Mercedes AMG F1 W07

[SectorOne]

Don't know if any is watching FP1 on Sky f1 in the UK, but Di Resta making a specific point of how soft the Mercedes is, and the slow mo was quote reminiscent of the picture (minus the sparks).

Seems like the photo very much *is* a representation of what Mercedes intend to happen through a corner of this type:

http://www.motorsport.com/f1/news/analy ... ng-841343/

Yea reading the article it seems to me this is Mercedes black magic suspension doing it´s thing.

The other cars were going through on the same line but even the ones that were fully loaded up, the attitude of the cars was different – and you could see the front wheel rising in the air. What is particularly interesting is that the rear wheel is massively loaded up and the front wheel is still mostly on the ground. So their suspension is working well.

[henry]

That is a wonderful picture that both informs and raises some further interesting questions.

By running the rear as soft as they do Mercedes will need to cope with more variation in the relationship of the floor to the road. I wonder if the purpose of the "comb" at the leading edge of the floor of to set up a flow under the floor that is harder to disrupt and/or easier to restore than that provided by a "plain" leading edge?

[bhall II]

Seems like the photo very much *is* a representation of what Mercedes intend to happen through a corner of this type:

http://www.motorsport.com/f1/news/analy ... ng-841343/

To withstand the effects of bottoming out? Absolutely, and it's nothing new...



To "seal" the diffuser and/or front wing by virtue of reduced ride height? Not a chance.

[Mark4211]

Close up slow-mo of the rear of Hamilton's car

https://my.mixtape.moe/quskew.mp4

[bhall II]

Here's something from the memory bank that might be of interest. (I've made extensive edits for grammar, because syntax and morphology are decidedly not among Scarbs' strong suits. I don't think he'd argue with me on that one, either. )

In the latter part of the year, it was suggested that teams were discarding the rear side springs to allow very soft rear ends; this has proved to be the case. In the past few years, teams have been removing rear torsion bars in order to gain greater control of suspension setup. This revolution has been quietly spreading, as many teams have now gone this route.

An early sign springs were being removed was the I-Racing game, which leveraged assistance from Williams to accurately model FW31. The game provided no scope for rear springs. Equally, comments made by Anthony Davidson at the Abu Dhabi Grand Prix suggested that McLaren’s extreme stiff front/soft rear lead to Button's problems with locking up the inside wheel under braking. Closer investigation with technical people close to the sport prove this to be case.

McLaren and Williams are highlighted as early adopters, but Toyota and Red Bull are also sporting the setup, which, by virtue of their gearbox supply deals, suggests that Force India and Toro Rosso also have the option. Although this seems to be a relevantly recent practice, as most teams first designed this into the 2009 cars, it may have been tested or raced before then.

The suspension has the joint purpose of controlling the car's attitude for both aerodynamics and tyre dynamics. These often contradictory requirements have lead to compromises, largely against tyre performance and more to the benefit of aero control.

Aerodynamicists want the car to run flat (or raked) with little change in roll or ride height. For mechanical grip, the car needs softer attitude control. This has lead to cars that feature quite stiff front ends and softer rear ends, both in roll and heave. A soft rear anti-roll bar creates more mechanical grip, which in turns needs to be controlled by a stiff front anti-roll bar. For aerodynamic reasons, the front wing and splitter like to be flat to the track surface to optimize downforce. This also tends to require a stiff anti-roll bar.

At the extreme end, this setup characteristic has been exhibited most clearly in McLaren's handling. The car gains traction from the soft rear anti-roll bar, but the stiff front anti-roll bar means that the rear-heavy car tends to roll at the rear, which picks up the inside front wheel going into turns.

As an aside, although McLaren run what has been called a stiff front axle, their apparent problem with grip over bumps going into turns is not necessarily a reflection of this setup, more that the car's aero requires tight ride height control. It's possible to run a stiff anti-roll bar and still have compliance for coping with bumps.

Continued at ScarbsF1...

I'm not saying anything about whether or not any part of this specifically applies to W07 in any way. It's just a bit of background information.

[toraabe]

That is a wonderful picture that both informs and raises some further interesting questions.

By running the rear as soft as they do Mercedes will need to cope with more variation in the relationship of the floor to the road. I wonder if the purpose of the "comb" at the leading edge of the floor of to set up a flow under the floor that is harder to disrupt and/or easier to restore than that provided by a "plain" leading edge?

This also makes them to have much more low speed grip

[f1316]

Seems like the photo very much *is* a representation of what Mercedes intend to happen through a corner of this type:

http://www.motorsport.com/f1/news/analy ... ng-841343/

To withstand the effects of bottoming out? Absolutely, and it's nothing new...

http://i.imgur.com/RrfyQxJ.jpg

To "seal" the diffuser and/or front wing by virtue of reduced ride height? Not a chance.

But I don't think, from the comments Mercedes themselves make, that it's a sign of losing (or near completely losing) underbody downforce; it's apparent that they're trying to allow that kind of 'softness' *without* losing underbody downforce.

As your article shows, this is quite the trick. But that picture does not seem to be an example of a lap where something I
in the car's setup was contrary to expectation, that's my point.

[basti313]

Close up slow-mo of the rear of Hamilton's car

https://my.mixtape.moe/quskew.mp4

Thanks! You can nicely see what it is about: An F1 car does not bounce up. In an event of compression, it goes down and the tires are pressed into the tarmac by the suspension. The aero does not play a role for the grip here as the force on the tire is the only thing that counts. When it goes up the car goes to its normal ride height and not further as "normal" downforce comes back. The tire is never unloaded. One has to think about another force, the downforce, and not about a normally damped system like on a road car.

This is the simple point: The force on the tire is always high, the grip level stays predictable, rather increased than lowered when the car goes into the suspension (thanks bhall for the note on the springs!).

[bhall II]

...that picture does not seem to be an example of a lap where something in the car's setup was contrary to expectation, that's my point.

The standing waves present in the left rear tire all but prove the tire is overloaded. That's not exactly an ideal condition, because standing waves greatly increase hysteresis losses (thermal degradation). While tires can usually endure infrequent standing waves, the phenomenon is virtually guaranteed to cause a blowout if allowed to be a regular feature of the car's setup. It's just a matter of time, and it will likely occur with no warning.

To add context to the aero side, every functionality proposed thus far is an example of something FRIC was designed expressly to prevent, and nothing about those characteristics has changed in the interim. Pitch sensitivity is still not beneficial and should still be avoided as much as possible.

The floor is sealing with the asphalt, must create a lot of df

They do the same at the front with the endplates, let the car roll and seal to the floor. That's why it makes me laugh when people suggest in the Mclaren thread that the car isn't good because it rolls too much...

Anyway, it speakes a lot about the operating window of aero on their car. I guess the lower rake is specifically chosen for this reason.

From general observation the car rolls through the corner, leaning on the loaded section, which in turn lowers the front wing on the loaded side. The same rings true for the rear of the car, with the loaded side of the floor being closer to the ground than the unloaded part.

The question is, whats the gain?

Drievablity. Weight transfer must also match the movement of air under the car to give good balance. My theory is that the air flow on either side under the car is starved depending on the radius of the turn and speed of the car. So the floor must pitch and roll with those changes to maintain some sort of orderliness of the flow and hence stability.

A transient loss of underbody downforce is simply an inescapable consequence of bottoming out. But, that doesn't necessarily mean it's catastrophic by default. It is what it is.

[turbof1]

My thoughts on the matter: you certainly do not want to have the diffuser completely sealed off. There is an optimum ride height where the car produces peak downforce. Going below this or indeed bottoming out means one vortex inside the diffuser will burst, creating assymetric flow inside the diffuser (yes. That is a thing, with the assymetry being dependent on tiny variables which determine which vortex bursts), thus creating reduced and assymetric downforce.

That does not mean indeed you will loose all downforce and all grip. You'll just loose some of it. It can even be the loaded tyre that gets the assymetric downforce, leading perhaps to neglectible losses.

Also, it is hard to define what is "too much sealing" or too "too few sealing". Given current ride heights confined by the plank and step, and tendency to rake, an extra sealing effect which mimics a lowered side fence of the diffuser, is probably beneficial. However, bottoming out does not seem desirable. Not for downforce, and not for plank wear.

What I feel that is going here on with that picture, is that everybody is putting too much focus the downforce side of things. What about inertia, total load on the wheel, weight distribution while cornering,... . I think you need to look this picture much from a standpoint of mechanical grip. The tyres which are being loaded into that specific corner, clearly are being pressed into the tarmac through the shift of weight. I'll go on a big guess here by stating they are sacrificing aerodynamic grip for mechanical grip, for that specific corner, and it's benefiting them.

[ringo]

We must also remember that the picture was for an instant in time. The car wasn't dragging itself on the ground through the corner.
As Paddy Lowe said, the pic took a really extreme case, meaning the car probably returned to a more sensible ride height after that peak instant after a millisecond

Nonetheless, i feel the rear suspension has both corners independent of one another, which would suggest no anti roll bar.
But i feel it is there, but it's just really complicated. It may use some force feedback from the ground to determine how to react and how to transfer the force over to the other corner, with the goal of keeping the rear of the car as flat as possible.

Stiff anti roll achieves the flat ride, but it negatively impacts tyre wear and grip i feel. So what they have done is improve tyre wear and grip and force transfer, while contrarily minimizing body roll. This means a really unusual and disjointed roll centers ( force based movement geometry if you will) on the rear axle.

This is my opinion, it sounds crazy, but something fishy is going on with this car.

As for diffuser sealing. The car has a "T" shapped bottom, so its not really possible for the diffuser strakes to touch the ground along it's complete lenght. Only if the track is bumpy will the diffuser come into contact with the ground. The arc of the bump probably has to fall within the wheel base, track width, before the body of the car will squat down and the diffuser strake comes into contact with it. Basically its highly unlikely that these diffuses will be completely sealed off. All we are seeing is discrete point contacts.

[bhall II]

Irrespective of anything else, the "sealing" bit is senseless.

Neither the diffuser nor the front wing can sustain aggressive AoA without the upwash created by edge/strake vortices to keep air flow attached. Otherwise, the component will "stall" in much the same way as a high AoA wing that doesn't have slot gaps.

Since vortices are generated when a high-pressure stream merges with a low-pressure stream, physically separating the high-pressure area outside the diffuser from the low-pressure area inside the diffuser will weaken, if not altogether eliminate, the diffuser's force-enhancing edge vortices.

Moreover, a lower ride height reduces both effective diffuser volume...



...and the ability of the inner strakes to generate their own force-enhancing vortices from the lowermost region of air flow under the diffuser. (Since that aspect has the potential to cause a storm here, please know that it's not my idea. You can blame it on Willem Toet.)



Within the framework of the current regulations, literally sealing the diffuser/front wing, or allowing ride height to fluctuate unchecked, are bad ideas unless you're trying to invoke a "stall." If there are exceptions, I can't think of any.

Think of it this way: if a deviation from your nominal ride height improves downforce coefficient, then your nominal ride height should probably be reconsidered.

[turbof1]

Well yes and no. You need to have some fencing from to keep the flow of high pressure within certain limits. Else pressure rises too much in the diffuser. Of course too low and you choke high pressure flow alltogether, resulting in the aforementioned vortex bursting.

Maybe we need to reconsider calling it "sealing". You'll never seal it completely off. What you have on these current f1 cars, are small diffusers which are anyhow very sensitive on their own right. It's combined with diffuser fences which are very high off the ground. This is not due own will, but due regulation. You can lower ride height, but that means you remove diffuser volume to have flow to expand into. So you look for means to virtually extend the sidefences of the diffuser further down by ejected high energetic flow alongside the bottom of the fence.

In this case it might be a question of diffuser expansion volume vs vortex strength.

I'm fully convinced that if the rules allowed for longer side fences, they would be longer. To a certain point of course. However, this has little to do with the picture. Obviously the sidefences and inside fences on the left side are touching the ground and are too low, which will choke the vortices inside the diffuser on that side.

But again, keep in mind car performance and grip is more then just downforce. This could very well be the optimal thing for the car to do in that situation.

[PhillipM]

You know they would be longer - look at the tyre testing cars.

[ringo]

I think we can steer away from the diffuser theory when it comes to the rear suspension travel for this instant.
It's applied more to the broader aerodynamic aspect of keeping the floor consistent over a certain ride height and reducing erratic transient behavior.
The second intent of this particular suspension movement has to do with the grip and wear of the tyres.