Official 2021 Azerbaijan Grand Prix Thread ***SPOILERS***

Official 2021 Azerbaijan Grand Prix Thread ***SPOILERS***

Author
Discussion

RB Will

7,065 posts

206 months

Thursday 10th June
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They should make them do a barrel roll through the tunnel at Monaco

CoolHands

12,869 posts

161 months

Thursday 10th June
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Yeah it should be like mariokart so they could overtake by going up the walls etc

honda_exige

2,735 posts

172 months

Thursday 10th June
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Excuse the kids video hehe but a McLaren F1 Aerodynamicist states over 30000N (3000kg) over 300kph of aero downforce at the 3minute mark of this video.

https://www.youtube.com/watch?v=JOWY0ayQoLA

Given that these figures I assume are going to be very underestimated I would say 4000kg at absolute vmax on a long straight like Baku wouldn't be too outrageous.

Leithen

7,631 posts

233 months

Thursday 10th June
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Cold said:
There's only one way to work out which car has the most downforce and that involves driving along the roof of a tunnel. thumbup
A well known motosport team did test in a secret (not a wind) tunnel…

TheDeuce

9,586 posts

32 months

Thursday 10th June
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kambites said:
TheDeuce said:
Confusing g-force and downforce again.
No I'm not, Go and read what I actually said.

You can calculate how much deceleration a frictional interaction can generate from a combination of the coefficient of friction and the perpendicular force being applied to the interface between the two objects. The former is reasonably fixed, at about 1.5 for an F1 tyre. The latter is a function of the downforce generated plus the basic weight of the object.

An F1 car with no downforce could decelerate at roughly 1.5g, ie slightly under 15m/s/s plus whatever it gets from aerodynamic drag. Doubling the force between the car and the road by aerodynamic means (ie adding the car's own weight in downforce) will double the frictional force and hence the peak possible deceleration due to friction to about 30m/s/s. If a car was generating 5 times its weight in downforce it should be able to brake at at least (5+1)x1.5x9.8m/s/s, which is 88m/s/s. A G-force of roughly 9g plus the significant deceleration it gets from drag.

My physics is a bit rusty, but I'm pretty sure that's right?

Edited by kambites on Thursday 10th June 20:37
I apologise, I see where you're coming from now. Yes, if the coefficient of friction for they tyre was known, and all conditions perfect (track temp and abrasiveness, moisture levels, wheel camber/toe, brake temps, wind speed and direction etc) then you could calculate peak downforce by judging g-force generated under braking from a set speed.

It would however be an awful lot easier and more accurate to cut out all the variables and stick the model of the car in to a wind tunnel and look at what it produces. This is what the teams do with each revision of the car, and what the FIA do when determining future regulation framework for design. The widely accepted 'target' between those two warring factions is that it should be in the region of 5 fold car weight. Exceed that and, to your point regards friction, g-force achievable under braking or lateral load would quickly exceed what a fleshy human can safely handle for a GP distance.


kambites

61,527 posts

187 months

Thursday 10th June
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TheDeuce said:
The widely accepted 'target' between those two warring factions is that it should be in the region of 5 fold car weight.
Widely accepted by whom, and with what justification? Are you sure this isn't a figure that some random person who doesn't know what they're talking about has come up with and everyone has repeated as gospel?

I'm not saying you're wrong, I just can't make the maths work. I'd be interested if anyone can find a direct quote by someone involved in the aerodynamic design of modern F1 cars rather than an "everybody knows" type statement.

A simple brake pressure vs speed plot at the end of a straight on a hot lap would be enough to work it out to a fair degree of accuracy. Or nstantaneous acceleration off the line before aero starts to take effect.

Edited by kambites on Thursday 10th June 22:21

CoolHands

12,869 posts

161 months

Thursday 10th June
quotequote all
kambites said:
Widely accepted by whom, and with what justification? Are you sure this isn't a figure that some random person who doesn't know what they're talking about has come up with and everyone has repeated as gospel?
Who do we know like that scratchchin

TheDeuce

9,586 posts

32 months

Thursday 10th June
quotequote all
kambites said:
TheDeuce said:
The widely accepted 'target' between those two warring factions is that it should be in the region of 5 fold car weight.
Widely accepted by whom, and with what justification? Are you sure this isn't a figure that some random person who doesn't know what they're talking about has come up with and everyone has repeated as gospel?

I'm not saying you're wrong, I just can't make the maths work. I'd be interested if anyone can find a direct quote by someone involved in the aerodynamic design of modern F1 cars rather than an "everybody knows" type statement.

A simple brake pressure vs speed plot at the end of a straight on a hot lap would be enough to work it out to a fair degree of accuracy. Or nstantaneous acceleration off the line before aero starts to take effect.

Edited by kambites on Thursday 10th June 22:21
Stalemate then. Your maths can only be as accurate as the endless variables allow. My 'hearsay' is only as accurate as we're confident in placing trust in what is generally reported to be the case.

I would say that your mathematical approach whilst admirable must be inaccurate due to so many unknown variables, and given that friction is never likely to be as high as it could be under perfect conditions, you're always going to come up with a slightly pessimistic figure for down force if you base it on G under braking alone, or any other friction limited trial.

I think that it's realistic that modern F1 cars generate 5 times their own weight as overall downforce - the static weight plus four fold at max velocity.

Sandpit Steve

3,067 posts

40 months

Friday 11th June
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Cold said:
There's only one way to work out which car has the most downforce and that involves driving along the roof of a tunnel. thumbup
I was watching an interview the other day with Adam Savage, from the show Mythbusters. He said that “Formula 1 car on the roof of a tunnel” was high up on the list of pieces they thought about but couldn’t do!

Something about insurance, and finding someone with an F1 car willing to help them!
(And a driver, and the mechanics of running the engine for a sustained period upside-down... They really did think it through!).

kambites

61,527 posts

187 months

Friday 11th June
quotequote all
TheDeuce said:
I think that it's realistic that modern F1 cars generate 5 times their own weight as overall downforce - the static weight plus four fold at max velocity.
Ah so firstly we need to get our basic terminology consistent - I'd call that four times their weight as downforce not five (as I'd say my road car generated no downforce, not 800kg of it). That certainly sounds far more plausible than what I thought you were saying, although still a bit on the high side.

TheDeuce

9,586 posts

32 months

Friday 11th June
quotequote all
kambites said:
TheDeuce said:
I think that it's realistic that modern F1 cars generate 5 times their own weight as overall downforce - the static weight plus four fold at max velocity.
Ah so firstly we need to get our basic terminology consistent - I'd call that four times their weight as downforce not five (as I'd say my road car generated no downforce, not 800kg of it). That certainly sounds far more plausible than what I thought you were saying, although still a bit on the high side.
For consistency:

A stationary object with no inertia experiences 1g

An 750kg car with no other force acting upon it applies 750kg compression across its contact patches.

So on the roof of a tunnel the car would produce the same circa 3000kg as aero downforce but less it's own weight, total downforce circa 2250kg.


kiseca

9,112 posts

185 months

Friday 11th June
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TheDeuce said:
Hmm.. The cars would either experience peak g-force or peak aero load, not both at once. One pretty much rules the other out..

I think around 4 tonnes at 200mph is about right. During peak sustained accelerative, decelerative of lateral loads, the car obviously isn't still travelling at 200mph. Not unless something has gone very wrong wink
That doesn't make sense to me? The g-force available is dependant on the aero load. Less aero, less cornering speed available.

kambites

61,527 posts

187 months

Friday 11th June
quotequote all
TheDeuce said:
For consistency:

A stationary object with no inertia experiences 1g

An 750kg car with no other force acting upon it applies 750kg compression across its contact patches.

So on the roof of a tunnel the car would produce the same circa 3000kg as aero downforce but less it's own weight, total downforce circa 2250kg.
I can't fault the logic of using the word "downforce" in that way, I've just never heard it before. Every other person I've ever talked to about it has used the terms "downforce" and "aerodynamic downforce" interchangeably.

marine boy

522 posts

144 months

Friday 11th June
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Just lifting off the throttle using drag alone an F1 car brakes harder than someone standing on the brakes in their road car

AlexIT

756 posts

104 months

Friday 11th June
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kambites said:
Yes but now we're talking about aero load, which can be estimated pretty accurately from instantaneous peak braking force which is, I'm pretty sure, of the order of 5g. That being the case I can't see how the cars can possibly be generating more than about 3 times their own weight in downforce.

Edited by kambites on Thursday 10th June 20:24
I think, that the problem using this way to judge the actual downforce is that the deceleration is so quick that the aero load decreases dramatically in fractions of a second, so while a 10G braking force at peak downforce might be achievable, by the time the pilot can put enough pressure on the brake pedal the speed has already dropped to a level where downforce is already much lower.

ajprice

20,596 posts

162 months

Friday 11th June
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I only accept labradors on your head as measurements for this kind of stuff.

allegerita

201 posts

163 months

Friday 11th June
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kambites said:
Ah so firstly we need to get our basic terminology consistent - I'd call that four times their weight as downforce not five (as I'd say my road car generated no downforce, not 800kg of it). That certainly sounds far more plausible than what I thought you were saying, although still a bit on the high side.
Calculations are difficult without more detailed information. My first, extremely basic iteration on the effect of the front and rear wings only:
Front wing dimensions are 2040 x 575 mm
Rear wing dimensions are 1050 x 800 mm
(source FIA technical regulations document for 2021, issue 7)

The lifting force can be calculated with Fl = Cl x ½ x rho x V2 x A

A = planform area
Cl is lift coefficient
Rho is density

Based on Cl = 3.5 at extreme angle of attack of 15 deg
V = 320 km/h or 89 m/s
Rho 1.25 kg/m3 for air
the lift force generated by the 2 wings only is approx. 34,795 N, which equals 4.7 times the car weight (752kg)

Note: lift in the above is considered negative, in other words downwards.

I completely neglect any air foil characteristics of additional aero elements and the car body, and any downforce generated underneath the car. The part in the above that requires more research is the Cl factor in relation to the angle of attack, which I estimated using older NASA simulation software.


Edited by allegerita on Friday 11th June 10:23

stemll

2,572 posts

166 months

Friday 11th June
quotequote all
Leithen said:
Cold said:
There's only one way to work out which car has the most downforce and that involves driving along the roof of a tunnel. thumbup
A well known motosport team did test in a secret (not a wind) tunnel…
Nah, that was Men In Black smile

https://www.youtube.com/watch?v=t9YfEZtQBtY

Leithen

7,631 posts

233 months

Friday 11th June
quotequote all
stemll said:
Leithen said:
Cold said:
There's only one way to work out which car has the most downforce and that involves driving along the roof of a tunnel. thumbup
A well known motosport team did test in a secret (not a wind) tunnel…
Nah, that was Men In Black smile

https://www.youtube.com/watch?v=t9YfEZtQBtY
Not fiction.

Laurel Hill Tunnel

kambites

61,527 posts

187 months

Friday 11th June
quotequote all
AlexIT said:
kambites said:
Yes but now we're talking about aero load, which can be estimated pretty accurately from instantaneous peak braking force which is, I'm pretty sure, of the order of 5g. That being the case I can't see how the cars can possibly be generating more than about 3 times their own weight in downforce.
I think, that the problem using this way to judge the actual downforce is that the deceleration is so quick that the aero load decreases dramatically in fractions of a second, so while a 10G braking force at peak downforce might be achievable, by the time the pilot can put enough pressure on the brake pedal the speed has already dropped to a level where downforce is already much lower.
You'd still expect to see 8G+ on the brakes at the end of long straits. Maybe they do and the graphics just don't show it.