What the 'Fric' is it?

[autogyro]

I seem to remember discusing ride height levelling and pitch compensating hydro pneumatic suspension systems on this forum some time ago.
Can anyone find the thread.
I think it focused on the red bull and pull rod suspension.

[bhall]

@Bhall

Mercury it could not be....It's on the list of banned metals no?

Beats me. It doesn't have to be mercury, though. Just an object of a given mass that can travel fore and aft to stiffen the front and rear dampers under braking and acceleration.

̶W̶h̶a̶t̶ ̶I̶ ̶d̶o̶n̶'̶t̶ ̶u̶n̶d̶e̶r̶s̶t̶a̶n̶d̶ ̶i̶s̶ ̶w̶h̶y̶ ̶t̶h̶i̶s̶ ̶s̶y̶s̶t̶e̶m̶ ̶i̶s̶ ̶l̶e̶g̶a̶l̶ ̶w̶h̶i̶l̶e̶ ̶R̶e̶n̶a̶u̶l̶t̶'̶s̶ ̶t̶u̶n̶e̶d̶ ̶m̶a̶s̶s̶ ̶d̶a̶m̶p̶e̶r̶,̶ ̶w̶h̶i̶c̶h̶ ̶a̶l̶s̶o̶ ̶r̶e̶q̶u̶i̶r̶e̶d̶ ̶n̶o̶t̶h̶i̶n̶g̶ ̶o̶f̶ ̶t̶h̶e̶
̶d̶r̶i̶v̶e̶r̶,̶ ̶w̶a̶s̶ ̶d̶e̶c̶l̶a̶r̶e̶d̶ ̶i̶l̶l̶e̶g̶a̶l̶ ̶i̶n̶ ̶2̶0̶0̶6̶ ̶-̶ ̶a̶f̶t̶e̶r̶ ̶i̶t̶ ̶w̶a̶s̶ ̶d̶e̶e̶m̶e̶d̶ ̶l̶e̶g̶a̶l̶ ̶i̶n̶ ̶2̶0̶0̶5̶.̶

Nevermind. I just answered my own question: the FIA is weird.

[Cam]

I am wondering if it has anything to do with the whole braking system. Remember the 'I pressed the brakes and nothing happened' ??

I am also wondering this. Mercedes successfully argued their 'not driver operated DDRS' but suggesting the trigger was a secondary feature, not the primary - could this be the same thinking?

Could the braking system pressurise/control the suspension on the same hydraulic line?

The Citroen Hydropneumatic suspension is an example of interconnectivity - of which Mercedes is mentioned as having it's own system - so they have experience with this.

This system uses a belt or camshaft driven pump from the engine to pressurise a special hydraulic fluid, which then powers the brakes, suspension and power steering. It can also power any number of features such as the clutch, turning headlamps and even power windows. The suspension system usually features driver-variable ride height, to provide extra clearance in rough terrain.

wiki

[Cam]

interconnected suspension

The hydraulic implementation provides several advantages regarding the installation in any kind of chassis. But the main issue is the ability to set different damping rates for every movement of the car.

Many cars require that pitch damping is different from roll damping. This is related to the different inertias and different spring rates associated with these two movements. Matching damping and spring rates is extremely important to gain grip, which means safety when in difficult or extreme situations.

With our system we can provide not only different settings for pitch and roll, but also for the vertical movement, so the stability can be improved without impairing comfort.

And then, the same car that behaves correctly at high speed in the road will negotiate difficult off-road paths beating any similar car that is equipped with conventional suspension elements.

Key Benefits:
• Increased stability
• More off-road traction and more corner grip
• increased braking capability in any situation.
• Improved steering
• The hydraulic version allows a better matching of different modes damping

Source

[FoxHound]

The lotus system was banned because it was mechanically operated.
Using the brakes, the system would work.

Mercedes idea is inertia based, and doesn't use electrics or mechanical input from the driver to work.

Couldn't Lotus have adjusted their system to work within the rules? If it is as much of a benefit as it's made out to be, then surely it would have been worth the trouble?

That's why thy pay the engineers the "telephone number" salaries these days.
But Rumour has it, that it was Mercedes who got the system banned when they provided their own schematics for a similar type of adjuster.

[DaveW]

In this article,Ross Brawn is quoted as saying:

"You want a nice softly sprung car, but you cannot do that because you compromise the aerodynamics too much.

"So every year I have been in F1 I have always tried to seek that ideal balance between suspension performance and aerodynamic performance, and it is no different today to how it has been for many years."

The article went on the state:

Although the early 1990s method of overcoming that compromise through active suspension was banned, the FRIC concept is allowed because the hydraulic system is completely passive as no on-board computers are reacting to what the car is doing.

Alongside its aerodynamic benefits, more pliable suspension should make FRIC cars better at tyre conservation.

After 2012's often wide-open competition, this year the frontrunning teams have jumped clear of the midfield pack, despite regulation stability.

It went on the say:

Brawn does not think that the leaders' pursuit of FRIC suspension is a major factor in that change.

But I guess he would say that.... Perhaps it is time to develop a better understanding of the concept...

[DaveW]

interconnected suspension
Source

The reference found by Cam is very interesting, and is very relevant for an off-road vehicle. However, the temperature coefficient of expansion of hydraulic fluid would, on the face of it, make it unacceptable in an F1 application.

[WhiteBlue]

The principle of FRIC should be pretty simple. The same as you can design a sensor that recognises the acceleration in one direction of a coordinate system you can design a system that uses such an input for hydraulic or mechanical amplification. That way you can design a suspension that reacts to longitudinal or transversal G-forces separately. There are mountains of options what you can do and all you have to do is select those that hit all the loop holes in the regs. Obviously variable geometries are not an option. But variable damping and spring rates are not prohibited by the rules AFAIK. So I can imagine what they have done without knowing the details. Hopefully we will learn soon how it is done. Ferrari, Red Bull and McLaren must be busy with development. FRIC is as useful to the 2013 cars as it will be for the 2014 turbo powered new designs.

[mx_tifoso]

Le's just hope that this isn't banned during the season or for 2014. Suspension development is tons more interesting than anything aero related imo.

[DaveW]

Just an object of a given mass that can travel fore and aft to stiffen the front and rear dampers under braking and acceleration.

G-sensitive dampers exist, and have been used in F1 since 1999, to my knowledge. "Interactive" (coupled) damping is not required.

Obviously variable geometries are not an option. But variable damping and spring rates are not prohibited by the rules AFAIK.

Actually, variable motion ratios are used quite widely in F1 (but I know what you mean). Variable dampers are also used (see above), and every aero car I meet (as well as some non-aero cars) use displacement sensitive spring rates. None require the suspension to be "interactive".

[DaveW]

Scarbs has just published an article on "FRIC" here.

[DaveW]

With apologies to Scarbs, and with the object of stimulating discussion, here are my inital thoughts on Scarbs interesting article:

How F1 suspension works

...An F1 car's suspension has to look after the chassis in two main modes: heave and roll. Heave is when the car is moving up and down vertically, when this occurs at just one end of the car, it's known as pitch.

This is not quite true. Strictly, rear axle travel with no front axle travel is combined heave & pitch motion about the c.g. that happens to cancel at the front axle.

FRIC

…..Both of these systems replace the springs and dampers of a normal suspension, so the system solely relies on the hydraulic fluid to hold the weight of the car. The fluid is therefore kept at high pressure within the hydraulic elements and pipework...

Why would they choose to do that? Springs are very efficient at supporting a vehicle. We used springs to support the vehicle even in a fully active system - saving weight and providing a relatively safe failure mode.

...Although outwardly simple the system has far more complexity when the detail is looked at. The system needs to incorporate flow control valves to provide the spring and damper effect of conventional suspension...

I would be surprised if flow control valves provided the spring effect of a conventional suspension.

...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.

….But perhaps the biggest complexity is when the team starts to link the roll and pitch circuits together. It's possible that the system could be used simply to control pitch and roll separately, but the car is rarely in just one of these modes…..In this condition you would want the pitch control to be good, preventing dive. But you would like a little roll to induce some mechanical grip….

As I understand it, Warp load controls the fraction of roll moment carried by the front axle, and hence the mechanical balance of the vehicle. Warp, or roll displacement only affects mechanical balance if it has something akin to a roll bar to convert that displacement to a load. It is possible to establish balance with roll out, roll in, or indeed no roll.

Incidentally, that would be another good reason to use physical springs in a displacement controlled suspension.

[FW17]

pat symonds on sky mentions even Marrusia runs front rear interlink.

But his explanation for the opposite to what Scarbs explained on the racers edge

[WhiteBlue]

The accumulation and the spring function may become clearer when you consider gas as one of the fluids in the system. The moving fluid mass would perhaps work against bubbles of gas in an accumulator at the end of the circuit.

Unfortunately I cannot read Scarbs article as it is pay content.

[Dragonfly]

People may get an idea by looking at the hydro-pneumatic suspension invented by Citroen. You have a liquid acting as a solid body to transfer suspension movement forces and parallel to that used for damping and a gas acting as a spring.