ColorChange

Professor:

The graph means nothing without the rest of the data for that session. Nothing.

This point is rather stunning, … stunningly wrong. It unequivocally shows Schumi trial braked always at Imola during his pole qualifying lap. It says many more things, but that is so obvious, and the primary point of my post, that to not see that reflects a huge lack of fundamental knowledge. Sorry.

Mike in Chi

"Mike LOL"

Good.

As more than a few here have pointed out, it would help to lighten up.
Just my VHO, not a personal attack.

APKhaos

I find it helpful to remember something my fave professor told us a long time ago:

"For every complex design problem there exists a set of solutions that are simple, elegant, and comprehensively wrong."

You guys have been more than tolerant, IMHO, of an individual with little apparent engineering/physics/vehicle dynamics education and no meaningful driving experience. Opinions are free. Opinions presented and defended as fact are expensive - for everyone who listens.

bob_dallas

Not exactly...

You advocate G Sum as a true measurement of performance. What are the components of G Sum? Gs and...Gs? Maybe I need your formula to answer that definitively.

Are you saying you can't calculate it because there are other variables that are unknown?

ColorChange

No Problem Mike, I agree.

APKhaos:
Do you care to back up your personal attack? Or are you a low character coward?

Bob D: Sorry, gave the definition in other posts. g sum= sqr[(lat g)^2 + (long g)^2].

bob_dallas

So by this definition a lat G has the same weight as a long G....So you are assuming a cars capabilities = a perfectly round friction circle or more accurately a "capabilities" circle?...meaning I can generate as many +/- long Gs as a can lat Gs? Otherwise they can't have the same weighting.

Bob Rouleau

Color

Quote: "I’m not sure I understand the question. We know exactly when Schumi is braking when he hits anything over 1 g in -long g's? You will notice, he never holds just 1 g pure braking. Whenever he is only braking (not trail braking), it is pretty much threshold braking and in the 3-4+ -long g range."

What I implied is that it is not evident when Schumi was trail braking because by lifting off the gas his car decelerates at about 1 G without ever touching the brake. I am confident that he does not trail brake at -3 to -4 G's. Consequently when I see neg 1 or thereabouts with lateral acceleration it is possible that he is simply going in under compression and not touching the brake at all. If you watch an F1 race you will hear this when they give us in-car camera clips. So seeing the lat/long plot doesn't tell me if the driver is braking or coasting since coasting slows the car down as much as your 996 TT with full-on ABS. Add to this the fact that simply turning the wheels into a corner further slows the car down and it seems clear that the plot can be misleading without additional information.

And yes, I did say that techniques applicable to an F1 car are inappropriate to a regular production car without the aero assists. I spent a few days with an F2000 car with wings and things and the driving technique is different.

bob_dallas

And another question - what's the reference point for G Sum to compare to so you know when you are close to this optimum?

Is it the same for every corner for all cars?

Is it the same for every corner for a given car?

Phil

Drivers Ed for most people = fun....lotsa fun...woohoo fun!!

Drivers Ed for the colorwhichchanges =g sum= sqr[(lat g)^2 + (long g)^2].


I might have to add that to my sig line........its very very impressive!

bob_dallas

And a couple more - trying to split these up to give you a chance to answer.

Is this an instantaneous measurement or an average from throughout a turn?

Let's say I get a G Sum of 1.11 for a given point - what does that tell me? Drive faster? Brake later and harder? turn in later? turn in earlier? put the car in reverse?

Picture this - you are coaching someone in your "Extreme Car Control Clinic" that you advertised a few months back. You have people go out with a DAS onboard and then bring you back the data which you plug into the computer and it spits out a number - 1.11 - now what do you do?

BTW - as an aside - how many people have you had sign up for your extreme car control clinic? Wasn't it planned for the April/May timeframe?

Phil

Bob,
I understand most of what you wrote above. My question is......
at what point would I put the car in reverse? after turn in? on the straights?
One other questions pops into my head.......what would happen if the number spit out is less than 1.11 or more than 1.11??
I have a DAS in my car.....its a rollbar, and has never spit numbers at me? did I get a bad DAS?

CMMTracknut

Colorchange

I have to say it is amusing how many people chime on your posts. I look at the data you post and I feel like I am trying to translate ancient chinese text that I did not study the night before. I consider myself a "car dude" but seriously. What do you do? I forgot, sorry.

I watch Mikey every race and scream and yell and laugh at how amazing he is. Makes the Mrs. want to go outside and garden or something. He really trailbrakes every corner? I have done this in a Formula Dodge necessary in turn 2 Seca or Key Hole Mid Ohio, but I thought(wrongly perhaps) these cars had so much frickin' down force that once initiate turn they would throttle in often to settle car. So much mechanical and aerodynamic force! Esp. the high speed big sweepers. I felt that trail braking was more for slower corners or to make up for understeering cars or tire situations.

C

bob_dallas

Phil...now you are finally getting it I think - if your DAS starts spitting numbers out at you then you must put your car in reverse immediately to exorcise those spirits...

Actually - since G sum is just a number we could invent an audible DAS that provides live feedback by simply calling out the number mid-turn...??

ColorChange

Bob D: You¡¦re good. I'll answer them all.

So by this definition a lat G has the same weight as a long G....So you are assuming a cars capabilities = a perfectly round friction circle or more accurately a "capabilities" circle?...meaning I can generate as many +/- long Gs as a can lat Gs? Otherwise they can't have the same weighting.

Yes, they get equal weighting in my model. For our cars, the fc¡¦s are reasonably round and the cars pull similar lat and long g maxes. For high aero cars, no, more elliptical exactly as the graph shows, especially at high speeds. For lower speeds, the fc is more circular, but still shows better braking capability and less accelerating capability. This is the classical ¡§heartish¡¨ shape. Where we are most interested in maximizing g¡¦s, from braking to strong acceleration, the curve is quite circular, it gets pinched in the extremes of braking or accel.


And another question - what's the reference point for G Sum to compare to so you know when you are close to this optimum?

Previous runs with the car (most of us) or really good models. Ferrari has both.
The best I know of is previous laps where you have exceed the fc and the data shows it. Then you know conclusively but like I said earlier, where there are no significant camber or elevation changes, the fc is quite consistent turn to turn.

Is it the same for every corner for all cars?

Heck no, all over the place depending upon the car, tires, set-up, driver ability, corner geometry, ¡K

Is it the same for every corner for a given car?

No. But it is surprisingly similar if you don¡¦t have camber or elevation changes.

Is this an instantaneous measurement or an average from throughout a turn?

The number is instantaneous; the maximization is taken over the full lap of the track.

Let's say I get a G Sum of 1.11 for a given point - what does that tell me? Drive faster? Brake later and harder? turn in later? turn in earlier? put the car in reverse?
It only will tell you if you are on or near the fc. You have to define the line, control turn in, etc.

Picture this - you are coaching someone in your "Extreme Car Control Clinic" that you advertised a few months back. You have people go out with a DAS onboard and then bring you back the data which you plug into the computer and it spits out a number - 1.11 - now what do you do?
If that is the max you could hit before the car skidded of the circle, you did well. If it was too low, tell the driver to go faster. Now, on a skid pad you normally use only the throttle. I discussed a more interesting test for trail braking and turn in where you approach a cone at maybe 80 mph. Hit threshold braking to 60 at which point you reach the turn in cone, and then trade long g¡¦s for lat g¡¦s and hit the skid pad at the proper max lat g speed and ride the skid pad. It is a real neat exercise because for most people, they didn¡¦t know they could trail brake so deep and so well and still make the turn.

BTW - as an aside - how many people have you had sign up for your extreme car control clinic? Wasn't it planned for the April/May timeframe?
6-speed was supposed to have a national meet in May but it doesn¡¦t look like that is going to happen, so without that, I will probably either attend a driving school or pay the instructors myself privately, or bothƒº.

Bob R
What I implied is that it is not evident when Schumi was trail braking because by lifting off the gas his car decelerates at about 1 G without ever touching the brake.
The car only decels at 1 g when they are around 300 kph. The slower, the less aero drag induced decel.

I am confident that he does not trail brake at -3 to -4 G's.
Sorry Bob, wrongo. Look at the line I highlighted on the right. He is pulling -3.0 long g¡¦s in braking while at the same time pulling about 1.6 lat g¡¦s!

Consequently when I see neg 1 or thereabouts with lateral acceleration it is possible that he is simply going in under compression and not touching the brake at all.
No. If you follow the majority of the traces where he brakes heavily, you see huge long g¡¦s, then trading long for lats, then lat for accel. The is trail braking and driving on or near the fc, or maximizing g¡¦s (I hope we can grant him selecting the proper line .. I sure do).

If you watch an F1 race you will hear this when they give us in-car camera clips. So seeing the lat/long plot doesn't tell me if the driver is braking or coasting since coasting slows the car down as much as your 996 TT with full-on ABS. Add to this the fact that simply turning the wheels into a corner further slows the car down and it seems clear that the plot can be misleading without additional information.

No again, like I said earlier, the car only has that big aero induced decel at high speeds, and that is the only time he can achieve 3-4 braking g¡¦s (now up to 5 braking g¡¦s by the way when the cars are set for high down force tracks). The rest of the time he has already braked so hard and dropped his speed that the vast majority of the braking he is applying is coming from his foot, not the highly aerodynamic cars.

And yes, I did say that techniques applicable to an F1 car are inappropriate to a regular production car without the aero assists. I spent a few days with an F2000 car with wings and things and the driving technique is different.

Certainly some are, but not the proven and accepted fastest concept of trail braking in most turns and most cars.

ColorChange

CMM

I am a chemical engineer by undergraduate training. I read a lot about race cars and vehicle dynamics.

I felt that trail braking was more for slower corners or to make up for under steering cars or tire situations.

This is most people’s perception and I think it is wrong. You should trail brake through most turns and in most cars if you want to be fastest. Again, we are not talking about racing conditions and define tail braking as braking applied during and/or after turn in. The amount of trail braking varies depending upon many variables but should usually be used to some degree.