I plan on taking the hot rod to some Drivers Edge events once a little more chassis work is done. Since I'm building the brake system this week, my little mind wandered over to the SLR we've got in the shop.
I took a little peek to see how McLaren did the brake cooling. It's pretty impressive.
What surprised me was the effort put into cooling the pads and caliper. I've seen lots of systems that put air on the rotor but never one concentrating this hard on the pads.



You can see that McLaren had serious concern about the heat generated due to the shielding on the brake hose and wires.



They did duct a little bit of air into the center of the rotor (small ducting) but it's only a fraction of the size of that duct heading towards the caliper. Notice the heat shielding this time on the tie rod. They also shielded with lower ball joint with a closed knuckle.





Is it common for the hard core racers to put this much concern into cooling the caliper and pads? Do you think it stems from the rotor and pad material? I don't remember the Champ cars and American LeMans cars having that kind of setup.
The rears have similar duct work but it's not nearly as heavy. The air is drawn from scoops in the under body paneling near the differential cooler.

I recall the problems that Ford originally had with the GT40 in the 60s. They were killing rotors at an alarming pace. It turns out that the cooling air was too cold. They diverted hot air from behind the radiator across the brakes and that solved the problems with rotor failure.
One of my friends with a street/track Supra had a problem with too little caliper/rotor clearance on his Supra during the One Lap of America. The rotors grew with the heat and rubbed the caliper. That caused more friction and ended up boiling his brake fluid at the end of a long straight. That very nearly became ugly. Once the brakes cooled down, the rotors shrank a bit and the problem was resolved. They self-clearance and he had no further problems through the remainder of the One Lap.

What do you see on the track day cars you run with? I recall you mentioning brake cooling in a recent post. That made me think of the '99 - '02 CLK55 rotors for our cars and ended up with me under the SLR thinking about my hot rod.

 

Also the SLR's wheel rim spokes are designed like an impeller blade, which also helps evacuate heat from the rotors.

 

Feets: That's serious race car stuff there... It looks like the set-up that my buddies have on their GT3 Cup cars. http://www.arlanmotorsport.com It is common on sports racers since many of them run enduro events (4 hours +) Take a look at a GT or DP class car that runs with ALMS or IMSA and you'll see some very tricked-out systems similar to that SLR... But you're talking about a braking system that runs upwards of $15,000...

It is a necessary evil though, especially for enduro events... If you have ever watched any of the 24 hour races on TV when they get into the night time broadcast you can see these cars zipping by with big red-hot brake rotors that glow in the dark bright red...

 

I was checking out the ALMS cars (GT and Protoype) at the Grand Prix of Houston but don't remember that much concentration on the pads/caliper. I thought most of their stuff was focused on the rotor.
I do enjoy seeing the rotors glow at night. That's just another fun part of the race. I'm also a junkie for the suspension cameras.
Upwards of $15,000? The SLR rotors are $12,000 each. The front pads are $2,400 for the set.

 

yeowza

 

Any of the SLR cooling ducts work on the Crossfire... rotor duct(s)? I know there's plenty of space in the bumper to work with along with plenty of space deep in the wheel well too... just a thought.

Nice shots by the way "feets"

 

I didn't even look at that. It would not be an easy swap I'm sure.

 

There is plenty of room in the bumper but it gets tight for the ducting, especially on the side with the AC accumulator (your driver's side) Here's what I have been doing in this area...

Brake Ducts

 

Interesting to note that the SLR has the calipers on the rear of the disc and the Crossfire has them high and in front.

Also, note that the SLR is taking air from the radiator/front cowling area and not the front corners. I suspect they are getting much higher airflow in that location.

Hmm...

 

Looking at that SLR cooling setup as opposed to those on a pure racing setup, they seemed to have made alot of effort to enclose the airflow. I think this may have more to do with controlling the carbon dust blowing all over the place, and possibly to prevent undesirable aerodynamic affects - just a thought.

 

Yes, I found that I had to modify my inlets from a round entrance following the curve of the valance, to one with a lip at the outer edge to getter better flow. In the corner foglight location I was finding the air is moving across the surface rather than into the port.

 

GREAT WORK WOODY! The only thing I want to do differently is... I want to use the openings on the bottom of the SRT fascia, instead of using the fog light holes. Only problem is I have no idea where/how to get someone to help fabricate it properly... without resorting to "duct" tape (get it "duct tape"). Ok whoa that was corny.

Thanks for your pics woody they really gave me a better understand on the path(s) I should take.

 

The positioning of the calipers seems to be more of a "put it where it fits" thing than anything derived from physics. They tend to be all over the place.
However, when you're dealing with these monsters, you put 'em where they fit. My new calipers are the same as those and I had to put 'em in the same place.

The duct work pulls from a dedicated opening in the front fascia. It's got a pit of a funnel shape to prevent air from spilling out and across the front bumper.

 

Yes, the front fascia would be the best place as it gets more direct air and the funnel part would definitely help with the air flow to the actual brake pad area.

I would presume it's in these areas?



Thanks for the feedback Feets!

 

Look carefully at the passenger side lower grille opening. You can see a partition behind the screen. The outboard side ducts the air to the brakes. The inner portion hits the radiator/condenser/intercooler/oil cooler conglomeration in the front of the car.

The thin slots in the bottom of the cover are simply decorative and are actually blocked.

 

Have you ever seen a car with an alternator/windshield wiper motor cooling fan?

They stuck one on the SLR.

 

Re-examine your diagram Feets... looks as if the windshield wiper motor is simply in the same diagram with the radiator, radiator mount and cowling.

Nice try though...

If you look up those other items I bet they are as I described above.

 

I have looked. At the car. It is indeed a cooling fan for the alternator and windshield wiper. It had to come off the car for an alternator swap.
The car left today otherwise I'd get a pic for you. We still have the black one on the showroom but I don't know how happy they'd be if I popped the hood and started playing around with it. They're kinda protective of the $457,000 jewel despite it having slammed a curb and destroying all 4 wheels and tires. Kinda hard to sell one with that kind of disclosure on it.

You'd be surprised at the stuff they're doing. Have you ever seen alternator gaskets? Yep! that's right! Alternator gaskets. The V12 motors have water cooled alternators. I can nab a pic of that screen when I get back to work tomorrow.

 

Wow, that's crazy... I would have never believed it otherwise. No wonder the car cost half a million... WAY over engineered!!!

 

It certainly is a fine piece of engineering! Our company has a monitoring system at the Mclaren Headquarters in Working where they build them, but I've not been able to find an excuse to go there. I do visit their race engine factory quite a bit though - the place is like an operating theatre! Andrew would be very much at home there.

Here's an interesting short clip from Martin Brundle's Supercar vid shot before they really got them into production:
SLR Video (8MB)