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I was a wilwood R&D Engineer for 2 years and have been crew in many forms of racing for over 20 years. After wilwood I spent 7 years in R&D with ecomotors.com. Keyboard warrior I am not.
I guess we're both laughing. No known metal rotor has those holes cast into them, even if they are those with cast-in holes they are still stress risers. If nothing else, review "Engineer to Win". That they were drilled as opposed to being formed by some other method is a small part of the total picture. Anything that changes the stress flow path or disrupts it is a stress riser.
As a metal working guy far too familiar with Mercedes rotors, I can tell you they were cast into the rotor, not drilled afterwards. If not, they had to be acid etched to get the cast finish inside the holes. Mercedes is also very proud of their rotors having the holes cast into them. Perhaps some 2 year brake engineer can humble the entire Mercedes Benz engineering staff but somehow I doubt it.
So, tell me how much R&D went into those cars I showed. I bet some of them received more extensive research than Wilwood did in the 2 years you were there.
If you were involved in racing for 20 years you should be familiar with the discoveries made during the Ford GT40 testing. They were fracturing rotors due to over cooling. The fresh air ducts were killing the brakes. Once they routed heated air from behind the radiator to the brakes the failures stopped.
That's a prime example of the real world pulling out surprises that engineers didn't consider.
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As previously stated, drilled rotors are put on those cars for the buyers, because they think they're cool. Not because they're a better solution. Marketing trumps Engineering & Science every time. So those rotors prove nothing about actual performance. Can you prove that those cars set their high water marks wearing drilled rotors? We all know that they're sold with them, proves nothing. Most real Engineers have a bit better grasp of things than keyboard engineers.
Surprise! I'm one of the guys who said drilled rotors are used because people think they're cool.
We all know that "real engineers" get their butts kicked by marketing on a regular basis. Keep spouting off with the whole engineer bit. I know a TON of engineers (worldwide) and can tell you some of those guys can't engineer their way out of a wet paper bag.
Frequently, "engineers" get caught up in minutiae. For the engineers out there, that means trivial stuff.
They go and go and go until they can't go anymore. They're measuring carbon content to the angstrom and studying the temperatures at which the base material goes from a plastic state to the liquid state despite the fact that you never want your product to get there.
Yes, all holes in rotors are stress risers.
Can you spot the stress risers in this pic?
If you said the vent holes, fastener holes, and contours around the fastener bosses you'd be partially correct.
How about this one?
See all of those slots? Those create fracture points that can not only move laterally but also across the width of the rotor by originating at the bottom of the cut.
ALL rotors have stress risers. You simply ENGINEER around them. Know that some tool paths will lead to more prevalent points of failure. Cutting will generally lead to an easier failure path than proper forming the features while casting.
You don't have to be a great engineer to know that metals have stress. All you have to do is measure a piece of flat cold rolled steel, cut into one side of it and measure the piece again. You will see deflection in the part due to stress in the steel introduced during rolling.
All formed structures are going to have some sort of stress. That stress is always looking for a way to get out. A good engineer will find the shapes and manufacturing processes that limit the failure rate of the finished product. Once you push that far away from the product's intended use it's time to call it done. In brake rotors you can limit the failure rate but you can't prevent it.
Pull the feather out of your engineer's cap and realize that other people sometimes know what they're talking about.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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