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But the ambitions of Peder Fisker, a leading engineer, were much larger than manufacturing of household appliances. In 1919, the company, quite unexpectedly, introduced its first bike Nimbus. The first model, a prototype of which was designed two years before, combined some promising features and stylish trends.
At first, you’d be amazed by the bike’s frame – thick-walled supporting pipe of large diameter. Similar designs were just coming into fashion in Germany. Two heavy-duty pressed bars formed the bottom part of the frame, closing the contour. In between a powertrain was located. It was an inline four-cylinder engine (746 cc, 9 hp) in one crankcase with a three-speed gearbox.
The cast-iron cylinders were casted separately. The gas distribution mechanism was made according to the “valve over valve” scheme. The inlet valve drive was fully open with the drive valves arranged in pairs: two between the first and second cylinder and other two between the third and fourth cylinder.
Inline engine made conditions to implement a drive shaft because the rear wheel disk, including the rear mudguard, were suspended to the rear part of the frame using two springs.
The fork was complex and had two compression springs installed in enclosed casings. In this configuration (model A), the model was manufactured until 1923 when it was replaced by the B model, which had a simplified fork, an upgraded carburettor and a new intake manifold. In 1927, the manufacturing of the B model was ceased because the company wanted to expand the output of the main products.
In 1934, the Nimbus brand suddenly appeared once again. The design of a new machine only partially resembled the previous models that were equipped with inline engines and a driveshaft. For the rest, it was a whole new bike. Its duplex frame was made only of pressed profiles that were very simple in shape.
The petrol tank was installed to the frame from above, similar to BMW and Zündapp. The rear suspension was rigid and the front fork was telescopic with springs inside the pipe arms. The steering wheel was a wide pressed plate, with the control knobs at the end, and in the center there were instruments and a switch for electrical equipment. Under the steering wheel, a central headlight was attached on the lower axle of the fork.
The power unit needs a detailed description. It was an inline four-cylinder overhead valve engine (746 cc, 22 hp). Cast-iron cylinders were casted together with the upper part of the crankcase. The bottom half was made of aluminium and contained an oil tank.
The removable cast-iron head of the cylinder barrel contained a camshaft covered with a special aluminium cover. The camshaft was driven by a vertical shaft, which was located in the engine’s front end; an electric generator with an automobile timer-distributor was vertically fitted over the front tailshaft.
The valves, equipped with spiral springs, were set in the V-configuration. Four valve rockers went out of the camshaft cover via individual openings on either side. So, rocker-valve pairs were accessible (opened). This was good for valve clearance adjustment, but as for the valve train, it reduced its service life despite the force-feed lubrication system. Another interesting feature of the engine was a forced ventilation of the crankcase via a carburettor.
A three-speed gearbox had a cunning gearshift control that allowed both a hand lever and a foot pedal (which was installed in the Luxus version since 1935) to be connected to the gear shift gate.
Moreover, the gear shift lever could be installed from either side at customer’s request. Rear brake foot pedal could also be installed on either side. A kickstarter pedal was an exception – it was located only on the left side and went under the frame.
In 1936, the fork was reinforced and the wheels got heavy-duty hubs. The bike could achieve 110 km/h, having 172 kgs of its weight. In this configuration, bike was being produced till the end of 1940s when it was upgraded for the last time.
The fork was slightly modified, the headlight moved from the fork’s bottom bridge to special side brackets under the handle bar, the saddle was suspended on the central springs (instead of accessible springs on either side) and was equipped with rubber hinges used as stoppers.
In this configuration the bike was manufactured until 1958, when the manufacturing was completely ceased (according to some reports, it happened earlier, in 1954), and spare parts were manufactured for another four years.
The Nimbus bikes were made in solo version and with a sidecar. They were sold to civilians, to the army and police and also exported abroad. In the history of motorcycles, the Nimbus probably is the only bike that has been produced for more than 20 years without much change.
|Manufacturer||Fisker and Nielsen, Denmark|
|Years of manufacture||1934-1958|
|Quantity produced, units||Over 12 000|
|Стоимость в современных ценах||N/A|
|ENGINE AND TRANSMISSION|
|Engine capacity, cc||746|
|Bore and stroke, mm||60 х 66|
|Engine rating||22 hp at 4500 rpm|
|FRAME AND WHEELBASE|
|Frame type||Duplex (stamped steel)|
|Wheel size||3,50 х 19|
|Ground clearance, mm||
|Seat height, mm||
|Gas tank size, l||
|Maximum speed, km/h||