Classic bike: Nimbus Model C

The 'Prince of Denmark' has a deserved place in the history of four-cylinders, from a country which wasn't at the vanguard of bike production

Although not a mainstream design, one of the most enduring engine layouts has been the in-line four-cylinder. It began with the Belgian FN in 1905 and continues today with BMW’s K 1200 LT. In the US, firms like Henderson, Cleveland and Indian made the in-line four highly desirable, but less well known was the Nimbus from Denmark.

Denmark wasn’t at the forefront of motorcycle manufacture and the Nimbus started out from origins other than motorised bicycles, as was usually the case in the early 20th century. With business partner Nielsen, Peder Fisker began manufacturing electric motors in 1906, switching to vacuum cleaners in 1910, and eventually motorcycles in 1919.

Fisker decided he could improve on the FN and his design was extremely advanced for the day. The in-line four included shaft-drive, and the riveted steel frame that could be easily repaired.

But throughout the 1920s the Nilfisk vacuum cleaner business was so successful that motorcycle production stalled – until 1934, when a new factory was built and an updated motorcycle developed, the Nimbus Model C.

Like its forebear, the Model C was also a shaft-driven in-line four, but the 746cc engine now included an overhead camshaft. The engine design was automotive in concept, with the lower half of the crankcase and cylinders cast together, and a one-piece detachable cylinder-head.

A single carburetor fed all the inlet valves on the left and the single exhaust exited on the right. An interesting feature was a connection from the carburettor to help extract crankcase fumes, at the same time lowering crankcase pressure and reducing oil leakage.

The valve gear was exposed, the crankshaft ran in two poured, white-metal bearings, and a three-speed gearbox bolted to a single-plate clutch. The gear change was initially by hand but became foot-operated after 1935 and as the rear wheel was unsprung the shaft-drive didn’t require a U-joint.

The engine only produced 22hp (16.2kW) so performance was leisurely. On a good day the Nimbus may have hit 110km/h, but it would cruise all day at 90km/h and when ridden with restraint it was very reliable.

The engine was also extremely flexible, pulling cleanly in top gear from 15km/h. The distinctive exhaust note was likened to the drone of a ‘bumblebee’. And at only 185kg, the Nimbus was by far the lightest four-cylinder bike available at the time.

In many respects the Nimbus was extremely advanced. Nimbus developed a telescopic fork in 1933 and introduced hydraulic damping in 1939. The frame was triangular in design and built out of flat spring steel, while the ignition system was handled by a coil and contact breaker with an automatic advance and retard.

After updates were added in 1936 (foot change, heavier front end and larger brakes) the Nimbus remained virtually unaltered until 1954.

One of motorcycling’s fascinating rare gems, the Nimbus gives a glimpse of the eccentricity that pervaded and was able to survive in the pre-war and immediate post-war era. It is the best-known Danish motorcycle, and truly the Prince of Denmark.

Thanks to Allen and Lorraine Smith of the Australian Motorcycle Museum in Haigslea (Qld) for the use of the Nimbus 1950 Model C featured here.
THE VALUE PROPOSITION
If you’re thinking about a Nimbus of your own, here are the numbers you’ll need to crunch:

Original price tag for a new Nimbus Model C – $750
Current valuation for one in mint condition – $25,000
Current valuation for one in good condition – $18,000

FAST FACTS

Only 14,215 Nimbus motorcycles were produced between 1919-1959, most sold in Denmark.
It is estimated that two-thirds of the Nimbuses made still exist worldwide, and about 4500 are currently licensed. There are five Nimbus dealers in Denmark and 95 per cent of spare parts are still available.
The rarest Nimbuses are the Models A and B ‘Stovepipes’, named for the six-inch diameter back-bone spine that also held the fuel. Between 1919-1927, 1252 were made and about 250 survive.
General production ended in 1954 but complete machines continued to be built from spare parts until 1959. Often fewer than 1000 were produced in a year, and many were fitted with sidecars.
Although it was obsolete by the 1950s and largely replaced as a workhorse by small cars and vans, the Danish Army and the Post Office kept ordering Nimbus motorcycles until supplies dried up. By 1977 some Nimbus models were still in use by the Danish Marines.

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Story courtesy of Motorcycle Trader.

Classic bike: Nimbus Model C

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