McLaren MCL38

[_cerber1]

I will say this: perhaps the author did not understand the point; he seems to be referring to a rumor from the paddock.
My opinion is that you can use metal with a high expansion or contraction ratio, and you can actually use temperature, for example to change the shape or size of the diffuser, through these rods.

[AR3-GP]

I will say this: perhaps the author did not understand the point; he seems to be referring to a rumor from the paddock.
My opinion is that you can use metal with a high expansion or contraction ratio, and you can actually use temperature, for example to change the shape or size of the diffuser, through these rods.

Exactly. The explanation in the post is a bit mistranslated I think.

The real benefit, if this is deliberate, is using heat/thermal expansion to lengthen the floor reinforcement rods which allows the floor to lower. The scrutineering test are done when the engine is off and the reinforcement rods are cold and "shrunken". It's quite clever if this is what Mclaren have done.

[Hoffman900]

I will say this: perhaps the author did not understand the point; he seems to be referring to a rumor from the paddock.
My opinion is that you can use metal with a high expansion or contraction ratio, and you can actually use temperature, for example to change the shape or size of the diffuser, through these rods.

Exactly. The explanation in the post is a bit mistranslated.

The deflection test are performed when the car is off and the material is cold. When temperature raises due to heat, the components expand. The reinforcement rods lengthen. It can allow the floor to lower. It's quite clever if this is what Mclaren have done.

Except the coefficient of expansion for that short of length, sitting in free air (so tons of convection), of any alloy is minuscule.

Using this logic, the exhaust would grow substantially (it doesn’t) or something like an exhaust valve that sees variation of 100* C in a single cycle would cause valve lash to change dramatically.

Let’s do a little math. Say it’s aluminum (high rate of expansion, 23/10^6C*), and the entire rod is heated uniformly (it won’t but hypothetical), and the stay is .5m long.

So say it’s a 32* C day and it heats up to 232* C.

Delta t = 200* C

L = .5m + 23/10^6C * 200 C * .5m

L= .5023m, so it grew .23cm or 2.3mm.

The rod is not heated uniformly sitting in free air and that’s for pure aluminum. Most aluminum alloys are half that rate of expansion, so figure 1.2mm or so, and that’s being very generous with assumptions. Steel alloys will be less and titanium even less.

[Farnborough]

In that first image, it looks more like the top of restraint is attached to the form on rear edge of wing central pylon, which is obviously structural.

Lower end of restraint passes through the top surface of diffuser, with effectively the "guide plate" able to slide a little on that stay.

Angle of attachment APPEAR more to side wall of diffuser nternal than top surface, looks designed to allow some level of geometry changes with the top surface of diffuser.

Clear view of wing movement (on MB a couple of weeks back) has the main wing moving in rearward arc, if the same here, then the pylon would likely deform more to oval form and move those central stay support outward.

The exhaust wouldn't SEEM to have enough location of structural support to be useful in mounting to it at that location.

[AR3-GP]

*snip*

The rod is not heated uniformly sitting in free air and that’s for pure aluminum. Most aluminum alloys are half that rate of expansion, so figure 1.2mm or so, and that’s being very generous with assumptions. Steel alloys will be less and titanium even less.

Even if the rod only lengthened by 0.5mm, the correlation to the z-height of the various parts of the floor is non trivial because the attachment points are points are hinged.

Teams are fighting over 0.2mm of ground clearance. It's a ground effect formula. It isn't something to look over if one can find a benefit. I'm not suggesting that such a system is worth seconds of lap time. Most things are small incremental benefits that when added together, produce a fast car.

If no team is looking to take advantage of this, then someone should. This is exactly the kind of incremental gains that teams chase that would have no meaning in any traditional industry.

[Hoffman900]

But it is trivial. The stay is at an angle so say it grows only .5mm, even if the floor is hinged a meter away, the change is trivial as it’s not a 1:1 change.

Figure the aggregate is 9.5mm on the top layer of a race track, there is more variation in the surface of the track’s aggregate (put a ruler across the track, and you’ll see the tracks surface between aggregate is greater than .5mm change), than there is in that difference that stay could provide in growth and that’s assuming very generous growth that doesn’t exist in the real world.

The tire deflects much more than that as well.

It was a silly theory / tweet by a middling former F1 driver from 20 years ago. Nothing more.

[venkyhere]

By @F1Techy

According to Franck Montagny , McLaren used a trick consisting of attaching the rear fixings of the floor to the exhaust, in order to exploit the heat emitted by it to expand the carbon and thus improve performance.

let me tell you mainly about this trick, it’s not about expanding, but more about conducting the heat to the diffuser which Lowers the air density and raises viscosity, It will help creating a lower pressure in the diffuser and faster flow across the throat.

Look at the pictures below McLaren actually fixed the clips on the exhaust.

https://pbs.twimg.com/media/GR8HMxEW0AE ... ame=medium

https://pbs.twimg.com/media/GR8jDMXWoAA ... name=large

Too far fetched IMHO.
Anyway the 'expansion' theory is shot down, because the rod is in tension, so any expansion would mean it 'sags' rather than bend the floor edge down further.
Regarding this thing making the rear floor acting like an 'air-heater', that too is moot, since it will be like holding an clothes-iron to the wind. The volume/sec of air moving is too much for 'expansion from obtaining heat via conduction'

It could just be case of finding a 'good spot' to fix the stays.

[SiLo]

By @F1Techy

According to Franck Montagny , McLaren used a trick consisting of attaching the rear fixings of the floor to the exhaust, in order to exploit the heat emitted by it to expand the carbon and thus improve performance.

let me tell you mainly about this trick, it’s not about expanding, but more about conducting the heat to the diffuser which Lowers the air density and raises viscosity, It will help creating a lower pressure in the diffuser and faster flow across the throat.

Look at the pictures below McLaren actually fixed the clips on the exhaust.

https://pbs.twimg.com/media/GR8HMxEW0AE ... ame=medium

https://pbs.twimg.com/media/GR8jDMXWoAA ... name=large

Too far fetched IMHO.
Anyway the 'expansion' theory is shot down, because the rod is in tension, so any expansion would mean it 'sags' rather than bend the floor edge down further.
Regarding this thing making the rear floor acting like an 'air-heater', that too is moot, since it will be like holding an clothes-iron to the wind. The volume/sec of air moving is too much for 'expansion from obtaining heat via conduction'

It could just be case of finding a 'good spot' to fix the stays.

Considering the amount of air running over that area of the car (cooling the metals down), plus the fact that near the end of the exhaust is nowhere near as hot as right next to the manifolds, I'm 100% certain it's just positioning and that's it. That theory is just really, really bad.

[michl420]

Conducting heat from the exhaust to the diffuser with this stay is obviously impossible. But using heat to make a stay longer is a thing to think about (floor edge stay).

[venkyhere]

Conducting heat from the exhaust to the diffuser with this stay is obviously impossible. But using heat to make a stay longer is a thing to think about (floor edge stay).

Anyway the 'expansion' theory is shot down, because the rod is in tension, so any expansion would mean it 'sags' rather than bend the floor edge down further.

[Hoffman900]

Conducting heat from the exhaust to the diffuser with this stay is obviously impossible. But using heat to make a stay longer is a thing to think about (floor edge stay).

Except

1) the rod is under tension
2) the maths don’t work for that, at all.

[AR3-GP]

I don't really understand what you guys mean when you say the rod being under tension invalidates the concept.

The reason that the rod is under tension can be for 2 reasons

1) Engineered preload in static conditions (a turnbuckle connection to allow preloading against the stiffness of the floor)
2) Diffuser suction at speed draws the connection at the diffuser downwards. This creates more tension. No different to loading a suspension bridge with cars on the roadway.


If the rod gets longer due to thermal expansion, the diffuser can go down more when the car is on the track.

[Owen.C93]

The crash structure is the only hard point in that area and it's more mass efficient to use a wire to stiffen the floor to that than to use extra stiffener features through the whole floor.

There's not even any FIA pull loads in that area so there's no need for some crazy heat activated wire.

This just sounds like someone joining dots that aren't even there.

[AR3-GP]

There's not even any pull loads in that area so there's no need for some crazy heat activated wire.

The diffuser creates suction. This means it pulls on the rod.

[Owen.C93]

I meant legality wise, not literally.

The stay is there to stop the diffuser losing volume and also for durability. They have stiffeners on the side walls of the diffuser because they have a tendency to bend inwards from the suction.

The floor takes 100s of kgs of load and it's most weight efficient to use wire stays to resolve that load to the chassis than it is to add titanium or carbon stiffeners.