A Visit To The Factory
I made my first trip to the U.K. for the Bonneville project in the summer of 1998, sitting down with Vaughan and Clifford as they brought me up to speed on the bike's progress. We looked at sketches, at Mockett's styling prototype, and discussed various elements of the project such as the type of power delivery Triumph wanted and such items as steering characteristics and suspension/ride qualities. Although the project was only little more than a year old, Clifford had already compiled a folder full of notes. In fact, Clifford acted as my eyes and ears while I was in Los Angeles, keeping me up to date on the bike's progress. He was a major help.
Summer and Fall, 1998
Styling Reviews, More Testing
Mockett's styling prototype was hugely important because it showed Triumph engineers and stylists how successfully (or not) their computer-aided designs translated to metal, plastic and rubber. Some, of course, didn't translate well. The initial frame design, for instance, was deemed aesthetically unfit for the look they wanted, and was scrapped for a slightly different cradle-style unit that was both stronger and more aesthetically pleasing. Shortly thereafter the Mockett prototype was shown to a slightly wider audience, who agreed on several changes already being considered by the styling team. These included changing the mufflers to the original "peashooter" design (a tricky packaging job), tapering the barrels to give the engine more of an "original Bonnie" shape, tucking the headers in slightly more, giving the front fender T120-like struts, redesigning the seat with a less-pronounced step, and revising the instruments. These changes gave the new Bonnie the basic look it'd have right through to production.
Toward the end of 1998 chassis testing heated up. Using a Euro-spec twin-cylinder bike from a competitor as a donor bike (a shortcut that significantly cut development time), engineers cut and re-welded its frame to mimic the exact geometry they'd decided on, then added the pegs, wheels, suspension, swingarm and handlebar they proposed for the Bonneville to replicate the rest of its (eventual) chassis setup. A key design brief was that the machine had to be "light, agile, and corner well." Rigorous testing showed the desired geometry to be spot-on; the bike was stable and secure at speed (much more so than the T120 they tested alongside it), yet still offered reasonably quick steering. (Although significant to the new Bonneville's story, the chopped donor bike was apparently very, very ugly. Clifford's resistance to my repeated requests to see or photograph it is probably quite telling as to just how homely it really was!)
Things heated up on the production side also. The chassis and engine teams were already at work compiling what are called "engineering lists," which detail the exact parts needed for the building of prototypes and, eventually, actual assembly-line production. From these and their blueprints would come "bills of labor," which assist the team in the costing and production of every single part of the motorcycle. My mind went numb when Clifford lead me through this process; I remember marveling at the complexity and cost of it all-and the huge potential for screw-ups.
Engine And Chassis Teams Rev Up
The engine team-now seven engineers strong-was moving especially quickly, and due to more than simply the projected December 1 date for initial engine start-up. Like the TT600, the Bonnie would use high-pressure die-cast crankcases, which are more consistent in terms of surface finish and quality than the sand-cast cases used on previous Triumphs. Problem is, HPDC cases are horrifically expensive to produce (a single die-casting tool costs about a million bucks), and have a lead time of well over a year. So it was vital the engine team get its engine testing done (using CAD program models to simulate dynamic testing) and finalize the crankcase design so the production of HPDC tooling could begin.
At this point, the design of nearly every component had been settled on, and prototype parts were arriving throughout the fall and early winter. The carbureted, air/oil-cooled vertical-twin would displace 790cc and use a centrally located cam chain to spin its double overhead camshafts (via a Suzuki TL-type hybrid cam drive for compactness), which in turn would move a pair of intake and exhaust valves per cylinder. Dual balancers were used as the engine was designed as a stressed frame member, and the transmission came straight from the company's six-speed triples, though with fifth gear blanked off, making the Bonnie a five-speeder with an "overdrive" cog. "We fit a lot of modern engine into a fairly compact space," Clifford told me. "It was a packaging nightmare; we'd wanted a dipstick but had to use a sightglass as there was simply no room for it!"
The first Bonnie engine ran on December 15, 1998, with little more than a few carb-jetting hiccups. The team-all of Triumph, really-was stoked. Initial engine testing then began, the teams first running the original prototype engine then others through all manner of timed-running and teardown/check phases. There were a few glitches, though nothing surprising. Endurance testing came next: The engines were run hard for extended periods of time, then torn down to check for wear and/or failures. The main changes made before committing to HPDC tooling production were minor: the countershaft sprocket was moved 3mm inboard (to help with peashooter-exhaust packaging), and the crankcase clamping design was altered for improved sealing.