Official 2021 Azerbaijan Grand Prix Thread ***SPOILERS***
Discussion
Excuse the kids video 
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.
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.
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
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.
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
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
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.
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. 
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!).
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. 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. 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.
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
That doesn't make sense to me? The g-force available is dependant on the aero load. Less aero, less cornering speed available.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
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. 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.
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. Edited by kambites on Thursday 10th June 20:24
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
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.
A well known motosport team did test in a secret (not a wind) tunnel…
https://www.youtube.com/watch?v=t9YfEZtQBtY
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.
A well known motosport team did test in a secret (not a wind) tunnel…https://www.youtube.com/watch?v=t9YfEZtQBtY
Laurel Hill Tunnel
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. Gassing Station | Formula 1 | Top of Page | What's New | My Stuff