Motorcycle Classics

Aurora R1010 Rotary Prototype

Robert Smith tracks down the Norton Aurora R1010 Rotary prototype.

It was 2011. I was visiting a cousin in Scarborough, North Yorkshire, England. Knowing I was an old bike fan, her hubby Simon told me of a local friend who owned a unique Norton motorcycle. That was all he knew. I grabbed my Nikon and hurried over.

In the driveway of a brick-built suburban home stood a blue motorcycle with a decal indicating that it had a rotary engine. But instead of the distinctive bulbous outline and generous cooling fins of Norton’s air-cooled rotary engine, I saw water hoses and a radiator. It was, I discovered, the fabled factory development hack “Ten-ten”.

Serial number R1010 was the machine the Norton factory used to develop both its air-cooled and liquid-cooled rotary engines. Presumably, 1010 would have housed the air-cooled twin-rotor engine used to power first the Interpol II and then the naked Norton Classic. In its later iterations, it would have been used to develop the liquid-cooled Commander and even the P55 sport bike engines. But all liquid-cooled Norton production rotaries hid their engine behind expansive bodywork — except 1010. So as well as being Norton’s R&D mule, 1010 is also the company’s only naked, liquid-cooled rotary!

BSA

In 1969, BSA hired Cambridge engineering graduate David Garside to develop a motorcycle engine using the Wankel principle. At the time, rotaries were seen as the way forward in internal combustion engines; and because of their high power-to-weight ratio and compact size, especially suited for motorcycles.

A rearview of a motorcycle

Garside and his team installed a Fichtel & Sachs fan-cooled single-rotor engine in a BSA Starfire chassis. The 294cc engine made 32 horsepower at 5,500rpm, but produced excessive localized heat, which caused distortion, reducing engine life. Sachs had tried routing intake air through the rotor to cool it, but this heated up the incoming fuel mixture, which reduced power. Garside redesigned the intake route, so that intake air still extracted heat from the rotor, but then passed to a plenum chamber to cool.

To move forward with the project, BSA either had to buy a license to build Wankel engines or contract Fichtel & Sachs to build engines for them. Although BSA Group was in dire financial straits, the board of directors voted to purchase a Wankel license from Audi-NSU in the summer of 1972. That license passed to newly-formed Norton-Villiers-Triumph on the government-mandated merger of Norton-Villiers with the BSA Group.

NVT

New Chairman Dennis Poore was a keen proponent of the rotary, and by 1973, Garside’s team had developed an air-cooled, twin-rotor, 588cc engine making around 70 horsepower. The engine was installed in several chassis over time, from a Triumph Bandit to a Norton Commando and a one-off oil-bearing spine frame; but eventually, a new frame was designed with the oil tank (for oil injection) and plenum built into a box section spine.

A blue motorcycle

NVT produced the last Norton Commandos around 1975-1976, meaning they effectively ceased motorcycle production. It was always intended the interlude would be temporary, but the return to large scale manufacture never happened. After NVT’s collapse in 1978, the canny Poore bought back the residual intellectual property including the Wankel license. Garside and his team were installed in new premises in Shenstone, Staffordshire.

Norton

NVT had been working on three interesting designs: a new parallel twin based on the 4-valve Cosworth Challenge engine; the stepped-piston crossflow 2-stroke Wulf; and the proposed Aurora, powered by a Wankel rotary. The Challenge project was stillborn when the bike proved no quicker than the aging Commandos it was intended to replace. And the Wulf was dropped so development could focus on the rotary.

Around 1979, Norton registered a prototype rotary, the P42, code named Aurora. It was fitted with the air-cooled, twin-rotor 588cc engine mated to a 5-speed transmission from a Triumph Trident, mounted in a new frame with Marzocchi forks, Radaelli wheels, Brembo triple disc brakes and Girling shocks.

A closeup on speedometers

By 1982 Doug Hele had rejoined Norton. One of his contributions to the Rotary project concerned rotor shaft bearing failures, which he resolved by reversing the air flow through the rotors, so that with oil injection, the rotor bearings were first to be lubricated instead of last.

In spite of an enthusiastic reception by Motorrad magazine in Germany, which managed to get an unofficial ride on a P42, the Aurora never went into production. Instead, Norton decided to focus on a police bike project. The air-cooled engine and box-section frame, with the same running gear as the Aurora prototype, was developed into the first production rotary, the police-spec P41 Interpol II. Norton had supplied Interpol Commandos to a number of police forces from 1970-on and was well positioned to offer the 588cc Interpol II rotary as a replacement. Around 350 were built between 1984-1989.

Civilian bikes

The first civilian Norton rotary was the naked Classic, built in 1987 in a limited edition of around 100 machines. The Classic was essentially a stripped-down Interpol II with a traditional Norton silver-and-black paint scheme. Feedback from Interpol user forces helped develop a reliable and lively engine, while the engine’s low weight and the absence of the heavy police fairing meant nimble handling.

A motorcycle seat

Dennis Poore died in 1987, and Norton was reformed as Norton Group PLC with a board of investors fronted by Philippe Le Roux. Their bold ambition was to produce a liquid-cooled luxury touring machine based on the Interpol II, as well as a race bike using a tuned version of the same engine. In 1988, an Interpol II with liquid-cooling was introduced; the P52, which was developed into the P53 Commander in 1989. Norton hoped to repeat the success of the Classic with the Commander (see Motorcycle Classics, August 2014), but the machine was criticized on a number of issues: heat rising from the engine; non-quick-detach luggage and other accessibility issues. Testers also disliked the mediocre cycle parts and suspension from the mundane Yamaha XJ900 (such as the non-adjustable Kayaba fork) — not the sporting items one might have expected from the Norton marque. Around 300 Commanders were built.

The ultimate expressions of Norton rotary power on the street were the P55 F1 and P55B F1 Sport models. These were essentially road-legal 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.

A motorcycle engine

The F1 used a Spondon aluminum twin-spar frame, White Power upside-down forks, a Yamaha 5-speed gearbox, and stainless exhaust. Its price in Britain was north of $16,000 when a BMW K1100RS sold for around $13K!
Testers still complained of excessive heat rising from the engine. Norton responded with the P55B F1 Sport with abbreviated bodywork improving airflow. Some consider the F1 Sport the finest of all the rotary Nortons. 66 were built, before Norton’s eternal financial troubles put an end to motorcycle production. In 1992, Norton was in the hands of a manager appointed by its creditors.

The tale of 1010

Mule, hack … development bikes acquire many epithets during their otherwise inglorious careers as factory test beds. Number 1010 is almost certainly the bike that Norton 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 is one that escaped, and when I photographed it in 2011, it was in the caring hands of Norton fan Ian Woolley.

Motorcycle parts.

The story goes that Norton employee Glenn Prentice bought No. 1010 during one of the frequent asset sales. Glenn owned the bike until his death in the early 2000s, when Reuben Fowles bought it from Prentice’s estate. Reuben decided he would try to restore the hack in the spirit of what it could have become. Job done, Reuben sold the revived bike to vintage motorcycle maven Frank Westworth, from whom Ian purchased it.

As Reuben acquired it, Ten-ten had been fitted with a prototype liquid-cooled engine, and the nice Italian Marzocchi fork, Radaelli wheels and Brembo brakes had been replaced with components from a Yamaha XJ900 — items that were eventually used on the Commander. The cable clutch had also been replaced with a hydraulic unit, which never found its way into production.

Rearview of a motorcycle

A new handmade gas tank and seat/tail unit were fitted, and the Yamaha instruments replaced with Suzuki items. The Asahi alloy wheels were slowed with Brembo brakes, though a contemporary four-pot design, and Koni shocks replaced the old Girling units. A Suzuki Bandit half-fairing completed the cosmetics.

But the heart of the bike was the compact liquid-cooled twin-rotor power unit of nominal 588cc making around 85 horsepower. Some might agree it would be better covered up, especially with the large radiator! But it is agreeably technical looking, its unconventional shape draped with componentry, like the two huge, shiny SU carburetors and intake stacks.

Ian pointed 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 ensured the oil level indicator was working OK, to avoid the possibility of catastrophic engine failure.

A motorcycle engine

Ian pressed the starter button and the engine burst into life, sounding like a cross between a sewing machine and a food blender. Evocative it’s not. But it is smooth, as Ian demonstrated by balancing a £1 coin on the filler cap while he revved the engine.

Ian rode 1010 regularly during his ownership, and declared it to be a fine motorcycle. Heat rising from the engine — a major complaint about the Commander — was much less of an issue without the touring bodywork, and the bike handled and stopped well. With 85 horsepower on tap, it went pretty well too. Shame it was the only one of its kind … So where is 1010 now? In 2015, it was listed for sale by Classic Superbikes and shown as sold. But the deal must have fallen through, because it’s also shown as “back in stock.” MC


Brian Crighton and the CR700W

The Norton Rotary story should have ended in 1992. With the company under administration, there was no money for further rotary development. Fortunately, one of the engineers behind the RCW588 race bike, Brian Crighton, couldn’t let the project die. After building a new race bike from a crashed Commander, Crighton continued development of the engine, using more durable materials like Nikasil, molybdenum, and silicon nitride on critical surfaces and the vital rotor seals. A closed gas-filled cooling system was used, combined with an exhaust venturi that drew cooling air through the rotors, rather than relying on the intake air.

A black motorcycle

The result of this development work is the 2021 Crighton CR700W, a 694cc twin-rotor track bike with 220 horsepower at 10,500rpm. The CR700W uses a Spondon frame, Dymag wheels, and top-quality suspension and brake components, while weighing less than 290 pounds.

If you want one of the 25 hand-built CR700Ws, you’ll be shelling out close to $120,000. If you can get one …

  • Updated on Feb 9, 2022
  • Originally Published on Feb 4, 2022
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