[patred]

All of a sudden, the frrax members show up ...

http://www.thirdgen.org/techboard/suspensi...ng-vs-v8-2.html

(IMG:http://www.frrax.com/rrforum/style_emoticons/default/burnout.gif)

Pat

[trackbird]

I'm bored so I'm "in". I simply presented another way to spend $25k on a 3rd gen (and maybe someone will decide to buy my car (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif) ).

[StanIROCZ]

Andris,
That spreadsheet of yours is intriguing. I’ve been thinking about making one myself for some time now but just haven’t put aside the time to do it. I have a theory about polar moment of inertia vs F/R weight distribution that I would like to try out.

Here is a thread on the very subject: http://www.frrax.com/rrforum/index.php?sho...+put+the+weight

Some people say to put all the ballast in the RR corner to improve weight distribution. Some say to put the weight towards the center of the car to reduce the polar moment of inertia.

My theory is that the best place to put the weight is track dependent. For autocross with tight turns there is a greater amount of force on the tires just to rotate the car (180 deg turn in 2 sec, for example). On a road course the turns are longer so the force to rotate the car is less (180 deg turn in 4 sec, for example).

Add to all this another thing that I want to put on paper/computer. 300 lbs of unsprung in the rear and 1170 lbs of sprung weight make a unsprung/sprung ratio of 26%. The front for example would be 150/1950 = 8%. What does this mean? The front unsprung weight will be controlled better than the rear. That means that moving weight to the rear will have another benefit beyond just the steady state tire model prediction. I'd like (again when I get time) set up the model and make a few plots of the force between the tire and the road vs time. Multiplying that by a tire friction curve will result in a plot of dynamic grip vs time. Taking the standard deviation of the population of points that make up that plot would give you a single number that can be used to express the dynamic performance of a given configuration.

There are other set-up related configurations that could be ran through such a model. Many of the results would be intuitive (less unsprung weight means a more consistent force between tire and road, for example) but I think the greatest benefit would be that it allows us to make some comparisons of different set-ups and the relative magnitude of a certain change. We could incorporate details that are in JonA's spreadsheet, aero, etc.

Some things that it could evaluate (expanding upon what you already have):
-weight distibution and sprung vs unsprung
-Big bar soft spring vs small bar big spring (adding (road) dynamic analysis to JonA's spreadsheet)
-3rd shock? (just for fun)
-ballast location
-etc

I realize that I am greatly over simplifying things but even simple models can be used to make relative comparisons.

Did I loose you?

Who thinks I'm a total nerd? (show of hands) lol

[nape]

Who thinks I'm a total nerd? (show of hands) lol

Not a nerd and I like the way you think. Let me know where to put my ballast once you figure it out (IMG:http://www.frrax.com/rrforum/style_emoticons/default/wink.gif)