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View Full Version : Physics you would actually pay attention to in school ... Racing :D



KnifeEdge_2K1
09-01-2004, 10:16 PM
http://www.miata.net/sport/Physics/index.html

this site has alot of cool stuff about weight transitions and racing lines trail braking centrifugal force, camber changes due to body roll ect.

ive only read the article on the racing line (kinda boring since i knew all of it) but it really gives a good explanation to WHY a classic racing line is better than taking the inside track as many people think

what i should add though is that the racing line is really only advantageous when you're alone (not fighting for a position)

let me explain

i expect you all to know the classic racing line in a 90 degree corner, the out in out method

this is the fastest possible way to take the corner because it optimises tire grip

now imagine a situation

you and another car are headed for a 90 degree right hander and you're on the outside (for the classic line) and he squeezes up right beside you, he brakes late and turns into the inside blocking your path, now at this point he's much slower than if he were to pull up behind you and take the proper line but since he's now infront of you you cant speed up and take the racing line without ramming up his ass, both your exit speeds are significantly lowered now but he has the better position and can manage to take the proper line on the next corners (assuming both your cars are equal power and you're not drafting him)

now in this type of situation (again depending on how it was set up) you may have decided to take a more centered line or played a game of chicken with him

in a chicane this is a different story since if he were to pull the same maneuver you could have lifted off early, turned tight on the first curve and turned wide on the other, he may have passed you in the first corner but you better line in the second will more than make up for it

a basic rule of thumb is the outside radius of the corner is NEVER advantageous in any situation (excluding the chicane example but there are many types of chicanes with different turnign radiuses which open or tighten and of different lengths)
the inside is really only useful if you want to risk braking late and popping in front of a guy, and the racing line is the best to take if you're in a time attack or alone either in front of the pack or behind (at which point you'll prolly be screwed either way)

RaptoR
09-02-2004, 06:56 AM
Very usefull link !!!
Thanks a lot, I'll read it ight now.

Matra et Alpine
09-02-2004, 07:24 AM
I'd recommend reading one of the many books written by racing drivers.

This is a good mathematical analysis to produce an ideal line in ideal conditions with an ideal vehicle. I've not read further and maybe he does cover it, but inthe real world with FWD, RWD and differing weigh bias it is quite normal for a corner to stay OUT longer before turngin in to the apex, for the apex to be slightly later and the exit to be less rounded. Definately THE route for mid engine RWD and for cars with 50:50 balance.

For the splice-type car behavior assumed, I conjecture that no line is faster than line . and he's probably right, just that no car acts in the idealistic way he calculates it :)

Also the road sruface makes a big difference.

This was one of the BIG lessons I learned whilst I transitioned from rally driving to track. MOST of the lines I had were wrong. The driver ('big' name :)) right away called it that I had rallied. "Your lines are all rallying lines, we need to forget that and learn the track lines" :)

WHen you start doing track time, it's worth getting some of the track professional drivers to sit with you and advise you on the variances from the "ideal racing line" for your car. You may be VERY surprised. The hairpin at Knockhill is a classic. Getting people to stay out WAY past "normal" turn-in is hard to convince them until they see the lap times !!!

Ferrari Tifosi
09-02-2004, 11:24 AM
Carroll Smith's line of books are great reads especially Engineer to Win. Lots of cool information on metallurgy and racing physics, suspension geometry setups, etc.

KnifeEdge_2K1
09-02-2004, 05:35 PM
aww dont i get points for bringing up such a cool topic?
oh yeah the guy covers that in the section slow in fast out advanced racing line section (its 2 sections combined)