What the 'Fric' is it?

[timbo]

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.

Good find. But I guess a clever lawyer might argue that any force acting on car results in a change of the loads on the wheels?

[ringo]

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

Well if they are some how related to load applied to the wheels, then you could have a point. Load applied to the wheels suggest only forces experienced by the wheels. You only have the vertical and tractive loads to utilize.
G sensitive dampers are legal since they react to acceleration of the wheel.
But they cannot be in such a way to react to the body of the car, or of the brakes.

[DaveW]

G sensitive dampers are legal since they react to acceleration of the wheel.
But they cannot be in such a way to react to the body of the car, or of the brakes.

Forgive me ringo, but g-sensitive dampers manipulate the cross-sectional area of the valves controlling the flow of fluid across the damper piston. Flow across the piston (i.e. the response of the damper) is, of course, initiated by changes in load applied to the wheels, and g-sensitivity will neither stop nor start this function.

[ringo]

Oh sorry..
Could you post more on the g sensitive damper?
I was of the impression it was just simple valving that reaction to the acceleration of the damper piston.

All the same, the passive system seems less and less able. Maybe i'm wrong, but i feel it's the minute attitude changes it is imparting that gives it some amount of advantage.

[DaveW]

Could you post more on the g sensitive damper?

Keeping it simple (real life only rarely that): a rear 3rd damper can be mounted to an F1 car with one compression port & two rebound ports. One of the rebound ports is controlled by a valve that can be made to close by a mechanical accelerometer aligned to be sensitive to longitudinal deceleration (the valve closes when the vehicle decelerates). Then it possible to design the ports so that damper works normally when all ports are open, but becomes very heavily rebound biased when the accelerometer activates. The damper will then hold down the rear axle, maintaining rear downforce, during the early part of a braking event.

For a typical F1 braking event, initial deceleration will be around 5 gn, dropping to 2 gn in less than a second, which is the order of time the accelerometer should be active. The loss in grip during this time is likely to be more than compensated by the gain in braking stability.

Note that the accelerometer will not cause the damper to move directly, nor will it stop the damper moving in response to a change in wheel load.

[ringo]

I see so this is in fact from the longitudinal movement of the car itself. Intereseting stuff, but by the letter of the law it sounds illegal.

[Pierce89]

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.

I'm not sure about the springing, but on damping the the RF to LF and RR to LR crosslinks only require 2 pipes each. 1 pipe from right side compression to left side rebound and 1 pipe from right side rebound to left side compression. You do that at the front and rear. Then, do the same between RF and RR, then between LF and LR. Bang! Pitch and roll control with 8 pipes rather than 24 and arguably no need for 3rd members. Any thoughts from DaveW?

[DaveW]

... but by the letter of the law it sounds illegal.

How so? The accelerometer does not cause the damper to move (the criterion, I believe), it simply modfies the motion when it does move. If the accelerometer is deemed illegal then, by implication, all hydraulic dampers are illegal, because they all, with no exceptions, change their load/velocity characteristics with temperature. The best even attempt to compensate by modifyng port area with temperature.

Even friction dampers are temperature sensitive.

[DaveW]

I'm not sure about the springing, but on damping the the RF to LF and RR to LR crosslinks only require 2 pipes each. 1 pipe from right side compression to left side rebound and 1 pipe from right side rebound to left side compression. You do that at the front and rear. Then, do the same between RF and RR, then between LF and LR. Bang! Pitch and roll control with 8 pipes rather than 24 and arguably no need for 3rd members. Any thoughts from DaveW?

Not really, but simplicity is a virtue.

My initial thoughts would only require one fore/aft link, two if the cross weight is to be controlled (assuming system lags permit).

[timbo]

Keeping it simple (real life only rarely that): a rear 3rd damper can be mounted to an F1 car with one compression port & two rebound ports. One of the rebound ports is controlled by a valve that can be made to close by a mechanical accelerometer aligned to be sensitive to longitudinal deceleration (the valve closes when the vehicle decelerates). Then it possible to design the ports so that damper works normally when all ports are open, but becomes very heavily rebound biased when the accelerometer activates. The damper will then hold down the rear axle, maintaining rear downforce, during the early part of a braking event.

For a typical F1 braking event, initial deceleration will be around 5 gn, dropping to 2 gn in less than a second, which is the order of time the accelerometer should be active. The loss in grip during this time is likely to be more than compensated by the gain in braking stability.

Note that the accelerometer will not cause the damper to move directly, nor will it stop the damper moving in response to a change in wheel load.

Can the same mechanical accelerometer change stiffness of hydraulic/gas spring?

[DaveW]

Can the same mechanical accelerometer change stiffness of hydraulic/gas spring?

Not really, but changing bump/rebound ratio of the dampers is quite an effective way of modifying running ride height. A hydro-pneumatic "spring" will change its rate with air/oil ratio, of course, and a serial damper (a la Citroen) will change that, but the effect should be quite small (hopefully).

[timbo]

but changing bump/rebound ratio of the dampers is quite an effective way of modifying running ride height.

I think controlling the front ride hide (as in antidive) is more fruitful?
But since your idea of damper allowing the rear to lower on braking event, could this be the case with Lotus this year? I noticed quite a lot of sparking on Raikkonen's car.

[DaveW]

I think controlling the front ride hide (as in antidive) is more fruitful?

You might like to review my initial thoughts, referenced above (essentially, I agree with you).

But since your idea of damper allowing the rear to lower on braking event.

Apologies, but I think you misunderstood. The idea of g-sensitive damping is not to lower the car, it is intended to stop the rear axle rising (too quickly) which could, in turn, cause the diffuser to "stall".

[timbo]

Apologies, but I think you misunderstood. The idea of g-sensitive damping is not to lower the car, it is intended to stop the rear axle rising (too quickly) which could, in turn, cause the diffuser to "stall".

Ah, thanks.

[Crucial_Xtreme]

Here is something recently seen in Bahrain regarding part of the Lotus FRIC


via AutoSport