SUSPENSION DESIGN AND CONSTRUCTION

FOR ALL TERRAIN VEHICLE

Ravindra Deshmukh

Mahindra & Mahindra Ltd.

R&D Centre Nasik.

ALL-TERRAIN VEHICLE

WHAT ARE THE DEMANDS FROM

•STRUCTURE

•SUSPENSION SYSTEM

•STIFFNESS- DESIGN FOR MAXIMUM

TORSIONAL STIFFNESS AND LEAST

WEIGHT.

•PROVIDE LARGE SUSPENSION

TRAVELS

•PROVIDE SUFFICIENT GROUND

CLEARANCE

•USE MAXIMUM TRACK POSSIBLE.

•DESIGN TO PROVIDE TYPICAL

TUNABLE FEATURES.

ROLL CAGE STIFFNESS

HOW TO EVALUATE.

•HOLD REAR SHOCK ABSORBER

POINTS .

• APPLY TORQUE AT THE FRONT

SHOCK ABSORBER ATTACHMENTS.

•MEASURE DEFLECTIONS AND

CALCULATE TORSIONAL STIFFNESS.

DESIGN STIFF JOINERIES AT JUNCTIONS

DESIGN STIFF ATTACHMENT POINTS

USE MAXIMUM TRACK POSSIBLE

KEEP GROUND CLEARANCE MORE

THAN 200 MM

PLACE WHEELS AT FARTHEST

CORNERS.

PLACE AGGREGATES LIKE FUEL

TANK , POWERTRAIN AS LOW AS

POSSIBLE.

PREFERRED SUSPENSION

TYPES

•EQUAL/UNEQUAL LENGTH

WISHBONES

•MACPHERSONS STRUT/

SEMISTRUTS

WHAT IS MY CHOICE

• EQUAL ARM DOUBLE WISHBONE BOTH FRONT AND REAR.

•LARGER SUSPENSION TRAVELS POSSIBLE.

•ADJUSTABLE ROLL CENTRE HEIGHTS

•CONTROL OVER CAMBER CHANGE RATE

•CONTROL OVER RIDE AND ROLL STEERS

WHAT SHOULD BE TUNABLE FEATURES IN

THE DESIGN.

•WEIGHT DISTRIBUTION.

DESIGN MOUNTINGS SUCH THAT SOME

EXTEND OF ADJUSTMENT IS POSSIBLE.

•SUSPENSION

•RIDE HT / SUSPENSION TRAVEL

•BODY ATTITUDE

•WHEEL LOADS/ SPRINGS

•DAMPERS

•STATIC SETTINGS OF WHEEL ALIGNMENT

GEOMETRY

•ROLL CENTRE HT FRONT AND REAR

•SWING ARM LENGTH

•HEIGHT OF STEERING RACK.

DESIGN OF SUSPENSION COMPONENTS

WISHBONES

KEEP CALCULATIONS SIMPLE.

DRAW FREE BODY DIAGRAMS FOR

LOADS ON WISHBONES.

DESIGN FOR STIFFNESS. STRENGTH

FOLLOWS.

CREATE CLEAN DRAWINGS

/SKETCHES FOR FABRICATION. KEEP

SHAPES SIMPLE.

CALCULATE STRESSES FOR SINGLE

EVENTS LIKE 5G IMPACTS AND KEEP

BELOW Y S

DESIGN OF SUSPENSION COMPONENTS

WISHBONES PIVOTS

•USE RUBBER BUSHINGS / OR SOLID

BUSHINGS

•ENSURE WISHBONE MOVE FREELY

AND DO NOT RUB AGAINST

ATTACHMENT BRACKETRY.

•RUBBER BUSHINGS IF READILY

AVAILABLE ARE PREFERRED . CAN

WORK AROUND THE COMPLIANCES

DURING TUNING.

DESIGN OF SUSPENSION COMPONENTSCOIL SPRINGS/ SHOCKS

•COIL SPRING OVER SHOCK DESIGNS

ARE EASY FOR TUNING. USE

SCREWED TYPE SPRING SEATS ON

SHOCKS

•CHECK THAT COIL SPRING DOES

NOT BECOME SOLID AT COMPLETE

BUMP TRAVEL.

•CHOOSE SHOCK ABSORBER

LENGTHS SO THAT THEY DO NOT

BOTTOM OUT AT FULL JOUNCE

TRAVEL.

•IF AVAILABLE TRY USING DIFFERENT

DAMPING VALUES DURING TUNING.

•REMEMBER YOU ARE MAKING A

RECREATIONAL VEHICLE.

USE BALL JOINTS AT UPRIGHTS

. ALLOW MORE ARTICULATION

•FIGURING A SUSPENION OF A CAR IS

ALMOST ENTIRELY A MATTER OF MAKING

USEFUL APPROXIMATIONS.

•IT IS NOT A EXACT SCIENCE

•BUT NEITHER IS IT A BLIND APPLICATION

OF RULE OF THUMBS

My e-mail address

deshmukh.ravi @ mahindra.com

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