RO­TARY

Motorcycle Monthly - - Knowledge -

Lay­out: An oval hous­ing with a tri­an­gu­lar ro­tor cir­cu­lat­ing around an off­set, lobed shaft to form in­let, ex­haust and ig­ni­tion com­part­ments. Ben­e­fits: Com­pact, high power-toweight-ra­tio, sim­ple de­sign.

At the age of 17, Ger­man in­ven­tor Dr Felix Wankel came up with the prin­ci­ples for an en­gine that would change the world. Un­like a con­ven­tional pis­ton mo­tor, which loses sig­nif­i­cant amounts of en­ergy as it changes re­cip­ro­cat­ing en­ergy into a ro­ta­tional move­ment, the en­gine he would patent just five years later would see ef­fi­ciency never known be­fore.

Work­ing in part­ner­ship with NSU in the 1950s, Wankel built a se­ries of pro­to­types and the ro­tary mo­tor be­gan reach­ing the pro­duc­tion lines in the early 60s; first be­ing used in NSU’s Spi­der car in 1964.

The bike world was keen to cap­i­talise on this in­no­va­tive con­fig­u­ra­tion and East Ger­man man­u­fac­turer MZ was the first to toy with a 175cc air-cooled ver­sion of Wankel’s de­sign, dou­bling the per­for­mance out­put of the equal­ca­pac­ity, con­ven­tional pis­ton mo­tor it had re­placed. Im­pres­sive as it was, reli­a­bil­ity prob­lems com­pro­mised the ro­tary en­gine’s suc­cess.

Over time, more and more brands took to Wankel’s de­sign, with Yamaha the first of the Ja­panese to show­case a ro­tary-en­gine ma­chine in 1972 – the RZ201 – which un­for­tu­nately never made it into pro­duc­tion. Suzuki, how­ever, saw huge pop­u­lar­ity with the RE5, which it launched in ’73.

Its price held it back and by ’76 Suzuki called time on the model that sold over 6000 units. Her­cules was next to pick up the ro­tary in 1974 – in tan­dem with DKW – be­fore sell­ing off all its tool­ing to Norton in ’77. By this point, Norton had been de­vel­op­ing its ro­taries for seven years, with the In­ter­pol II – a model built ex­clu­sively for the po­lice – even­tu­ally mak­ing the pro­duc­tion line in 1984.

In ’87, 100 ex­am­ples of the ro­tary Norton Clas­sic were re­leased, with 85bhp on tap. The Com­man­der came next, but that too failed to sell in large vol­umes.

Every­thing changed in 1990 when the Norton F1 racer cleaned up in the 1989 Bri­tish F1 cham­pi­onship.

The fu­ture for ro­taries looked bright once more, but prod­uct sales failed to come and the ro­tary was even­tu­ally floored with Norton’s demise.

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