Walter Kaaden and two-strokes

Given the interest in the two-stroke gif in an earlier post, it seemed appropriate to mention Walter Kaaden, the German engineer responsible to a very large extent for the development of the
expansion chamber.

Kaaden (1919-1996) was a rocket scientist during WWII and after the war was an engineer with MZ motorcycles, by then trapped in the new East Germany. With pitiful resources and materials but huge intellect and ability, he recognised the potential of harnessing the pressure waves in an exhaust to not only aid the clearance of burnt gasses, but also to pressurise the combustion chamber while the exhaust port was still open, returning what would have been wasted charge back into the cylinder. His discoveries and their application on grand prix motorcycles brought MZ success that belied their humble resources and restrictive circumstances. All this is dealt with in great and entertaining detail in Mat Oxley's book, Stealing Speed, which we blogged about just over a year ago. Read it.

In the meantime, I'll leave you with a story. More than ten years ago now, I was lucky enough to interview Alan Shepherd (he died in 2007) an English grand prix racer who rode for MZ during the Sixties. The main story I was chasing was of his dramatic Boy's Own adventures at the 1964 US GP at Daytona, involving Kaaden, and maybe I'll go into that another time. However, during the interview, he gave me this glimpse of Kaaden's genius in action:

"One year at the TT, I think it was 1963, I ran through the pits just once on the 250 MZ. Walter questioned me when I got back, and bear in mind he'd only heard the bike for a few seconds. 'Alan, your 250,' he said, 'Are you confident that it is in good order?' Well, at one stage in the acceleration the engine sounded slightly duller than at other stages, but that was all. In this practice I was top of the leaderboard, or second, and was perfectly satisfied.

"Walter said to his mechanic, 'Please check the timing on the right hand cylinder, if you find it to be exactly correct, and the points gap to be exactly correct, check the carburettor and if you find nothing, please change the needle position to one notch higher.' In the evening practice the slight dullness had of course gone and my times were much improved because of the cleaner acceleration. How did he know it was the right-hand cylinder? That man was absolutely amazing. A genius in every respect." MP