Optimum G weight Transfer

[Phil1988]

Hey everybody,

got a few questions about weight transfer. Read a lot in the forum an in Millikens and Smiths book but it was not satisfying enough to me..

So a friend of mine was at the Optimum G seminar. And now we startet to calculate the weight transfer of our car. The Optimum G script is very great and huge in detail with the equations. But we got simple understanding problems with the physics..

Lateral Load transfer rear axis /wheel by Optimum G:

?Fz_lateral: Lateral Suspended Geometric WT + Lateral Suspended "Elastic" weight transfer + Lateral Non Suspended WT + Weight force / wheel

Ok...I have all these equations..

Lateral Non Suspended WT: Weight transfer from the unsprung Suspension Members and so on. Seems clear and logic because of the different COG and Mass.

Weight force: Logic

Lateral Suspended Geometric WT + Lateral Suspended "Elastic" WT: Does not seem logic. Okay the elastic component: When i look a this NOT steady state cornering like in a slalom, there is a elastic component because of deflection from springs, arb, frame and so on.. But at steady state cornering. From where comes the elastic component? In my meaning it has to be geometric at all.

Suspended Geometric WT= SM*lat_acc*RCheigt/track_rear

Suspended "Elastic" WT= SM*lat_acc*(COGsm-RCrear)/track_rear

In my meaning the suspended mass has the lever arm from (COG_SM_rear_axis - rollcenter_rear_axis)

Can someone explain?

Regards Phil

[Owen Thomas]

Typical weight transfer equations like the one you posted are not a function of time, so there is no theoretical difference between the amount of weight transferred in a transient and in a steady state corner (provided the input values are the same).

To answer your question, you should read up again on the definition of geometric vs. elastic weight transfer. Consider the following: are your springs compressed (deflected) in a steady state corner?

[Z]

Originally posted by Phil1988:
... got a few questions about weight transfer.
...
Lateral Suspended Geometric WT + Lateral Suspended "Elastic" WT: Does not seem logic.
... at steady state cornering. From where comes the elastic component?
Phil,

As Owen suggests, you should make sure you understand the definitions of "Elastic" and "Geometric" WT.

Briefly, EWT comes from the deflection forces of the suspension's springs, as they compress or stretch away from their static ride height positions. GWT comes from forces in the suspension's control arms, and is perhaps best thought of as acting along the wheelprints' n-lines.

As an example to think about, if your car is softly sprung, then in a slalom it is quite possible that EWT is "negative", or in the opposite direction to GWT. That is, EWT can be reducing weight on your outside wheels, and increasing weight on your inside wheels.

Z