96DXCivic
96DXCivic Reader
10/14/08 5:43 p.m.

I was looking at Tune to Win by Carroll Smith. At lateral load transfer section of the book, he has an equation to lateral load transfer. Then having calculated the lateral load transfer he gives the cornering force of the car. How does he get from one place to another? Have I missed something?

Apexcarver
Apexcarver SuperDork
10/14/08 6:36 p.m.

probably the coefficient of friction for the tires...

the weight that presses down on the area of contact for the tire is involved with your transfer. take that, the size of your contact patch, the coefficient of friction (which IIRC is related to the weight pressing down on it.. i think ive seen it expressed both ways) and there you have the cornering force..

if you ask REALLY nice i might get all the formulas and stuff from my dynamics or physics texts for you.. but not today.. dont feel like touching my textbooks after the calc 2 exam i had..

IIRC its somthing like (mew)K*normal force.. where (mew)k is involved with surface area (i usually get (mew)k as a given quantity, but i did do it with area involved in the problem in PHYS-261 )

you can probly find it on wiki from there, but if you really need it i can look it up tomorrow.

to get much of consequence out of having the formula you would really need some detailed data on your tires (coefficient of friction at a given temperature) whereas IIRC smith gives it to you primarily so you can understand the affect that load transfer has upon ultimate cornering force. (load transfer being a tradeoff with surface compliance given by the shock/spring/sway not being a solid structure.)

(edit* wow... and to think i can pull this from memory after being brain fried from a calc 2 exam.. this education stuff may be paying off )

96DXCivic
96DXCivic Reader
10/14/08 7:05 p.m.

The equation for lateral load transfer is (lateral acceleration x weight x c.g. height)/ track width. So if it includes lateral acceleration and corning force is involves lateral load transfer (as Carroll Smith seems to indicate that it is), wouldn't that remove the need to know the coefficient of friction?

Keith
Keith GRM+ Memberand SuperDork
10/14/08 7:27 p.m.

Yup. The load transfer is a function of lateral acceleration. So it's not too hard to go back and forth as long as you know the other constants in the equation. In fact, that's how you can figure the CG height of a car, by tilting it to the side and measuring the weight on the wheels. You've got the lateral acceleration, the load transfer, the track width and the weight.

jstein77
jstein77 HalfDork
10/14/08 8:19 p.m.

Corning force? That's how big a lump you get on your head when your wife hits you with her cookware.

Oh wait, you meant cornering....

Nevermind.

96DXCivic
96DXCivic Reader
10/14/08 9:05 p.m.

So I am still confused how to get back and forth between cornering force and load transfer. And I can believe I misspelled cornering force twice. And they say college makes you smarter.

Apexcarver
Apexcarver SuperDork
10/14/08 9:55 p.m.

in that case im confused about what your confused about...

what variable are you missing in that equation?

the harder you turn the less force holding down the inside tire..

96DXCivic
96DXCivic Reader
10/14/08 10:08 p.m.

I still don't know how to getting the cornering force of the car from the lateral load transfer. But turns out I don't need that after all.

Keith
Keith GRM+ Memberand SuperDork
10/15/08 2:46 p.m.

You posted the equation yourself. Just spend some time looking at it :)

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