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The Nimbus was a Danish motorcycle produced from 1919 to 1960 by Fisker and Nielsen of Copenhagen, Denmark, also manufacturers of "Nilfisk" brand vacuum cleaners (now Nilfisk-Advance). Two basic models were produced, both with a 750 cc four-cylinder engine.
In partnership with H.M. Nielsen, Peder Andersen Fisker produced electric motors and, from around 1910, the first vacuum cleaners in Europe. Fisker believed he could develop a motorcycle that had its own form, and in late 1918 decided to construct a prototype to his own design.
It had a four-cylinder inline engine of 746 cc (45.5 cu in) capacity, which drove the rear wheel through a shaft drive rather than the chain usually used at that time, and a power output of approximately 10 hp. Its top speed was around 85 km/h (53 mph) with a sidecar fitted. It had both front and rear wheel suspension, and soon acquired the nickname of Kakkelovnsrør ("Stovepipe") due to the thick, round pipe between the saddle and handlebars which as well as forming part of the bike’s chassis contained the petrol tank. Two more machines were constructed in 1919, but mass production did not begin until 'Fisker & Nielsen' became a limited liability company in 1920.
Disappointed by poor sales, Fisker began entering the Stovepipe in all the races that he could, often with a sidecar attached, and built up a good reputation for the machine. However, the introduction of a sales tax on motorcycles in 1924 and an economic recession resulted in production being phased out from 1926 on after 1,300 machines had been produced.
Type C 
With his son Anders, Fisker started designing a new machine in 1932 and in 1934 they demonstrated a new Nimbus motorcycle, the Type C. It retained the shaft drive, a completely redesigned ohv and ohc engine of 18 (later 22) hp, and a frame made from steel strips riveted together, which were shaped to go around the gas tank much like on the pressed steel frames on several other motorcycles of the period. Front suspension was by telescopic fork; although this was introduced a year before the BMW R12, the R12's fork had hydraulic damping upon introduction while the Nimbus's fork did not have hydraulic damping until 1939. Its distinctive humming exhaust note led to it being nicknamed Humlebien ("The Bumblebee").
The first customer received his Type C in the summer of 1934, and the Bumblebee soon became the best-selling motorcycle in Denmark, sold by an efficient dealer network. The Danish Post Office, Army, and Police became customers. In 1939, as World War II loomed, the Danish government spent DKK 50 million on motorising the army - which bought many Type Cs.
During the occupation by German forces from 1940 to 1945 it was difficult for Fisker & Nielsen to obtain the materials needed for motorcycle production and only about 600 machines were made during the period.
Right after World War II a much improved ohv engine was built and tested. Seeing, however, that the factory had no trouble selling every motorcycle built, it was decided not to make any major investments in new tooling. Instead more minor improvements were made to the existing models, usually making it possible to upgrade older models.
The Danish Army bought around 20% of Fisker & Nielsen's total production, while the Postal Service also bought many, using them as late as 1972. The Danish police was also a large customer, but phased out their Nimbuses much earlier in the late 1950s and early 1960s, when it became too slow to keep up with modern cars and motorcycles; the top speed of a stock solo bike was only 120 km/h (75 mph), and that for brief bursts only. Few were exported.
In the 1950s some further prototypes were built, like a four-cylinder with a rotary valve and carbon seals as well as a two-cylinder model with rear suspension, neither of which reached production. Several prototypes with rear suspension and an Earles front fork were also built.
Innumerable details of "The Bumblebee" were changed during its lifespan, the few major ones being a switch from hand to foot gear change, larger brakes and an improved front fork. Still, the basic design was never updated and, as interest in motorcycles declined in the late 1950s as a consequence of the availability of cheap cars such as the Volkswagen Beetle, production ceased in 1960, when the last contract from the army was delivered.
Surviving examples 
Of around 12,000 "Bumblebees" produced, today more than 4,000 are registered and running in Denmark alone, and likely a few hundreds are used outside of Denmark, mainly in Sweden, Germany and the US. An estimated further 4,000 or so also exist, either in museums or otherwise not currently registered.
Even today most spare parts are readily available as well as relatively inexpensive. Thanks to the design's inherent reliability, using a Nimbus on a daily basis is still considered easy and economical. Nevertheless (and with some notable exceptions), today most Nimbus owners rarely ride more than a few thousand kilometers a year. Also, as the Nimbus often came from the factory with a sidecar attached, many of the ones on the road have recently been fitted with such.
- Clement Salvadori (July/August 2006). "1957 Nimbus Type C". Motorcycle Classics. Retrieved 2009-08-17.
- Setright, L. J. K. (1977). Bahnstormer: The story of BMW Motor cycles. Transport Bookman Publications. p. 47. ISBN 0-85184-021-3.
- Duchene, Paul (May 2008). "Bike Buys: Nimbus–The Prince of Denmark". In Duchene, Paul; Lombard, Stefan. Sports Car Market (Portland, OR USA: Sports Car Market) 20 (5): 136. ISSN 1527-859X. Retrieved 2012-12-30. "Nimbus developed telescopic forks in 1933 and introduced hydraulic damping in 1939."
- Phillip Tooth (May/June 2008). "1952 Nimbus Type C: The Danish Bobber". Motorcycle Classics. Retrieved 2009-08-07.
- "Nimbus: Halo of Danish motorbike production". Denmark.dk. 7 December 2007.
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