What the 'Fric' is it?

[RideRate]

If i may as riderate, could you put in bullet form or in a table, the FRIC properties in terms of the motion of the car; heave roll etc. versus the typical systems used.
I feel that would more solidify what we are aiming to find out in this thread.

IF this was the system (basically the old Kinetic suspension) it would behave as follows:

Mode - Interconnected behavior
Heave - no resistance
Warp - no resistance
Roll - resistance
Pitch - resistance

So if a mode has resistance from being interconnected it can be nearly infinite (hydraulically locked) or set by an accumulator. The idea is the roll and pitch rates are desired to be higher than the wheel and heave springs dictate. If fric offers no resistance then that mode is just set by the traditional components.

So you'd get highly compliant warp mode (ideal) with minimal pitch and roll variation for the aero platform. If you're really clever there is a way to link multiple accumulators in roll to actually tune TLLTD.

You still set ride height at df levels with the heave springs. However, now that you have reduced the maximum pitch angles under accel and braking and the max roll angles under cornering you can now run the car at a slightly lower ride height overall.

[ringo]

How does this impact on anti dive geometry design, if any?

[mep]

So if a mode has resistance from being interconnected it can be nearly infinite (hydraulically locked) or set by an accumulator.

The problem is that the tires contribute quite a lot to the displacement on one corner. Therefore the effect of the hydraulic link is limited.

[RideRate]

So if a mode has resistance from being interconnected it can be nearly infinite (hydraulically locked) or set by an accumulator.

The problem is that the tires contribute quite a lot to the displacement on one corner. Therefore the effect of the hydraulic link is limited.

I do think we all understand that and the resistance in any mode from the link will be between the chassis and wheel center. Obviously, compensating for tire squish would be the last piece of the puzzle. However, I'm not sure yet how it can be done legally and hydraulically because it's going to require some introduction of energy into the system and that quickly gets banned every time.

[RideRate]

How does this impact on anti dive geometry design, if any?

Antis would work like normal but with the suspension stiffnesses so high in pitch and roll they could be reduced I'd assume. The one behavorial change would be that any antis that normally cause a pitching (antidive, antisquat, etc.) or rolling (anti-roll, pro-roll) moment will have thier forces transmitted across the car via the hydraulic interlinks so that the pitching or rolling motion is resisted like always and the vertical anti forces become heave inputs.

[DaveW]

IF this was the system (basically the old Kinetic suspension) it would behave as follows:.....

Curiously, I did rig test a Subaru fitted with the Kinetic suspension in 2006. I believe the vehicle was put together as a demonstrator by Kinetic. Sadly, any observations I might have made on the properties of the suspension were blighted by friction/stiction, amounting to 200N per side at the front axle, and an impressive 600N per side at the rear axle. The vehicle returned a month later having been rebuilt, I believe, but the friction characteristics remained.

A "standard" Subaru WRX returns friction/stiction values of rather less than 100N per side at both axles.

So, I hope your proposal is not like "the old Kinetic suspension", not the example I tested, anyway. It does illustrate, however, the importance of being aware of the difference between intent and achievement.

[RideRate]

So, I hope your proposal is not like "the old Kinetic suspension", not the example I tested, anyway. It does illustrate, however, the importance of being aware of the difference between intent and achievement.

So your point is that someone once put this concept together in a poorly designed fashion? How shocking.

[DaveW]

So your point is that someone once put this concept together in a poorly designed fashion? How shocking.

You appear to be easily shocked. I am sure that, on reflection, you will understand the point I was trying to make.

[gt6racer]

Riderate,
I've seen many articles on FRIC, many with their own opinion on what it is and what it does. Most agree it has pitch stiffness, whereas some also claim roll stiffness. You are the first I've seen acknowledge that these modes could be simultaneous. Can you please share the evidence that suggests to you that it works in both roll and pitch ?

[RideRate]

Riderate,
Can you please share the evidence that suggests to you that it works in both roll and pitch ?

Let me state for the record, I do not know and have no evidence. However, as an engineer who knows the end goal of suspension on an aero dominated car, I know what would make sense. Aero dominates and ride height (heave), pitch, and roll are very sensitive aerodynamic factors. You will (read should) sacrifice to control those modes before you chase anything else.

Knowing the importance of aerodynamic platform, if I know we can interlink the suspension in a way that absolutely minimized both pitch and roll variation and the driver could actually drive it, would I not implement both? In other words, it's obvious to me that if we can control both then we must do so. Especially given there is some mechanical grip positives to go along with 2 pieces of aero gain.

This is no proof, but in these two linked articles they mention the system being used to control both roll and pitch:
http://somersf1.blogspot.com/2013/04/in ... -fric.html
http://www.sportskeeda.com/2013/04/16/u ... on-system/

One note, there is a distinct event that would be of concern given my proposal of the system. However, I think with testing and more complex system design this could be alleviated so the system could function as desired. If this does turn out to be the fundamental layout of the system I'll be exceptionally curious on how they are tuning roll stiffness distribution, since I think that's the good question.

[gt6racer]

Riderate, Thanks for your reply. We are on the same page based upon similar information.

I would suspect roll split is tuned by changing the mechanical advantage of the cylinders at one (or both) ends of the car. This would be easier and quicker than changing cylinder bore sizes.
It would also be possible to set the system up such that adjustments to system pressure would change the roll split at the same time as changing overall stiffness, but such a set-up would not be so desireable for other reasons.

[DaveW]

Aero dominates and ride height (heave), pitch, and roll are very sensitive aerodynamic factors. You will (read should) sacrifice to control those modes before you chase anything else.

Interesting... Do you think that the requirements would apply equally to an open bottomed tin top and a heavily regulated, aerodynamically sophisticated open wheeler, if the system was available to both?

[RideRate]

DaveW,
I can't so broadly answer that since it depends on the speeds at which you are racing and what your aerodynamic design and wind tunnel testing tells you. Likely, the balance of sensitivities will change and new ones may arise. However, it's very likely the requirements would still apply in both cases, sure. Especially if we're at high speeds on a track.

Having said that let's take a vastly different example. Say in the case of WRC, where the system's purpose was for a different reason. Its main purpose was to allow low wheel rates for mechanical grip, impact isolation, and landings. The system allowed you to do this while giving very good roll resistance to control angles and please the driver. Before the system, very soft wheel rates and very high roll rates were not two things that could go together. So this would be a distinctly different and unique type of case using the same system for different requirements.

[Smokes]

I use hydraulic control fluid in very large systems, typically 180litres plus, the entrained air will show very little compliance, and take typically 7 month to settle out and end up being around 3 percent of the initial volume.
The biggest issue we have where compliance is shown is when the fluid froths and holds more than 20% air it becomes very compressable.

[DaveW]

Before the system, very soft wheel rates and very high roll rates were not two things that could go together. So this would be a distinctly different and unique type of case using the same system for different requirements.

I believe that the system acts as a hydraulic roll bar across one axle. Penske (Ferrari 333, etc.), and then Ohlins (Audi R8), did something fairly similar (reversed) for sports cars, principally to add rising heave rate. The warp control function adds capability, at least in theory. Interestingly, perhaps, rally drivers don't care much about lateral balance (in gravel, they just want to induce oversteer, and then use power to change direction). Equally interestingly, Maclaren, which I believe uses the system in the road version of the MP412C, has abandoned it in favour of conventional roll bars in the race version.

Smokes: Interesting. What is your application?