Frequency reponse of shock absorber piston in F1 car

1. May 11, 2007

LM741

Hello everyone!!!

This might be bit of the 'electrical engineering' topic - but maybe someone out there can help :)

Does anybody have any idea of what the maximum frequency of a piston in a shock absorber of a forumula 1 car is?
What do i mean: How many times does the piston (in a shock absorber) move up and down, past the reference point, in one second. The reference point is defined as the point where the piston sits when the car is stationery. I ave googled this tones of times wih no luck - i've emailed "f1 experts" but without any reply - if anyone knows of some expert ( or someone that would know such info.) could perhaps ask..please! oh yes - all i need is the maximum freuency - which would probably occur during full speed.

Please if anyone can give me some idea. I would guess about 50Hz.

Thanks guys
John Criticos

2. May 11, 2007

NoTime

A shock adsorber is designed to prevent any oscillation.
Many designs are non linear was well as being non symmetrical.

The idea, if the suspension is properly designed is to fully disapate all the stored energy of the spring by the time the suspension returns to the normal curb height position.
If it oscilates at all it's defective or not proper for the rest of the suspension.

I suspect what you want is the one shot travel time from some compressed position back to the neutral position.
If you know the spring constant and unsprung weight you can probably get a ball park figure.
Non linear damping will lower the time though.
The shortest time allowed is how fast the spring can move the wheel back to the neutral position with no damping.

Also if you are moving the car back up as opposed to pushing the wheel back down the mass will be different.

Chances are that someone who might know would consider their suspension tuning a deep dark secret.

Best I can do.

3. May 12, 2007

LM741

"If it oscilates at all it's defective or not proper for the rest of the suspension."
NoTime>> i couldn't disagree with you more. Whilst the car is in motion - the piston is going to move up and down! Hence the oscillations. It will oscillate!! The quality of the shock absorber just determines the degree to which the piston will oscillate. But the statment pf yours, quoted above, is totally incorrect - at least i think so.
Thanks, anyway.

4. May 13, 2007

NoTime

Oscillation implies continued movement without additional energy input.
An ideal shock adsober will fully damp any movement of the suspension by the time the suspension returns to the neutral position.

While the car is on a flat road, moving at a stright line at constant speed the suspension (and the shock piston) should not move at all.

The shock is a damper designed to adsorb energy.
Of course the shock piston will move if you hit bumps or potholes, but that's quite different from oscillation.
A car with shocks that allow oscillation is dangerous.

5. May 13, 2007

Stingray

As an aside, almost all cars are underdamped. Typical street cars have damping ratios of ~0.2-0.4 (though the dampers are nonlinear, so this isn't completely well-defined). Any more than that gets extremely uncomfortable.

Anyway, I don't understand the original question. The answer depends completely on what the car's doing and the surface it's being driven over. Are you asking about the resonant frequencies of the chassis? The amount of damping? The highest frequencies that are important to control? For the last question, I think that the you'll get your answer by looking at the rumble strips.