Hey Tech dudes...any ideas? - The Technical Forum Archive (2024)

JForce

• 

Member

• 13,847 posts
• Joined: March 01

Just want to talk about whether or not it would be theoretically possible for an F1 car to drive upside down at top speed. Of you drove it into a round tunnel, and then drove up around the tunnel, would it stick?

What I reall am interested in is is it possible with the flat undertray, or would you need to get asn older ground effect F1 car. Have the aerodynamicists caught up, that is, does a modern F1 car, with a flat under body, and limits on wing elements, create as much aero downforce as an old car with a scuplted undertray?

Hope someone can help, without making me feel too stupid about my lack of knowledge...

desmo

• 

Tech Forum Host

• 28,266 posts
• Joined: January 00

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

MRC

• 

Member

• 308 posts
• Joined: June 01

This may be nitpicking, but something to keep in mind.

When the car has no downforce it has 1g (*600kg) of downward force or otherwise 600kg of normal force poinitng downwards. If you have 2g's downforce, then the normal force on the wheels is 3g's or 1800kg total. When you flip the car over, you have to subtract 1g just to keep the car neutrally bouyant. Then you have to subtract another g to simulate the weight of the car on the ground with no downforce. Now you have 1g of downforce left. So the car can do it, but now my point/question. What is the drag at the downforce generated for this to happen? There must be enough normal force for the tires to have enough tractive capability to go against the aero drag. Probably able to do it, but I really don't know what the drag would be to generate the required downforce.

olschak

• 

Member

• 186 posts
• Joined: May 01

olschak

• 

Member

• 186 posts
• Joined: May 01

here's something I must add:

Do not try this at home

MRC

• 

Member

• 308 posts
• Joined: June 01

mat1

• 

Member

• 351 posts
• Joined: April 00

Originally posted by olschak
here's something I must add:

Do not try this at home

mat

olschak

• 

Member

• 186 posts
• Joined: May 01

RV_Canada

• 

Member

• 3,490 posts
• Joined: May 01

olschak

• 

Member

• 186 posts
• Joined: May 01

Sean L

• 

Member

See Also
Teachers, nurses and Disney fans adore Hey Dude loafers — they're nearly 50% off
• 5,084 posts
• Joined: October 99

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

MRC:

Good point, I didnt think it through all the way. My question is however, why must you subtract 2g's of force when placing the car upside down? I am not understanding the reasoning behind this.

Its like slot cars... not the machine ones, the toy ones.... like hot wheels;) They can run upside down for a while, but I know they are not producing 4x their weight in force because the track would detach.

TheDestroyer

• 

Member

• 1,731 posts
• Joined: April 00

Great googly moogly! Stallone and Drivel even make into the tech forum threads!

I'm even more amazed now that this piece of shyte movie can become so damn pervasive.

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

TheDestroyer

• 

Member

• 1,731 posts
• Joined: April 00

Yes, very much so Adam...

Only two reasons to see this movie:

1. Estella Warren
2. Gina Gershon

So if you're looking for more than just eye candy don't see it.

Truth be told, as gorgeous as these two are Drivel is still not worth seeing...

MRC

• 

Member

• 308 posts
• Joined: June 01

Adam, for the upisde down F1/Champ Car if you had 600kg of downforce to work with let's say, then the car would have no normal force acting on the tire, thus no traction available. At this point you have no forward thrust. If you have 1200kg of downforce then you have 600kg of normal force acting on the tires. I'm making the large assumption that you would need the equivalent of the a car with no downforce on the ground to act against aero drag, but as stated before, I've got no idea what that would be.

As for slot cars, they are being accelerated towards the center of the loop by the force exerted by the track. Centipetal force as people would say is keeping the car sticking to the track.

Mark

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

I'm making this more complicated than it should be.

1998 Formula One Car
Monza Trim
Lift-to-drag ratio: 2.75:1
Downforce:
2500 lbs. @ 200 mph, with 909 lbs. of drag
Monaco Trim
Downforce:
3000 lbs. @ 165 mph

My question, how in the heck are these cars capable of 4+g turns if they arent creating that much weight in downforce... surely the tires cannot have that high of a coefficient of friction... can they?

http://www.technical...pic=187&forum=2

Ben

• 

Member

• 3,186 posts
• Joined: May 01

Race tyres are well capable of coefficients of friction as high if not higher than 2.

Ben

moog101

• 

Member

• 1,760 posts
• Joined: June 00

Originally posted by TheDestroyer
Great googly moogly!

you rang ;)

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

OK, but that leaves the question... 4+g's of lateral acceleration? All due to the tires? It looks as if by those numbers in 98 that they were producing roughly 3 times the car weight in downforce, accounting for how much of the lateral force created?

I mean if the tires really were the only cause of the cars cornering capability, then they would do with wings.

I just am unsure when it comes to this thread... shouldnt the amount of downforce being created be the sole determining factor of how many g's the car would be able to pull laterally?

TheDestroyer

• 

Member

• 1,731 posts
• Joined: April 00

TheDestroyer

• 

Member

• 1,731 posts
• Joined: April 00

No because if that were the case they wouldn't need tires at all

Seriously, you have to factor in the amount of downforce the car is generating in addition to the amount of force the tires are capable of generating.

It's not lateral acceleration, rather the amount of force the car and tires can generate to counter the lateral acceleration (aka centripetal force).

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

Well tire adhesion has its limits, downforce helps approach these limits, otherwise what you are saying is if produced 8000lbs of downforce with my truck, and the tires only had 1g of adhesion, I could corner at 3g's, or am I misunderstanding you.

What would they use besides tires?

Overall I completley understand the concept, but what really threw me off was the whole upside down, neutral bouyance, and simulation on the ground tire adhesion that MRC posted.

My truck weighs 4000lbs. btw

SalutGilles

• 

Member

• 2,149 posts
• Joined: November 98

well, I'm not exactly a technical genius, what with my field of study in english, but I did stay in a holliday inn express last night. ergo, I will thrust my opinion on everyone.

As i see it, the question is not one of downforce at all, as f1 cars have more than enough for pulling the car upwards. Like an aeroplane, just different, sorta. Lift is certainly not the problem.

The difference here is the propulsion mechanism. whilst the aeroplane uses jet or propeller propulsion, the f1 car relies on the tires to scoot it along.

so the only problem I can see would be the transfer from the ground to the ceiling. it would have to be done so that the downforce remained at a relatively high figure, otherwise all thrust would be lost, and with it, speed and downforce. so that's the thing of it. as long as you didn't lift, though, and made the transfer gradually enough, methinks it would work quite well.

conversely, does a roadcar producing lift use less power to achieve a set speed than a roadcar at a constant weight, or not. basically, if you took a car, and fitted it with wings to weigh just 100 pounds or so at, say, 150 mph, and then flipped them upside down, and made the car 100 pounds heavier at speed than at rest (I'm assuming this would work, and then we could just forget about the drag produced altogether) would the theoretically lighter car use less power, and run farther on a tank of gas or not?

and then I wonder if weight is merely a penalty under acc/dec, or if there would only be a friction issue, and therefore a tiny payoff.

hell if I know!

olschak

• 

Member

• 186 posts
• Joined: May 01

SalutGilles, I think the aeroplane / car comparison is a good one. Even in an aeroplane you can have the propulsion problem. If you climbed with an aeroplane too quick you would lose speed and ultimately end up under the limit of flying. That is you're too slow to have enough upforce to keep the plane flying. Then the plane starts to tumble and crash eventually. Bloody good pilots get the plane out of the tumbling motion, dive down and pick up the speed simply by gravity.

Ben, do you have any source on the internet where you get you 'greater-than-two' performance limit for race tires from ?

The upside-down problem is somewhat different from the cornering scenario because in cornering you do use tire friction both for maintaining speed and for cornering. You always trade one for the other with every motion of your steering wheel when at the limit.

SalutGilles, the weight thing in ideal circ*mstance doesn't bother you in cornering. In real life tire use during cornering, heat transfer and everything, I'm talking energy here, is far worse on a heavy car because you're always using the same tire material. You simply cannot zoom everything up and down in scale. For those non-linear influences, that is twice here wouldn't make twice as much there, the materials and sometimes absulte dimensions count a great deal.
It's like animals and cells - large animals have more of them, not bigger ones, and as a consequence are more complex.
From a non-scientific perspective it looks like heavy cars live long and light ones are quick and die even quicker.

moog101

• 

Member

• 1,760 posts
• Joined: June 00

just speed the bloody thing up till it makes 2G downforce, whip it through a 1/2 turn and watch in amazement as it can **still** corner upside down better than a lot of road cars with it's 1G extra downforce.

Not hard

Grandeur? Oh Yes

olschak

• 

Member

• 186 posts
• Joined: May 01

JollyRoger

• 

Member

• 58 posts
• Joined: March 01

Sorry, but I must give my 2 cents worth.

Just because the truck gives more downforce in a straight line doesn't mean that it will give more USEFUL downforce in a corner. The main point here is that the trade off for the down force created by the extra weight in that the car now has much more force acting to BREAK traction in a corner, despite this extra force acting to keep the truck stuck to the ground. Frictional forces are the most important in cornering IMHO, and downforce helps to compund this effect. A truck increases this but also increases the frictional forces required to maintain traction in a corner.

Was waiting for someone much more knowledgable than me to point it out, but realised there was actually an opportunity for somebody with as limited knowledge as me to be helpful!

olschak

• 

Member

• 186 posts
• Joined: May 01

JollyRoger
you may be right here. In addition to what I said before:

don't try this at home, don't try this with your pickup-truck on public roads!

100cc

• 

Member

• 3,178 posts
• Joined: December 00

Originally posted by TheDestroyer
Yes, very much so Adam...

Only two reasons to see this movie:

1. Estella Warren
2. Gina Gershon

estella warren is in it, I gotta go buy the vcd!!!

I've heard the "an f1 car generates enough downforce to drive upside down" line in many places, some ads for example, so I guess it has to be true to a certain extent. That would be one wacky thing to watch. If you really think about it, it does seem odd to have something move the wrong way around.

AdamLarnachJr

• 

Member

• 525 posts
• Joined: June 01

In theory:) at least for the driving up side down part, thats why they can get away with saying it:)

The whole purpose of downforce is to keep the tires on the ground, wether its a truck or F1 car its all relative, but I do see what you are saying, that being the heavier a vehicle is, the more traction it would require to that of a lighter vehicle with the same proportional amount of downforce.

jdowns

• 

Member

• 98 posts
• Joined: June 01

I think people are getting confused with the use of g's to describe downforce, and g's to describe latteral force. Downforce doesn't cause latteral (sideways or front/back) acceleration, it just pushes 'down' (relative to the car).

If you add up all the forces acting against the road (600kg car, 1000kg of downforce, and any centripedal forces), then multiply that by the coefficient of friction (someone here said 2, but I don't think it'd be much higher than 1.2), then you have 1600*1.2 = 1920kg's of possibly latteral force. Since the car weighs 600kg's, 1920/600 = 3.2 g's of possible latteral acceleration.

If you're driving upside down, then the downforce will be up, but the weight of the car will be down, so you have 1000 - 600 = 400 kg's, times 1.2 (grip of the tyres) = 480 kgs, 480/600 = 0.8g's of latteral acceleration.

Latteral acceleration is a combination of acceleration or breaking, + sideways acceleration. If you think you'll need 100 kg's of forward force to maintain whatever speed you want upside down, then you need 100 / 1.2 (tyres again) = 87kg's of force against the roof (_after_ you take into account the weight of the car), so you'll need at least the weight of the car, + 87 kg's = 687 kg's of 'downforce' from the wings (acting upwards if you're upside-down).

I guess my point is, you subtract the forces (in kg's or lb's) first, then multiply the total by the coefficient of friction of the tyres, then divide by the weight of the car to get total possible g's. Since the coefficient of the tyres will vary from tyre to tyre, track to track, and even at different parts of the track (dirt, road surface, etc.), total latteral g's will vary, even with the same amount of downforce and speed. (ie. '2 g's' of downforce may give 3g's of cornering in one part of the track, but only 2 g's at another, depending on the surface - g's downforce doesn't equal g's cornering).

Hmmm, that sounds clear as mud

MONTOYASPEED

• 

Member

• 8,110 posts
• Joined: April 01

Hey buddies,

Do you guys know how many kgs of downforce a Formula One and a Champ Car have?

I would like to find out how many G's they could have. I also have another question. When you talk about "so it has X G's of lateral acceleration", at what speed are you talking about? If I am not mistaken the amount of G's depends on the corner and the speed of the car.

Sorry if I am making simple questions to you guys but as I said in my thread about downforce and weight, I want to clear some dudes to some friends of mine.

Thanks in advance.

jdowns

• 

Member

• 98 posts
• Joined: June 01

MONTOYASPEED,
look at http://www.cart.com/News.asp?ID=816. It doesn't quote any figures, but it's on a cart web space, and says in part "On a lap of a road course, a Formula 1 car would win this comparison hands down. It would accelerate faster, brake more efficiently and take corners faster.". Since most teams are different, and most teams change fairly often, I doubt you'll get any really accurate figures (the ones quoted about by AdamLanarchJr are probably the best you'll get).

Also, downforce is very configurable. I heard someone say that the teams can configure over twice the downforce for circuts like Monaco as circuits like Hockenheim. Downforce (aero downforce) is dependant on speed, but also on configuration. If you look at the maps at http://www.atlasf1.c...es/calendar.htm you can see what sort of cornering acceleration F1's can get on different tracks with different setups.

Another complexity is that champ cars often run on ovals with banked turns. This further adds to their cornering ability (weight + downforce + banked 'force'). F1 only has one banked turn on it's calendar, and it doesn't produce any serious g's.

I think it's Apples vs Oranges, and is dependant on so many things, but I'm sure F1 would kick butt in the cornering dept on similar tracks (which will never happen, would make champ cars look like chumps ;) ).

MONTOYASPEED

• 

Member

• 8,110 posts
• Joined: April 01

Thanks again jdowns.

I know that it is like Apples vs Oranges but I tried to make a comparision between them because I said that if a Formula One team design a special chassis to run in a superspeedway (with their actual engine and the same weight as they have now) they would kick CART cars' butts.

As I said before, they think that the CART car would win because it has more weight than the Formula One car and they believe that because of that the CART car produces more downforce than the F1 car which is lighter and has a better relation weight/HP even though that in ovals teams don't want downforce.

Ben

• 

Member

• 3,186 posts
• Joined: May 01

Tye data is virtually impossible to get hold of. Some data in Race Car Vehicle Dynamics gives a Goodyear F1 front tyre a friction coefficient of up to 1.8 at light loads (friction coefficient is obviously load sensitive and not constant by any means).

This tyre was pre 1995 and possibly from a time when Goodyear was sole supplier to F1. I think it is perfectly possible therefore to make a tyre of mu>2. Certainly the 'qualifiers' of days gone by would have been.

jdowns has certainly made a very concise point about how downforce translates to cornering power.

Ben

MattPete

• 

Member

• 2,547 posts
• Joined: January 00

Originally posted by JollyRoger
Sorry, but I must give my 2 cents worth.

Just because the truck gives more downforce in a straight line doesn't mean that it will give more USEFUL downforce in a corner. The main point here is that the trade off for the down force created by the extra weight...

It's not the extra weight that's the problem (technically, that's downforce), it's the extra mass!;)

MattPete

• 

Member

• 2,547 posts
• Joined: January 00

Originally posted by MONTOYASPEED
Hey buddies,

Do you guys know how many kgs of downforce a Formula One and a Champ Car have?

I dunno about F1, but I got a quote of 4500 lbs (2041 kg) for a Champcar in road course trim from someone in the business.

DEVO

• 

Member

• 2,637 posts
• Joined: November 99