What the 'Fric' is it?

[GSpeedR]

You might be interested to know that some F1 suspensions for the last few years have achieved a roll/warp stiffness ratios of around 5. Perhaps an interconnected suspension allows similar ratios to be achieved with fewer contraints.

That is interesting, and admittedly higher than I expected without front/rear connections. Is this due to a large front/rear roll stiffness disparity? I would imagine that even with such a high roll/warp stiffness ratio, teams could see better mechanical grip if that ratio could be increased. The advantage of hydraulic implementation is probably due to packaging and 'fewer constraints' (reduced complexity?), but perhaps also due to the higher ratios than can be achieved compared to a mechanical equivalent.

[DaveW]

... teams could see better mechanical grip if that ratio could be increased.

But only, I think, if the vehicle has a natural balance, or other ways of achieving balance. If corner weighting is required, then I guess that a relatively finite warp displacement would be preferred.

[Crucial_Xtreme]

Here's Mark Hughes take on FRIC in which he confirms hydraulic linkages, valves, accumulators, & actuators are used, with said system being tuned by valve sizes & bleed valves. I'm just posting because Hughes & AS in general have good informations.


via AutoSport

[WhiteBlue]

It still doesn't tell us how it works and it leaves the design specifics open to speculation. I still think it will have gas accumulator springs on all four corners and the spring pressure differentials will control the cross and longitudinal damping rates. We will eventually see how it is done exactly.

[Dragonfly]

Here's Mark Hughes take on FRIC in which he confirms hydraulic linkages, valves, accumulators, & actuators are used, with said system being tuned by valve sizes & bleed valves. I'm just posting because Hughes & AS in general have good informations.

So it seems myself and other people here have been right in our assumptions.

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OT: As a Citromaniac I think it's a shame PSA killed slowly what once was a distinctive feature and pride of the Citroen brand.

[Tommy Cookers]

arguably this sort of suspension is advantageous to the enthusiast's car and driving
because it gets a better result from relatively small wheel travel
ie Hydrolastic and (when interconnected) Hydragas
remember the MG F

slow loss of (Hydra)gas after some years led to non-ideal (over) repressurisations, and lost the original qualities
(but H was liked by some 'boy racers' for 'screwdriver tuning', maybe they changed the liquid fill too, for lowering)
loss of gas gave a distinctive look, presumably we now call this a warp offset
was there loss or degradation of liquid fill in service anyway ?

if this sort of suspension features in F1 it must appear again in road cars ?

[autogyro]

arguably this sort of suspension is advantageous to the enthusiast's car and driving
because it gets a better result from relatively small wheel travel
ie Hydrolastic and (when interconnected) Hydragas
remember the MG F

slow loss of gas after some years led to non-ideal (over) repressurisations, and lost the original qualities
(but was liked by some 'boy racers' as 'screwdriver tuning', I wonder if they changed the liquid fill too, for lowering)
was there loss or degradation of liquid fill in service anyway ?

if it features in F1 it must appear again in road cars ?

We used to shorten the reaction struts that fitted into the displacer units and changed both the pressures and the fluid used.
That was on the basic Leyland Mini.
To improve the rear for competition, we did away with the rear subframe and fitted a beam axle set up with coil overs.
That allowed a more predictable hydralastic front end to play with with only two displacers front left and right.
The roll control from two linked front dispalcers with various valving and pressure reservoirs gave good results.
Leyland did look at a Metro XR4 system that would have resulted in an unbeatable rally car but all that was during the funeral of the British car industry, so it matters little today.
It is an ideal system for light road cars, although electromagnetic suspension is far better suited for the future and EVs.

[ringo]

That article isn't saying anything substantial.
It's telling me riding around on 3 wheels is advantageous and that in itself is.. I don't know what to say.

I can't get anything from this. It's not teaching us anything about the suspension.

[DaveW]

Here's Mark Hughes take on FRIC in which he confirms hydraulic linkages, valves, accumulators, & actuators are used, with said system being tuned by valve sizes & bleed valves. I'm just posting because Hughes & AS in general have good informations.

I hate to say this, but whilst Mark Hughes' article is very interesting, it also contains several inaccuracies - ".. using hydraulic fluid as the springing medium .." being one.

There are obvious differences between a mechanical suspension and an hydro-pneumatic (HP) equivalent, and it would be expected that one would be better (more efficient) at some functions than the other, and vice versa. For example, the HP version would be better at equalizing out static cross weight (if that is required - it might not be if the c.g. is laterally offset), whilst the other would be better at controlling static ride height.

I have put together a simple (static) model of the HP system, and have concluded that I would be uncomfortable running one on an F1 vehicle without either bars or springs - adjusting the mechanical balance, or even "a couple of turns of spring preload" would be a hassle, for example, as would a packer gap change without physical bump rubbers & shims.

I fact, I suspect both Scarbs' & Hughes' articles should be read in the certainty that any information leaked by a team running an HP system would primarily be intended to confuse (the competition).

[Lycoming]

With pneumatic springing, I would have concerns about repeatability of adjustment. It's relatively difficult to set pressure precisely, plus it inevitably leaks a bit and changes based on temperature. You can probably minimize the effect of all of that, but I don't think you will ever be able to set spring rate as accurately and precisely as you can with steel springs, which obey hooke's law very closely.

[Tommy Cookers]

That article isn't saying anything substantial.
It's telling me riding around on 3 wheels is advantageous and that in itself is.. I don't know what to say.
I can't get anything from this. It's not teaching us anything about the suspension.

I know what you mean, but .......
just over 50 years ago, Lotus were winning hundreds of open-wheeler races
the same was said then about (their) apparent 3 wheel cornering
at least it helps the powered end of the car

F1 front suspension geometry is disadvantaged by the aero driven structural configuration
anyway is required to give a large 'jacking' effect in corners to reduce compression of the suspension on the outside of the corner
so that the suspension will allow what us oldies regard as 'kerb hopping' (done when running relatively straight)
this geometry forces less than ideal camber gain
they attempt to alleviate this problem by using a rather large (currently notorious) static negative camber

since active ride was banned 'dampers' have developed to allow some of the characteristics previously considered unique to AR
ie dynamic stiffness very strongly variable with velocity etc, 'programmed' at buildup and by setup
'self-pumping' for ride height correction
and these sort of effects combined

surely passive devices can also adjust gas spring volume etc ?

[autogyro]

Racing Mini's always relied on getting the rear inside wheel off the ground in corners.
It was said that the fast mini drivers could always be recognised by how high the rear wheel was.

With the huge front weight bias there was little need of anything on the rear as it just followed the front in principle.
I have even seen an ultra light racing mini pitch forwards under braking right onto its roof.

The Lotus Cortina racers lifted rear wheels if the tyres were grippy enough and the suspension hard enough.
It was a way of using a very tight (high torque setting) Salisbury platted limited slip diff to maximum effect without excess tyre wear.

[ringo]

I was doing up some sketches yesterday. And i see why journalists are of the impression that the FRIC tips the nose up. This is a misjudgement based on what they interpret. They have taken the crosslinked theory as gospel and have worked with only that possiblity.
I have realized that cross linked, ie piston of one strut connected to rod of second strut works to stabilize in extension, ie if the front wheel drops in a pit and rear is to to follow. It will level up the car appropiately.
However if there is a bump in the road, the nose will tip up with a cross link, ie the car will be further pitched upward since the rear will drop.
What i realised is that in order to account for both extension and compression (bump and a drop) the suspension has to be both cross linked and straight linked. Check valves are used to control with circuit is being used.
This would negate the theory that the nose will pitch up will going down a straight. Which isn't really adding up.

What i also realize is that what makes things more complicated and i haven't look on this as yet, is that a bump and a drop is one thing; geometrical occurrence, but i haven't considered what happens with a forced based displacement of the suspension.
Under braking with a weight shift to the front.

I agree that when it comes to tuning the springs and dampers it will present a problem. Also the effects of temperature on the air spring. The size of the air spring is even more a problem. The smaller it is, the worse it will behave as a spring.

So far I've found that each strut pairing, front right to back right for example, must have four pipes connecting them together. For front right to back left, if twist is considered then that's another four pipes. So if we do this for all, we may go as far is 6 * 4 = 24 pipes and 24 check valves in a system if all are to be connected to each other.

[timbo]

IMO it can be a pure inertial system acting on control-valves. When subjected to g-forces it triggers pressure changes in pneumatic springs.

[DaveW]

IMO it can be a pure inertial system acting on control-valves. When subjected to g-forces it triggers pressure changes in pneumatic springs.

There are many things that would be possible with a renewable source of high pressure. Otherwise, attitude must be controlled by damping, I think. That option would be possible without cross linking the suspension (i.e. with g-sensitive dampers).

Regulation 10.1.2 states "The suspension system must be so arranged that its response results only from changes in load applied to the wheels". Taken literally, g-sensitive dampers are legal by that regulation, since they only ever respond to changes in load applied to the wheels. A g-force action that causes the suspension to move directly would probably not be legal.