Motorcyclists I’ve Known Who Have Been Practical Problem-Solvers

The late Don Tilley, whose big Harley-Davidson shop was in Statesville, North Carolina (the capital of NASCAR engineering), told me that the most fun he'd ever had was traveling with moonshiners and having to spend a long night being perfectly quiet in a car lost in tall corn. Although not many years older than myself, Don had the dignity of an old-time rural grandfather, and I therefore instinctively called him "sir."

When the AMA’s Harley-Davidson 883 spec roadracing class came into being, nearly every Sportster engine on the track smoked during braking for corners. But not the engines Don built. When Detroit needed the special knowledge—not available in any engineering school—of Smokey Yunick, they sent a company jet for him. Don Tilley, too, was summoned but to Milwaukee. “Those engineers don’t much like talking to a fellow like me,” he said afterward.

When I once asked him about the sometime drag-race practice of drilling holes down from a piston’s crown into the crevice above and behind the top piston ring, he said, “If you make 12 of those little holes like that, that top ring will just bore out the top inch or two of the cylinder from the extra friction. All you want is enough pressure to hold the ring on the bottom of its groove. Anything more than that just adds friction.”

Tilley went on to explain that the vertical clearance of the top ring in its groove is chosen to control the rate at which combustion pressure "inflates" the ring. If pressure enters the ring backspace too slowly, the ring's inertia as the piston decelerates near TDC will lift it off the bottom of its groove, causing its seal to collapse. If pressure enters too rapidly, the ring is pressed outward against the cylinder wall hard enough to generate significant extra friction.

Every conversation I had with Don Tilley had at least one such nugget of deep understanding about some subject I had never thought of.

Another reason to be there was the company Tilley kept. I had met former Harley-Davidson racing manager Dick O’Brien before, but the relaxed atmosphere of Tilley’s Daytona garage gave his conversation an unexpected depth, talking candidly about the flathead KR and its problem with wet sumping. And otherwise I would never have met Yunick, who reckoned a major reason he survived the war was that he and his B-17’s crew chose to do all the maintenance on their airplane themselves—self-defense. Yunick was experimenting with HCCI (homogeneous charge compression ignition) before automotive engineers had even given it its present name.

I met John Britten in his Daytona garage shortly after he and his crew had arrived in a daze from New Zealand, halfway around the world. The bike they’d built (yes, pouring the crankcase in sand molds) would become an important reason why the world would soon see big high-revving twins as a legitimate challenge to the ruling four-cylinder bikes from Japan. John and Homer Knapp were pulling fascinating parts out of their pockets and talking enthusiastically about them. “I wanted to know what rod ratio to use so I thought, ‘This con-rod from a Cosworth DFV works well in Formula 1,’ ” he said as he pulled an F-1 rod out of yet another pocket, “so I gave mine the same 1.8 ratio.

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“I like to work from first principles,” he announced to no one in particular. I would see that in spades on his future visits, when he displayed what he had learned about carbon fiber in making his bike’s frame from it, then plunged straight into making carbon wheels. He and his merry men had created and programmed the engine’s electronic fuel injection. Using a famous 20-mile stretch of straight road in New Zealand, they had tackled motorcycle aero drag in a radical but successful way: finding a higher top speed with no lower fairing at all but with the very minimum of frontal area. It seemed that whatever problem he addressed disassembled itself for him into clearly understandable parts. Complex things were clear to him.

I had encountered Ian Gunn previously and knew he was a Ducati enthusiast and amateur racer. I did not know that he was the creator of the Gunn diode—the “microwave source on a chip”—during his time at IBM’s Watson research lab. At Daytona, he told me a story that revealed a lot about common sense and its relation to engineering.

One day, he was minding his business in his office when some engineers tapped on his door. Seems they’d been assigned the task of speeding up the search time of a computer disc drive but seemingly had no idea how to begin. One of them had seen Gunn doing something to his motorcycle in the parking lot and had reasoned he must know something about practical things. So here they were. Gunn explained that he wasn’t a mechanical engineer by training, but that he’d be happy to look at their problem.

The read head in such drives is at the tip of a pivoted arm, which can sweep it across the surface of the rotating disc to read or write data from its many tracks, much like the tonearm of a record player. The problem was to make the arm move faster. The read-head arm that the group had built for initial testing was of constant cross-section. It was obvious to any practical person that such an arm had too much of its weight at its moving end; look at a horse, whose legs taper all the way to the fast-moving hooves.

Taking a bit of paper, Gunn drew a tapered arm of thin sheet metal, whose edges had been flanged up to stiffen it, lightened by a series of holes of decreasing size. The engineers were seemingly delighted by this and rushed off to get to work. A few weeks later, the tapping on his office door was repeated, and the disc drive group announced that the drawing on the bit of paper had been the key to meeting the read-time goals set for the new drive.

“That short conversation established me as some sort of mechanical wizard,” Gunn said, “and thereafter I was brought all kinds of problems outside my education.”

Motorcyclists have to be practical problem-solvers, and Ian Gunn, the distinguished physicist, was also a motorcyclist.