What the 'Fric' is it?

[DaveW]

Whiteblue & Dragonfly: I understand what you saying, but that was not the point I was trying to make. Flow control valves will not affect the spring stiffness of the accumulator gas, and, since the gas will be at system pressure, the accumulator cannot compensate for changes in volume of the fluid as the temperature changes (I think). The Citroen system moves oil and out to achieve the required ride height.

Apologies, WilliamsF1, but I didn't quite understand your second sentence....

[WhiteBlue]

The question is would an adjustable spring rate for the air spring be required. And if yes are there other ways to achieve it? The inertial reaction could also be influencing things in the pneumatic system. What if the accumulator bladders are also connected? The damping at least sounds very straightforward.

[Blackout]

You cant see any damper or spring in this photo (Merc G-Box - 2011)... maybe they're inside the box. And maybe Merc replaced them with a 'fully' hydraulic system like Scarbs said...


On the last Lotus Gearboxes you can't see any damper or spring too. but classic anti roll dispositives are visible...

[FW17]

Apologies, WilliamsF1, but I didn't quite understand your second sentence....

Was not very clear there;

Scarbs - Interlink is to prevent squat and dive (during deceleration and acceleration)

PS - Interlink to provide squat and dive (or maybe I understood it wrong)

[Vale46]

In this film Craig Scarborough 'll explain:
http://www.youtube.com/watch?v=cg-K-VrX ... e&t=18m55s

[FW17]

Does the interconnect necessarily need to be hydraulic?
Cant this be achieved by a mechanically connecting the front and rear rockers (with something like throttle cables)?

Last year commentators (forgot who) mentioned that the Mercs had done a shoddy job on the pull rod suspension, did not have a proper location for the heave damper that they had to go hydraulic. Guess that is why the front rear is hydraulic in their case (speculation anyway) while others have mechanical linkage.

[Dragonfly]

Whiteblue & Dragonfly: .............
The Citroen system moves oil and out to achieve the required ride height.

That's true. But at a given ride height and if there are no significant leaks the system is almost encapsulated. This on a road car with mechanisms invented in the 50-ties of the last century. I can speculate that with current technology fine tuned proportioning valves can be made and used on pure passive basis. In the more late 'hydroactive' variation of Citroen a third accumulator is being connected or disconnected to the front and rear contour and this changes the damping and spring characteristics of the suspension. Done by a ECU on the car and forbidden in F1 but I think again a pure passive system may be designed to do this.
As for the mechanical linkage, A few mm diameter steadily fixed steel tubing is a far more simple and effective way to transfer forces between front and rear with the help of small amount of liquid flowing inside. In this case the hydraulic liquid is regarded as incompressible.

[DaveW]

OK. Lets start with a few basic facts, if I may.

A front-rear linked suspension is not going to be efficient at transferring fluid between the axles, not at the 9-10 Hz frequency required to affect the pitch mode, anyway. Fluid friction and compliance would be much too high.

Pre-FRIC F1 suspension vertical stiffness range at low airspeeds would be between 400 and 750 N/mm at the front axle and, perhaps, 80 N/mm at the rear axle. The front tyre weighs in at around 390 N/mm. Simple arithmetic should convince you that the front damper will not do its fair share of the energy dissipation, at least not at the heave mode. It follows that the front tyre will not be controlled properly, and because of that the rear damper(s) & hence tyres will have do to more than their fair share of the work. Hence both tyres will be worked harder than they might be.

The reason for using (stupidly) high front spring rates is to control front ride height.

Now, the soft rear suspension will displace much damper fluid as the down-force builds up with increasing airspeed (until it encounters a stop). That fluid could realistically be used to pump up the front damper(s). But that will increase the front ride height - not good news, perhaps, unless the front spring stiffness is reduced to compensate.

There you have it, in my view. Front ride is retained, the front damper(s) can do a fair share of the work, and both front and rear tyre load variations are improved. Perhaps that is why some vehicles are easier on their tyres.

One is left with the vexed problem of controlling the effective length of the fluid coupling (I leave aside Dragonfly's suggestion of a mechanical linkage for now). You might think that is not an issue, but some of my LMP2 customers who struggle to obtain any kind of consistency from a hydraulically coupled third element would disagree, & would very much like to know the solution.

[WhiteBlue]

DaveW, you are obviously very knowledgeable about the general subject but it appears that you do not know much more than we do about the Merc system. Personally I would love to hear and see solid technical information how the system works. So far in the testimony we had quoted from Scarbs we also did not learn anything specific except that the dampers are replaced by hydraulic cylinders and that the front and rear suspension is hydraulically linked. That was known before. The only valuable information is the fact that Merc until this day seems to be the only team that has a pure hydraulic FRIC system without additional mechanical subsystems.

If someone knows more how the system works I would love to hear the details.

[wunderkind]

DaveW, you are obviously very knowledgeable about the general subject but it appears that you do not know much more than we do about the Merc system. Personally I would love to hear and see solid technical information how the system works. So far in the testimony we had quoted from Scarbs we also did not learn anything specific except that the dampers are replaced by hydraulic cylinders and that the front and rear suspension is hydraulically linked. That was known before. The only valuable information is the fact that Merc until this day seems to be the only team that has a pure hydraulic FRIC system without additional mechanical subsystems.

If someone knows more how the system works I would love to hear the details.

I think the system is very similar to system found in the Citroen WRC car from a few years ago. The main thing is that the Mercedes-AMG engineers have finally got the system to work in a way that is fast acting but also gradual in its load transfer to give the drivers confidence.

[DaveW]

... but it appears that you do not know much more than we do about the Merc system...

or the Enstone system, for that matter. You are quite right, of course. This forum has an impressive record of reverse engineering aerodynamic solutions (sometimes before competing teams), and I thought it would be interesting to try a mechanical problem for a change....

[Pup]

I don't know if this adds anything to the conversation or not, but I was reading up on dual-travel mountain bike suspensions this morning and it reminded me a bit of this fric business...




Essentially just two dampers in one, long and short travel, and mechanically switched A/B, so not particularly sophisticated in that respect.

Anyway, it made me think of a rudimentary system where the interconnection among the dampers at each wheel is but a switch between two modes. Perhaps it could be a starting point for something more sophisticated - don't know but I figured I'd throw it out there.

[ringo]

No disrespect to scarbs, but he's not knowledgeable on the subject of suspension clearly, neither vibration theory.
He's simply going off what he reads or is told. So i wouldn't really take his words seriously. He's doing enough for the layman to have an idea how the system may work, even though he's not 100% correct.
Until you have an engineer writing articles you wont get much insight into formula 1 technology.

Why would one believe that there are no springs on this setup?
Or dampers?
I am looking at the damper, it's colinear with the pull rod.



Also a damper doesn't have to look like a typical damper, it only needs to be a device that does the same thing, so if it is hydraulic, aren't most dampers used hydraulic dampers anyway? See what i'm saying.

I think if we want to figure out this FRIC thing, first we need to write down what it is we want to acheive from the F1 car suspension wise, then look on what the current none Fric system offers and what limitations it has.
After finding out the limitations, you then devise what is to be done to to reach our goals in what we want the suspension to do.
Then finally you design a system with equivalent hydraulic components and that's your FRIC.
It's to fill in those gaps that the unconnected system has.

[ringo]

FRIC may be the hydraulic equivalent of electronic damper control.

This is an exerpt from BMW. Maybe we can say that there are some favourable features that could apply to F1.

Electronic Damper Control (EDC) automatically or manually adjusts each damper to suit the driving conditions meaning you enjoy outstanding comfort along with the best in BMW on-road safety. EDC reduces variations in wheel load, ensures tyres have excellent traction and counteracts bodyshell movement regardless of the weight your automobile may be carrying or the state of the road's surface.

Benefits for: tyre degredation, corner traction, reducing fuel load during the race, good compromise for qualifying setup?

Sensors constantly monitor all factors influencing the vehicle's behaviour and occupants' comfort, in order to precisely adjust the damper control. In a fraction of a second, the signals are analysed by the EDC microprocessor and orders are sent to the actuators on the shock absorbers, which, with the help of magnetic valves, are variably adjusted to provide optimal suspension. Thanks to Electronic Damper Control, the tendency for the nose to dip when braking is practically eliminated. The influence of potholes and unevenness on the road surface is reduced to minimum.

In addition to increased driving comfort and improved roll characteristics on the tyres, EDC also contributes to vehicle stability and safety. By reducing the nose's tendency to dip when braking and improving the tyre traction, EDC shortens the braking distance when braking heavily. The damper adjustment means that even when braking with ABS the vehicle chassis remains upright on the road and all four wheels have the largest possible contact to the surface.

Now clearly FRIC is passive and probably wont go to the full extent of this computer controlled system, but it could be able to address some limitations experienced by typical suspension, adding flexibility to setup and improving on the highlighted areas. Maybe it gives small gains for the individual factors, but makes for a better total package when the car works better in these areas. Especially when we look on how they positively influence the aerodynamic envelope.

-wheel loads
-traction
-fuel load
-pitch
-braking stability and distance

[dren]

...accumulators are needed to account for the change in volume of fluid in the system when the temperature varies…

How do accumulators account for a change in volume? This surely implies that the accumulators store & replenish fluid in the system with no pressure difference to drive it. Citroen did it, but used a high pressure oil supply to drive the operation.

I'm guessing he means a diaphragm with pressurized gas behind it to absorb an increase in fluid volume when temperature increases so the pressure stays stable. I've used these at work to control pressure spikes in our fuel oil line durring the summer months.