Pratt & Miller: Faster

It’s two-and-a-half weeks since the number 73 Corvette Racing C6.R took the checkered flag at the 24 Hours of Le Mans, capturing the trophy in the LM GTE Pro class, besting a Ferrari 458 Italia by two minutes, 29 seconds. It’s two-and-a-half weeks since the number 74 Corvette Racing C6.R, after leading its class for almost 16 hours, was put out of the race in hour 17 after being severely damaged in a crash.

And there are the two Corvette Racing C6.Rs, far away from France, largely disassembled in a 100,000-ft2 facility in New Hudson, Michigan, being prepped for another race, this time for the American Le Mans Series (ALMS), in which the cars are campaigned.

In another part of the building there are two other cars (actually, the building is rife with cars, from classic restored vehicles to a 750-hp Corvette C6RS, which began life as a Z06), these for Team Cadillac. They’re CTS-V Coupe racers for the SCCA World Challenge Series.

And there, in still another section of a facility that is almost surgically clean and orderly despite the fact that they’re doing everything in it from machining metal on Haas machining centers to curing carbon-fiber composite body panels in a Jensen Industry oven, is a crew of people working on what will become the Motus MTS sport tourer motorcycle (motusmotorcycles.com), a bike with a 160-hp engine that’s a stressed part of the space frame chassis, a frame that is shrouded with highly styled composite bodywork. They are prepping the bike for its production launch, which is scheduled to occur in 2012.

To get to this place you’ve walked through offices where there are designers and engineers hard at it, working on design and structural analysis for an array of customers, be they commercial or military. (And if they can’t get the necessary analysis done there, they connect with their colleagues at Corvid Technologies (corvidtec.com) in Mooresville, North Carolina, where there is a supercomputer running computational fluid dynamics programs—commercial and in-house developed.)

This is the operational headquarters of Pratt & Miller that Francis W. Wilson, quality engineer, is walking you through. Pratt & Miller has been around since 1989, and has more than proven its capabilities in design, development, and (low-volume) manufacturing ever since. (A company slogan is “Design. Develop. Build. Race. Win,” which encompasses in broad strokes its processes and objective.) It is a place where there is a focus on the competitiveness that can be achieved through doing this quickly, imaginatively, and efficiently. A focus on competitiveness born of many years working with the likes of Corvette Racing.

Wilson, who has been with Pratt & Miller for some 3.5 years, is a mechanical engineering graduate from Kettering University. His focus, he tells you, was on powertrain. Which seems appropriate for a place where there is such a tremendous emphasis on racing. Except for one thing: “The one thing we don’t do is powertrain.”

But they do plenty of everything else, particularly as related to developing winning race cars, as well as doing engineering work for non-automotive customers.

Part of the nature of what they do at Pratt & Miller—the design, develop, and build portions, in particular—for things like race cars necessitates, Wilson explains, a lot of reverse engineering. He cites the inserts for car seats. Unlike for production cars, where seats are designed to accommodate the widest possible portion of potential people, race cars at the level of racing that Pratt & Miller participates in has seat inserts that are tailored to individual drivers.

So to create a seat, they have a driver come in and develop the foam around him. This is then fitted into the carbon fiber seat, then laser scanned. The scan data is then sent to the design office, where, Wilson says, “It gets surfaced a little neater.” Then the inserts are machined from foam. This is repeated as necessary.

Or consider the development of the highly sculpted forms that are created in clay for the motorcycle. The physical model is laser scanned, and then the data is used to create a better, more precise CAD model. Then a mold is machined, and parts produced.

Sometimes they do scans of parts to compare the as-built with the CAD model.

To do the scanning, the Quality Assurance facility is equipped with two FARO (faro.com) Quantum ScanArms (12-ft and 6-ft sizes) that are fitted with V2 Laser Line Probes; PolyWorks software is used along with it. There is a third FARO arm there, as well, an Edge, which is a new product that uses a compact Laser Line Probe for scanning. Wilson is familiarizing himself with the new piece of equipment.

(Speaking of familiarization: the FARO arms are articulated devices that can be readily manually manipulated to scan or dimensionally measure parts. The arm can be fitted with a hard measuring probe or a laser line scanning device. In the case of the laser scanner it has an accuracy of ±0.002 in., a repeatability of 0.002 in., and it captures 640 points per line and has a scan rate of 30 frames per second, which translates into 19,200 points per second.)

“We use the arms a lot to save time. Yesterday, we did four or five reverse engineering jobs,” Wilson says, adding, “A designer could spend hours and hours trying to build a CAD model.” Scanning saves a lot of time.

Asked what they would do without the scanning capability for something like the seats, he says that it would have been done with height gauges and tape and templates and such: “It would probably take weeks.” And weeks aren’t the sort of thing that they have in abundance.

Wilson says that because the arms are portable, they go outside of the QA room into the shop with them. He recalls being under a military vehicle, measuring the chassis, suspension, and inboard mounting points. “It was sort of tough when snaking around control arms to get to a point,” he says with a smile.

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Quickly Creating the Cadillac CTS-V Coupe Race Cars

The development of the CTS-V Coupe race car was performed in less than eight months, starting in June 2010. Because it races in the SCCA World Challenge series, there are rules that must be followed, such that, for example, the body is actually produced in the GM Lansing Grand River plant, where the daily-driver CTS-V Coupes are also built. But unlike the conventional unibody that the less-extreme cars have, in this case there are reinforcements and a race-designed safety cage under the skin, and there is an engine developed by GM but built by Katech Engine Development (katechengines.com) under the hood—a 6.2-liter V8 that actually produces less horsepower (460 hp @ 5,400 rpm vs. 556 hp @ 6,100 rpm)—than the engine in a standard CTS-V Coupe (in order to meet the SCCA regulations).

Two cars were built for the team at Pratt & Miller. In all, more than 6,300 hours were spent in design, and 17,000 hours for fabrication. On July 26 they started to pull clay molds of key components; on September 30 the molds were complete; by October 27 they had their first body. On January 7, the first car was unveiled at the North American International Auto Show in Detroit. Ten days later they ran a test on the second chassis at Sebring International Raceway. The auto show car was back at Pratt & Miller on January 24; it joined the other car at Sebring from February 20 to 21, 2011.

The CTS-V Coupe race car was built at Pratt & Miller for Team Cadillac, which campaigns two cars in the SCCA World Challenge Series. While the car is based on a production model, there were significant modifications engineered by the team at Pratt & Miller.