Air-spring coupled anti-roll bar

[Brian Evans]

I had an interesting conversation this morning about a formula car application that was using air-spring cannisters to couple the suspension to the ARB. The ARB was sized to have essentially infinite rate and all tuning was done with pressure in the air spring cans.

Any thoughts on this? Any teams doing this?

Brian

[John Valerio]

interesting idea, i could see it having merit in some systems, but i think for our application you're just introducing more stiction to the system. also your infinite rate bar would probably have to be pretty beefy to approximate an infinite rate, which will add more weight on top of the air springs themselves. it would be nice for adjustments, but then again blade ARB adjustments aren't that difficult or time consuming.

[Ashley Denmead]

Hi Brian,

We use a hydro-pneumatic anti roll system on our car. It has proven to be very versatile and tunable.

cheers

Ash

[flavorPacket]

the late-90s lola champ car had a coil-sprung droplink that acted the same way. delphi has a hydraulic system that does the same thing. With that system, you can actually effect roll damping or preload the arb ahead of time for better response. ZFSachs and ArvinMeritor also have similar systems. It's pretty neat, but I don't think a superlight formula car is the correct application. Our 07 car's entire anti-roll system weighed .65 lbs..

[DJHache]

Modern A1GP cars (also Lola's) have the same feature, a coil-sprung droplink to allow ARB adjustments. It's pretty clever but it adds a fair bit of stiction in the system. The advantage on the A1GP is that the ultrastiff ARB has very small arms and it keeps the frontal area very small. Basically it's for good packaging.

[Brian Evans]

Talked to a buddy of mine who has been a crew chief/team manager in high level teams (Le Mans, ALMS, Grand Am). He basically said a spring is a spring, matters little how it's packaged (blades, simple bent bars, coils, air) except that packaging does indeed matter a great deal in some cases.

He brought up another idea that is in use in some senior categories - using a damper to couple the ARB to the suspension. You need one only per ARB, and as the damper is velocity sensitive you can tune it to be agressive in turn-in, and soften for maximum grip in the center of the turn, and again have a different effect of corner exit.

Kind of a neat idea, I thought, but too complex for me to use!

Brian

[flavorPacket]

I don't buy that, because your response will be different depending on which way you turn. One way, the damper gets actuated right away, and the other way it's actuated through the ARB. Unless your ARB is super super stiff, this will throw your time constant way off.

[Christopher Catto]

Anybody got pics or diagrams of the ZF / Lola / A1GP / setup? Would kindof explain a little better the advantages of these systems. Only found this on google

http://www.freepatentsonline.com/20060290079.html
but no clear diagrams.


can't think I've seen that setup on any other formula cars (F3, F1, GP2) but that may be due to their very stiff ARB rates or very small packaging space in the footwell.

IMHO adding dampers everywhere is a theoretically clever idea but in practice rather OTT. Think if your steering had a damper (like a bike), then your throttle had a damper, then your.... you know, you end up tuning the valving for everything on your car! I'm sure you could shave a bit of time off by smoothing the driver's steering input with a MR damper that's linked to a gyro and the ecu/logger.

It's the future, but do I like this future? NO. Just like when they changed footballs from good ol fashioned leather to some kind of plasticized crap just so Nike can get money and so it has a friction coefficient of 2...

[DJHache]

We run a damper on the throttle in GP2

[flavorPacket]

chris, you're absolutely right. Personally I think all these mechanical systems should be replaced by hydrualic ones, ala kinetic/creuat.