 Nimbuslitteratur © 2024 Niels Øwre |
Denmark - the Nimbus Four
It took the German Blitzkrieg just one short day to over-run small, flat, peaceful Denmark. The day was 9 April 1940, and from then on the Danes were there to produce bacon and butter for the Nazis' breakfast.
On the motorcycling front just one make and model was taken up by the army, the Nimbus Four; built by Fisker and Nielsen of Copenhagen. The firm was unique in that over its years of production, first from 1919 to 1928 and then from 1934 to 1958, it built just one model, and the first was to the same general specification as the last.
The basis of the machine was an in-line four-cylinder engine with shaft drive to the rear wheel. The early machines had inlet over exhaust valves, girders and a spring frame. This last was again odd in that it was made from flat steel strip; the tank was welded to it and so was part of the structure, an early monocoque in embryo.
The 1934 model was different. The engine now had an overhead camshaft, which was shaft driven from the front. The vertical shaft was also the dynamo armature, just as on MG cars of the period, and a line of rockers poked out of each side of the camshaft housing. They operated exposed valves set either side of the combustion chamber and stayed that way to the end. The ignition distributor went on the front of the camshaft.
One carburettor went on the left of the engine, its small size restricting the power to 22 bhp from the 750 cc capacity. The exhausts joined on the right and a pipe ran from the rear of the manifold down to the silencer. Its poor style and line matched the rest of the machine, which was a bizarre combination of the modern and the antique.
The clutch and three-speed gearbox bolted to the rear of the engine. Gear changing was by hand, with the lever emerging at the rear of the tank, although later models were fitted with footchange. Starting was by a transverse pedal on the left and the final drive by exposed shaft and bevels. The lubrication of these was extremely crude and they had to manage with some grease at service time. The valve stems were looked after in the same casual manual way, but the lubrication system was a high- pressure, wet sump type to suit the plain bearing crankshaft with its two mains. The gearbox was lubricated from the engine via the clutch shaft.
The Nimbus frame continued in flat strip but became rigid at the rear. At the front went telescopic forks, so the marque may well have preceded the much more publicized BMW as the first in the world to offer this feature.
The wheels were conventional with drum brakes while the tank fitted between the top frame members. Saddle and pillion seat were sprung using rubber loops at the rear mounting until rubber went into short supply and then normal springs were used. On some models the front mudguard was very heavily valanced, and the Danish Red Cross used it to take the traditional marking on their all-white machines.
Postwar the four continued with only minor changes, but the firm also built prototypes with rotary valves. The first was a four that worked well and was followed by a tandem twin, but neither went into production as the firm decided to stop motorcycle manufacture.
Below left 20 mm cannon on Nimbus sidecar outfit Quite a heavy gun for such a platform
Military motorcycles of World War 2: All makes from Europe, Russia, Japan and The USA 1939-1945