McLaren MCL39

[CjC]

The races take on the rear brakes

https://www.the-race.com/formula-1/clue ... ke-design/

[Farnborough]

The races take on the rear brakes

https://www.the-race.com/formula-1/clue ... ke-design/

This is echo of that which I've already written in preceeding post on this thread.

[FittingMechanics]

With the comments Key made in 2022 (about having issues with the flow stalling or reversing) I think it's a good bet to assume that the trick is with internal piping that stalls under lower speeds, so they rims are not cooled as much when doing a slow prep lap, and then are cooled a lot when you are at top speed.

This would allow them to get temperature into the tires on a warmup lap but it would cool much better at high speeds (and in the race) keeping their rear temperatures in check.

Only problem I see with this is that I'd expect them to have worse warmup after a pitstop.

[Farnborough]

With the comments Key made in 2022 (about having issues with the flow stalling or reversing) I think it's a good bet to assume that the trick is with internal piping that stalls under lower speeds, so they rims are not cooled as much when doing a slow prep lap, and then are cooled a lot when you are at top speed.

This would allow them to get temperature into the tires on a warmup lap but it would cool much better at high speeds (and in the race) keeping their rear temperatures in check.

Only problem I see with this is that I'd expect them to have worse warmup after a pitstop.

This doesn't APPEAR to be part of the component set we see in images posted within this thread. It all looks to be aimed toward "screening" by separated and intelligently so, air path handling to prevent as much heat as possible from reaching the wheel/tire assembly.

There's not really conclusive evidence of fast warm up to support that hypotethical as far as generally visible. It seems to be the most tenuous if taken in context of getting really fast pace (attributed to warm up) in Q sessions. Where as the "cooling" side of equation seems very firmly on display against their peer group performance.

[FittingMechanics]

This doesn't APPEAR to be part of the component set we see in images posted within this thread. It all looks to be aimed toward "screening" by separated and intelligently so, air path handling to prevent as much heat as possible from reaching the wheel/tire assembly.

There's not really conclusive evidence of fast warm up to support that hypotethical as far as generally visible. It seems to be the most tenuous if taken in context of getting really fast pace (attributed to warm up) in Q sessions. Where as the "cooling" side of equation seems very firmly on display against their peer group performance.

Just putting more cooling should be a simple thing for teams to do. I really don't think the "trick" that everyone is trying to figure out comes down to "bigger brakes". Or that it's just "isolate the brakes from the rims".

Reason why I am mentioning stalling is two fold. Key mentioned that it was the problem they experienced so it's likely that they were playing around with it. Second is that we used to have cars that are good in race pace but bad in qualifying, probably because they had more cooling (and vice versa). So these cars struggle to warm up their tires on warmup laps but then in the races can keep temperatures under control. This McLaren is able to fire up their tires quickly for qualifying, but then keeps them cool over a lap or race distance. Best of both worlds. This could be done with a braking system that allows heat into tires when you want to warm it up and dispose of it when you don't need it anymore.

[mwillems]

It's also great from starts, wet or dry, SC or standing. Evidence so far points to a car that can get heat into its tyres quicker than others.

[SiLo]

It could be that they generate good heat in the tyres because they have lots of downforce, and run more usually with extra drag BECAUSE they can keep them cool, so they worry less about overheating them.

[Vanja #66]

Special outlook at McLaren brake duct design



Starting at the beginning is a good place to start - brake ducts are aerodynamic surfaces designed to guide the airflow around the brake discs and callipers, to improve and enhance their cooling capabilities. In 2022, blow-through-wheel ducts were outlawed and this meant teams needed to start over and redesign everything about them

4 years later, we now have a myriad of brake duct designs all over the grid, some working better than others. The questions about McLaren's solution are valid but - in my view - overblown and I will explain that later

The main things to remember about brake ducts now are:

they are very complex and very optimised for clean airflow
they are multi-level ducts within the internal wheel volume
they are enclosed on the outside with a mandate cover called the "cake tin"



https://t.co/vMvP1k3a3U

Rosario made a phenomenal illustration, displaying the complexity of multi-level flow management withing these fantastic brake duct designs. You probably won't be surprised to read that all these complex ducts have one common problem - handling internal losses

These losses are their biggest problem in terms of pure aerodynamics, ducts need to feature clean flow paths, as unobstructed as possible. Obstructions, poor fits, poor surface finish are all things that mean internal loss of pressure and velocity. These not only increase internal drag, they also mean poor cooling performance as the air pressure drop happens before it reaches the target

As ridiculous as it may sound, we may now be entering a phase where going for better cooling of brakes may be a better performance path than cutting drag by allowing brakes to run hotter. By keeping tyres cooler, you can extract better performance and ensure you keep them in their optimal window for longer



An interesting video by B Sport was published last week, from a former F1 design engineer Martin Buchan, and I've grabbed a few screenshots posted below

If you can keep this "cooling" material in the same phase all the time, while allowing it to absorb lots of latent heat needed to start the phase change where it keeps the same external temperature - you can have your cake and eat it. Or in this case - you can line some of that material on the inside of cake tin and keep the heat away from tyres when you don't need it

Martin flirts with an idea of McLaren using flow path regulator, switching between running hotter and colder air between brakes and drums depending on the temperature of tyres and some parts of assembly

when you want to warm-up your tyres, the hot air from brakes goes around other components
when you want to keep them cool, the flow is reversed

This is the right idea to solve a complex issue, but unfortunately it would be very illegal due to rule 15.1.3 defining shape-memory materials and later defining it as prohibited in 15.4.1

"A material that is configured to move reversibly between two (or more) different shapes when it is subjected only to a non-mechanical uniform stimulus (thermal, electrical, magnetic, optical, etc.), or exhibits a reversible phase change when subject to an applied stress. For clarity, this does not include consequential geometric changes that result solely from the effects of thermal expansion."

Here we also have a part of definition of "Phase Change" which is seemingly prohibited. This also may seemingly prohibit "Phase Changing Materials" but in my view - only if the phase change actually happens

If you can keep this "cooling" material in the same phase all the time, while allowing it to absorb lots of latent heat needed to start the phase change where it keeps the same external temeprature - you can have your cake and eat it. Or in this case - you can line some of that material on the inside of cake tin and keep the heat away from tyres when you don't need it

Both of these ideas remain to be verified, in my view some advanced materials that absorb lots of heat without changing their external temperature are almost definitely used







As usual, when you optimise your design for one set of parameters and achieve exceptional results within that set of parameters - your will probably suffer more than others when you design works outside of predetermined set of parameters. The same goes for race cars - if your car is highly optimised for running in clean air, you will suffer more in dirty air

First things first - dirty air influence consists of several intertwined phenomena

1) loss of downforce due to loss of energy in turbulent wake of the car in front
2) to make up for 1) the driver behind starts pushing his tyres more and more to make up for lost aero grip
3) tyres start to heat up more and mechanical wear increases
4) tyres start to slide because aero-mechanical balance is already disturbed and this sliding hurts even more

So - when you have more downforce, you will suffer more. McLaren fits this description, but arguably not much more than Red Bull in high-speed sections. Where McLaren differs seems to be their brake duct optimisation and how much they depend on this system helping keep the tyre temperature in check.

When you are met with loss of clean air towards the brake duct and you highly depend on it - you will suffer more than others.

Illustration on the left taken from F1-CFD paper, with lead author being former Head of CFD for Ferrari and Sauber, Torbjörn Lars Larsson

https://t.co/twjb9tJDqi



To illustrate more on this topic, I've taken two more screenshots from this video by David Penner - now an Aerodynamicist in Mercedes F1 team. You can find his full article on 2021 Wiliams CFD on LinkedIn

https://t.co/6ErmX1Kaw9

As we can see, the loss of total pressure energy also means a loss of pressure behind the car - because this is the leading feature of turbulent wake

Turbulent flow of any fluid is good for heat transfer because the flow keeps getting mixed. Laminar flow keeps the same boundary layer adjacent to the heated "wall" body (like brake discs in our case)

However - we shouldn't confuse this with the turbulent flow getting sucked into brake duct inlets. This is simply bad because this is not where you want turbulent air, it drops the pressure locally and introduces even more losses. You want high-energy, high-pressure clean flow towards your brake ducts at all times





inal thoughts on this topic, probably least important but could be useful

As a fluid, the air has different thermal conductivity properties. It conducts more heat at higher temperature, but it also conducts less heat at lower pressure

3rd and 4th graphs are from another excellent scientific study of braking systems:

https://t.co/FNlzHoGvjt

I've posted these to show two things:

as the air speed increases the heat flux increases too
as ambient pressure decreases, the heat flux decreases too

"The braking system analyzed here is typical of a racing car. In Formula 1, the GP is held in Mexico, which takes place at an altitude of around 2300 m above sea level, far from the typical conditions found in the traditional circuits, which are located at sea level. In this grand prix, the brakes are very stressed; the atmospheric pressure is lower (0.8 Pa) than the ambient pressure at sea level and consequently lower than the air density."

This is another big takeaway when comparing running in clean air and dirty air - the local "ambient" pressure is lower when following another car because you are running in its turbulent wake, where the pressure is lower than ambient pressure anyway



Other images here -> https://x.com/AeroTechVH/status/1922217811293962723

In Conclusion:

Brake Ducts today are the most advanced ones in this generation of F1 cars
this means they now suffer even more when running in dirty air vs running in clean air
this is probably hurting McLaren the most, because their car is more optimised for running in clean air than any other car on the grid

[vorticism]

Another elephant in the room is the compact engine cover of the MCL39. It seems to have about half the cooling outflow area as the RB21 & RB20. The cannon exit is about half the size, although a little taller, so I can’t say with accuracy how small it actually is. A smaller cannon exit should mean you can run less rear wing while still making the same downforce. The RW should behave more efficiently in the absence of radiator outflow. All this may lend credence to the various claims that RB had some aero development issues with their cooling/inner-aero. If Mclaren can get away with smaller cooling exits then this says something about either their superior inner aero or their Mercedes power unit, or both.

MCL39 also has some clever suspension details which RB21 (Or is it RB20 v.3?) does not, including the severely raked steering arms, interesting in their own right. There must be internal linkages added inboard which translate the transverse east-west linear motion of the steering rack 45*. The rear suspension outboard upper connections are separated. The RB20v.3 has a singular attachement at the top of its rear upright. Multilink vs a-arm, of sorts.

Do these various details add up to Mclaren’s superior tire management? Speculation has been heating up, but is the influence of brake ducts being blown out of proportion?

[Hoffman900]

With the comments Key made in 2022 (about having issues with the flow stalling or reversing) I think it's a good bet to assume that the trick is with internal piping that stalls under lower speeds, so they rims are not cooled as much when doing a slow prep lap, and then are cooled a lot when you are at top speed.

This would allow them to get temperature into the tires on a warmup lap but it would cool much better at high speeds (and in the race) keeping their rear temperatures in check.

Only problem I see with this is that I'd expect them to have worse warmup after a pitstop.

Except this is exactly when you don’t want it to stall as low speed corners on a race track typically come after the the biggest brake zones, which would produce the most heat.

[vorticism]

I'll attempt a non-brake-duct related explanation for Mclaren's performance. The MCL39 has numerous features which none of the other teams have in full:

narrow engine cover
small cannon exit
narrow front nose
venturi RW stay (speculative; see below)
most sophisticated internal aero
highest cooling outflow velocity
possible wing-flex DRS
multilink upper suspension arms
totally unique steering arms & internal rack linkages
RB18+ floor fences
RB18+ reference plane steps (“boat”)
RB18+ general suspension layout front & rear
RB18+ sidepods
RB20 shark mouth inlets

The size of the cooling outlets indicates that Mclaren have the highest cooling outflow velocity. Greater velocity allows them to move the same air mass through smaller outlets. It is evindent in some photos that the MCL39 has the most developed internal ducting; that’s the secret there, which is to say, nothing really to do with the radiators themselves nor the power unit or the coolant, all of which are so regulated anyway that I can't expect them to be performance differentiators on their own.



One unique part they have is their rear wing stay. It resembles a venturi duct. Cooling outflow would be drawn, heated, then expelled. Speculatively that might impart greater velocity to that parcel of air. Important beneath the rear wing. The quicker the radiator outflow, the more invisible it is in terms of the wake passing throught the RW/BW/diffuser area, improving the efficiency of all the rear aero. Compare to the RB21 whose stay has has a smaller gap to the exhaust pipe.






At the front, they have a narrower nose than the RB21. This effectively gives them larger front wing legality boxes, which they can use to make bigger wings that increase downforce or to simply run a wider and vertically shorter wing with a better aspect ratio.




Given how well they’ve designed several parts of the car, it stands to reason that they also have very good if not the best brake duct performance--but the brake ducts are only one piece of the puzzle; perhaps their proximity to the tyres is leading to a false association.

More efficient front wing, least disruptive cooling outflow, maybe some wing-flex DRS... In short, the MCL39 probably has the best lift:drag ratio of all the cars. In practice, they could achieve similar downforce levels with less drag, or greater downforce levels without increasing drag, relative to their competitors’ cars. Reducing the drag force reduces the overall stresses endured by the tires, thus providing slightly cooler tires that last slightly longer, and by association offer a broader operating window i.e. the drivers can go more aggressive to get the quick heat-up which the drivers of other teams cannot risk i.e. the operating window has a higher peak transient temp tolerance because they always have a ‘normal’ or ‘preservation’ driving speed that heats the tires less, due to reduced drag forces put through the tires. Mclaren’s tire management may just be a result of the RB39 being the sum of its well-honed parts. Mclaren took the good practices of the RB18 series cars and polished them further.

As for PCM in the brake drum/tin, there could only be a small amount in that thin walled part, maybe 100 cc at most. So is it more that thermal conductivity changes, and nothing to do with thermal mass, per the hypothesis? As for bi-metallic strips acting at louvres/doors/vanes, that would be moveable aero, too easy to identify, ban, and risk DSQ.

[.poz]

With the comments Key made in 2022 (about having issues with the flow stalling or reversing) I think it's a good bet to assume that the trick is with internal piping that stalls under lower speeds, so they rims are not cooled as much when doing a slow prep lap, and then are cooled a lot when you are at top speed. .

warming up rear tyres is a non issue AFAIK

[AR3-GP]

The size of the cooling outlets indicates that Mclaren have the highest cooling outflow velocity. Greater velocity allows them to move the same air mass through smaller outlets. It is evindent in some photos that the MCL39 has the most developed internal ducting; that’s the secret there, which is to say, nothing really to do with the radiators themselves nor the power unit or the coolant, all of which are so regulated anyway that I can't expect them to be performance differentiators on their own.

Is this accurate? Mclaren has additional outlets further forwards on the left and right side which you have not highlighted. They are not "small". There must be mass continuity so the airflow from the rear exit is not automatically "higher". Some of the air mass has exited already from the pair of outlets located further forwards. Therefore, assuming the two cars have similar heat rejection requirements and similar internal losses, it is not apparent that Mclaren would have much "greater" cooling exit velocity from the central cooling exit at the rear.

[vorticism]

Is this accurate? Mclaren has additional outlets further forwards on the left and right side which you have not highlighted. They are not "small". As there must be mass continuity, then the airflow from the back is not automatically "higher". The Red Bull does not have forward exits in that picture. So assuming similar engine/intercooler heat rejection requirements, I don't think it's straightforward to say one car automatically has higher cooling exit velocity.

The drawing is accurate to the extent the images are the same size scaled to the common exhaust pipe diameter and rain light size. As for the hypothesis, it is what it is. The MCL39 louvers are smaller in area than the green spaces in the cannon comparison, and this includes after the cannon height difference is also removed from those green spaces, which is to say, the total outflow area of the MCL39's combined louvers and cannon is smaller than RB21's cannon. Both cars utilize lower suspension arm portal outlets so these were not considered.The total MCL39 cooling outflow area may be something on the order of 95% of the RB21. Also I did not include the RB21's spine outlet, which when included should favor estimation errors toward the hypothesis.

I compared cannon outlet sizes because the cannons are in closer proximity to the RW. The louver outflow will be accelerated by the local/ambient free stream thus that % of the cooler outflow is reduced in terms of its influence upon the RW/BW/diffuser vs. had they expelled it right in front of the RW like RB. Consider the '22 Ferrari did this in the extreme with all louvers and no cannon.

[Brahmal]

Could they possibly be ducting some internal airflow through the suspension/driveshaft shrouds into the brake assembly?