What you are looking at is the engine and gearless transmission of a 1923 Ner-A-Car motorcycle. In the pioneering years of the automobile, gearless “friction” transmissions were popular - and then they vanished.


The friction transmission was a very simple form of “gearbox” which did away with many of the early problems of sliding gear transmissions by simply omitting the gears and clutch altogether. The photograph at left should help make clear how the thing worked. On the back of the engine crankshaft a large aluminium disc was mounted.Behind this was an axle carrying a wheel at right angles to the aluminum disc. When the wheel was brought into contact with the disc power was transmitted from the disc through the wheel, to the axle, and then by chain to the differential and drive axle. The ingenious bit is that the friction wheel could slide back and forth on its axle and be brought into contact with the aluminum disc at various positions along its diameter - effectively giving various “gear” ratios. In theory this would allow for infinite adjustability of ratios, but in practice the ratios were limited to a selection of stops along the friction wheel’s travel. But having a five or eight speed transmission when most cars had two speeds, and doing away with gears in an era before synchromesh existed meant that in many ways friction transmissions outdid their geared competitors.

The Lambert automobile was the first make to successfully use this style of transmission, but the limitations of friction drive became apparent as cars got heavier and more powerful. As well, clutch and gearbox technology progressed rapidly and the early advantages of the system were no longer so advantageous. By the 1920s this type of transmission was well on its way out, with the lightweight Metz cyclecar and the Ner-A-Car motorcycle being stubborn holdouts against geared transmissions.

By the way, The Ner-A-Car motorcycle looks like what I’d imagine a Taishō era Kaneda would ride.

The title of this article is admittedly a bit of a trick. As there are now modern CVTs which allow one to choose from a selection of preset ratios mimicking a gearbox - but as has been demonstrated above the idea is not a new one. It’s an old one that’s come back with the help of newer, better technology. The possibilities available haven’t yet been fully explored (24 preset speeds like a bicycle? a floor mounted shift lever? a manual clutch pedal? who knows what the future might hold?). Although personally I’d still rather have a Ner-A-Car than a Subaru Forester.

And if you’re a real nerd, here’s a great video demonstration of the friction drive in an antique Metz


Ner-A-Car photo credit to Craig Howell.

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