Brian Crighton's rotary revival
By Ben Purvis
There have been several efforts to bring rotary engines to bikes - the Suzuki RE5 and Hercules W2000 spring to mind - but Norton's 1980s and 90s efforts shine above the rest thanks to its loophole-exploiting race successes.
Norton's rotaries scored British superbike titles and a memorable TT win, with Steve Spray, Trevor Nation, Ian Simpson and of course Steve Hislop all winning on board the machines. The 588 cc Wankel rotaries in the company's RCW588 and F1 racers offered huge straight-line performance advantages over 750 cc four-cylinder, four-stroke rivals thanks to the difficulty in establishing an effective equivalency formula in racing. Engineer Brian Crighton was the brain behind those rotaries and now his own name is appearing on a spiritual successor to the machines.
The Crighton CR700W looks very much like the last rotary Norton - the NRV588. Intended to race at the TT in 2009, and itself a direct development of the 1990s machines, Crighton was behind that bike. Freed from the need to comply with racing rules, his CR700W is probably the most powerful rotary bike that the world will ever see.
Its heart is a 690 cc twin-rotor engine, designed by Crighton for Rotron Power, which makes a variety of Wankel engines for use in aircraft, drones and other applications. Incorporating all the knowledge Crighton has gained from previous efforts, in uses innovative cooling solutions and materials to help solve the problems of apex seal wear that dog traditional rotaries. Power is rated at 220 hp at 10,500 rpm, with 105 lb-ft of torque at 9,500 rpm, from a tiny engine with just three moving parts. It's just 34 cm long, 24 cm in diameter and weighs a mere 24 kg, or 43 kg when the bespoke six-speed transmission is fitted.
With no need for road-going kit, the bike itself is incredibly light, too. The frame follows the same extruded alloy Spondon design of the 90s racers, while the bodywork - which mimics the NRV588 - is carbon fibre, so the whole bike is just 129.5 kg dry. Carbon fibre Dymag wheels help keep the mass to a minimum, while customers will be offered a choice of Öhlins or Bitubo suspension.
Crighton himself, now 73, will hand-build the bikes at the Rotron factory, and just 25 are due to be made. Unsurprisingly, they're expensive, with a starting price of £85,000
(€ 100,000).
Crighton said: "In so many ways the CR700W is the culmination of my career's achievements. Developed with my excellent lead engineer, Shamoon Quarashi, it encapsulates the absolute best of my engineering wisdom. And I believe the result is the ultimate track and racing motorcycle."
Alex Head, CEO of Rotron Power, adds: "The CR700W is a unique motorcycling masterpiece and a true work of art, born out of Brian's passion and genius when it comes to creating extraordinary engines and race bikes. It is more powerful per cc than any other normally aspirated engine in the world, with a greater power-to-weight ratio than the Aprilia RSV4, or even the supercharged Kawasaki H2R.
"The performance speaks for itself, yet despite the numbers it is far from a highly-stressed racing engine that needs rebuilding after every race weekend, and instead, thanks to its low-revving design, ultra-low friction materials and unique internal geometry, it is resoundingly robust and reliable, and will run a full season before requiring internal inspection. There are few machines as exclusive, with performance and uniqueness to match."
