RedlineMan

Thanks... I think;

It makes about as much sense now as it did before I didn't know what you were talking about! I'm a hammer and welder kind of guy!

Hmmm... I know what you mean. I'll quote myself again.

"When the time comes to close the books and turn the key, theory goes out the tailpipe. The only thing that tells the plain truth is the clock." - Me.

Geo

That would be rather surprising. Almost all SA dampers adjust rebound only (or try to). The realitiy is that most have some very very minor impact on compression, but it's negligible.

Alan C.

Im going to take two Tylenol PM's and go back to bed. When I wake up I'm going to run out and buy some of those 'color' blocking lenses.

fatbillybob

I read this thread with great interest and now LMAO! As a rookie with neither a very sensitive $ss-o-meter nor DAS, its nice to know that what I take from this thread, which is something I always suspected, is that it appears that seat-time is what you need. Finally, I thought that I was the only guy on Rennlist with a "hammer and welder".

ColorChange

John: In simple terms, Fourier transformation allows you to take displacement or even accelerometer data and convert it into its frequency components. Why would you want to do this you might ask? The frequency range of various components indicates the likely cause and effect of the situation. 2 hertz and slower is usually driver related. Faster things are usually the car as a whole, bars, etc., and faster still things are springs, tires, shocks etc. So, if you do an FFT of an accelerometer attached near your hub, you can very clearly see the effects of what the shock setting change did.

kurt M

That is good stuff! What is the method to translate the data stream into action? If this change or data is observed, then what? What is the paper to metal bridge? What is the goal or end point that is desired? Tires on ground. How do we translate data into ajustments?

I get the G sum and data transformation. It is the translation into action or into actionable gamets that is still missing in all of this. This is not a poke but a real question.

What do we do with the data? Where can I find gamets that can be tested?

SundayDriver

I have to admit that I am not very good at translating data into action in terms of car changes. Now overlay a faster driver's traces and there is much to learn.

What I have gotten, in terms of car setup, from data, is generally confirmation of something I thought I felt. A HUGE step in car setup is learning to trust what you feel. When you KNOW what the car is doing, you can make effective changes. It starts by feeling real unersteer and real oversteer. What follows (at least for me) was feeling the balance of the car as it goes through transitions. Finally, you learn to feel what the car is doing in different parts of a corner. Then you can start to tune. Data has always helped me confirm what I feel and has helped my confidence in that feeling. WHen the shocks suck, the shock data looks different than when they are working. But the data does not tell me what to do, as I have to decide what the car is telling me in other places on the track as well.

Now if you are working with aero, the data can tell you how much and where the center of pressure is. That can keep you from chasing bad ideas in tuning.

I have worked with a professional data engineer who worked IRL, CART, etc and according to him, data was very little, if any, help on setup. I am sure that with the massive data and the number of engineers in F1 that they can do much better, but for us mere mortal and low level gods, I don't think it does much for us in terms of setup.

Mike S.

John...tighter or losser? Fess up, you've been watching NASCAR

All...we use FFT frequently (little pun in there for the engineerds out there) to diagnose problems with the equipment we build. Here's a simple use in ole' automobile land. Say you start to hear a peculiar (abnormal) noise coming from the gearbox. An FFT of this noise/sound/vibration will disclose all the individual tones/frequencies that make up the sound. Plus, it also tells you how loud each sound is. One tone will be the frequency or speed of the engine which is the input to the gearbox, another frequency will be the driveshaft, and then there will be others like what's called the meshing frequency of the engaged gears. Now with a baseline FFT of a proper sounding gearbox in one hand and the FFT of the noisy one in the other, let's say you see a the loadness of the tone/frequency of pinion gear speed is abnormally high. You then can suspect you have a cracked or are maybe missing some part or pinion gear tooth. Experience with correlating the noisy FFT with the damage you find when you pop the baby apart will hopefully allow you to be smarter about when to fix the problem and what kind of damage to expect when this happens next time. Of course upon hearing this sound, a real good tranny guy who has reasonable experience with this gearbox, says "bud, you got a pinion gear about to go."

There's little question that data of the right kind, amount, and at the right time(s) will generally allow one to be better and/or learn faster...whatever the task. I believe that applies to laying down the fastest lap possible, if that's your goal. For me, I simply get a kick out of driving on the track. Just want to have fun and then come home and hug the family. If I could ultimately drive smooth and be skilled to handle any track situation, oh baby. I have spent the last 25 years as a mechanical engineering technocrat and the last thing I want to see is an instructor whipping out his laptop at the end of the session and telling me that on lap 3, turn 9, I botched the turn in point...and here's the plot to prove it. Just give me a good instructor who knows his stuff and is great at communicating'n'teaching, and for the skill level I'm at, I'll learn quickly and have a great time doing it.

Ok, with all this engineering banter here, I'll chime in on this post topic. There's a term called "critical damping". In words and applying it to rebound for a car going down a straightaway and hitting a single bump, it's when the value of damping selected results in the fastest return of the car to it's stable ride height. It would be my guess that this is fundementally what you're after. You wind up only having only a single, but ever diminishing bounce (cycle of vibration). Too little damping, and you will have multiple, less diminishing bounces. Too much damping, and while you'll have no bounce, it will take longer to return to the (desired) stable ride height. Way too much damping and/or a large bump and sufficient speed and you're tire is off the pavement. Skilled drivers like many of you can "feel" this, engineers can measure this....guess I'll be doing a measurement.

Mike "wanting to be a hammer and welder guy like Mr. Redline Man"

RedlineMan

Thanks Tim;

I have spent the first half of my life coming to the realization that I have a "learning dissability" if something concerns numbers and/or takes intense concentration. I will probably spend the rest of my life trying to figure out how to get around it. I actually understand that! Thanks for talking TO me!

Mike;

You're perfect. I completely understand everything you offered. Makes perfect sense, and would obviously be highly useful. I think you may be the rare humble engineer. My Hammers & Welders are always ready!

SundayDriver

Great comments. As to critical damping, the answer (as with most of this stuff) is yes and no. You are trying to do far more than control the osciallations of the chassis/wheel. And you are trying to do it with vastly different input velocities and frequencies and with different loads on the wheel and... and ... and. It is a much more complex problem than finding ciritical damping. And then you don't know which system you are trying to contol. Is the chassis fairly stable at that moment and you are trying to control the wheel & tire or is the wheel stable and you are trying to control the chassis.

If you start digging into the internals of how racing shocks work, you will find all sorts of variable devices. Valves with needles (including very expensive materials that maintain openeing area across all temperatures), shim stacks and methods to change fluid paths (circuits).

It makes my head spin.

Professor Helmüt Tester

If you ever get a chance, spend some time talking to the guys who design shocks for Penske. They have bizarrely varied background, and love to talk about how the technology evolved (think James Burke's series "Connections"). What they can talk about (the stuff that doesn't require that they kill you afterwards) is pretty freaking cool.

Shocks are the single most misunderstood and underappreciated component on a race car.

M758

Mike S.
In nutshell you nailed what you try to with dampers. As you know however single bump is very simplisitic case. The challenge comes in that there many many "bumps" on any on track and then you need to add in time depenant variable loading (weight transfer). Thus you cannot determine one critical damping ratio to perfect for any track. Roundy Rounders actually have much easier time at this since they only have really 3 corners to deal with. So much less variation in their loading. However they all know this so their damper adjustments are really on much finer scale. Road Racers need to turn left and right at various rate and have ups and down to deal with too.

Thus the "set-up" for crital damping much more challenging. Damper turning involves two basic elements. First the basic ball park set-up. This gets you close enough on a particualr track to close to the pace. Then you need to tweak this set-up for the track. This often means making the car better in certain places to achieve an overall result. In some case this does not even lead to the lowest lap time as being fast were one can pass or needs to defend position may in fact be more crutial.

It is for this reason that even F1 teams that have the resources to do all sorts of data analysis still rely on driver feed back and a "stopwatch" to large degree. All the other tool at their disposal are there to supplement their basic input.

Mike S.

Yeah, you guys are right. Thanks for responding and offering additional important perspective and information. It made me think more deeply about this. I certainly agree with what you said. Everything is indeed a lot more complex than a single bump on a straight. Add in the considerations you mentioned (road surface and weight transfer), as well others (aero downforce, component non-linearities), and your right, achieving critical damping is not an "end all, be all" goal. The system and conditions are not static, but change.

FYI, I picked a simple situation so I could just introduce the critical damping concept here to provide a way to understand how too little or too much damping will effect the response of the car (system) in a simple situation. Plus, you get a feel for the fact that there is an optimal amount of damping for a given situation. I can now appreciate much more that it changes meaningfully for not just different different tracks, different points on the track, at different speeds, for different lines, with different tires, at different....

Mike

forklift

Doing some searches on shock tuning this evening, I found this thread which is both educational and entertaining. I have also found some good links on the web I thought I would pass on:

http://www.wtrscca.org/tech.htm#suspension

http://bimmerhaus.com/tech/shocktuningTN.html

http://www.penskeshocks.com/Adjusta...ch%20Manual.pdf

I can’t find my “Tune to Win” book I bought a few months ago…damn it. I might have to get another.

I am getting ready to dive into the world of double adjustable and my head is already spinning. I know, I was warned.