Can Someone please explain to me "Ground FX"?

[Sodemo]

Hi,

I sort of know what ground FX are, but i'm not 100% sure.
I understand the basic principle is to get the bottom of the car as close to the ground as possible.
I know there was an F1 car many years ago which had a fan at the back, which sucked the car to the track surface.

Also maybe a secondary question: what actually caused the cars of the late 80's/early nineties to kick up sparks (i mean which part of the underbody)

I know the front wing endplates used to kick up sparks too (like in that Mansell V Senna pic at Barcelona 91).

[Ray Bell]

The cars ran so close to the ground that they had little skid plates at strategic points, these being made from Titanium, which created the sparks...

Ground Effect, as I understand it, is using the effect of the ground in combination with the underside of the car to create a venturi.

A venturi creates an effect with the air rushing through it that means as the air accelerates to fit in the smaller gap it causes a vaccuum and then sucks the car to the ground. The side pods on these cars had sliding skirts that 'sealed' the sides to prevent air from escaping or intruding via that path.

Hope someone else can do a better job.

[marcus]

Thats a good enough explaination for me Ray ..
but sadly the days of all that are gone to be replaced by a wooden plank of all things...they still have a rear diffuser so there is some ground effects there but greatly reduced from what it used to be.



CHEERS
Marcus

Qoute Ray Bell
You really mean the 1984 and 1985 Australian Champion Driver (Gold Star Champ), don't you, marcus?

[riusnow]

Ray Bell: you got it.

You can also think of it as an upside down airplane wing with the 'lift' pointing towards the ground.

[Ray Bell]

Not exactly, ruisnow... as it has been explained to me.

An aircraft doesn't have any surface above the wing, the very term 'ground effect' relies on having that close proximity. The year prior to Lotus turning out the Type 79 'ground effect' car they had gone quite well with their Type 78 'wing car' which wasn't - apparently - so dependent on the close running with the ground, though it did anyway... and yes, it really was an inverted wing section.

Beyond that you need an expert! But please, all the experts assure me that 'ground effect' is different to a wing!

[DNQ]

Bring back the titanium skid-plates! Why can't they have a titanium skid block instead of a wooden one?

[Ray Bell]

This might be a cost factor...

Hang on? Cost factor in F1? Never!

No, I think part of the reason for the timber plank is so that it will show wear (remember Schumacher's wearing away at Spa one year?) and thus there will be less of an inclination to run cars so close to the ground that they will contact and suffer that wear.

And maybe they are paid for by the FIA?

[BD]

Ray Bell has it mostly right.
The idea behind venturis and "ground effect" is to lower the pressure beneath the car. They lower the car itself to minimize the volume of air that can go under the car, lowering the pressure. By speeding up the air, using venturis, pressure is also lowered as air is moving faster under the car, relative to above the car. The side skirts prevent air from getting underneath the car from the sides.
Lowering pressure creates a vacuum effect. The cars werent actually "sucked" to the ground, they were more easily pushed to the ground from the higher pressure above the car. The use of fans to push air out from under the car had a huge effect, advantage, and was therefore promptly banned.
Even without "ground effects"(basically side skirts) F1 cars still get most of their downforce from the chassis. Somewhere around 40% of the total downforce.
I dont think the conventional hourglass shaped venturi is allowed, but they have found other ways to speed up the air underneath the car. The diffusers are very important to control what the air is doing, and can make a huge difference. Such as the Jaguars new floor and diffuser which was introduced at Monaco with great success.
McLaren probably has the most downforce produced from the chassis. Judging by the fact that they have no winglets, and such(like Ferrari) and are basically competitive.(their performance problems this year have nothing to do with the chassis)
The Arrows cars probably produce the least amount of downforce from the chassis. Though it was designed this way to be aerodynamically efficient, at the cost of low downforce.
Hope this helps
BD

[BD]

"...F1 cars still get most of their downforce from the chassis. Somewhere around 40% of the total downforce."

This doesnt make sense.
What I mean is that compared to any other single component on the car. Roughly 30% from the front wing, and 30% from the rear wing. Of course these are adjustable, so the percentages are more like averages throughout the year.

[Total-F1]

If you have a flat bottomed car, that air just runs straight past, obviously, and there's no performance gain - it's when the bottom of the car is kinda scooped out that you get the loew pressure, because there's only a certain amount of air coming in, and there are spaces to fill...the sucking in of more air creates the downforce...

And the diffuser is probably the second most important piece of equipment on the car, after the wheels!

And the plank isn't made of wood - it's a special fibreglass concoction, else they'd have all sorts of bloody problems in the wet!

[riusnow]

Ray Bell: the comparison I was trying to make was to show that the design of an airplane wing produces lift, just like the design of ground effects produces downforce.
You are quite correct the key word is 'ground' and that is different than a wing.
I was trying to keep it simple, although BD explained it very well. I didn't know if I could explain it that good.

[RWC]

Here's a link to some ground effect research which adds to what Ray & BD said.

www.itfl.co.uk/racetech/issue30/Workshpaero.htm

The under plank was introduced to increase the-car-to road clearance so as to reduce ground effect & also the danger of cars running too low and bottoming out which wasn't very safe.Yes as Ray says, the plank is to show who's been trying to run too low to the ground.As there is no need for the Titanium blocks anymore,we miss out on the spark show!
Also i heard that some teams are impregnating the planks with tungston to lower the center of gravity!!