Multiple brake pads on one disc

[Steven]

Watching some images of the MP4-4 in another thread I realised there are 2 brake pads on the rear brake discs. I didn't remember anymore.

Anyway, I suspect such systems are currently banned, but I actually wonder if it would still be beneficial to have multiple pads. The two important things I see as a problem are heat and weight.

Considering the heat currently in discs under breaking, could any more brake force be applied to the discs without putting them in flames?
And second, the added weight may be a problem for cornering and such.

Any ideas on this?

[scarbs]

Yup, multiple pads are banned. The theory with multiple pads is that each piston can press its own pad against the disc, as its the leading edge of the pad that creates the greater friction, this makes the same swept area more effective. Where as with a single pad, the two trailing pistons (with a six position f1 calliper) do much less work than the leading piston. Thus the trailing pistons are often smaller diameter or receive less line pressure, to reduce their pressure on the pad.
I imagine F1 brakes could be uprated if allowed under the rules, increased line pressures (powered brakes..?), stiffer callipers and mountings, as well as more pistons\pad (and thicker than current 28mm discs). Of course it’s the pad and disc material that have to cope with this all. I’d expect it wouldn’t be a hard task to develop the materials to cope with the extra thermal loadings.

[Belatti]

Yup, multiple pads are banned. The theory with multiple pads is that each piston can press its own pad against the disc, as its the leading edge of the pad that creates the greater friction, this makes the same swept area more effective....

Do F1 brake pad designs have grooves in order to have several "leading edges"?

[Giblet]

The grooves are there on road cars to dissipate heat, but carbon fibre brakes and pads work best with much higher heat then steel. Grooves would make it hard to get the brakes up to temperature, and decrease surface area.

[scarbs]

No F1 pads have a flat biting surface. if there were grooves they would be ineffectuall as the pad is stiff and wouldnt give the edge any extra bite.

Note the pads have been drilled to keep the calliper piston cool

[mx_tifoso]

Considering the heat currently in discs under breaking, could any more brake force be applied to the discs without putting them in flames?

Not neccesarily, increasing brake cooling through larger brake ducts would probably compensate for the increased heat dissipation in that particular area.

Although the additional heat from the brakes would possibly affect surrounding areas, such as tire temperature, suspension. Materials sensitive to extreme heat would need to be replaced more often, or would need additional protection.

-----Current F1 CF brake sytems reach temperatures up to 1200°C during actual cornering-----

And second, the added weight may be a problem for cornering and such.

Would the addition of four more brake pads overall have a significant affect on the cornering speeds and/or capabilities?

Does anyone have a thought as to how much an actual F1 brake pad weighs?

Besides, there wouldn't be four more similarly sized brake pads, the current pads would be reduced in size, in order to allow the new incoming brake pads to properly fit.

1 pad per caliper -> 2 smaller pads per caliper.

I come to that idea because the wheel diameter will not undergo change, simply the brake pad design (and caliper design as well).
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@ Scarbs: Great photo. Is CF for this application usually that color(powdery grey)? Before use I would imagine.

[Giblet]

Adding sprung weight to the wheels would be a nightmare for handling in relation to other cars.

[scarbs]

I doubt splitting the pads up would add much to unsprung weight. Any way the improved laptimes from better brakes, would offset any of those issues.

Yes CF pads and discs are always powder grey, the disc face shine sup a bit with runing, but its still very much a flat finish.

[DaveKillens]

The FIA regulations severely limit the brakes, and force specific solutions. The brakes cannot receive assistance apart from the driver. The caliper has to be aliminum. Only one caliper per wheel, and maximum six pistons per caliper.
That's a lot of limitations, and it's not difficult to see that the engineers cannot design for all regimes, especially the transition between high speed, high downforce into the low speed, mechanical grip levels going into tight turns.

[ss_collins]

Ligier/Prost tested an airliner style full disc pad about ten or eleven years ago if memory serves (ie three discs - the outer two fixed and the centre one spinning)

[nae]

not strictly on topic but a good read

http://www.stoptech.com/tech_info/tech_ ... pers.shtml

I do so like the guys writing style and the tech insight

[scarbs]

As an aside, F1 callipers do not need to be aluminium, just a material no stiffer than 80GPa. Brembo and AP use Aluminium lithium alloy. I'm sure about Akebono or Alcon.

[ss_collins]

Is it 80 or 40 craig - not at works so tech regs not to hand. I have a load of research stuff on materials tuning

[ginsu]

This suggests it's limited to 40 GPa. Maybe more for calipers?

According to FIA regulations, metals with a specific modulus greater than 35 GPa/g/cm3 (35 GigaPascals per gram per cubic centimetre) must be submitted to NPL for a specialised tensile test. The test gives F1 teams greater confidence in the quality of their test data and therefore their ability to comply with FIA specifications.

[Ciro Pabón]

Novel? I don't know. But if somehow you could avoid the contact of pads and discs and air, totally, and I mean completely, entirely, and "pump" all heat from them through diffusion, without cooling them with air, encasing them in an "air-proof" case, then, this applies:

"... as a matter of very real practical interest, there is a very fundamental difference between nuclear reactions and chemical reactions for the production of energy. Nuclear reactions can proceed without the employement of oxygen, something nearly always used in combustion processes.

First of all, we all know the wonderful sucess of the very famous submarine, the Nautilus... Second, in employing nuclear reactions, one has the opportunity to use special materials which are not resistant to oxidation. For example, graphite at very high temperatures like 4500 Fahrenheit has the same strength-to weight ratio that the gas turbine alloys have when operating at their temperature limit of ... 1700 F.

The refractory materials, tungsten and molybdenum, which retain good strength to very high temperatures, have not found extensive employement because at high temperatures they are attacked by oxygen... for example, one could imagine a nuclear reactor... employing helium as the working fluid, graphite for the reactor structure, reinforced with tungsten as necessary, and driving a gas turbine operating at a very high temperature with blades made from molybdenum.

The explotaition of this fact, the absence of oxygen, has not yet been extensively employed."

So, to sum up, I wonder if the use of discs and pads in vacuum extends their life or improve their braking abilities somehow. After all, at high temperatures, oxygen erodes even ordinary materials, not only molybdenum.

On the other hand, I wonder if heat can be pumped quickly enough from them if they are in a vacuum.