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 Dicko
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| posted on October 14th, 2015 at 10:20 AM |
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Reducing lift utilising cooling and intake air
The characteristic of the T1’s body to create lift at “high” speed is well known. I remember in 98 seeing a drag bug flying into to a wheat
field at the end of the Santa Pod track, UK.
What do you guys think about using the intake and cooling air to reduce pressure below a T1?
I’ll try to explain my thinking. At 4000rpm the stock early cooling fan moves approximately 312lps, a stock 1600cc engine is pumping approximately
53lps so all up approximately 365lps. Travelling in 4th at 83mph or 134kph the volume of air travelling underneath a T1 (100mm ground clearance) is
approximately 4,840lps. So if you could route the cooling and engine intake to draw from beneath the car you could reduce the air volume by
approximately 7.5%, thus reducing pressure and therefore reducing overall lift. A larger engine could increase this effect but from my research it
seems it’s the cooling fan that shifts the majority of the air in this situation.
Using this technique the size of wing could be reduced, reducing drag and therefore increasing Vmax and acceleration.
Any thoughts or additions to this idea? Has this already been done?
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Smiley
A.k.a.: Daniel Stephens
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| posted on October 14th, 2015 at 07:20 PM |
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I think what you are describing would actually cause the front of the car to lift more.
Consider this. The air that you want to use still has to pass under the front of the vehicle to get to the engine intake/cooling fan. So it will cause
the front of the car to lift just the same. Then you are sucking some of this air out at the rear wheel area to feed the engine. This will create a
lower pressure at the very back of the car causing it to suck down.
It would probably work on a front engined car or if you drew your air from the underside of the front, but that won't work on a rear engine bug.
I'm also not sure that it would make much of a difference anyway. I think aero mods/streamlining would make a bigger difference. As well as
lightening the back of the car or transferring the weight to the front of the car.
Just my thoughts, I could be completely wrong.
Smiley 
If you said I was a Volkswagen man, you'd be right.
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coletrickle
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| posted on October 14th, 2015 at 07:59 PM |
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It would be great if it was that simple.,my mate bondo works at Dan Gurneys in the wind tunnel and i quized him and he said yes but complicated you
need to seal the sides completely.Alfa did it with the flat 12 f1 car in the late 70's and they sucked the air out with a snow mobile motor.That
worked so well the rules say only one engine allowed.Next port of call is the lotus 78's sliding stainless steel skirts no front wing and an under
body diffuser.Also a hillbilly trick is tunnels from under the car to below the back window to move the air from under to over the car.But like bondo
said go your hardest.Beetles suck and anything you do will make them better.
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Dicko
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| posted on October 15th, 2015 at 08:37 AM |
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Thanks guys
More of a thought experiment than anything else. Good points well made, I was thinking to make it even moderately effective you would need some sort
of sliding skirts a la Lotus, so not really practical for a drag pulling wheelies etc. I hadn't considered potential lift at the front.
I don't wholly agree with your mate's assessment of the beetle but that's half the fun of owning them - making improvements!
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modnrod
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| posted on October 15th, 2015 at 10:53 AM |
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Using the fan to create a venturi under the vehicle on a drag bug probably won't work very well.
Generally they don't use one.
It can't be lower than 3" at the front or it plays up the staging beams, but apart from that, slam it, chop it, stretch it, and use flat aero plates
like all modern cars underneath.
Reducing frontal area by 30% reduces necessary HP at 120mph by, uhmmm........shitloads.
Shitloads is a technical description by the way.
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lou0060
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| posted on October 15th, 2015 at 03:27 PM |
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great topic Dicko, I to have done some research and although mine is more for circuit racing the same principles would apply. I have some links to
aero stuff at home so will try and post them tonight, but just quickly I see your problem already....
stock 1600...
just throw more horsepower at it and hang on! how much horsepower you ask, see modnrod for that.......
1971 karmann ghia Cabrio - Cruising 
1963 beetle Sunroof - gathering dust 
1968 race beetle - twin turbo Subaru - stress relief 
1960 beetle - old school low & slow  |
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Dicko
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| posted on October 15th, 2015 at 04:35 PM |
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Yeah you got me, I know nothing about drag bugs but I thought I'd post it here as it's likely to get the best replies.
So maybe more effective (if at all) on a circuit car. Looking at the Brabham BT49, the rules said that the car had to be a certain height above the
ground, but the way the rules were written this only applied in the pits. So Gordon Murray simply designed skirts that were lowered to the ground once
out on the track
lou0060 yeah of course more power but then could this technique be used to decrease lift no matter what power you run?
modnrod That's one of my most used technical terms!
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lou0060
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| posted on October 15th, 2015 at 05:35 PM |
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check this stuff out;
http://www.autospeed.com/A_108675/cms/article.html
http://www.gerrelt.nl/section-aerodynamics/roofspoiler-explanation.html
https://www.youtube.com/watch?v=BHlxVtRHPfk
1971 karmann ghia Cabrio - Cruising
1963 beetle Sunroof - gathering dust
1968 race beetle - twin turbo Subaru - stress relief
1960 beetle - old school low & slow |
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Dicko
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| posted on October 16th, 2015 at 12:15 PM |
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I had seen the autospeed (great website) and gerrelt info previously but not the CFD video, its fantastic. Looks like a front splitter would work
wonders to reduce front lift. thanks!
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