Lotus 78 wheel effect on sidepod Venturis?

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g-force_addict
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Lotus 78 wheel effect on sidepod Venturis?

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For the Lotus 78 and other similar cars with sliding skirts and Venturi tunnels below their sidepods

Drawing a straight line following the skirts you will cross the rear tire
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Isn't some air coming out from beneath the sidepods blocked by the rear tire?
Wasn't this creating a bottleneck as the airflow must turn to escape either between the rear wheels, outside of the wheels, or even over the rear wheels?
If this is a minimal downside, Could they have made the sidepods wider?
Would front wheels hinder flow to these wider sidepods?

Why they didn't use a raised nose to provide more airflow to the car-wide Venturis?
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Just_a_fan
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Asking why the designers of 1977 didn't use ideas from 2000 is like asking why the first jet fighters didn't use thrust vectoring jet engines...

They didn't have the understanding of vehicle aerodynamics that the teams have now. The Lotus 78 wasn't a refined design, it was a "first guess" in effect. It was just the new ground effect idea applied to the current (of the day) designs. Ground effect was a new concept found entirely by accident. Even though a modern view of the design shows areas where it could have been greatly improved, at the time it was still a huge improvement on the cars of the day.

Bear in mind that the front wing, on a ground effect vehicle, is a trimming device rather than a pure downforce device as in a modern F1 car. In some cases, the ground effect cars ran without front wings at all.

As an aside, the term "ground effect car" is used as a historical description however all F1 cars have been ground effect vehicles ever since. They may not run tunnels and skirts but they still run in ground effect.
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Lycoming
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Re: Lotus 78 wheel effect on sidepod Venturis?

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If you jack up the front wing, you need to move the tunnels forward to compensate, or else you get quite a bit of understeer. You also begin to obstruct driver visibility and raise the center of gravity height. And if you move the tunnels forward, that is something that can easily degrade performance of the tunnels due to interactions with the front wheels, potentially obliterating anything you gain from less effect from the front wing wake.

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Tim.Wright
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Re: Lotus 78 wheel effect on sidepod Venturis?

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g-force_addict wrote:
Isn't some air coming out ...?
Wasn't this creating .....?
Could they have .....?
Would front wheels ....?
Why they didn't use ...?
Because, to actually put a running car on a track, particularly one with a lot of cutting edge (at the time) technology, at some point you need to stop all the intellectual masturbation and start cutting metal. A design that gives you 1sec per lap is useless if it never gets built.

Judging by the success of the lotus 78, its fair to say that any extra time spent at the drawing board (and less time testing) could have been considered wasted.
Not the engineer at Force India

wesley123
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Re: Lotus 78 wheel effect on sidepod Venturis?

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I do think that later, and other people's designs noticed the wheels interaction and the blockage they cause, as other teams have had larger upsweeps in front of the tires. Possibly trying to solve the problem.

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Also the Lotus 80 kept the bodywork away of the rear wheels. So I do believe the problem was quickly acknowledged, but as Tim.Wright says, there is a point where you need to stop drawing and start building
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henra
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Re: Lotus 78 wheel effect on sidepod Venturis?

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g-force_addict wrote:Isn't some air coming out from beneath the sidepods blocked by the rear tire?
Wasn't this creating a bottleneck as the airflow must turn to escape either between the rear wheels, outside of the wheels, or even over the rear wheels?
You can safely assume it was blocking the exit. You can conclude that also by the fact that the Lotus 79 adressed exactly the problems you mentioned by channeling the diffuser exit to the inside of the rear tyres and by improving airflow into the sidepods:
http://stevelitchfield.com/lotus/story.html.

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Marcus-F1
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Beautiful interview with Norbert Singer, explaining how the aerodynamics were determined back in the day. Not an F1 car, but the 962 Porsche Le Mans race car. It was nothing more than educated trail and error.

http://www.youtube.com/watch?v=PZxC-knQmkM

Sombrero
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Two different solution to minimize the air dam effect caused by rotating rear wheels on the Lotus 78.

The Ligier JS11 and JS11/15 (seen here) used an air extractor to divide the airflow before the rear tyres. Part of the airflow was extracted from below up to the rear tyres. These cars had massive downforce at low speed.

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The WIlliams FW07 used an inside rear cover (on the right) to minimize the effect of the wheel rotation. I remember the story of a Lotus mecanic caught in Germany or in Austria spying that part of the car one night...

Image
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Huntresa
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Marcus-F1 wrote:Beautiful interview with Norbert Singer, explaining how the aerodynamics were determined back in the day. Not an F1 car, but the 962 Porsche Le Mans race car. It was nothing more than educated trail and error.

http://www.youtube.com/watch?v=PZxC-knQmkM
What does he mean when he says they took air from the side for the ground effect ?

shelly
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Re: Lotus 78 wheel effect on sidepod Venturis?

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He measn that the concept of "sealing" is a bit more subtle than most expect. That car underbody was relying on flow from the sides, like current f1 cars partly do for their diffuser.
Another example: old gp2s had partial length sideskirts
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xpensive
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Re: Lotus 78 wheel effect on sidepod Venturis?

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I think the Ferrari 312T4 solution was a little more elegant than Ligier's above;

Image

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Sombrero
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Ferrari 312 T 4

Image

The airflow pattern differs totally : when the Ligier is "extracting" air from below the venturi profile, the air coming out of the Ferrari is coming straight and only from the upper part of the venturi profile. Absolutely no air is being "extracted" from below the venturi profile in the T 4.
Image

In reality the Ferrari 312 T 4 and the T 5 were bad ground effect cars because of the 180° V-12 engines. The 312 T 4 did well because of the dominance of the Michelin radial tyres over the Goodyear in 1979. Renault was the only other team with Michelin tyres that year but the Renault V-6 turbo engines had a poor reliability. One year later, Goodyear stroke back and the 312 T 5 was out of the game : 10th place in the constructors WC in 1980...

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Re: Lotus 78 wheel effect on sidepod Venturis?

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I stand corrected, great image that, never seen it from that angle before, but the engine installation was nice;

Image

The venturis had just started developing in 1979 and peaked in 1980. But moreover, Ferrari was already focused and working
on the 126C by then, they actually had it running during practice at the Italian GP at Imola in the September that year.

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I wonder if the venturis went all the way up in front of the rear wheels on this version?

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SachaG
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Re: Lotus 78 wheel effect on sidepod Venturis?

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Sorry, I can not see the photos you mention on display -- I just see a mini-icon with a crashed screen
s
Sombrero wrote:
Sat Nov 16, 2013 9:04 pm
Ferrari 312 T 4

http://p3.storage.canalblog.com/31/43/1 ... 142290.jpg

The airflow pattern differs totally : when the Ligier is "extracting" air from below the venturi profile, the air coming out of the Ferrari is coming straight and only from the upper part of the venturi profile. Absolutely no air is being "extracted" from below the venturi profile in the T 4.
http://www.autowp.ru/pictures/f/ferrari ... 2_t4_5.jpg

In reality the Ferrari 312 T 4 and the T 5 were bad ground effect cars because of the 180° V-12 engines. The 312 T 4 did well because of the dominance of the Michelin radial tyres over the Goodyear in 1979. Renault was the only other team with Michelin tyres that year but the Renault V-6 turbo engines had a poor reliability. One year later, Goodyear stroke back and the 312 T 5 was out of the game : 10th place in the constructors WC in 1980...

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Stu
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Re: Lotus 78 wheel effect on sidepod Venturis?

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You are unlikely to get any form of response in such an historic thread - the site where the pictures are lodged has likely been put behind a paywall at some point in the last nine years
Perspective - Understanding that sometimes the truths we cling to depend greatly on our own point of view.