What the 'Fric' is it?

[DrewP]

All through this topic there's talk of load being helped by FRIC's actions. From what I know of load transfer, it's not impacted by suspension per se (it'd have the same value on a rigid and a softly damped chassis), which can only impact the speed at which it happens.
With that in mind mind doesn't FRIC only minimise susp. movement (roll/pitch), thus helping aero and suspension geometry, but not changing load transfer, thus not affecting the amount of grip each wheel has (other than said positive effect on geometry))?

Please correct my way of thinking as it's a similar conundrum that's bothered me with road cars, such as Porsche's PDCC, which many motoring hacks cite as a way of reducing load transfer, rather than roll/pitch.

You are right, the main benefit of the system is to control suspension movement and thus has little to no significant bearing on steady state load transfer and the resulting wheel loads. When we say grip we are speaking of the dynamic load variation (at the contact patch) from road inputs and irregularities. This is 'grip' that can be improved via shock and spring tuning since it is a vibrations problem.

Thanks for the clear reply (in the first part, at least

Regarding the 'grip' you're referring to, I thought that FRIC mainly impacted what you'd call from suspension's perspective slow bump/rebound (movement caused by braking/cornering/acceleration), while what you've described seems like forces dealt with in fast bump/rebound settings. Unless having FRIC onbard allows you to have softer springs/dampers/bars, which would then translate to dealing with vibrations better?

Hope what I'm asking isn't too dumb for this forum, but there's no other place on the web straddling the laymen's and engineering brains' worlds.

[RideRate]

DrewP,
I will be speaking of FRIC in the sense of what I've speculated thus far on how it works.

So the idea is that a system like FRIC decouples certain car behaviors, which as you speculated opens up freedom to tune the behaviors that are unaffected by FRIC. FRIC isn't necessarily impacting low speed behaviors, but behaviors of certains modes of interest (pitch and roll). But while doing so it doesn't change the vehicle's rates in other modes such as warp or one wheel bump. With a traditional suspension any increase in the pitch or roll rate would also have an impact on on warp and one wheel bump rates, thus impacting grip. So yes, in essence FRIC allows you a setup with softer single wheel rates while also running very high pitch/roll rates. This, a traditional system can't do.

Check back through the thread, we cover all this pretty well. It's always the same problem with suspension, balancing compliance for comfort/grip with platform control for stability/aero. FRIC is just an F1 legal system that helps minimize the compromises.

[DaveW]

.... So yes, in essence FRIC allows you a setup with softer single wheel rates while also running very high pitch/roll rates. This, a traditional system can't do. ... FRIC is just an F1 legal system that helps minimize the compromises.

Interesting stuff, much of which I agree with.

The main issue I am trying to understand is how the the "old Kinetic system" you explained so elegantly earlier in this thread can be used to obtain the characteristics propounded by Gary Anderson in the video clip I posted here (essentially, a splitter height that remains constant with changing airspeed).

Perhaps RBR uses a different strategy?

[RideRate]

.... So yes, in essence FRIC allows you a setup with softer single wheel rates while also running very high pitch/roll rates. This, a traditional system can't do. ... FRIC is just an F1 legal system that helps minimize the compromises.

Interesting stuff, much of which I agree with.

The main issue I am trying to understand is how the the "old Kinetic system" you explained so elegantly earlier in this thread can be used to obtain the characteristics propounded by Gary Anderson in the video clip I posted here (essentially, a splitter height that remains constant with changing airspeed).

Perhaps RBR uses a different strategy?

Kinetics is the conceptual idea behind what I guess FRIC would be. The Kinetec setup is ONE specific example of how the hydraulics can be arranged (a pretty good one) but far from the only option. I think we've already agreed that extra circuitry is involved with the F1 systems to handle more modes and allow isolated rate tuning, especially considering they have more dampers/cylinders to work with than what the Kinetic system was designed to do.

I'm sure with some variations in plumbing what you reference above could be achieved. I haven't sat down and worked out what the behavior would be, but I think you could trade control of pitch and/or roll for heave. Same concept, different application with maybe some differing resultant behaviors, maybe some are of no concern. But if we interconnected so that the heave mode could be decoupled, we could then run a very high heave rate, and would we then not have constant splitter height at varying loads/airspeeds? Without a penalty in wheel rates?

[DrewP]

With most of my assumptions now corroborated by you guys (FRIC has little to do with load transfer induced grip) there's one more thing I'd be delighted to see explained.
Is a road car system such as Porsche's PDCC active roll bars (which is completely different technically but has the same aim of reducing roll) rightly described by journos as responsible for the car (ex. the new Turbo, as reviewed in EVO magazine) not responding to cdynamic hanges of load caused by lifting off or trailbraking? (lifting in old 911's causes oversteer, as per the laws of physics, while due to PDCC it reportedly doesn't in the new models)

[DaveW]

Mmm...

A quick Google failed me, but the PDCC system appears to be a way of cross weighting the car on a per-axle basis. If that is the case, then it should be possible to turn a steering input into a "trajectory demand" by controlling cross weight to maintain neutral lateral balance. This might help. Whether the PDCC does this is another matter, however.

[WilO]

I think DaveW is spot on here, regarding the PDCC system (Merc. and BMW have or have had similar systems).

Any time I see an active ARB system, I suspect it's part of a vehicle stability system. As the tire(s) approach their limit of force production, they are highly non-linear and apparently no longer 'listen to' steer input. As such, the only remaining way to modify tire force production is by changing the normal load the tire sees. They are often marketed as performance -oriented 'platform control' systems, I suspect because it's an easier sell to a BMW M3/M5 customer....

[RideRate]

So I did a quick diagram cause I was curious if I could get something that looked workable. I have it plumbed using 4 wheel dampers and 2 heave dampers so the system would have these behaviors. I think.

1) Heave under hydraulic interconnected control, rate set by accumulator #1
2) Roll under hydraulic interconnected control, rate set by accumulator #1 in one direction and accumulator #2 in other direction
3) Warp free and controlled by combination of wheel springs and heave (now really pitch) springs
4) Pitch free and controlled by combination of wheel springs and heave (now really pitch) springs

So we would have very good platform control over ride height (heave) and roll. Read very stiff in roll and heave. However we would still be compliant but tunable in pitch and warp.

Since accumulator #1 sets both roll and heave rates the way to tune the balance of the two would be with varying working areas of the heave vs wheel dampers.

Warp and pitch are controlled by the same springs, but since the pitch spring is actuated half as much per wheel travel in one wheel bump than in true pitch there is a good bit of room to negotiate balance of pitch rate to warp rate.

Just thought I'd give an quick example of how adaptable this system can be. I'm sure if I can come up with this in 20 minutes then there are even better ways to plumb it for heave control and that's probably what is going on in F1.

[DaveW]

RideRate: A diagram would be useful...

[DaveW]

As far as I've understood the fric system without a pump can only decouple some modes and permits to have softer springs and dampers on each wheel maintaining the same heave control and pitch/roll variation. If configured so it should maintain the same aero propierties but should increase the mechanical grip of the car at low speed and on bumps. The other setting is the one which permits to have minor rool and pitch motions so that to obtain a better aero behaviour but with no advance on the traction side. Between this two settings it is possible to chose a sort of intermediate solution to obtain part of the aero advance and part of the traction advance. Is it all correct?

I guess that is what we are discussing. The short answer is yes, but with constraints imposed by the hardware and fluid properties.

Then the other qustion regards the presence of a pump in the system. Is it forbidden at all or it is only forbidden that it is controlled by electronic.

This should help. para10.2.2 appears to ban any powered device (mechanical or electrical). I guess that probably does not include "self-powered" devices because, arguably, a damper is an example of a "self-powered" device.

[DaveW]

para10.1.2 & Para10.2.3 are both somewhat contentious. I believe F1 teams disagree on interpretation.

There is some logic to the idea that changes that affect the response of the suspension without actually causing the suspension to move are OK, provided that those changes are not "adjustment" changes. That interpretation would allow damper characteristics to vary with temperature, acceleration, etc. Arguably, any other interpretation would ban hydraulic dampers altogether.

For "FRIC", it is worth noting the regulations don't treat each "corner" of the suspension in isolation....

[RideRate]

This thread is extremely interesting!
As far as I've understood the fric system without a pump can only decouple some modes and permits to have softer springs and dampers on each wheel maintaining the same heave control and pitch/roll variation. If configured so it should maintain the same aero propierties but should increase the mechanical grip of the car at low speed and on bumps............ Is it all correct?

You got it.

Then the other qustion regards the presence of a pump in the system. Is it forbidden at all or it is only forbidden that it is controlled by electronic. Somewhere in the thread I've read the article of the f1 rules which states that the suspension system should react only to suspension movement. Is that article that avoid the possibility to have a pump? And if so would an hypotetic pump which takes energy from the movements of suspensions be illegal?
Thank you,
Xwang

From what we've seen in precedence is that anything that introduces onboard generated energy to the suspension parts/system is deemed illegal. In other words you cannot use hydraulic or electrical power to do such things as 1) cause or resist suspension motion and 2) operate any type of actuator that adjusts the suspension's characteristics. Basically nothing that is generically deemed active or semi-active no matter if electronics are involved. If it's passive, you're good thus far.

[DaveW]

... In other words you cannot use hydraulic or electrical power to do such things as 1) cause or resist suspension motion...

Here is a good example of "contention". A conventional damper might well be described as a device that "resists suspension motion by hydraulic power", power in this case being defined by the area enclosed by the force/displacement trajectory. That power is supplied by the engine, of course.

[gixxer_drew]

I just couldn't help but comment on such an interesting discussion which I am disappointed I missed until now! I have to say I am onboard 100% to DaveW's original explanation. I think at the level of suspension development in F1, with what you can do here...anything mechanical is second order to what could be achieved aerodynamically. I would look for positive side effects, but not as targets.

Dave, could you explain more on your 7mm ride height change result? As you may know, 7mm for an F1 car is downforce (and drag for that matter) on the order of "sweet jesus". So I am curious as I was not totally clear under what circumstances that is achieved? It sounded like that was across your test, but I do not know what that translates to in terms of say, a lap? Or is that still unknown?

The things I would want to do with such a system!!! I dont even know where to start. I might start with set the CoP migration to be stable across all speeds, allowing me to more tightly tune the balance and that already nets an increase. Decrease average ride height, reduce plank wear, goes on and on. I think this is quite different than the older systems based on the descriptions. The concept is the same, but not in practice.

[DaveW]

Dave, could you explain more on your 7mm ride height change result?

I used old F3000 results to provide a model of the vehicle, and downforce data used in the rig test amplified up to provide estimates of front & rear downforce at high speed.

In reality, the downforce and the vehicle responses would be influenced by bump rubbers that limited the rake and ride height at high speeds, but I wanted to find out how much control a "FRIC" system could provide, so I left out the bump rubbers & played with parameters. The results were undoubtedly artificial, but they did demonstrate that front ride could be controlled in exchange for a loss in rear ride height, without compromising unduly low speed set-up.

The exercise was one "brick in the wall" of arriving at strategy for setting up a "FRIC" system.