Suspension design by_ravi_deshmukh
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Transcript of Suspension design by_ravi_deshmukh
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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