Most engineers like to use finite element analysis software to test parts models they design. Racing engineer John Calhoun goes a big step further: He runs his vendors design FEA on the 3D parts models . It's a novel strategy he thinks more engineers should use to save time and ensure performance.
"Instead of asking for a sample of the part, I ask for the solid model," says Calhoun, of Charlotte, NC-based Roush Yates Racing Engines (formerly Robert Yates Racing). Then he and his teammates add the loads they expect the part to see and do FEA runs to see if it will withstand the stresses encountered on the race track. He uses COSMOSWorks and COSMOSMotion for the analyses. "If the analyses point out problems, we make the required changes, send the model back to the vendor, and ask him to manufacture the part according to our model," he says.
Use of CAD, FEA, and PLM are nothing new in racing. Virtually every auto-racing team uses software as a key design tool throughout their engine- and chassis-development process. And many parts vendors will send racing teams the numerical results of their own analyses, along with the components they are supplying. But Calhoun's strategy of using FEA on the actual solid models of parts his vendors would like to supply appears unique. It's a process he believes ensures optimal design. "Many engineers actually do request models from vendors, but they drop the request when the vendor refuses," Calhoun asserts. He doesn't drop it. "If one of our vendors doesn't want to send the solid model, we tell him we can't do business with him," he says.
To be sure, it may be difficult to convince every vendor that such a practice is good. "It all depends on your relationships," Calhoun says, and on your ability to convince the vendor that you have no intention of competing with him by manufacturing the product yourself or sending the model to a third party to manufacture it. But it's a practice that can pay big dividends, as Calhoun has discovered countless times.
Collaboration is Key
Take the case of the defective "dog ring." It's a perfect example of how both a vendor and a customer can benefit by collaborating to improve a critical component.
Deceptively simple in appearance, the 3-inch-diameter disk has teeth that engage in the transmission every time the driver shifts into a new gear. While at most oval tracks shifting is at a minimum—usually only when entering and exiting the pits—some races on the NASCAR schedule where the tracks require frequent shifting, which makes dog-ring performance critical. "Every time the driver shifts, the dog ring slams into the new gear," Calhoun says. If the driver shifts with a smooth motion, the "slamming" will be gentle and won't damage the teeth. If the driver is a rough shifter, the teeth could wear fast and not engage. And if the gear isn't designed properly for the racing environment, it won't matter whether the driver is smooth or rough—the constant shifting in a race will batter it. "The dog ring doesn't enhance performance," Calhoun says, "but if it doesn't work right because it's prematurely worn, it will kill your chances in the race."
The racing team had seen some dog-ring problems earlier. So, Calhoun asked Indianoplis-based EMCO Gears for the solid model of its dog ring so the RYR team could run its own tests. Seeing an opportunity to partner with its customer, EMCO sent Calhoun its FEA model of the part, which had performed well for the preceding five years. Then, Calhoun and his team added their own loads. "We did our analyses and found that the part wasn't optimized for the loads we expected it to face," he recalls. So he and his team, which does its CAD modeling with SolidWorks, re-modeled the part, reducing the stress by 20 percent while adding only 1.6 ounces of weight. EMCO accepted the redesign, manufactured the part, and the RYR team used it in its next race. The part worked so well that the team shared the design with other teams, who also started using it.
And, EMCO included the redesigned part in its catalog.
Path to Perfection: The original model of the dog ring, left, worked well for five eyars, but new race conditions caused failures. But failured didn't occur in the radius where vendor EMCO's analysis indicated was the highest stress. It occured between the "dogs" and the crack propagated radially from the root of the spline. EMCO's redesign, center, used a pocke connecting the dogs and added material above the spline between the dogs. Based on its own FEA, the RYR team further redesigned th epart, right, reducing stress by 20% while adding only 1.6 ounces.
Calhoun and the Roush Yates team use a similar strategy in the design of other components for their racing engines, including bracketry that holds alternators and power steering pumps, as well as valve train components like rocker arms, retainers, valve tray cover plates, and connecting rods. Some of those parts the team designs itself with SolidWorks. For others, as in the case with the dog ring, they run their COSMOSWorks analyses on the vendors' models.
Ready to Rock: Joe Gibbs Racing uses I-deas NX Series software for design and analysis. This engine model was scaled down for wind tunnel testing.
COSMOSWorks is written to work with SolidWorks. What if the vendor does their design in a software package other than SolidWorks? No problem, says Calhoun. "All we want is a solid model, so we'll ask for a STEP file or a Parasolid file that's accurate on material properties and shows us the end result of the machining process." Their goal is to increase RPMs and horsepower without cutting strength, he adds.
It's a win/win, says Calhoun. He and his race team get an optimized part they feel comfortable with, and the vendor gets the advantage of their design services—for free.
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