Chris Nachtmann's introduction to machining was at his parents business, where he had worked, off and on, since childhood. At the same time, he was getting exposure to drag racing from his father, a life-long participant of the loud, heart-pounding sport.
Nachtmann's inherited love of drag racing and its mechanical aspects led him to become a clutch specialist for Alan Johnson's Top Fuel team from 1997 to 2002.
Later, while running his parents' business, he tinkered with clutches. To handle new jobs for the company, he learned NC programming with the aid of GibbsCAM Production Mill.
"It was easy to learn, and helped me save the business," acknowledges Nachtmann. "I learned to model and machine everything with wire-frame geometry and really cranked out parts."
Although he had mastered GibbsCAM quickly, he waited for the opportunity to use it for a clutch design that would address the "plague of clutches."
Nachtmann faced a high-tech plague. First, the 8,000hp engine's change in rpm caused the standard titanium pressure-plate covers to deflect, showing measurable "dishing" of as much as 0.050" in 10 to 15 runs. Nachtmann knew that covers required greater rigidity, and that adding thickness and support ribs would solve the problem.
Second, an old track myth dictated that "memory" induced warp in titanium. That was one of the metal's characteristics Nachtmann wanted to investigate. He worked with a metallurgist for three months. They dispelled the blame on memory and, together, developed a high-temperature alloy much stronger than the titanium in standard use.
In 2003, when a racing team approached Nachtmann to develop a clutch, he was prepared. He modeled the clutch in wireframe geometry.
"Just lines, arcs, and toolpaths with GibbsCAM Production Mill" he says. "It worked great, and it got my ideas on the track. After 300 runs, our covers show warping of two thousandths or less."
Of the components he has made, Nachtmann says, the pressure plate cover was the toughest. "There are lots of pockets, radii, and tight tolerances to making the fibs, and the lever-slot depth is really critical. If it's different from cover to cover, the levers will sit higher or lower. A tiny difference will change or disable clutch performance and cause the dragster to 'smoke the tires at the hit' of the throttle."
As "the clutch guy" on Johnson's crew, Nachtmann hated unpredictable performance. "That's why I'm meticulous in maintaining lever-axle depth across...