On Thu, 06 July 2000, dg50@daimlerchrysler.com wrote:
You wrote:
> The Peru Tour is instructive, for two reasons. 1) It's the first event this
> year where Kent and I met up on a wide open, straight-up fight and 2) It's
> the first National event where a small, light, but not particularly
> powerful front-driver has shown up.
>
> # 1 I find interesting, because I've noticed that as the courses get
> shorter and tighter, I tend to do better against the Supra. As they open
> up, the gap opens up, all else being equal.
>
> # 2 is interesting too, as the same goes for this car, only backwards. As
> the courses get shorter and tighter, this car (A VW Sirocco) does better
> and better. In fact, he's savaged me at the last couple of local events, on
> slow, tight, narrow courses. But the tables were turned in Peru. This car
> weighs 1800lbs (we weighed it at the event) which is a little more than
> _half_ of my car (and LESS than half of the Supra) but he was still
> outgunned, power-wise.
>
> So imagine that we had an index for courses. a "1.000" course is a 2 km
> long straight stretch, 25m wide. A "0.001" course is your typical CCM
> course - 10' wide, and snaking though every possible atom of pavement in a
> 200m^2 pad, with no turn less than 160 degrees, and no radius larger than
> about 10m.
>
> On the 1.000 course, you'd expect to see Supra, Talon, VW, with large
> intervals between the cars because of the large power differential. On the
> 0.001 course, it's reversed: VW, Talon, Supra, because of weight, size, and
> tire area.
>
> Now if you had some sort of magic pavement, that you could redraw courses
> by turning a knob, as you turned the knob from 1.000 to 0.001, you reduce
> the power advantage differential until you reach the point of course
> complexity where all three cars are equal (or at the very least, where the
> differences between them fall into the noise from driver ability)
>
> Now consider this - let's say the "equality point" is at 0.500. This means
> the VW has an advantage roughly 1/4 of the time, the Supra has an advantage
> 1/4 of the time, and all three cars are even roughly half the time -
> **assuming that the distribution of actuall course complexity is linear**.
> If the actual distribution of course complexity is a bell curve centered on
> .500, then the Supra gets an advantage rarely, the VW gets an advantage
> rarely, and most of the time the class is fair.
>
> Now, let's assume that the "equality point" is not .500, but .250, and that
> the course distribution is a bell curve centered on .500. If this is the
> case, then the Supra has a slight advantage more often than not, and a
> large advantage rarely, while the poor VW has a strong advantage rarely,
> but a slight disadvantage more often than not. This is an unfair class.
>
> So it seems to me that there's a pair of important data points missing - at
> what course complexity value is a given car's performance equal to
> another's, and what is the frequency distribution of course complexity?
>
> I would guess too, that different events have different average
> complexities. Nationals and Tours may have a .700 complexity, Pros a .500
> complexity, and local events a .300 complexity. If the spread is this wide,
> then a given class's "fairness" may vary widely with the kind of course the
> cars are running on.
>
> It would be _very_ interesting to come up with some sort of measurable
> course complexity value, and then plot results in classes against the
> complexity value, and see what correlations one could discover.
>
> Except for one thing - I haven't a clue of how to do that. Any ideas?
>
> DG
I have kept your message around for the better part of a week thinking about
it.....also a busy weekend with a local 2-day regional event.
Like yourself, I have noticed a similar situation but it seems to have been
more painfully obvious here in Calgary.
Whenever I used to see a "button hook" and a series of tight turns/slalom (we
used to run in a smallish mall parking lot made up of two lots separated by a
central median and a narrow lane in between which limited course layouts a
bit), I used to warn the designer that he was playing into my hands. My Miata
(minimal mods and stock engine - C/SS in Canada and C/SP in SCCA I guess) would
negotiate those tight turns and hooks much faster than almost anything that
runs locally - particularly the Camaros, Corvettes and Mustangs and other such
cars. However, whenever there was a course with wide open straights and plenty
of room to get on the loud pedal the bigger and more powerful cars would gain
back whatever advantage I had in the tight bends.
Of course it is not quite that simple. I have also noticed that the Miata (can
apply to other smaller cars as well) has very good ability to change direction
that bigger cars do not share - perhaps primarily because it is narrower (&
suspension geometry...design...etc. etc.)? Therefore in a course where almost
continuous cornering occurs the less powerful but better handling cars will
tend to shine.
And what about formulae? Well, if you have Autocad or some other drawing
software engineers and architects use you might be able to predict at what
point in corner radius variation and straight section length that a smaller
car's advantage is more or less equal to a bigger car's power advantage in
straight sections.
The above is very simplified since there are a whole series of other factors in
play here...perhaps narrowness of vehicle is a key?
I remember running motorcycles on an autocross course many years ago - there
were several of us (strange story there but I won't get into it here).....the
slowest bike would typically beat the fastest car by something in the order of
5 seconds......not many mod cars around in that area though. The fastest
motorcycle would be at least 10 seconds faster on a 60 second course. Why? It
certainly wasn't cornering speed but rather the narrow track of the
motorcycles...a slalom was a piece of cake. So perhaps the width of a car is a
bigger factor than we think - a narrower car can run bigger radius arcs on a
given course which means it can carry more speed given the identical cornering
G capability.
That is enough for now......Given enough time there would certainly be plenty
of geometry to calculate and get a "fair" course that would be equal for all
cars. However due to the variation in car size/width, suspension, and
power-to-weight ratios you could never design a course that would be fair to
all comers. I think you could write a book on this topic! :^)
Regards,
Reijo
Reijo Silvennoinen, CSCC Nat'l Event Rep.
Calgary, Alberta
Calgary Sports Car Club (CSCC) web site:
http://www.cscc.ab.ca
Canadian National Autoslalom Championship (CNAC) list:
http://www.onelist.com/links/solocanada
CNAC web site:
http://CNAC2000.erc.bc.ca/
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