17 replies to this topic

[red300zx99]

Now the concept of a third spring is nice, as you get to decouple roll and pitch within the suspension settings. But what is one looking to do when implementing one into a car. What should thwe ideal setting do and what would a stiffer or softer third spring do to performance?

[Greg Locock]

"Now the concept of a third spring is nice, as you get to decouple roll and pitch within the suspension settings"

Just like a conventional suspension - or do you think the a/r bar is ballast?

"But what is one looking to do when implementing one into a car. What should thwe ideal setting do and what would a stiffer or softer third spring do to performance?"

The maths, and the desired corner rates are pretty much the same as if you have a conventional setup, the difference is that the two springs control the roll rate, and the 3rd spring controls pitch, as an adder.

In a conventional setup the roadsprings set the pitch rate, and the antiroll bar is an adder for roll.

The advantage is that your roll rate can be softer than your pitch rate, difficult, but not impossible, to achieve with a conventional setup.

[red300zx99]

Softer springs=more mech grip. We need all of the help we can get. Sure it's possible with a conventional setup, but we aren't allowed to have a conventional setup in the rear. Only 2 springs, no roll bar. Anyways, how would one figure how much squat is desired so that a spring rate can be figured for the thir element.

[Antoine]

I have study the third spring on front suspension of a race car.
I worked on the kinematics on Adams software!
The third spring and damper is interesting when you have a very high downforce
you could work on the dampers to modify the pich speedand on the spring to control the ride heigh and the aero balance due to the floor effect!

[red300zx99]

Not working with a high downforce car, about 100lbs in front and 500lb at rear at 100mph. Increaed stability in braking and acceleration are the main objectives, well that and softer springs.

[superbad]

If you don't have a lot of downforce, I wouldn't mess with a third spring. You get some strange effects when the third spring kicks in. It's very difficult to sort out, and the main advantage is really to keep the car from bottoming under high downforce loads.

Not having a rear roll bar isn't a disadvantage at all. Let the thing roll. If you aren't ride height critical, and you have good suspension geometry, a little roll isn't going to hurt anything.

Otherwise, I would look at progressive rate springs (either variable helix or air springs). They can give you a nice soft wheel rate, but limit ultimate deflection under roll and pitch. They too can be a little tricky to set up though. Air springs are nice because you can make quick changes to the rate and progression.

Originally posted by red300zx99
Not working with a high downforce car, about 100lbs in front and 500lb at rear at 100mph. Increaed stability in braking and acceleration are the main objectives, well that and softer springs.

[red300zx99]

We've tested progressive springs and 2 springs for 1 coil-over, and they work. Makes set-up alot easier and all and the driver likes what they do to the car, one problem, they are illegal according to the rule book and easy to spot.

[Greg Locock]

Have you tried constant contact bump stops? Our cars now use long PU foam inserts on the shock rod, these give a very progressive spring rate.

[red300zx99]

Hmmmmm, will check on the legality of constant contact bump stops, but I can see that causing a problem with the officials even if it isn't in the rule book. They could easily call that a progressive spring.

[Antoine]

I never try but I think it's very difficult to set up a car with a third spring if you dont have a very high donwforce to control!

and what about anti rebound?

[red300zx99]

What about anti-rebound?

[Antoine]

Do you try?

[Greg Locock]

Not too sure by what you mean by anti-rebound. Oh, that does remind me, we now fit polyurethane 'spring aids' INSIDE our shock absorbers, as rebound springs.

You could do the same in jounce.

Fairly hard for the scrutineers to detect what is going on in there I think!

[Antoine]

I think your right!
but why do you try to cheat?

[red300zx99]

Not cheating, seeing how close to the line we can get without pissing off an official. It's great fun, you should try, especially gratifing if you win.

[Antoine]

Be sure I know that!
But when I change something in "my" racecar, I prefer asking about it the official to be sure that I 'm rigth!

So I was rigth on something in the start of this season, some other racecar copy my modification and after 5 or 6 races, 60% of the championship use this kind of modification; it's very gratifing for sure!
But someone thought that it was not very beautiful so this modification became illegal at mid season!
It's the game!

[red300zx99]

Just wondering why you would ask. I may ask for a clarification of the rules, but if I blatantly say what I'm doing then intelligence is sread like you said. I don't want that. When I make a modification I'm looking for an advantage. If everyone in the pits knows about it and is doing the same thing then where is the advantage?

[Antoine]

My modification was about aerodynamic so it's easy to copy!