About dampers in bump vs rebound

Very basic here because I also only adjust by feel, like I said before:

The mass (kg) of the car builds a spring-mass system. Those systems are present in many domains of physics: mechanics, electronics, pneumatics etc.

A problem (well, in many cases it's also the goal but with the car it's a problem) occurs when this system starts to oscillate (car wobbles in a specific frequency after being "triggered" by a bump e.g.).
To prevent that, you'll need to add damping/resistance. In electronics, this is a resistor and in car dynamics, it's the damper.
The critical damping defines the threshold between an unstable and a stable system.

My personal advice: this topic is not understood on a forum like this. People study that stuff at university, you know. If you really, really care then I suggest for you to work your way up from Wikipedia or find a guide that explains the significant values (such as critical damping) well enough so you can use them for your setups.

 

You need to create your own math channels being the derivative of suspension travel.

I would not bother with telemetry, iirc the data acquisition for the suspension travel is 20 Hz which is considered way too low irl for any damper related work. (I've seen 250 Hz+ suggested as minimum)

 

So basically the "adjust until it's not too nervous nor too wobbly" still aplies, I assume.

To be fair I didn't even care too much about setups until the day I decided to take on the challenge of making the 650s driveable. On many instances it made me wanna rip my wheel and throw it off the window, but I probably would never know what I know now about setups if I hadn't done that. Some say they can drive it on default and have no issues, for me it just used to lose the back end every time I turned the wheel.

 

Well suspension is the only thing I might use it for. For everything else, I don't really need telemetry. :/

 

Are you sure it's only 20 Hz? That would mean just 2 sample every tenth of a second, or a sample every 4 m travelling at 300 km/h
From the telemetry I've posted here
http://www.assettocorsa.net/forum/i...s-in-bump-vs-rebound.46777/page-2#post-911738
seems indeed such a low sampling rate, but it's a wide extract.
I'm away from home now, but in the weekend I will check a zoomed area with the graph plotted vs time instead vs distance and count the samples.
I agree that a low sampling rate is useless to check the fast dampers behaviour of a F1 car.
Do you think that this could be in some way related with the spiky graph of the rear left tyre load of the SF15-T going through the Renault corner?
IIRC the physic frequency of AC is much higher, like 333 Hz or so.

 

Thanks, didn't dig too deep into RaceStudio yet to see if it can do stuff like that. Will look into that next week.

Personally, I'd much prefer MoTeC over it, tbh.

Edit: looking at the docs, Race Studio can do it.

 

I caught interest in the numeric approach to damper tuning. For starters, what do I need to install to see tyre load, suspension travel etc.? Wanna try to prove myself right with the fast damper theory. Thanks.

 

To start I suggest MoTec and a good project to read properly the telemetry log.
With the ACTI app here you will find all:
http://www.racedepartment.com/downloads/acti-assetto-corsa-telemetry-interface.3948/

 

Hi @MrDeap, I think it is useful to get the fundamentals right so we can work from there. Can you do me a favor and answer some quick & basic questions to see how we can help you:

(Please only MrDeap)
1) What purpose have dampers on a (race-) car?
2) Dampers have to be set differently for different cars. What specs or factors of a car dictate damper settings?
3) Are damper settings more or less important than springs?
4) What do you think the numbers in the Dampers setup menu in Assetto Corsa mean?
5) You have a RWD car. You increase front bump. Does the car oversteer more or understeer more under acceleration out of a corner?

The other thing is to seperate arguing over principles, which is fun, from looking at specific use cases. Please pick a (race-) car, maybe one you've been experementing with, post its setup and what do you thing happens when you change a particular setting. We can look at this specific car and give you tangible and useful advise that way.

Other people have also done plenty of work themselves, this is some further info:
http://www.optimumg.com/technical/latest-articles/
http://www.rqriley.com/suspensn.htm
http://www.fsae.com/forums/showthread.php?9062-Damping-Rates
http://www.kaztechnologies.com/downloads/kaz-tech-tips/ (loads of useful stuff)
http://home.scarlet.be/~be067749/58/c2/
http://white-smoke.wikifoundry.com/page/Suspension Geometry
http://www.vsusp.com
http://racingcardynamics.com/
https://www.slideshare.net/billharbin/vehicle-lateral-load-transfer-parts-iiiimar13
http://www.assettocorsa.net/forum/index.php?threads/how-to-adjust-setups-for-gt3s-in-v1-9.38177/

 

What I understand at the moment.

1. Reduce vibration coming from the road imperfection
2. The force(mass, aero, acceleration, braking, gravity), the center of gravity of the car & the road condition(considering the limitation, longer strut is needed).
3. Since it reduce the vibration from the start, I suppose it has a higher impact since the spring has a default setting.
4. Default is a predetermined setting that is suited for the overall package. You have defined predetermined step to play with.
5. If the exit is involved, oversteer.

 

Thank you for your answers.

1) Partially correct. Dampers convert kinetic energy of the spring into heat. They form a spring-mass-damper system and reduce the amplitude of the oscillation of the springs over time.
2) Correct. Damper Ratios and Damper Rates (DR, Ns/m) are derived from the ride frequency, sprung mass (CG, aero load) and road condition (smooth or bumpy).
3) Wrong. Dampers are less important in a car setup than springs and ARBs, because these have a larger effect on handling. Damper values are also partially derived from ride frequency (spring rate). See 2).
4) Wrong. These are placeholders and don't mean anything.
5) Wrong, understeer. If you increase front bump, you increase the front stiffness and this damper reacts with more force and/or time to the corner load. This load is transfered to the tyre and its friction coefficient (grip) always decreases with vertical load. Therefore, the car understeers.

I really appreciate your curiosity and interest in this subject, but I urge you to read up on theory first (e.g. Race Car Vehicle Dynamics by Milliken) and then apply this knowledge experimentally in Assetto Corsa. For a sim, it does a pretty good job at approximating reallity.

 

I kinda liked the movie better, still waiting for @Aristotelis videos in that matter.

Sent from my Moto G (4) using Tapatalk

 

For #3 I didn't understood the question. Like if I was limited to the suspension tab screen. The bump value affected more than the rebound value. Spring rate is kind of cheating as it is also part of the damper. ARB mechanism also affect both damper.

#4 I don't understand that answer

#5 Guess I'm probably doing it wrong. I always though without pushing having a stronger front damper, would promote less likely to understeer. I wasn't sure how to answer as it was for the exit since I adjust the front bump mostly for the entry. I almost answered it does nothing.

 

I don't understand this. When weight is coming off the front wheels under acceleration, isn't the effect of the damper governed by rebound rather than bump stiffness? I thought it was a deliberate trick question, the answer being that it would have no effect.

 

Two quite simple videos about dampers (bumpers and rebounds) but very graphical.

 

I admit in racing term, if the car is well setup & would deliberately increase the front bump, the car would understeer at the exit.

Thinking about it...
I wonder if increasing both front bump value to max on the suspension tab on RWD car over the default in AC would result understeer at the exit.

 

this one explains it very well
http://www.kaztechnologies.com/wp-c...er-from-FSAE-Book-by-Jim-Kasprzak-Updated.pdf

 

@Georg Siebert gave plenty of very interesting & very useful links to understand the roles of the suspension.

Thanks for sharing also @Leonardo Ratafia

 

I thought the same, now I'm more confused then ever about dampers lol

EDIT: someone has to stop Aris copy-pasting and put him to make those videos

 

And you're right. Answer 5 is incorrect. The bump has no significant influence in that situation IMO. @BrunUK put it right in his post.

Also @Georg Siebert, you say:

That would mean that a tyre has maximum grip when it's maximum unloaded. It would mean that the inside tyre through a turn has more grip than the outside one, that the rear grips up under braking etc. IMO it's absolutely wrong.

Edit: One more example - screw downforce - the additional load on the tyre will decrease the grip of the tyre. Let's introduce lift on the next batch of LMP1 cars.

This is why I recommend for everyone who really wants to learn about dampers to run far, far away from this thread and go for these KW vids, Youtube, Wikipedia etc. The topic is too complicated to be captured with words, only. At least some basic sketches and numbers are needed.