Mules” lead lives of inglorious servitude so that fully-developed production bikes can go on to bigger and better things. This is the story of Ten-Ten, a Norton prototype mule that finally found the kind of loving, caring home it truly deserved.
Ten-Ten: Not just another hack
Though Norton ceased motorcycle production in the mid 1970s, they always intended the interlude would be temporary. The company had been working on two interesting designs: a new parallel Twin based on the Cosworth-designed DOHC, four-valve Challenge engine; and the Aurora, powered by a Wankel rotary. The Challenge project was stillborn, especially when the race-bike version proved no quicker than the ageing Commandos it was intended to replace. That just left the rotary.
The BSA Group had purchased a Wankel licence from NSU in the 1950s, but had never capitalized on its investment. The intellectual property rights passed to Norton-Villiers-Triumph when that company acquired the remains of BSA around 1972. The rotary engine project was tasked to one of the British motorcycle industry’s most talented development engineers: Doug Hele. Hele developed the Daytona-winning 500 Triumph Twins and 750 triples as well as the first Bonneville to lap the Isle of Man TT circuit at over 100 miles per hour.
As early as 1979, the company registered a Norton prototype P51 Aurora rotary fitted with an air-cooled, twin-rotor engine of nominal 583cc capacity. (Then as now, the swept volume of a rotary engine doesn’t correlate well with conventional engines, leading to a 40 per cent capacity handicap in some racing formulae. That would make the Norton equivalent to around 1000cc for a conventional four-stroke.) The engine was mated to a five-speed transmission based on a Triumph Trident unit and mounted in a new frame with Marzocchi forks, Radaelli wheels, Brembo triple disc brakes, Girling shocks and a neatly integrated tank and seat/tail unit.
In spite of an enthusiastic reception by one influential magazine in Germany that managed to get a ride on a P51, the Aurora never went into production. Instead, Norton decided to focus on the P41, a police-spec bike introduced in 1984 using the air cooled engine and sold as the Interpol 2. A limited-edition version of the air-cooled civilian bike was eventually sold around 1987 as the Norton P43 Classic.
Excessive heat output—always a problem with rotary engines—led to the development of a liquid-cooled motor to power the 588cc P52 Commander, a fully-faired touring bike. The ultimate expression of Norton rotary power on the street was the P55 F1 and P55B F1 Sport models of 1989. These were essentially street versions of the RCW588 race bike that Steve Spray rode to the British Formula 1 championship in 1989, and Steve Hislop used to scoop the 1992 TT. But by 1991, Norton was in the hands of a manager appointed by its biggest creditor, Midland Bank, and motorcycle production ceased.
MULE. HACK. DEVELOPMENT BIKES acquire many epithets during their otherwise inglorious careers as factory test beds. Number 1010 Norton prototype is almost certainly the bike the company used to try out the power units and equipment that would eventually find their way on to the production bikes—if a total of fewer than 1,000 bikes across all models counts as “production.” Mules usually end up in the junk yard or broken up for parts. Number 1010 (Ten-Ten) is one that escaped, and is now in the caring hands of a Norton fan in Scarborough, North Yorkshire, England.
The story goes that Norton employee Glenn Prentice bought Ten-Ten Norton prototype during one of the frequent asset sales. Mr. Prentice owned the bike until his death in the early 2000s, when Reuben Fowles bought it from Prentice’s estate. Mr. Fowles decided he would try to revive the hack in the spirit of what it could have become.As Fowles acquired it, Ten-Ten had been fitted with a prototype liquid-cooled engine, and the nice Italian fork, wheels and brakes had been replaced with components from a Yamaha XJ900 Diversion—items that were eventually used on the Commander. The cable clutch had also been replaced with a hydraulic unit.
A new hand-made gas tank and seat/tail unit is now fitted, and the Yamaha instruments replaced with Suzuki items. The Asahi alloy wheels are once more slowed with Brembo brakes, though now a modern four-pot design, and Koni shocks replace the old Girling units. A Suzuki bandit half-fairing completes the cosmetics.But the heart of the bike is the compact liquid-cooled twin-rotor power unit of nominal 588cc making around 85 hp. Most would agree it would be better covered up, especially with the large radiator attached. But it is agreeably technical looking, its unconventional shape draped with componentry, like the two huge, shiny SU carburetors and breather stacks.
Mr. Woolley points to a toggle switch mounted in the dash. It’s used to test the oil level warning light: as rotary engines use a total loss lubrication system, the oil level falls during riding. So the test switch ensures the oil level indicator is working okay, to avoid the possibility of catastrophic engine failure.
Woolley presses the starter button and the engine fires into life, sounding like a cross between a sewing machine and a food blender. Evocative it’s not. But it is smooth, as Woolley demonstrates by balancing a £1 coin on the filler cap while he revs the engine.
The good news is that he rides Ten-Ten Norton prototype regularly and declares it to be a fine motorcycle. Heat rising from the engine—a major complaint about the Commander—is much less of an issue without the touring bodywork, and the bike handles and stops well. With 85 hp on tap, it goes pretty well too. Shame it’s the only one of its kind.
– Robert Smith, Oct.Nov 2011 (issue #276)