Question 3 for ten points...

At what speed does 'Downforce' actually begin to take a noticeable effect?

2 more questions to go!

 

over 100 i should think
depends on the spoilers though

 

Right he's gone for 100+ i shall have <99mph
Si (playin da stats)

 

http://www1.union.edu/~losawj/Figures%20to%20be%20included%20in%20the%20article. doc

This should help you out...

I know it's about NASCAR's but it was a general question

sorry can't remember how to make it a hyperlink.....doh

 

[pedant]Downforce takes effect at zero mph, the weight of the car is a type of "downforce".[/pedant]

If you are talking about aerodynamic downforce, that can also take place if a car (with wings) is doing zero mph, particularly if you are parked in the middle of a hurricane

Most road cars generate lift though, i.e. downforce never occurs at any speed!

 

As has been said, most cars generate lift due to their "aerofoil" profile (Bernoulli's theorum) Look what happened to the Audi TT!! Most spoilers are at BEST, just that - spoilers, and help to kill the lift. The Escort Cossie "teatray" on the other hand, produced positive downforce but I'm buggered if I can remember from what speed!
My entry is therefore the Escort Cosworth at 80mph.
JohnD

 

If the car produces any down force at all then it will happen 0.0000000000000000001m/s but that's not noticable, what is? You tell me.

And if you had 1000kg of downforce (easily possibly) whould you notice it going in a straight line without accelerating or braking, no.

What a ******* dumb question.

btw Downforce increases with square of speed if anyone cares.

Paul

 

If you look at the shape of a road car, the path of the airflow over the top of the car is longer than that underneath, so that means lift instead of downforce, unless the latter is blocked by an airdam or the underbody has gound effect designed into it. So unless you quantify the size of the rear wing and its shape and angle of attack (see, I have learned something from my earlier post on flying), there is no way to calculate an answer. The tricky bit is when will downforce overcome inherent lift and start pushing the car down on the road?

 

Ferrari enzo. Downforce at 110mph 334kg, at 185mpg 785kg. Flaps then cut in cos generating this much downforce slows the car down, so "merely" 585kg at 218mph. IIRC F1 cars have more downforce than weight at 100mph, so could in theory drive upside down on a tunnel roof as long as they kept going. Brake hard and they fall off, though, which would be a bit irritating if you were in (or under) it.

Unfortunately, I've never driven either.

 

It is generally accepted amongst racers that 'useful' downforce from aerodynamic aids generally starts at a speed of around 120mph.

Stupid Question? Not if your *** depends on getting around a corner in a bathtub doing 150mph it isnt!

Mak.

 

if you're interested in downforce at 150mph, then what the hell are you harping on about downforce at low speed for?

You can put higher downforce wings on at the expense of drag (which also is proportional to the square of the speed) but in a GT/F1/Champ car you want to be doing over 80mph most of the time, so you're interested in downforce at 60mph.

Conversly, if you run a hillclimb car you're going to be interested in as much downforce as you can get at any speed under 100mph or so.

Or you could use a big fan and skirts to generate downforce at standstill, as they did in the Brabham "Fan Car" which whipped everyone before promptly being outlawed.

As mentioned above the car shape might be conducive to uplift, but flow regime is more complex than a 2d wing profile. The low pressure on say the roof will pull the higher pressure air from the sides and under the car. This can cause vortices forming from the C pillar. These vortices can affect the flow of air over the rear of the car to such an extent as to overcome the lift from the low pressure region at he start of the roof line. Spoilers can influence this flow, reduce drag, stabilise seperation blah blah blah blah blah blah blah and so on.

Anyway to answer your question straight, you can begin to get some sensible downforce at about 60mph with a reasonably sized wing, but a ground effect car could probably do even better, and with less drag penalty. But the same setup would not be ideal for doing 200mph, which is why ferrari use active aerodynamic aids.

Paul

 

Ummm generally accepted amongst which racers exactly? Presumably the ones that have never actually driven a race car...

 

pavlo-**** off,your boring everyone!

it was a light hearted question not a question on a physics exam paper.

[Edited by jonny gav - 8/26/2002 12:54:02 AM]