Damping Ratios

[Silente]

Hi!

I am new of the forum but i have seen a lot of interesting topics so i try to put my question too.

Let's talk about dampers.

I normally identify their behaviour using damping ratio and analysing it's value through the whole curve Force vs Speed.

Some books suggest , for a single wheel model, to use 0.7 for Damping Ratio, but here my doubt comes.

I have seen a lot of very very fast racecars using Damping Ratios above 1 (so overcritic damping) at least a low speed, usually less then 25 mm/s. We have to say they normally had some aero load, but at least in slow corners maybe we can say it is negligible.

Moreover this cars often uses damper curves without the "knee" between fast slow motion, or with just a very slightly difference between the slope of this two parts of the graph.

Thaking for given that low speed damping is useful to control wheight Transfer Transition and high speed to control Ride comfort and, more important to our purposes, response on bumps, curbs etc, how would you choose your Damping ratio?

Which value would you chose for low and high speed and why?

Then, how you would compromise between heave and other body movement like roll and pitch?

[Silente]

Hi!

I am new of the forum but i have seen a lot of interesting topics so i try to put my question too.

Let's talk about dampers.

I normally identify their behaviour using damping ratio and analysing it's value through the whole curve Force vs Speed.

Some books suggest , for a single wheel model, to use 0.7 for Damping Ratio, but here my doubt comes.

I have seen a lot of very very fast racecars using Damping Ratios above 1 (so overcritic damping) at least a low speed, usually less then 25 mm/s. We have to say they normally had some aero load, but at least in slow corners maybe we can say it is negligible.

Moreover this cars often uses damper curves without the "knee" between fast slow motion, or with just a very slightly difference between the slope of this two parts of the graph.

Thaking for given that low speed damping is useful to control wheight Transfer Transition and high speed to control Ride comfort and, more important to our purposes, response on bumps, curbs etc, how would you choose your Damping ratio?

Which value would you chose for low and high speed and why?

Then, how you would compromise between heave and other body movement like roll and pitch?

[salad]

Try these articles for damping.
http://www.optimumg.com/techtips_techtips.htm

When you say you've seen race cars over damped in the low speed, how do you know they are overdamped? Also, do you believe it is overdamped in ride, roll or pitch? Each situation requires a different amount of damping, and if you read all of the spring and damper articles, you will see that using just 4 dampers to control all aspects of the car is a compromise.

The compromise must be found with testing of the car on the track. Make sure you know exactly what your shocks are going to do when you adjust them before going out too.

[Silente]

I read optimumg g tech tips, they are very interesting and this is where i start from for my calculations.

The car i described use coeeficient of damping higher than than critical one in heave, but because of roll inertia which is not so big, it ends to be overdamped at least in roll too.

About this topic, how would you calculate roll damping from a normal 4 damper configuration?
i did it dividing roll movement in the same amount of rebound on one side and bump on the other, taking as negligible the movement of roll axis.

How would you calculate the same damping coefficient for pitch? Do front and rear dampers give a contribute following the same idea (one end in bump and the other in reboud)?What about springs (for example in braking: do front springs work alone or the car receive also an opposite force from the rear springs, and what about aero load)?

[exFSAE]

What car is this you speak of?

If you're talking high-downforce open wheelers or sportscars, their damper setup is not necessarily apples to apples with a tiny, purely mechanical grip car as FSAE tends to be.