McLaren MCL39

[Andi76]

It's obvious McLaren have some non-linear thermodynamic device operating on their wheel hub.
My crude guess is that McLaren have the mechanical equivalent of an electronic transistor (operating in it's saturation region) where 'amount of heat' would be the current and 'temperature' would be the voltage. The implemention might be a multi-metal 'sandwich' in the construction of the axle/driveshaft to which the wheel rim and brake disc are attached. The brake disc will come in contact with the axle via one metal, and the entire 'heat sink' (wheel rims/wheel bearing/cooling ducts) would come in contact with the axle via another metal. The 'gate terminal' could be something equivalent to a bimetallic strip which reacts to a temperature threshold and opens/closes (or diminishes/enhances) the heat flow between the two metals, creating opportunity to maintain both tyre temp and brake temp separately as required.


Edit : just came to know from Redbull thread that someone called B sport has posted a video in social media, calling out the same idea. Trust me, it's a coincidence, I haven't watched that video. Secretly I am glad that the same idea occured to someone else, kind of allowing me a 'not that stupid afterall' notion about my thoughts.

It would make sense for McLaren to use a phase changing material like the one currently circulating. Remember the brakes finding fire in testing last year. I thought that was very unusual at the time because for an F1 team that would be amateurish work. But they were certainly in the early stages of developing a phase changing material and a system with it, hence the burning of the brakes. Likewise, the fluid residues that were mentioned last year could have been the residues of a system that was not yet 100% perfect and not completely sealed or sufficiently developed in terms of phase changing.

[Macafangrskg]

It's obvious McLaren have some non-linear thermodynamic device operating on their wheel hub.
My crude guess is that McLaren have the mechanical equivalent of an electronic transistor (operating in it's saturation region) where 'amount of heat' would be the current and 'temperature' would be the voltage. The implemention might be a multi-metal 'sandwich' in the construction of the axle/driveshaft to which the wheel rim and brake disc are attached. The brake disc will come in contact with the axle via one metal, and the entire 'heat sink' (wheel rims/wheel bearing/cooling ducts) would come in contact with the axle via another metal. The 'gate terminal' could be something equivalent to a bimetallic strip which reacts to a temperature threshold and opens/closes (or diminishes/enhances) the heat flow between the two metals, creating opportunity to maintain both tyre temp and brake temp separately as required.


Edit : just came to know from Redbull thread that someone called B sport has posted a video in social media, calling out the same idea. Trust me, it's a coincidence, I haven't watched that video. Secretly I am glad that the same idea occured to someone else, kind of allowing me a 'not that stupid afterall' notion about my thoughts.

It would make sense for McLaren to use a phase changing material like the one currently circulating. Remember the brakes finding fire in testing last year. I thought that was very unusual at the time because for an F1 team that would be amateurish work. But they were certainly in the early stages of developing a phase changing material and a system with it, hence the burning of the brakes. Likewise, the fluid residues that were mentioned last year could have been the residues of a system that was not yet 100% perfect and not completely sealed or sufficiently developed in terms of phase changing.

And if the phase change material is our secret it toke us 1.5 year to perfect. In f1 terms with budget limit and testing limit it will be ages until other teams catch up to us. And for us it time that we need to out develop them for the new regulations. It is almost catch 22 situation.They have to develop this solution but they can afford to do so

[deadhead]

are phase changing materials legal in F1?

[Macafangrskg]

are phase changing materials legal in F1?

As long as there none moving parts for aerodynamic purpose yes.But history taught us that FIA can jump in and ban something that is legal in the letter of law like mass dumber or the f duct with the tunnel that McLaren had in 2010

[Emag]

Just to be clear, this is just the leading theory at the moment because of the B Sport video (it also makes sense). However, it is not exactly confirmed that's exactly what they're doing there, so for all we know, it could be something else.

After it popped up, the topic was really intriguing and I tried to do some personal research on it. After reading a bit more, it sounds really difficult to pull off, but I am also not aware of recent advancements that might have happened in the field to negate some of the issues I could see with it during my reading. There's too many technical challenges one needs to go around to integrate this successfully, because the area of application (inside the cake tins) is really tricky and limiting, both in spatial and environmental factors. Apart from worrying on getting the benefits out of it, you need to be careful not to mess up the primary purpose of those parts, which is to manage brake temperatures.

Considering the limitations previously mentioned, you would definitely be forced to run an extreme solution with potentially really thin PCMs which kind of creates more problems in terms of reliability, because if something fails in the system and you get some sort of "leakage", it could potentially be catastrophic / race ending.

Now, Lando did have that brake issue in China, but I am not sure if it was related to the rear brakes specifically, or if it was a generic hydraulic failure. Nevertheless, just one failure is not enough to conclusively prove PCMs use.

Apart from the technical challenges, there's the regulations to consider as well. And to be honest, even after reading the relevant articles on the technical regulations documents for last year (not sure if the 2025 ones are available), it's quite difficult to pinpoint whether or not use of PCMs is legal or not. An argument could be made for both, however using SSPCMs (Shape-Stabilized PCMs) could definitely help to avoid some "liquid cooling" problems, which aren't permitted. SSPCMs don't melt like traditional PCMs so it helps avoid reliability issues I mentioned as well, however their latent heat storage capacity is not as great, potentially rendering them ineffective for this use case. But I haven't made nearly enough research on the topic to make that claim with confidence.

Legality issues aside, there's something else to consider from the technical regulations that might make a solution like this quite ineffective as well. Specifically, the following segment from article 3.13.2 Drum :

For each drum, a circumferential, continuous (around an arc of 360°), and uniform
aerodynamic seal must be fitted in the outboard of the two annotated volumes, in order to
prevent any significant aerodynamic or heat transfer flow between the drum and the axle.

This restricts the already tight space you have to work with even further.

In addition, the adjacent article 3.13.3 on the Scoops has a list of multiple legality box constraints which are an absolute pain to work out specifically, but I can't imagine introducing a new sheet of different material in there doesn't comply with at least one of them, which makes the integration even trickier.

Long story short, it's a really cool subject that got me reading into it. It's also a really complex thing to get right for this sort of application. Not only for it to be legal, but also to provide benefits without sacrificing reliability or braking performance, however I would not put it past F1 engineers to figure stuff like this out. I really love intricate ideas like this. If this is indeed what they're doing, is really really impressive. But as I mentioned, we might be getting a little carried away here. Sometimes (not always), things are simpler than they look. Although I have zero clue how else they would have managed to create such an efficient temperature management solution that seemingly has the rest of the grid stumped as well.

[Hoffman900]

^ great post. And thanks for typing that up.

[vorticism]

Edit: Just noticed the "SSC" classification for wheel covers, which means one supplier makes and supplies that part to all the teams. Despite there being some freedom in the rules for the construction of that part, it wouldn't matter if that supplier made a clever part or was asked to make a clever part, because every team is supposed to get the same design. This should rule out Mclaren having unique wheel covers, unless there is some minutia in the rules that allows them to make their own versions. However the wheel deflectors (the various wings on the wheels) and the drum (cake tin) are LTC which means each team makes their own. Which may be part of the reason the cake tins are suspected. I'll leave the cross sectional sketch, as at least that is still accurate and helps visualize the general arrangement and potential thermal paths.

[.poz]

already posted before by someone else but what is the small oarage part near the upper wishbone ?
there a sort of part number and a logo on it

[Farnborough]

already posted before by someone else but what is the small oarage part near the upper wishbone ?
there a sort of part number and a logo on it

https://pbs.twimg.com/media/GoLFNbVbwAA ... =4096x4096

That looks like the "tether" for safety, which has identification and spec on it I think.

They run inside the wishbone carbon covers but have to be completely separate in form and attachments to chassis and wheel upright in design to comply with safety regulations.

Some of the chassis you can see clearly on front where they mount to central tub, the MB car for example.

[venkyhere]

That could remain hollow if the cover is sufficent to act as a cooling fin only, or, if the cover is made as a hollow vessel, fill it with wax. A significant volume could be held there as the space seems to comprise 1 or 2 litres. Choose a formulation that melts at the desired temperature ( I assume somewhere around 200F/100C) to help limit the peak temperature of the magnesium wheels. Whether this would be used to attenuate fluke temperature spikes only, or for a melt-freeze cycle during each braking event, I can’t say; but it’s a significant volume relative the amount of magnesium that comprises the wheel. Worth the weight penalty? Liquid-gas phase change chemicals might also be feasible as used in heat pipes. Either way: boil/melt at the wheel interface, condense/freeze on the cover face. Or eschew all that complexity and simply use it as a heat sink fin.

appreciate your effort to put up the sketches.
The concern I would like to highlight regarding the bold highlighted portion in the quotes above :
It's not just additional unsprung weight burden on suspension, it's also additional rotational inertia burdern on the driveshaft, as the additional 2kg (let's assume density=1) is going to sit like a 'ring' around the hub - that will be like 'gearing up' the car a little.

[.poz]

Choose a formulation that melts at the desired temperature ( I assume somewhere around 200F/100C) to help limit the peak temperature of the magnesium wheels.

i have done a quick research and the most commons materials suggested with a phase changing temp between 100 and 200 C have a problem: the boiling temp is low (usually less than 300 C) for something so near to the brakes

of course probably something exotic (eutectic ?) exist or it can be placed inside a sealed high pressure vessel

[Farnborough]

already posted before by someone else but what is the small oarage part near the upper wishbone ?
there a sort of part number and a logo on it

https://pbs.twimg.com/media/GoLFNbVbwAA ... =4096x4096

There's also detail in that material (white immediately surrounding disc) under higher magnification, which looks close to chopped strand glass fibre in makeup.
That would seem to be supported by a light carbon skeletal framework to keep it acceptably clear of rotating disc inside it.
Those materials will work within the heat range (similar use of exhaust header wrap in enclosed car installation) to contain radiant output simply.

You can also see that there's vented supply or extraction to centre location of the disc for blow through cooling of carbon disc rotor radial holes.
You can see it's not full circumference in the above, suggesting the entry is through % area, with extraction after exit at disc peripheral into that primary shield at the remaining % at centre.

In effect then, there's this first shield closest to disc rotor surface, then the "silver" casing next, going outward in order, finally the carbon "tub" we sea clearly with whole assembly built up.

Quite a labyrinth in all. Each flow path could have both exit and entry "porting" dedicated to it within the external air handling located on inner face of suspension upright assembly.

[AR3-GP]

already posted before by someone else but what is the small oarage part near the upper wishbone ?
there a sort of part number and a logo on it

https://pbs.twimg.com/media/GoLFNbVbwAA ... =4096x4096

There's also detail in that material (white immediately surrounding disc) under higher magnification, which looks close to chopped strand glass fibre in makeup.
That would seem to be supported by a light carbon skeletal framework to keep it acceptably clear of rotating disc inside it.
Those materials will work within the heat range (similar use of exhaust header wrap in enclosed car installation) to contain radiant output simply.

You can also see that there's vented supply or extraction to centre location of the disc for blow through cooling of carbon disc rotor radial holes.
You can see it's not full circumference in the above, suggesting the entry is through % area, with extraction after exit at disc peripheral into that primary shield at the remaining % at centre.

In effect then, there's this first shield closest to disc rotor surface, then the "silver" casing next, going outward in order, finally the carbon "tub" we sea clearly with whole assembly built up.

Quite a labyrinth in all. Each flow path could have both exit and entry "porting" dedicated to it within the external air handling located on inner face of suspension upright assembly.

I agree that there is more to learn about this unusual brake disc shield. No other teams has this construction.

[Farnborough]

It would be reasonable to project that most of those close to disc rotor carbon framework/ducting make use of phenolic resin to work within that range.

Projection of homogeneous operation would have absolute maximised regeneration retardation, minimised disc rotor use and hence heat at that point , which may take it very close to it's realistic operational temperature threshold in pure braking terms .... but enough to survive race distance.

The tire heat characteristics look more "shielded" to prevent heat into them, as opposed to switching from quick warm up to heat protection.

The minimised heat at maximum seems to be a safe observation, the facility to warm at exponential rate .... seems to be more tenuous in real empirical data driven fact.

Rears should always be easy to get heat into anyway, fronts are more problematic in that aspect with lack of motive torque to help.

[vorticism]

Note the general arrangement of the brake cooling ducts has been the same since the start of the '22 regulation. Fully ducted disc inlet and outlet flow is baked into the ruleset. The radial outflow from the disc follows its own discrete path (the snail shells visible around the disc on all the cars) toward an outlet nozzle whose location is spec'd; it's a dedicated path partly because it has to be, given the high temperature of the ejecta, and is sealed & insulated with some kind high temp stable glass/mineral wools & foams. If it weren't there'd be risk of the hot brake outflow acting like torches as it leaked onto other components inside an otherwise sealed container (the cake tin) that contains flammable & meltable parts. In '22 there were pics of more crude installations of such foam, as well as some associated brake fires. The disc outflow collector doesn't fully enclose the disc because the brake caliper is in the way. Given the size of the calipers something like 60-70%(?) of the disc perimeter is being used to eject heat.