Probably the sleeve valve motor is by Barr and Stroud but as far as I know, was fitted to very few bikes of the period, although George Brough offered a Superior model with this type of engine. I do not know if the Sunbeam engine went into production. The sleeve design was adopted by Argyll cars a century ago; more recently and, most significantly, by the Napier Sabre H24 and Bristol Centaurus aero engines.
Lest the fanciful notion that I’m some sort of Nimbus freak gain wider public acceptance, I attach a shot of yours truly, Honda-mounted at The Bungalow last year. I managed to get within 36 minutes of the record! But I reckon that a creditable effort by a little 500 single with an octogenarian plus rider battling others insisting that they share my road with them.
Nevertheless, in view of the above, I feel a little hesitant in posting a drawing of another rotary valve engine - a design which with further development might have achieved some technical and commercial success. As with all similar arrangements, as well as the sleeve valve construction, heat transfer was a fundamental problem - I had a 1918 Daimler with double sleeve valve engine and so have some practical understanding of the problem! But advances in “conventional” design rendered most of these departures from technical orthodoxy unnecessary.
And whose design is this novel valve arrangement? Whisper it in confidence to only a trusted few; it was a NIMBUS!
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