RO­TARY STUN­NER

New Crighton boasts 200bhp & 136kg – hold tight!

Motorcycle News (UK) - - This Week In Mcn - By Jor­dan Gib­bons Ad­di­tional re­port­ing by Mick Duck­worth

When Nor­ton launched the ro­tary-en­gined RCW588 in 1989 it took the rac­ing world by storm. De­spite be­ing a small oper­a­tion the firm won the Se­nior TT in 1992, took the BSB cham­pi­onship in 1994 and lap records across the land fell like au­tumn leaves. Now the man be­hind the project, Brian Crighton, has re­turned with a 200bhp track weapon.

The new bike will be built in part­ner­ship with Rotron, a ro­tary spe­cial­ist where Crighton works in R&D. Af­ter an in­jec­tion of fund­ing, the in­ten­tion is to pro­duce 100 of these feath­er­weight pow­er­houses in track trim, with a road-go­ing ver­sion to fol­low.

The smooth-spin­ning heart of the bikes, dubbed the CR700P, is a 700cc twin-ro­tor en­gine, which pumps out 200bhp at 11,000rpm and has a peak torque of 110ftlb at 9500rpm. The en­gine cast­ing is taken from the Nor­ton RCW588 race bike, but Crighton has made sig­nif­i­cant changes.

“The ro­tor hous­ings on the 588 were 62mm wide but these are now 88mm wide, which takes it up to 700cc,” says Crighton. “I didn’t want to make the en­gine wider, so I took the space from in­side by mak­ing the in­ter­me­di­ate plate much nar­rower, which has given us a big­ger dis­place­ment en­gine that’s only 3mm larger.

Clever cool­ing

“This is built with a pro­to­type en­gine us­ing the Nor­ton end cas­ings. For pro­duc­tion we’d have to make our own, so I thought we might as well de­sign our own en­gine. The new one will have gear drive in­stead of belt and I’ll shorten the en­gine with a stacked gear­box. There are also some big changes to the cool­ing sys­tem,” he re­veals.

Disco in­ferno

With all ro­tary en­gines, the ‘pis­ton’ has no con­rod, so it sits in­cred­i­bly close to the main bear­ing, which in turn trans­fers a lot of heat to the bear­ing, which is hard to cool. While the CR700P is kept cool by a turbo that blows air through an in­ter­cooler un­der the seat, a new de­sign will al­low Crighton to wa­ter-cool the in­side of the crank­shaft, which will bring the tem­per­a­tures down con­sid­er­ably.

“It also in­creases the life­span,” says Crighton. “We’ve ac­tu­ally had an en­gine run­ning non-stop for over 1000 hours, day and night. That’s the equiv­a­lent of fly­ing around the world twice.”

The other prob­lem has al­ways been with emis­sions and oil con­sump­tion. The ro­tor tip seals are made from steel, so oil has to be mixed with the fuel to lu­bri­cate them. While this isn’t a prob­lem for a race bike, it’s a big prob­lem for a road bike and could make meet­ing emis­sions tar­gets dif­fi­cult, but Crighton has a way around that too.

Whitham: ‘It’s quick!’

‘We’ve had an en­gine run­ning non-stop for over 1000 hours’ BRIAN CRIGHTON

“I can’t say too much but we’ve de­vel­oped a new coat­ing to go on the tip seals that barely needs any lu­bri­ca­tion at all. In fact the petrol is enough of a lu­bri­cant and that re­ally cuts down on the oil prob­lem. As for emis­sions, we’ve got more de­vel­op­ment projects that are a bit se­cret but we can def­i­nitely get through the Euro4 emis­sions tests.”

But fancy tech­nol­ogy aside, how does it ride? Well the pro­to­type has had plenty of track time, in­clud­ing some test­ing by James Whitham at Mal­lory Park who de­scribed it as “f***ing quick”. Once the new en­gine is com­pleted, Crighton hopes to start pro­duc­tion im­me­di­ately, al­though he con­cedes it won’t be cheap.

“We haven’t sorted the price but it’s go­ing to be ex­pen­sive. That said, it’s go­ing to be one of the clos­est things you can get to a Motogp bike. There are pow­er­ful bikes out there, but they can’t come close to the weight and feel of this.”

Crighton shows MCN’S Gib­bons around the ro­tary

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