Current downforce levels?

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lolzi
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Joined: 22 Aug 2010, 14:08

Current downforce levels?

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Hi,
I saw Gary Anderson write on the autosport site that "The current breed of F1 car will create something in the region of 1200kg of aerodynamic downforce at 155mph". To me, this seemed a bit low compared to what I'd seen earlier, so I looked for other numbers. I found that, according to Mulsanne's Corner, the 2003 Lola Champ Car produced "3039 lbs. @ 150 mph, with 966 lbs. of drag".
Can it really be true that an "old" Champ Car produced substantially more downforce than a current F1 car - surely I must be missing something?

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matt21
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Joined: 15 Mar 2010, 13:17

Re: Current downforce levels?

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1200 kg of downforce sounds to me like Canada- or Monza-spec package.

If you take a lateral force of 4g than you should end up with around 2500kg downforce.

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raymondu999
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Joined: 04 Feb 2010, 07:31

Re: Current downforce levels?

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Let's see now. Suzuka Dengner 1; according to FIA graphics, is 2.8G and 185km/h; that's 1792kg worth of Normal force providing that friction. That's about 114.95 mph. Taking away the car's resting weight (I'm taking 640kg as the car weight) that leaves 1152kg of DF.

155mph is 249.44832 kph; which in turn is 69.2912 meters / second

If we assume that DF = a*(v^2); where the "a" coefficient remains static throughout the range of velocities, 1152 = a * (51.3888889 meters / second)^2
We get a = .436228488

Using this again on 155mph, we get:

DF = .436228488*(69.2912 meters / second^2)
DF = 2094.450925954

So DF = 2094.450925954kg at 155mph.

I haven't done physics for a very long time; and I know DF = a*(v^2) is probably a gross overgeneralisation of the whole thing, but yeah.

If I'm hideously off the mark... well... be nice :mrgreen:
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shelly
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Joined: 05 May 2009, 12:18

Re: Current downforce levels?

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Downforce is 1/2*1.2[kg/m3]*ScZ[m2]*speed^2[m/s] - result in Newton to be divided by 9.8 to get it in kg.

Putting ScZ=4m2 we shoud have a good estimate for a medium to high dowforce setting.
Last edited by shelly on 20 Sep 2011, 14:45, edited 1 time in total.
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shelly
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Joined: 05 May 2009, 12:18

Re: Current downforce levels?

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You can not extrapolate dowfnorce from cornering speed if you do not have information about the adhesion coefficient of the tyres
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Tim.Wright
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Joined: 13 Feb 2009, 06:29

Re: Current downforce levels?

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shelly wrote:You can not extrapolate dowfnorce from cornering speed if you do not have information about the adhesion coefficient of the tyres
This.

Using a simple particle representation downforce is:
Fz = (Ay x mass - µ x mass x g)/µ

In this case µ is the friction coefficient of the full vehicle which is not possible to calculate without a lot of extra data. Therefore any guess at downforce will only be as good as the guess of the µ value.

Tim
Not the engineer at Force India

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godlameroso
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Joined: 16 Jan 2010, 21:27
Location: Miami FL

Re: Current downforce levels?

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It's crazy right? Some group C cars had in the region of 4,000kg of downforce, more power and higher top speeds, and they were still slower than today's F1 cars. I'm using Suzuka as a benchmark, although I know the circuit has changed slightly over the years(First corner, and the 130R ring a bell). The group C cars would get laps in the mid to low 1:4x's. Current F1 cars do it in the mid 1:3x's even with a full tank, pole last year was a 1:30.something, makes you wonder. Also slightly off topic, anyone here think the RB7 can do the 130R with the DRS on?
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shelly
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Joined: 05 May 2009, 12:18

Re: Current downforce levels?

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I have made a quick check and 1200kg at 155mph is consistent with ScZ=4m2.

I agree with Anderson
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Just_a_fan
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Joined: 31 Jan 2010, 20:37

Re: Current downforce levels?

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godlameroso wrote:It's crazy right? Some group C cars had in the region of 4,000kg of downforce, more power and higher top speeds, and they were still slower than today's F1 cars. I'm using Suzuka as a benchmark, although I know the circuit has changed slightly over the years(First corner, and the 130R ring a bell). The group C cars would get laps in the mid to low 1:4x's. Current F1 cars do it in the mid 1:3x's even with a full tank, pole last year was a 1:30.something, makes you wonder. Also slightly off topic, anyone here think the RB7 can do the 130R with the DRS on?
1. Grp C cars were heavier than current F1 cars 800kg vs 640kg
2. Grp C had less power than current F1 cars c.650 vs c.700-750
3. Grp C tyres were probably not as good as modern F1 tyres
4. Grp C brakes were not likely to be as good as current F1 car brakes

1. and 2. will limit acceleration out of corners compared to F1 cars
1. , 3. and 4. will increase braking distances compared to F1 cars

Reducing the time taken in the transition from high speed to apex speed to high speed is more important in lap times than a high top speed alone.

I would say that 3. and 4. are probably where F1 holds the key advantages.
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shelly
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Joined: 05 May 2009, 12:18

Re: Current downforce levels?

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1 and 3 also give that a modern f1 will have higher corner speed (for a given downforce level)
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godlameroso
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Re: Current downforce levels?

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What about the Peugeot 905, that car was 750kg, and had an F1 engine, and it was still slower. I guess the tires, and the efficiency of the aero plus the better chassis manufacturing allow for an easier car to drive on the limit, relatively speaking. I'm sure it's very difficult to drive an F1 car, let alone one of those old school prototypes.
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shelly
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Joined: 05 May 2009, 12:18

Re: Current downforce levels?

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@godlameroso: tha 905 was much heavier and had a detuned f1 engine.
So it is not question of the car being easier on the limit: more power, less weight, better tyres make it a diffrnet game.
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Just_a_fan
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Joined: 31 Jan 2010, 20:37

Re: Current downforce levels?

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godlameroso wrote:What about the Peugeot 905, that car was 750kg, and had an F1 engine, and it was still slower. I guess the tires, and the efficiency of the aero plus the better chassis manufacturing allow for an easier car to drive on the limit, relatively speaking. I'm sure it's very difficult to drive an F1 car, let alone one of those old school prototypes.
It was 110kg heavier than a current F1 car (750kg vs 640kg) and had less power (about 650bhp I think).

The XJR-14 (about the quickest of the breed) was in the same ball park as it's contemporary F1 cars but was still a few seconds a lap slower than the best of those.
If you are more fortunate than others, build a larger table not a taller fence.

Just_a_fan
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Joined: 31 Jan 2010, 20:37

Re: Current downforce levels?

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shelly wrote:1 and 3 also give that a modern f1 will have higher corner speed (for a given downforce level)
Good point.
If you are more fortunate than others, build a larger table not a taller fence.

Richard
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Joined: 15 Apr 2009, 14:41
Location: UK

Re: Current downforce levels?

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As others have noted, we need to know the tyre adhesion/friction to consider linking downforce with lateral G. Lets grossly simplify this to a traditional coefficient (jersey_tom and Ciro Pabon are having a heart attack as they read this).

viewtopic.php?p=98891&f=1
viewtopic.php?f=11&t=10276

Lets use a coeffiecnt of 2.0. Also why not use straight line G rather than lateral on cornering, the maths is easier. So lets say max G when braking is 5G.

That means the tyres require a vertical load of 2.5G. Subtract car weight (1G)to leave 1.5G from the aero. So downforce is in the order 1.5 times car weight = 960kg for a 640kg car. I'd summarise that as downforce being between 800kg and 1500kg

That sounds reasonable to me considering we sound like an angler talking about the size of the fish that got away while holding out our arms and saying "it was this big".

Re CHAMP cars - 3039lb is 1378kg. Given that the champ car weighs more than an F1 car (wiki says 400lb or 180kg) then the downforce numbers seem compatible. The heavier car needs more downforce to stay on the track around fast bends. http://en.wikipedia.org/wiki/Champ_Car# ... comparison
Last edited by Richard on 21 Sep 2011, 16:07, edited 1 time in total.

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