Nimbus Motorcycles

Today in Motorcycle History

The History of the Nimbus Motorcycle

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The old Nimbus

Peder Fisker was the founder of the company Fisker & Nielsen, whose main product was vacuum cleaners. He had no previous interest or experience with motorcycles, when one day he spotted a motorcycle parked in the street. The way this motorcycle - likely a Belgian FN - was constructed so offended his sensitive engineer soul, that he decided that he had to build a better motorcycle. And by then he already had the production apparatus at hand. The Nimbus model A/B (1919-23) became popularly known as "The Stovepipe" because of it's huge frame backbone/gas tank. The model B (1924-27) is basically an A model with an improved front fork. Sporting rear suspension, a unit construction engine/gearbox, as well as a shaft drive, it was very advanced for its time. The 746 cc engine with an IOE type valve arrangement produces 8-9 bhp, which is sufficient for a 70 kph (45 mph) cruise speed and a top speed at about 100 kph (65 mph). The gear box has 3 speeds and a multiplate wet clutch. Gear change was by hand. I do not know if "The Stovepipe" actually was better than the FN, but it was, as mentioned above, undeniably advanced for it's day. The model A/B did well in long distance races, often with Peter Fisker at the controls, frequently winning by virtue of reliability rather than speed. The "Stovepipe" did, however, cost about as much as a Ford model T, so it never became the big seller its maker had hoped for. Altogether 1252 were produced.


Inlet Over Exhaust

Aka the F-Head, the IOE system was widely used in early four-stroke engines. Italiano: valvole di aspirazione sopra quelle di scarico; contrapposte.

The new Nimbus
Anders Fisker, the founder's son, was the main force in designing the Nimbus model C and getting it into production. "The Bumblebee", a nickname it got because of it's humming exhaust note, was built from 1934 to 1959, with a few more being assembled in 1960. The overall design was kept in all these years, but innumerable detail changes were made. Almost all of the 12,000 built went for the home market. The frame was made of strips of steel and steel plate, all riveted together so it would be easy to repair a damaged frame. The handlebar was unusual too, in that it was a steel plate which also housed part of the electrical system and, on the pre-war model, the speedometer as well.Early models of the telescopic forks had no damping whatsoever, but a common trick at the time was to bend the inner tubes a bit to get some stiction. A few years later some crude damping devices were tried, but it wasn't until '38 or '39 that the oil damped forks appeared on the Nimbus "Sport" and "Special" models. The "high" forks were introduced in 1949. How much of a damping effect there actually is in either design, remains a matter of debate.The 746 cc four cylinder OHC engine produces 22 bhp (early versions 18 bhp), has a very flat torque curve and has no chains whatsoever. The clutch is a car-type single dry plate, and the gearbox has 3 speeds. Early versions had a hand gear change, while the foot gear change as well as larger brakes were introduced on "Sport" and "Special" models as early as 1937. Dry weight is 185 kg (app. 360 lbs.). The main reasons for ceasing production were the following:

1) The final customs barriers, introduced after the war and protecting the expensive to produce Nimbus against foreign brands, fell in those years, so one no longer needed an import permission or US $ for buying vehicles. 

2) The model C design was hopelessly outdated by that time anyway, and would probably have died a natural death 5 or 6 years earlier, had it not been for the above reason. 

3) Anders Fisker was by then seriously ill with sclerosis, and had to retire. Since it was his enthusiasm and that of his father which had kept the motorcycles in production in the first place, there wasn't any real support within the factory to continue spending money on what realistically looked like an unprofitable product. The factory never made all that much money on the motorcycle production,- it was the vacuum cleaners and the tool production that kept the shareholders happy.

4) Inexpensive cars had become widely available and motorcycle sales dropped almost overnight. 

The prototypes
A smaller size engine was tried in the late 50's, on a 2 cylinder experimental model, which basically was a 4 cylinder block with the two center cylinders cut off. At the same time there also was quite some money and time invested in an experimental rotary valve design, both on the "cut" 2 cylinder model and a couple of 4 cylinder engines. They made less horsepower than the OHC engines, and were all but impossible to start when cold, but the perennial problems with leakage at operating temperatures had apparently been overcome.  Right after the war another prototype engine was built and tested, incorporating a host of improvements like a fully enclosed cylinder head with conventional valves. However, at the time the factory could sell easily every Nimbus produced, so the was no particular reason to invest in new tooling for another engine. Common wisdom has it that the continuous development of the new engines, as well as that of experimental front forks and frames with rear suspension, was only done out of respect for the now very ill Anders Fisker. 

The dinosaur survives

Riding a Nimbus gives some perspective to the technical evolution of motorcycles over the last forty years. Still, the bike copes remarkably well with today's traffic conditions. The rubber band sprung seat is comfortable over even the worst potholes (though not for distances in excess of 30 miles), the 22 hp engine will ensure a 70-90 kph (45-55 mph) cruising speed for a solo bike. Riding with a sidecar, and a sidecar final gearing, reduces the cruising speed to 60-80 kph (40-50 mph) (although I know of people who mercilessly flog their engines - 100 kph (65 mph) with a sidecar - and seem to get away with it).The 2 bearing crankshaft and a marginal lubrication system limit continuous high-rpm running. Thanks to its narrow profile it has remarkably wide lean angles, occasionally compensating for brakes that, in the age of the disc brake, leave something to be desired. Never intended to be sold outside Denmark, the bike will generally run cool enough in a country with no hills and a white winter/green winter climate. To compensate for the above we have a bike which was designed with function more than aesthetics in mind: Very few special tools are required for all but completely dismantling a Nimbus. A screwdriver and 4 sizes of wrenches will be all an owner needs in the tool kit. But then, it was designed by and for motorcycle riders, rather than by non riding engineers or a design staff. An estimated 8,000 C models remain today, with currently 3,500+ registered and in running condition (in 1998 it was still the 5th most registered brand). It's hard to estimate how many Nimbuses have made it out of the country, but the figure is definitely in the hundreds. There are at least 30 in Australia, probably 50+ in Germany, and I saw a number of them when I rode my '52 model C across the USA in 1982. 

Reliability & spares

The model C was considered far more reliable and easy to maintain than other contemporary brands. However, due to high Danish labor costs, its expensive design, a decision to make as many components as possible in-house, as well as the obvious inefficiency of batch production rather than assembly lines, it was rather expensive. At the end op production in 1960, a Nimbus outfit cost about the same as a VW Beetle. But then any Nimbus was a high quality product for its day, which is good for us who ride it as an everyday vehicle. The rule of thumb is that a well taken care of model C will not need a serious engine rebuild until after 50,000-80,000 kilometers (18,000-50,000 miles). Which is at least two or three times the comparable figure for other contemporary brands. Spares are still easy to come by, in the sense that about 2/3 of all parts are being manufactured as new, and the prices are manageable. Getting parts that are specific to one particular pre-war year can be a problem, though. Going to the swap meets will usually solve the problem. Parts from various years are usually interchangeable, so many owners "upgraded" their machines with newer parts along the way. Currently there are 5-6 Nimbus dealers in Denmark.

Being a hero

Occasionally I've met people on the ferries to Germany, who are impressed that I dare ride this old bike outside of the city limits. I still enjoy telling them that riding to Spain, across The United States or around the Atlas Mountains of North Africa is considered no big deal on a Nimbus. Consequently, the rest of the Danish vintage/antique motorcycling community doesn't regard the model C as a "real" vintage bike, as ownership of one seems to lack the crucial element of masochism so dear to many old bike enthusiasts.

Consequently, the rest of the Danish vintage/antique motorcycling community doesn't regard the model C as a "real" vintage bike, as ownership of one seems to lack the crucial element of masochism so dear to many old bike enthusiasts.

The clubs There are many local Nimbus clubs in Denmark, as well as in Germany, Australia and the USA.

Danmarks Nimbus Touring, with its 1,700+ members, is by far the largest Nimbus club in The Known Universe. The club has managed to bring together Nimbus enthusiasts at a time when Nimbuses are being transformed from being an everyday tool to a hobby vehicle. Not a moment too soon, as many of the people who know most about the bikes have reached and age where their warranties start to expire. Most recently a Nimbus Museum, containing most of the club's artifacts, was established.

Nimbus Tidende, the excellent club magazine, brings how-to articles, advertising for parts and services, buy/sell ads, as well as it offers space for touring articles, rally announcements, personal feuds and whatever such a magazine is supposed to contain. It comes out 5 times a year, but is written almost exclusively in Danish.
Kim Scholer
The club: Danmarks Nimbus Touring Box 284 
9900 Frederikshavn
Tlf. 98 42 66 65 
Fax: 98 42 66 64 
e?mail: dnt at image.dk
Homepage: www.nimbus.dk

One of the American clubs:
c/o Peter Orum
P.O.Box 384
St. Charles, IL. 60174
tel: (708) 695-0028 / (708) 741-1790

The magazine:
Nimbus Tidende 
c/o Kim Scholer
Broagergade 8, 1 th
DK-1672 V
tel: 33 31 92 08
kimscholer at NOSPAMemail.dk

Vagn Gjerlang
Skovalleen 33 B
DK-2880 Bagsværd
tel: 44 98 94 00 

Source: Makis MC Classic