Vehicle Performance

A Presentation on

Vehicle Performance

S Srinivasa RaoScientist ‘F’

CVRDE, Chennai1

Combat Vehicle & Research Development Establishment, Chennai- 600 054.

Content• Vehicle performance Parameters

• Vehicle Resistances (Passenger Vehicle)

• Adhesion Limit

• Tractive Effort Calculation

• Vehicle Performance Diagram

• Vehicle Acceleration

• Tractive Effort Diagram

• Various Vehicle Resistance (Tracked Vehicle)

• Vehicle Performance2

Combat Vehicle & Research Development Establishment, Chennai- 600 054

Vehicle performance Parameters

Maximum speed of vehicle

Gradient climbing

Acceleration

Steering

Terrain negotiation

Tilt negotiation

Braking

Reverse motion

3Combat Vehicle & Research Development Establishment, Chennai- 600 054

Vehicle Resistance (Passenger Vehicle)


•ROLLING RESISTANCE

•ROAD SURFACE RESISTANCE

•SLIP RESISTANCE

where

Wheel Resistance (FR)Wheel Resistance (FR)

where,


Coefficient of Rolling Resistance (fR)


Dynamic wheel radius (rdyn)

Distance travelled per revolution by the wheel which is rolling without slip at 60 kmph.


Gradient Resistance (FSt)Gradient Resistance (FSt)


where,

Air Resistance (FL)Air Resistance (FL)

assuming zero wind velocity.


Acceleration Resistance(Fa)Acceleration Resistance(Fa)

where,Rotational inertia coefficientVehicle massMass moment of inertia of rotating elements about driving axleAcceleration resistanceVehicle acceleration


Total Tractive Resistance

Total Tractive Resistance


Combat Vehicle & Research Development Est.

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1. Mass of vehicle = 1000 Kg

2. Good earth track (fr =.045)

3. Gradient = 30 degree

4. Air Density = 1.199 kg/m3

5. Drag Coefficient = 0.3

6. Projected area of vehicle = 2 m2

7. Rotational Inertia coefficient = 1.2

Assume no wind flow and acceleration.

Total Tractive Resistance = ??

Exercise:

Adhesion Limit

where, = Static coefficient of friction


radius Wheel

ratioGear EfficiencyTorque Engine effort Tractive

ratioGear

speed Engine Speed Vehicle

Lock up mode

Torque Converter mode

ratioGear

ratio speed T.Cplot) matching T.C speed(From Engine Speed Vehicle

radius Wheel

T.C.RatioEfficiencyratioGear plot) ngT.C.Matchi mTorque(fro Engine effort Tractive

Tractive Effort Calculation


Vehicle AccelerationAcceleration of the vehicle at various gears is calculated by finding the excess power/torque available after overcoming the tractive resistance.

For acceleration performance of the vehicle during movement on level surface:

where, = Excess traction

= Rotational inertia coefficient

= Vehicle mass


Tractive Effort Diagram


Vehicle Performance Diagram


Vehicle Resistance (Tracked Vehicle)


pyspcb KZCZKbR 25.02

21tan

2Cos

NK rPY

Where ,

C = Cohesion ,

W = Gross Vehicle Weight = 35000 Kgs

NC , Nr = Bearing Capacity factor of Dry Sand

= Angle of internal shear

K , KC = Modulus of Terrain Deformation

Z = Sinkage in terrain = Angle of internal shear

2)( CosTanNK Cpc

Bulldozing resistance is defined as the force required to push the (terrain) soil mass at a sinkage Z ahead of the track or wheels

Bulldozing ResistanceBulldozing Resistance

s 19Combat Vehicle & Research Development Establishment, Chennai- 600 054

12

1

n

ZKb

KbRn

CC

n

KbK

blW

Z C

1

2

Where ,

Rc = Compaction Resistance

W = Gross Vehicle weight

K , KC = Modulus of Terrain Deformation

Z = Sinkage in Terrain

n = Co-efficient of Terrain in Dry Sand

b = Track Width

l = length of track in contact with sand

Compaction resistance is the motion resistance encountered due to compaction of the bearing substrate material ie the soil in the vertical direction.

Compaction ResistanceCompaction Resistance


)3222( VWRr FOR VEHICLES GVW > 20 TONS

)5.2133( VWRr FOR VEHICLES GVW < 20 TONS

W = Gross vehicle weight (Tons)

Rolling resistance is built up of hysteresis loss in deforming tyres or friction in tracks, loss in deforming the ground beneath the vehicle frictional losses in hubs and part of the drive train.

weight veicleGross

resistance Rolling resistance rolling fefficientoCo

(Newton) resistance Rolling rR(Kmph) speed VehicleV

Where,

Rolling ResistanceRolling Resistance




TRACTIVE EFFORT DIAGRAM

0

50000

100000

150000

200000

250000

0 10 20 30 40 50 60 70 80

SPEED IN KMPH

TR

AC

TIV

E E

FOR

T IN

N

TORQUE CONVERTER MODE

35 DEG

30 DEG

20 DEG

10 DEG

5 DEG

ENGINE : GREAVES ENGINEMAX POWER : 550 HP @2300RPMMAX TORQUE :1938 NM@1650RPMFIRST GEAR : 4.385SECOND GEAR : 2.6885THIRD GEAR : 1.6310FOURTH GEAR : 1.0INPUT GEAR RATIO : 1.9090TORQUE CONVERTER RATIO : 2.0SPROCKET RADIUS : 0.31955 M

FIRST GEAR

SECOND GEAR THIRD GEAR FOURTH GEAR


Vehicle PerformanceMaximum Speed:• Assuming vehicle moving on level surface with uniform speed• Intersection of traction resistance curve with traction available curve

Gradability:• Entire excess traction is used to negotiate the gradient

Acceleration:• Assuming vehicle moving on level surface


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Questions ??

Combat Vehicle & Research Development Establishment, Chennai- 600 054


Documents

Vehicle Performance