Important suspension parameters 3

GregLocock · Jul 31, 2003

I'd like to compile a list of the suspension-related kinematic characteristics that need to be specified when designing a vehicle from scratch. By its nature this is a top down approach.

WHOLE VEHICLE:

Sprung mass

Sprung CG X and Z

Moments of inertia

Maximum steady state lateral acceleration

Ground clearance

roll stiffness (degrees per g of lat acc)

AXLE

position

track

tyre size, hence rolling radius

Jounce travel

rebound travel

track gain in roll

roll center height at design load

roll centre height gain

WHEEL

semitrack gain, ie lateral displacement of contact patch per unit of jounce travel

camber gain

toe gain

KPI

scrub radius

wheel offset

castor

castor gain

castor trail

unsprung mass

static camber

What have I missed? I realise some of these aren't kinematic, and some are interrelated.

Cheers

Greg Locock

pmwltd · Jul 31, 2003

Greg:
A couple of others that might fit into the list would be ride frequency, including front to rear percentages and lateral weight transfer percentage distribution front to rear. Another piece of the geometry would be steering axis angle. I am sure there are others

Dave

hpfreak · Aug 1, 2003

Anti-x
spindle length
roll steer
hub trail

patprimmer · Aug 1, 2003

Torsional stiffness of the body structure

Stiffnes of the major suspension mounting points, ie on a McPherson Strut, do the strut towers move around

Regards
pat

rocketdoc · Aug 4, 2003

Why just "steady state" lateral acceleration (rarely happens)?

How about transients?

GregLocock · Aug 4, 2003

Because you don't worry about transients when you set the hardpoints up, typically. They are handled by tuning the completed vehicle, not analytically (with a few exceptions).

Cheers

Greg Locock

TestDriver · Aug 13, 2003

Roll axis gradient and any gradient change relative to roll. Related to caster and caster trail would be pin lead/trail. What about desired Ackerman percentage/change, steering ratios and so on.

Ramon Mendoza

chassismatt · Mar 30, 2004

Hi Guys, I'm new to the forum- I just discovered it and it appears to be a good source of collabortion. I have worked in vehicle dynamics for the past 5-6 years doing both analysis (ADAMS and other smaller tools) as well as ride and handling development. Can't wait to talk with you all some more!

on to this topic:

Other compliance related parameters that are very important are:
Lateral force steer (deg/g)
Aligning torque steer (Nm/deg)- one of the largest contributors to the front cornering compliance after the tire cornering coeff.
Lateral force Camber compliance (small effect)
Aligning torque Camber compliance (small effect)

The other one I didn't see was TLLTD (tire lateral load tranfer distribution) or "roll couple distribution" which you guys all know is very important for limit understeer)

2SlowJoe · Mar 31, 2004

Ride Steer and Roll Steer
Ride Camber and Roll Camber
Side View Swing Arm Angle (SVSAA)
Lateral Stiffness (at ground w/o tire)
Fore-Aft Stiffness (at wheel center w/o tire)
Lateral Force Camber Compliance
Tractive Force Steer
Brake Force Steer

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Important suspension parameters 3

GregLocock

Automotive

pmwltd

Automotive

hpfreak

Automotive

patprimmer

New member

rocketdoc

Aerospace

GregLocock

Automotive

TestDriver

Mechanical

chassismatt

Automotive

2SlowJoe

Automotive

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