"4-Way suspension" work alike?

[PhillipM]

You think damping requires hydraulics?
This is basic textbook stuff you have forgotten?

Since I have a Bentley in with friction disc dampers for a refurb at the minute, that's a pretty silly assumption.

But then so is the fact that another spring working against the primary one will give some damping change. If you have twin springs on a valvetrain, or in a coilover, one inside the other, it is the interference between coils that gives the slight damping to prevent the spring itself becoming excited (because they will shimmy sideways near critical frequency, dual coils prevents that by giving two different frequencies and support for one near critical from the other spring) - that's not happening here.

Hell, you ask me if I've forgetten textbook stuff yet you call them a 'snubber' in the post before that - you do realise that a snubber works on constrainment through mechanical friction and an inerter, yes?
So NOTHING like just adding another coil spring to an existing system?

[Piledriver]

Please respond with something better that "I design suspensions" as a reason or desist.

I would like to be able to model this setup and approach some level of understanding.
It may be simply that the effective spring rates go through the roof or almost to zero with any significant motion from rest.
(and yes, it is very progressive, and my wheels are not velcro'd to the driveway, and the suspension does have full travel... although the spring rate at full extension is probably approaching zero by the time it hits the stops.)

And my head is not up my arse, I have been called crazy, but never stupid.

I'm not selling anything.
I know it works. I have actually used it.I use it DAILY.
I admit we do not fully understand WHY it works as well as it does.
I am not the only delusional user.
If we understood that we could improve on it, or at least optimize it.

[KentT]

The two spring valvetrain example has zero relevance to this setup... in that example, both springs are mounted in the same way, both top and bottom, and both are set up to resist only compression. The second spring could actually be replaced by a stronger primary spring and function the same way -- in fact, it it a normal upgrade route to go from a HD single spring per valve to two softer dual springs.

Here, we have one very strong spring that is also mounted to provide support only under compression. But, we have another, weaker spring that is mounted to provide no support at rest, in the normal, centered position, but resists both compression and extension of the larger spring. Then there's the shock in the center to dampen oscillations in movement. The smaller spring, mounted on the shock, helps to pull that shock back to the normal, centered position, and resists any oscillations in that shock that would move it from that centered position, whether up or down. That second spring, mounted on the 4-way shock, is a progressive spring, providing more resistance the farther it moves from its centered position. It provides added progressive dampening of the suspension by working with the existing shock...

For your example of a valvetrain to be similar, the second, weaker inner spring would have to be mounted to push/pull the valve to the half-open position. It clearly is not...

[PhillipM]

The two spring valvetrain example has zero relevance to this setup... in that example, both springs are mounted in the same way, both top and bottom, and both are set up to resist only compression. The second spring could actually be replaced by a stronger primary spring and function the same way -- in fact, it it a normal upgrade route to go from a HD single spring per valve to two softer dual springs.

Here, we have one very strong spring that is also mounted to provide support only under compression. But, we have another, weaker spring that is mounted to provide no support at rest, in the normal, centered position, but resists both compression and extension of the larger spring. Then there's the shock in the center to dampen oscillations in movement. The smaller spring, mounted on the shock, helps to pull that shock back to the normal, centered position, and resists any oscillations in that shock that would move it from that centered position, whether up or down. That second spring, mounted on the 4-way shock, is a progressive spring, providing more resistance the farther it moves from its centered position. It provides added progressive dampening of the suspension by working with the existing shock...

For your example of a valvetrain to be similar, the second, weaker inner spring would have to be mounted to push/pull the valve to the half-open position. It clearly is not...

You are confusing damping force (not dampening, you're not wetting the damned thing), with spring forces, they're not the same thing.
Many of you seem to think there is something magic about the spring being clamped and resisting oscillations up or down, I don't see why you find this so surprising, as as soon as you consider a standard spring is loaded with the vehicle weight, that's exactly what a normal spring does - if it didn't your vehicle would never return to ride height.

As for reasoning Piledriver, yes, I can respond with graphing it out if you like, but I like that I have to provide those when you have half a dozen pages here of you and others going 'my works like this in my head and that's it' without ANY math or reasoning. Guess I'm not as special as you guys eh?

[KentT]

I know the difference between damping and spring force. These springs pull the suspension back to an "at rest" position, resisting further oscillations up or down...

If you try the old "bouncing bumper test" commonly used to check for worn shock absorbers, these will rebound to "center" and not move further -- no further oscillation or up and down movement....

If that is not damping the normal suspension's spring action, then what is it?

I've clearly stated that these are not 'magic" --- but I continue to iterate that they are unique to the market...

I don't see why you can't understand that these are installed in a "no-load" orientation -- not supporting any vehicle weight -- while normal springs that you keep referring to are always under load if the wheels are on the ground. Similarly, these springs are locked to the shock resisting any effort of the normal springs to "unload" when you go over a bump or weight otherwise shifts off the front end...

You keep coming up with examples and analogies that simply do NOT match how these things operate...

[PhillipM]

I know the difference between damping and spring force. These springs pull the suspension back to an "at rest" position, resisting further oscillations up or down...

If you try the old "bouncing bumper test" commonly used to check for worn shock absorbers, these will rebound to "center" and not move further -- no further oscillation or up and down movement....

If that is not damping the normal suspension's spring action, then what is it?

I've clearly stated that these are not 'magic" --- but I continue to iterate that they are unique to the market...

I don't see why you can't understand that these are installed in a "no-load" orientation -- not supporting any vehicle weight -- while normal springs that you keep referring to are always under load if the wheels are on the ground. Similarly, these springs are locked to the shock resisting any effort of the normal springs to "unload" when you go over a bump or weight otherwise shifts off the front end...

You keep coming up with examples and analogies that simply do NOT match how these things operate...

You keep coming up with weird tests that tell you nothing - the speed and extent of the oscillation will change with spring rate and friction/stiction, of course it will be different, you're changing spring rates. If I put 1000lb/inch springs on a Radical racer and push one corner down for a bounce test, it won't even move far enough to test it, and it'll settle so fast (because the suspension frequency is so high) that even with no hydraulic dampers bolted on you'd never tell by eye what was happening.

How about, instead of giving me the results of a meanless test that's been influenced by other factors - you tell, me, exactly, how adding the springs changes the DAMPING force generated. And don't come back with 'They resist the standard springs' that's a spring rate change, not damping, that's not even close to the same thing.

They're not unique, there's a similar system on the race Atom's but it's actually useful as it doesn't clamp the spring but winds down it to give you almost infinite spring rate adjustments.

[Piledriver]

Plot the combined spring action.
Plot the damping ratio over the range of motion.
(they typically go over ~stock shocks)

Spring rate and system frequency doesn't effect damping? Really?

Phillip, you insist these do not work but have not tried them.
Seems you easily could but prefer to insult us here, rather than actually testing anything.

[PhillipM]

Damping coefficient != damping force.

And either way you go about it, the springs are still not 'acting as dampers' as you both keep continually posting. Hell, the only person that does seem to have a bit of a clue is Helowrench.
You keep telling me I haven't tried them, but when we ran torsion leaves years back in the front of the buggy they were setup to do the exact same thing, the secondary torsion bars in the rear also do the exact same thing, although in both cases set to keep the crossover out of the ride height area (because it makes the car less predictable on the limit)

[Piledriver]

Damping coefficient != damping force.

No one said otherwise.

The ~stock shocks have a fixed friction up, and a different fixed friction in extension.
The spring force varies over the travel, so the damping ratio varies.

Preloading (pulling) the rear DOWN ~1" took the weird out of the handling on my DD, softened the roll resistance and seemingly springing out back, and it seems to ride as well as or better than stock, certainly no worse than my 914.
(found that trick the first time when I used these ~30 years ago.)

[PhillipM]

No, the damping coefficient is linked to the spring rate, not the spring force. The spring force doesn't matter because the damper force curve varies with velocity (which is tied to spring force), so they cancel each other out and only the slope of the damping force vs the spring rate is relevant.

Which is why with variable rates you can't get your dampers working ideally all the time, unless you do it through rocker arms to vary the damper leverage as well, or use a version of a bypass damper (although the commercially available Fox/King/Bilstien units are too crude in operation to do it).

You pulling the rear down is exactly what the rail's setup was, albeit with the torsion leaves set to come in later for the same effect.to keep the switchover/unpredictability out of the normal ride height area.

[Piledriver]

Without the preload (or pre-unload?) it acted like a far too stiff rear sway bar.
With it , the car responds extremely well and predictably, and even rides OK.
It swallows craters, but is choppy on small washboard surfaces.

(The front springs could be much softer, but a square doesn't particularly ride like a sofa stock)

Considering similarly preloading the front, but want to maintain the F/R balance.
I'm not sure I'm visualizing what is happening correctly, but works=win.

I'm just trying to get a handle on what rates are proper, and if different damping setup would help.
I guess experimentation is the really the only method in this case.

I'm sure there is never perfect damping under all conditions unless you have a computer running the dampers in real time.
(There apparently IS an app for that if you have certain suspension setups)

[PhillipM]

I'm not a big fan of swaybars at the best of times, I use them for correcting cornering habits if I have the spring rates where I want them for pitch and heave and have exhausted other avenues, or occasionally where I set a car up without any corner springs/bars to give roll control (otherwise it'd fall over) but that's it.

You'll never get perfect damping without pre-analysing the road ahead first, as there's a time delay, and even then, the fanciest dampers you can get can't alter everything on the fly, eventually, the physics of pushing a piston through fluid bites you on the arse no matter how much of it you try to adjust.

[KentT]

Damping
Damping is the control of motion or oscillation, as seen with the use of hydraulic gates and valves in a vehicle's shock absorber. This may also vary, intentionally or unintentionally. Like spring rate, the optimal damping for comfort may be less than for control.

Damping controls the travel speed and resistance of the vehicle's suspension. An undamped car will oscillate up and down. With proper damping levels, the car will settle back to a normal state in a minimal amount of time. Most damping in modern vehicles can be controlled by increasing or decreasing the resistance to fluid flow in the shock absorber.

http://en.wikipedia.org/wiki/Suspension ... e)#Damping Not that I consider Wikipedia an authority, but it serves as a pretty good dictionary...

These help control the motion and oscillation of the stock suspension, returning it to the normal "at rest" position.... Keep playing semantics all you will -- but again, if this isn't effecting the damping then what is it?

It is not just changing the spring rate, because at full extension of the stock suspension (fully unloaded) these added springs on the shocks will reverse the direction of travel, and retract the suspension back toward its "at rest" position...

[PhillipM]

No, that's just a very poor definition as there are far more things that affect control and oscillation than just damping. D
amping is a method of disspating energy in a controlled matter to reduce oscillations or control movement - springs don't dissipate energy in a controlled matter, they store and release causing oscillations.
I'm not playing semantics at all, you just evidently don't know what damping is, it's as simple as that.

You are just changing the spring rate, do the math, work it out, graph it if you must.
You. Are. Just. Changing. The. Spring. Rate.

[KentT]

Repeat until you're blue in the face, but that doesn't change facts...

Parse words until you write your own Oxford English Dictionary, and that doesn't change facts either...

These added springs help control oscillations of the primary springs in the torsion bars. Period. End. Of. Story.