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#41 Pavel

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Posted Dec 22 2010 - 04:31 PM

View PostLee200, on Dec 22 2010 - 02:34 PM, said:

Thanks Pavel or these.  I'd not seen them before.

Do you have the next month's installment which supposedly covered the theory behind slipstreaming?
This are not my scans. Someone posted it on RSC in same topic about drafting. So I don't have article from the next month.

Every time when we talk about slipstreaming there are references to 1966 Reims GP. If I'm right, weather at Reims always was very hot (and in 1966 too). Reims track run through the fields and there are no many trees around. So under the sun air upon asphalt warm up even more. Warm air have lower density. So 'tunel' in the air after car don't close as quick, as in cold weather, I think. And this don't work on most of others track. For example half of the Monza is under the trees.

#42 M Needforspeed

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Posted Dec 22 2010 - 04:36 PM

Sorry, post edited.That's not the 1966 race Brabham talk about, but the 1964 F2 race, with the modest Ford SCA engines.

Edited by M Needforspeed, Dec 22 2010 - 04:43 PM.


#43 Bob Simpson

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Posted Dec 22 2010 - 04:41 PM

View PostRudy Dingemans, on Dec 22 2010 - 02:10 PM, said:

(I still don't buy Bob's reasoning of slipstreaming on bicycles, I don't think that exists (it just reduces the head wind if you tuck in behind the cyclist in front, but front drag reduction is not the same as a slipstream - which "sucks you forward" and bicycles just don't go fast enough to punch such a hole in the air needed to do that). But apart from that, I think he has part of the explanation here.)
Here, we're getting into problems with definition between "slipstream", "draft" and "drag reduction".   To me they are all the same, but I could be wrong.

There have been some high speed records in bicycling where the rider tucked in behind a special wind block (both terms "slipstream" and "drafting" are used in that articled BTW).  The car and bike got up to 150 mph but I read in other reports that if the rider had gone back another half meter, he would have been battered by the wind and lost all advantage.  There was, in fact a pushing effect on the rider due to the design of the wind shield.

The air behind a regular car is much more complicated.  There is turbulence with the air going forward or not at varying speeds depending on where you are in all three axes.

Edited by Bob Simpson, Dec 22 2010 - 04:58 PM.


#44 Pavel

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Posted Dec 22 2010 - 04:44 PM

Thanks M Needforspeed,
Intresting: with f2 car at 142 mph - 400 yards, and with f1 car at 190 mph - ?

#45 Phil

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Posted Dec 22 2010 - 05:02 PM

View PostM Needforspeed, on Dec 22 2010 - 04:13 PM, said:

To break another car out of your "tow" you had to pull at least 400 yards ( 435 m) ahead of it
400 yards is 366 metres.

#46 M Needforspeed

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Posted Dec 22 2010 - 05:07 PM

View PostPavel, on Dec 22 2010 - 04:44 PM, said:

Thanks M Needforspeed,
Intresting: with f2 car at 142 mph - 400 yards, and with f1 car at 190 mph - ?


answer ain 't easy, at faster speed, fluid certainly moves with different dynamics, and others effects can appears as well as disappears.

#47 M Needforspeed

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Posted Dec 22 2010 - 05:08 PM

View PostPhil, on Dec 22 2010 - 05:02 PM, said:

View PostM Needforspeed, on Dec 22 2010 - 04:13 PM, said:

To break another car out of your "tow" you had to pull at least 400 yards ( 435 m) ahead of it
400 yards is 366 metres.

thks.post edited.There is two conversion mistakes in the book !

Edited by M Needforspeed, Dec 22 2010 - 05:16 PM.


#48 M Needforspeed

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Posted Dec 22 2010 - 05:20 PM

View PostBob Simpson, on Dec 22 2010 - 04:41 PM, said:

View PostRudy Dingemans, on Dec 22 2010 - 02:10 PM, said:

(I still don't buy Bob's reasoning of slipstreaming on bicycles, I don't think that exists (it just reduces the head wind if you tuck in behind the cyclist in front, but front drag reduction is not the same as a slipstream - which "sucks you forward" and bicycles just don't go fast enough to punch such a hole in the air needed to do that). But apart from that, I think he has part of the explanation here.)
Here, we're getting into problems with definition between "slipstream", "draft" and "drag reduction".   To me they are all the same, but I could be wrong.

There have been some high speed records in bicycling where the rider tucked in behind a special wind block (both terms "slipstream" and "drafting" are used in that articled BTW).  The car and bike got up to 150 mph but I read in other reports that if the rider had gone back another half meter, he would have been battered by the wind and lost all advantage.  There was, in fact a pushing effect on the rider due to the design of the wind shield.

The air behind a regular car is much more complicated.  There is turbulence with the air going forward or not at varying speeds depending on where you are in all three axes.


Incidentally, Bob, do you remember José Meiffret ?

  Towed by a Talbot 4.5 L 50's F1 car,in 1964, he got as fast as 215 km/heure, on the long straight between Toulouse and Noé, not far from home.When you came, you had perhaps crossed that road .

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Edited by M Needforspeed, Dec 22 2010 - 05:38 PM.


#49 M Needforspeed

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Posted Dec 22 2010 - 05:26 PM

and before, behind a 3OO SL.They added this ugly but efficient turbulence-free bodyshape.

Attached Files


Edited by M Needforspeed, Dec 22 2010 - 05:32 PM.


#50 richard cooke

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Posted Dec 22 2010 - 05:31 PM

View PostM Needforspeed, on Dec 22 2010 - 05:07 PM, said:

View PostPavel, on Dec 22 2010 - 04:44 PM, said:

Thanks M Needforspeed,
Intresting: with f2 car at 142 mph - 400 yards, and with f1 car at 190 mph - ?


answer ain 't easy, at faster speed, fluid certainly moves with different dynamics, and others effects can appears as well as disappears.
In gpl the distance increases with speed squared, so at 190 mph the distance would be 716 yards and assuming the Indy car mentioned was doing 235 mph its distance would be 1096 yards, and it would take 9.5 seconds to cover that distance.

Richard

#51 richard cooke

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Posted Dec 22 2010 - 05:33 PM

View PostM Needforspeed, on Dec 22 2010 - 04:13 PM, said:

what's remarkable is that if you go 400 m back at Reims, there is a good chance your car is still going downhill, and the car towing in front is in a lower position and thus isn't on the same altitude airflow ...How the effect can be so strong or simply felt?    
It’s probably best not to think of the lead car towing the following car.  Instead think that the lead car has given the air forward speed and until that air stops moving forward there will be a benefit to the following car.  Or like a tail wind that is dying down.

Richard

#52 M Needforspeed

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Posted Dec 22 2010 - 05:43 PM

View Postrichard cooke, on Dec 22 2010 - 05:33 PM, said:

View PostM Needforspeed, on Dec 22 2010 - 04:13 PM, said:

what's remarkable is that if you go 400 m back at Reims, there is a good chance your car is still going downhill, and the car towing in front is in a lower position and thus isn't on the same altitude airflow ...How the effect can be so strong or simply felt?    
It’s probably best not to think of the lead car towing the following car.  Instead think that the lead car has given the air forward speed and until that air stops moving forward there will be a benefit to the following car.  Or like a tail wind that is dying down.

Richard

thks Richard, but what about the altitudes ? .The more remote the car behind is, the more the air forward spedd flow enlarge, isn it ?

Edited by M Needforspeed, Dec 22 2010 - 05:43 PM.


#53 richard cooke

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Posted Dec 22 2010 - 05:56 PM

View PostM Needforspeed, on Dec 22 2010 - 05:43 PM, said:

View Postrichard cooke, on Dec 22 2010 - 05:33 PM, said:

View PostM Needforspeed, on Dec 22 2010 - 04:13 PM, said:

what's remarkable is that if you go 400 m back at Reims, there is a good chance your car is still going downhill, and the car towing in front is in a lower position and thus isn't on the same altitude airflow ...How the effect can be so strong or simply felt?    
It’s probably best not to think of the lead car towing the following car.  Instead think that the lead car has given the air forward speed and until that air stops moving forward there will be a benefit to the following car.  Or like a tail wind that is dying down.

Richard

thks Richard, but what about the altitudes ? .The more remote the car behind is, the more the air forward spedd flow enlarge, isn it ?
The only thing slowing the air is the stationary air around it so the cone will expand and the speed in the middle will reduce, but will be stronger than on the edges.

The change in altitude means the following car will be in a weaker part of the cone.  The last part of the Reims straight undulates so the effect should be small.  For the following car the brow of the hill should be the weakest part but at the bottom of the hill it will be getting the full benefit.

Richard

#54 JASE

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Posted Dec 23 2010 - 12:12 PM

Been a while since I've posted anything, but I couldn't help but put my own opinions forward on this.

The talk about the the slipstreaming effect being too strong in GPL is absolute rubbish, and it seems to be coming from people who simply don't like the fact that a slower driver can keep up or even pass at certain tracks based on the tow effect alone. BUT THIS IS HOW IT WAS!!!!

Reading quotes from drivers of the period ( I too have the EXCELLENT Jack Brabham book ) and, better yet, watching footage like the finish of the 1969 Italian GP on youtube, it's easy to see that at certain tracks the guy in front had all the work to do to keep the other guys behind, purely because of the power of the tow. As racing progressed through the years and aerodynamic down force increased, so too did the amount of turbulence behind a race car. Straights are much shorter these days too, and so now we don't see slipstream passing very much at all. But it was the primary means of getting by another car at circuits like Reims and Monza in the '60's, and if you did get by you had to expect to be drafted in turn, it was how they raced.

I think there are too many online racers out there that don't like going to any track and getting passed on drafting alone. They argue that reducing slipstream effect is more realistic, but every piece of evidence out there that I can see contradicts these arguments. I do all my racing against the AI, and I often wish that we had a means of switching between slipstream models depending on the type of racing we do. I had a race at Monza with the '65 mod using the old slipstream model, and after crashing out I continued to watch in amazement at the drafting battle between Surtees, Clark, and Hill for the rest of the race. It wasn't real-life motor racing and yet it was so exciting to watch! I then updated the mod and now, with the new slipstream model, the AI just don't seem to slipstream pass each other very much at all, at any track. I ask everyone, is that supposed to be realistic?

#55 Rudy Dingemans

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Posted Dec 23 2010 - 03:28 PM

View PostBob Simpson, on Dec 22 2010 - 04:41 PM, said:

View PostRudy Dingemans, on Dec 22 2010 - 02:10 PM, said:

(I still don't buy Bob's reasoning of slipstreaming on bicycles, I don't think that exists (it just reduces the head wind

There have been some high speed records in bicycling where the rider tucked in behind a special wind block (both terms "slipstream" and "drafting" are used in that articled BTW).  The car and bike got up to 150 mph

Yeah, I know about those, but that's not what you or me were talking about. In regular cycling, there is drag (and head wind) reduction but no real slipstream. Cyclists just don't punch a hole in the air, which at such lower speeds closes up right away. Behind a high-speed 200+ BHP car, it's different.

View PostJASE, on Dec 23 2010 - 12:12 PM, said:

The talk about the the slipstreaming effect being too strong in GPL is absolute rubbish, and it seems to be coming from people who simply don't like the fact that a slower driver can keep up or even pass at certain tracks based on the tow effect alone. BUT THIS IS HOW IT WAS!!!!

Nobody is disputing that the original GPL67 draft was flawed, and that extending it is (in all likelihood) more realistic.

My only point is that it's too strong at great distance in later mods and patches. Doesn't mean it shouldn't be there; just less drastic in the final "dying part" of the draft. Especially for the smaller cars of 65 and 66.

Part of that is because the current draft model is too perfect at distance - typical virtual-world simplification. In reality, it'd get disturbed due to all kinds of outside influences and die down after a few hundreds of yards. (Of course, the air in GPL is *perfectly still* apart from draft.  :huh: )

As it is now, it's a bit like standing right by the roadside of a highway and having a big truck whoosh by at 100 mph, and your hair being sucked towards the truck - except nine seconds later, it's still doing that instead of having gradually fallen back down again.

It's not the effect or the distance in itself, it's the reduction rate at great distance.

View PostJASE, on Dec 23 2010 - 12:12 PM, said:

I do all my racing against the AI, and I often wish that we had a means of switching between slipstream models depending on the type of racing we do. I had a race at Monza with the '65 mod using the old slipstream model, and after crashing out I continued to watch in amazement at the drafting battle between Surtees, Clark, and Hill for the rest of the race. It wasn't real-life motor racing and yet it was so exciting to watch! I then updated the mod and now, with the new slipstream model, the AI just don't seem to slipstream pass each other very much at all, at any track. I ask everyone, is that supposed to be realistic?

Everyone knows (or should know) that GPL's AI uses a drastically simplified physics (or rather "on-track movement") system that has virtually nothing to do with the physics of GPL, used for the player's car. So, AI movement means just about nothing in this respect. Their unwillingness to pass is probably because the AI is flawed as well - probably hampered by the "wall" you now hit (more than GPL67) as you pull out of the draft.

Regards, Rudy
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#56 Lee200

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Posted Dec 23 2010 - 04:39 PM

View PostRudy Dingemans, on Dec 23 2010 - 03:28 PM, said:

Everyone knows (or should know) that GPL's AI uses a drastically simplified physics (or rather "on-track movement") system that has virtually nothing to do with the physics of GPL, used for the player's car. So, AI movement means just about nothing in this respect. Their unwillingness to pass is probably because the AI is flawed as well - probably hampered by the "wall" you now hit (more than GPL67) as you pull out of the draft.

Yes, the AI do indeed use simplified physics compared to the player.  While on one hand they share the same engines, they certainly use a different set of equations to govern their cornering ability.

I must not have been paying attention in class when Professor Nigel covered the new draft patch that was included with the '66 mod (and now the '67 sports cars).  When I went back and looked, the AI apparently use the exact same drafting physics as the player car which came as a surprise.  I've never tested any of this so I can't comment on whether the AI actually benefit by this or not.  From watching the AI at places like LeMans, the slower cars such as the Porsche 910 do seem to go faster in a line than separately though.

There are so many other variables involved with how the AI work that it may be difficult to see any difference in their performance solely due to the draft.

:wave:

#57 M Needforspeed

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Posted Dec 23 2010 - 05:36 PM

one thing I see on the long straight at Solitude is a GT car well back alone come back quicker when there are two AIs together than when only one .

  The enormous sucking effect you are describing Rudy,isn 't on my GPL install.Are we playing a different game ?

  If AI's are 400 yard behind you, would you affirm they'll catch you only in one lap ?
  If yes, you have a point, if no ...  

let's suppose you are running constant laps time .If they need 4/5 laps, isn 't far from what happened on real period races. And 1964 F2 cars had a rather small frontal area.
  Could Brabham be a liar ?

  Did you check their speed in replays when they are 15" behind, a gap where with the 65 carset drag wld have no effects ?

Edited by M Needforspeed, Dec 23 2010 - 05:50 PM.


#58 richard cooke

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Posted Dec 23 2010 - 06:21 PM

The benefit of a tow has been estimated to be worth 2-3 sec a lap at Monza, with the 5 sec a lap in the article posted by Pavel being the highest I have ever seen.

400 yards would be covered in 4.5 seconds at 180mph so the AI, in an equal car, should close that in about two laps.

Richard

#59 borcellini

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Posted Jan 11 2011 - 01:14 PM

very interesting topic.

thank you all for referential materials, links to articles and stuff!

I appreciate greatly effort to be "realistic" or close to the real-life original.
But on the other hand I would not overvalue that.

For my personal fun with GPL I do not need to have slipstreaming exactly as it used to be in real Grand Prix's racing.
I am just trying as hard as I can to use it to improve my virtual times in my virtual races, and often other way too, trying not to loose virtual position in virtual race.

So if slipstreaming would made me too much faster or not faster enough in GPL than it would do in real life, does not bug me much.

Day before yesterday I did qualification for full lenght 67 Grand Prix at Monza against 19 AI opponents.
I qualified 11th (very happy) and I crashed dozens cars to do so. How real is that?

#60 mcmirande

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Posted May 17 2018 - 02:33 PM

Hello everybody

Which mod (excluding the original cars) do you think has the slightest slipstream effect? I know that is very difficult to say which is "the most realistic"...

Cheers. Marcos




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