Important suspension parameters 3

[GregLocock]

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]

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]

Anti-x
spindle length
roll steer
hub trail

 

[patprimmer]

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]

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

How about transients?

 

[GregLocock]

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]

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]

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]

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