Monday, February 18, 2008

1928 HUMBER OVERHEAD-CAMSHAFT

The 1928 Humber single-cylinder 3.49 OHC 
Here's a rare bird; Humber was one of the original motorcycle makers in Britain - according to 'The Autocar' of June 6, 1896, ' the first practical motorcycle made in this country was completed last week when Humber and Co. finished a bicycle fitted with a Pennington two-horsepower motor...'. Humber started life in 1868 making bicycles, and branched out to making cars about the same times as they added an engine to one of their bicycle frames.
From a book scan; note the acetylene lights - no provision for a generator even in '28
By around 1903 the cars especially became very successful, with motorcycle and bicycle production developing alongside. The factory backed a racing team in the Isle of Man TT in 1911, and won the Junior TT (PJ Evans aboard) with their 350cc inlet-over-exhaust-valve v-twin. The factory also made sporting flat-twins (a la Douglas), and a machine which they copied from no-one; a 3 cylinder flat triple! One cylinder in front (78 x 78mm), two at the back (58 x 78mm), nominally 6hp, but which works out to 785cc.
The Humber is a handsome machine, and very light, with an early example of a saddle tank
The success of the Humber cars and their excellent construction became the undoing of the motorcycle branch, as the Rootes Group (which had already absorbed Sunbeam, Hillman, Singer, Commer, and Talbot cars) took over the factory in 1930. Rootes had no interest in motorcycles, and rather than selling off this side of the business (it was, after all, the worst year of the Depression), they 'hauled down the motorcycle flag'.
Note the oil pump on the Humber-built motor - it's a metered, total-loss system...at least the oil begins at the camshaft...
This 3.49hp ohc machine (no catchy name like 'Lark' or even 'KSS') therefore represents the pinnacle of 34 years of motorcycle production, and was the top of their line, 'a very refined and sporting mount', according to 'The Humber Story; 1968-1932' (Demaus and Tarring, 1989).
A period shot of the Humber from The Motor Cycle magazine Olympia Show edition of 1928
It's a very interesting little overhead-camshaft engine of their own make, with and adjustable oil feed directly to the cams via an oil pump on the cambox, although the engine lubrication is still total-loss. In general layout they certainly took their cues from the best, as it looks very much like a Velo K series, and even more closely resembles a racing Koehler-Escoffier 500cc ohc machine, which also has a total loss system, although not the oil pump directly on the cambox. The cambox itself shares the same rocker mechanism with the unfairly maligned Walter Moore Norton CS1 of 1927-29, in that the rockers exit the SIDE of the casting (see drive side detail photo), and don't move up and down through a leaky slot one either end of the cambox. It's so much easier to add aan oil seal to a rocker shaft as on this machine, than try to seal a 1.5" long open slot....look at the back of any Manx or my mkIV KTT after a hard ride, and you'll know immediately what I'm talking about.
The timing side of the engine reveals the rocker arrangement, emerging from the side of the rocker box a lá the Norton CS1
The rest of the machine is typical of the late Vintage period; bought-in forks (Brampton), gearbox (Albion), wheels (Webb or Enfield hubs), carb (Amac), magneto (ML), etc. The factory would have of course made their own frames, and probably petrol tanks, as they must have had sheet metal pressing capacity for their cars... OHC machines are very rare in the Vintage period, and a motorcycle of such limited production like this one is an especially unusual discovery.
1" diameter handlebars and nickel-plated controls are apropos the pre-1930 general introduction of chrome plating and 'open' handlebar levers


1 comment:

Anonymous said...

Hi Paul

Great to find the cammy Humber on your blog. We're restoring one that has come back to the UK from Australia, so I was pleased to see the photos, especially of the paint scheme on the tank, since ours is a faded all-over blue. Check out our website - www.bmct.org

Best regards

Andy Bufton
The British Motorcycle Charitable Trust