs Standing Tire Vertical Spring P=65 psi Standing Tire Vertical Spring P=45 psi Standing Tire Vertical Spring P=O psi Standing Ti re Lateral Spring Rate on Smooth P=65 psi Fz=7556 lbs. Standing Tire Lateral Spring Rate on Smooth P-65 psi Fz=5533 lbs. Standing Tire Lateral Spring Rate on Smooth P=65 psi Fz=3522 Ibs. Standing Ti re Lateral Spring Rate on Smooth P=65 psi Fz=1516 lbs. Standing Tire Lateral Spring Rate on Smooth P=45 psi Fz=7542 Ibs. Standing Ti re Lateral Spring Rate on Smooth P=45 psi Fz-5517 lbs. Standing Tire Lateral Spring Rate on Smooth P=45 psi Fz=3534 Ibs. Standing Tire Lateral Spring Rate on Smooth P=45 psi Fz-1531 Ibs. Standing Ti re Lateral Spring Rate on Rough P=65 psi Fz= bs. Standing Ti re Lateral Spring Rate on Rough P=65 psi Fz= bs. Standing Ti re Lateral Spring Rate on Rough P=65 psi Fz=3543 lbs. Standing Ti re Lateral Spring Rate on Rough P=65 psi Fz=1531 lbs. Standing Ti re Lateral Spring Rate on Rough P=45 psi Fz-7532 lbs. Standing Ti re Lateral Spring Rate on Rough P=45 psi Fz bs. Standing Tire Lateral Spring Rate on Rough P=45 psi Fz=3.513 lbs. Standing Ti re Lateral Spring Rate on Rough P=45 psi Fz=1508 lbs. Side Force Responses to Positive ST ip P=65 psi Side Force Responses to Negative Slip P=65 psi Side Force Responses to Positive Slip 45 psi Side Force Responses to Negative Slip 45 psi Side Force Responses to Positive Slip P=O psi Side Force Responses to Negative S 1 i p P=O ps i Standing Ti re - Lateral Peak Friction Coefficient Standing Tire - Longitudinal Peak 'riction Coefficient

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35 Sus~ens ion Pro~ert ies Gra~hs S-1 Vertical Rate - Rear S-2 Roll Rate - Rear S-3 Roll Steer - Rear S-4 A1 igning Moment Compl iance Steer- Rear S-5 Vertical Rate - Front S-6 Roll Rate - Front S-7 Roll Steer - Front S-8 A1 igning Moment Compl iance Steer - Front

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