Light Weight Material for Disk Brake Rotors 2

[patprimmer]

I am interested in the carbon/carbon rotors or other lightweight solutions to reduce rotating mass in a drag race car.

I know carbon/carbon are used in F1, so should be durable enough for a drag race car, and should significantly reduce the inertia of the wheel hub assembly.

I guess I will also do a Google search, but I expect I will get more qualified and objective advice here.

I already asked this question in another thread in another forum, but I think this is a more appropriate place, and so as to avoid hijacking another thread, I will transfer the answer already received over to here, and then red flag that post and answer

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
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[ZoRG]

Please do let know how it all turns out, I am quite interrested.
I may have found another supplier willing to supply carbon/ceramic discs a little cheaper, but obviously no where near the Aluminium mmc prices. Hoping to get it for US $500 per wheel unfinished and $1000 per wheel for a machined product. I can afford that

 

[NeilRoshier]

What is the upper temp capability of MMC rotors as described?

 

[ZoRG]

For Aluminium MMC Its not the rotors, I think the pads can only handle 400C.

 

[NeilRoshier]

that is not much temp, have lotus solved this problem?

 

[ZoRG]

No, lotus went back to iron discs because the supplier of the mmc discs went bankrupt. It doesn't sound that high, but it is, since the mmc discs cool quite fast, the elise is also a very light car.

Maybe on a heavier car it might be a bit of a problem, I am not sure. You have the same problem with carbon/ceramic discs if you try and use organic pads (Same grade as MMC discs can be used on carbon/ceramic discs), the pads just can't handle much over 400C. However if you use carbon/ceramic pads, you can go over 800C. If you look at the porche carbon/ceramic discs as well, they don't use carbon/ceramic pads, and their have been plenty of reports of the pads catching on fire. It doesn't seem to do any harm though.

 

[CanEngJohn]

The MMC rotors had a really high heat capacity. That was one of the Engineering specs that drove the concept.

As I recall from 6 years ago, under similar braking conditions MMC would only reach about 2/3 of the temperature a cast iron rotor would see. This was due to the better heat capacity and dissipation characteristics. It would take more heat to move the rotor temperature on an MMC rotor than it would in a cast iron.

I know you are thinking - wait we are talking about aluminum. The key to a MMC product is not the main matrix, it is in the additives. The aluminum was excellent at heat dissipation but the additive was excellent for temperature stability and heat absobtion. Each used its strength in this application.

Where a Cast Iron rotor might see 400 deg. C a MMC rotor might only see 275.

 

[ZoRG]

I thought this was cause they dissapated alot of the heat into the wheels?

 

[patprimmer]

I would assume the heat has to go somewhere, if there is not more surface area to dissipate it to the air, it must be lost to the wheel or the hub and wheel bearings.



Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NeilRoshier]

What is the MMC rotor life like compared to cast iron? I am curious why alcon et al have not produced an after market MMC rotor, everything I am hearing sounds positive for some motorsport e.g. hillclimb

 

[patprimmer]

And drag racing.

For drag racing life is not even really an issue, as they might only do 6 or 8 stops at a meeting and 50 to 100 stops per season.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[CanEngJohn]

What is the MMC rotor life like compared to cast iron? I am curious why alcon et al have not produced an after market MMC rotor, everything I am hearing sounds positive for some motorsport e.g. hillclimb

There are a number of reasons. The first and strongest is cost. In an automotive aftermarket environment a single rotor would probably cost over $200US. The average person would not see a significant benefit to justify the cost.

The second reason - pads to match up with the rotors are expensive. See item 1 comment about average person.

Last I checked there were some lingering engineering issues such as excessive noise.

Because of the application originally mentioned is more weight driven and the availability of funds is appropriate I figured this might be something to check out. As mentioned I am not completely up to date on all the information but I gave information on where someone could start to find out more.

 

[ZoRG]

$200 is nothing compared to aftermarket steel rotors. And excessive noise can be a selling point in "some" circles. I have a feeling there is a bit more to it than that. That $200 price tag does not sound correct, especially if you factor in diamond tooling. for a disc set on one car you will require 1-2 diamond tips, and 2 - 4 drills. They don't come cheap. Being in the manufacturing industry I can see where this becomes a problem, indexing the cutting tip after every cut becomes very time consuming.

 

[swall]

Aluminum has a higher heat capacity than iron on a weight basis.But since aluminum has only 1/3 the density of iron, an aluminum rotor of the same size will have less heat capacity than an iron one. My recollection is that Duralcan developed a formula that used heat capacity and thermal conductivity to come up with the necessary configuration for an mmc rotor to replace an iron one and offer a weight savings with no thermal penalty.

 

[ZoRG]

As a affordable alternative, have a look at ebay, there are carbon rotors going from $50-$200 US. Just make sure you can get some matching pads.