air bagged suspension...

"Joe_Limon" (Joe_Limon)
05/03/2014 at 18:37 • Filed to: None

Hmmmm... Please judge my idea...

Imagine having air bag suspension on your sports/super cars. Only when pressurized they don't change ride height, they simply change the spring rate of a porous/chamber filled rubber block. Thus allowing your vehicle to dynamically adjust spring rates on the fly, tightening up in time for the corners, and softening on the straights.

DISCUSSION (18)

Yossarian > Joe_Limon
05/03/2014 at 18:39

Isn't that similar to what the McLaren 12c does?

E30Joe drives a Subaru > Joe_Limon
05/03/2014 at 18:40

Go on...

Joe_Limon > Yossarian
05/03/2014 at 18:42

In my current understanding, the Mclaren uses conventional coil springs, but the suspension is hydraulically linked to preload individual wheels.

Joe_Limon > E30Joe drives a Subaru
05/03/2014 at 18:43

Now imagine purchasing these rubber blocks that are sized/shaped to swap into conventional coil spring locations.

E30Joe drives a Subaru > Joe_Limon
05/03/2014 at 18:45

I like it. You could go from a comfy cruiser to a track rat in seconds. Implying the system worked as well as I think it would.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Joe_Limon
05/03/2014 at 18:47

Uhhh.... Electromagnetic suspension does this, but still maintains a normal spring.

Anima > Joe_Limon
05/03/2014 at 18:47

You mean something like this but with air?

Joe_Limon > Arch Duke Maxyenko, Shit Talk Extraordinaire
05/03/2014 at 18:57

I disagree, electromagnetic suspension varies damping, not spring rate, if you adjust damping you still get the same roll as you would with softer springs.

tromoly > Joe_Limon
05/03/2014 at 19:02

So how does damping rate influence spring rate? And further, how does damping affect rate of roll? Remember, the systems are coupled.

Joe_Limon > tromoly
05/03/2014 at 19:39

Increased damping stiffness causes tyre loads to transfer faster, as do increased spring rates. However that damping effect is dependent on the rate of transfer with dampers, and is independent with springs.

As an example, stiff dampers and soft springs will make a vehicle feel responsive to sudden inputs, but slugish/sloppy/rolly with prolonged loading.

Conversely, soft dampers and stiff springs will provide ample response in all scenarios, but the lack of damping will cause over response/oscillations.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Joe_Limon
05/03/2014 at 20:38

That's why dual rate springs are used on cars today.

Joe_Limon > Arch Duke Maxyenko, Shit Talk Extraordinaire
05/03/2014 at 20:54

Dual rate springs can be a great compromise. But they do have their drawbacks. For example, they provide a non linear cornering response. A car with progressive springs won't have responsive handling unless it has very stiff shock absorbers. In which case you lose out on some of benefits of softer springs.

tromoly > Joe_Limon
05/04/2014 at 13:40

So if you have the damping and springs "matched" dynamically, then increase spring rate as you're proposing, won't that give the drawbacks you've listed in your second example?

Why can't an adjustable ARB be used to provide the net increased spring rate you speak of?

Joe_Limon > tromoly
05/04/2014 at 14:17

Personally I view arb's as yet another compromise. Ideally, the vehicle won't use them since they remove the independent part of independent suspension. Disruptions in one wheel travel through and disrupt the other wheel. Which is why a select few super cars like the new Mclarens got rid of them.

Ideally, both your spring and damping rates would change with each other. Damping to improve response, spring rate to control body roll and generally maximize the tyre contact patch.

tromoly > Joe_Limon
05/04/2014 at 17:25

Isn't that possible with a progressive rate linkage?

Joe_Limon > tromoly
05/04/2014 at 18:05

Progressive rate anti roll bar?

tromoly > Joe_Limon
05/04/2014 at 22:27

Sorry, forgot to clarify. Running a bellcrank-actuated suspensin system, wouldn't a progressive-rate bellcrank provide a very similar thing to what you're proposing? As roll increases, the effective spring and damping rates increase as kinematically the shock package develops a greater effect on the system. So wouldn't this, in effect, allow the suspension to stiffen more in hard cornering whiel also eliminating the need for an ARB?

Joe_Limon > tromoly
05/04/2014 at 23:22

Such a system would allow many improvments, offering a soft ride for every day driving, and optimum spring/damping rates while at the limit. The only potential quibble I can see is that such a system would require a designated amount of body roll before the firmer suspension would take effect. Whereas a setup that is simply stiff all the time would require less body roll to achieve a similar spring/damping characteristic. It would be a far smoother transition than say... Rubber bump stops. Unfortuneatly initial turn in and sudden inputs while not at the limit will cause the vehicle to feel/behave more like a soft luxury vehicle than a sporty vehicle.

With an electronically controlled spring/damping rate, you can que sportier handling setups via toggles, or even run an algorithm looking for early cues such as sudden input responses on the steering wheel or throttle.