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NSU 250 Twin 1954
1954 NSU. 250 TWIN. In the twenties it was not uncommon for a
T.T. race average to be boosted by a few m.p.h. from one year to the next. But
it was virtually unprecedented in modern times when, in 1954, Werner Haas hurled
his twin-cylinder N.S.U. round three laps of the Mountain course to record the
first "over-90" win in the Lightweight race, for his record average speed of
9088 was over 6 m.p.h. faster than Fergus Anderson's 1953 record speed of 8473
m.p.h.
Undoubtedly a star part in this dramatic victory was played by the machine which
Haas rode.
The N.S.U. factory had raced twins in 1953, but they had
certain shortcomings, to overcome which the unit was virtually redesigned in the
winter of that year. The race average shows how well the bugs were eradicated.
Apart from such obvious aids to high-speed work as twin-leading-shoe' brakes at
front and rear, the machine was surprisingly similar to the roadster N.S.U.
"Max" as far as frame and forks were concerned. There the similarity ended.
Unit construction was employed for the parallel-twin engine
and gearbox, which had no fewer than six ratios. Primary transmission was by a
pair of spur gears (so the engine ran "backwards"). Both cylinder barrels were
deeply spigoted into the crankcase and a cross-shaft in the "top" of the
crankcase drove the distributor via skew gears and the bottom bevels of the
vertical shaft drive to the twin. o.h. This shaft drove to the inlet end of the
camshaft gear train, so that any backlash in the system would have ininimal
effect on the induction.
The factory claimed an output of 42 b.h.p.—as much as most 1961 "350s"!
SPECIFICATION
Engine: inclined parallel twin 250 c.c. d.o.h.c; drive to
camshafts by shaft and bevels. Ignition: coil and distributor.
Transmission: gear primary drive to unit-construction six-speed gearbox; final
drive by chain.
Frame: welded pressed-steel spine; pivoring-fork rear suspension.
Forks: leading link.
The Rise and Fall of the NSU Empire
From Knitting Machines to World Championships and Finally,
Obscurity
By Dave Tharp, Virtual Museum Curator
Lightweight street motorcycles just never caught on in the
Americas -- except for a brief time in the late 1960s when you could meet "the
nicest people on a Honda." However, in Europe, bikes displacing under 500cc have
always been the workhorses, providing economical transportation, serious sport
and touring capabilities, and even towing sidecars.
In 1910, NSU set a US coast-to-coast "cannonball" speed record.
Because of this big-bike myopia, many riders have consistently overlooked the
excellent European lightweights, including the NSU -- arguably the best of them
all.
At the turn of the 19th century, the small factory town of Neckarsulm, in
southern Germany, was the home of a company that manufactured automatic knitting
machines as well as a successful line of "safety" bicycles (bicycles with two
small wheels and a chain drive, as opposed to the "penny-farthing" big-wheeled
types). This company went by Neckarsulm Strickmaschinen Union (Neckarsulm
Knitting-machine Union), a name that described their business accurately enough,
but is quite a mouthful for the non-Germanic. Hence, they eventually adopted the
initials NSU.
Before the name change, their bicycle subsidiary's name -- Neckarsulmer
Fahrradwerke -- was just as difficult to pronounce, but it did appear on the
tanks of their first motorcycles. These appeared in 1901 (two years before the
first Harley-Davidson), and consisted of a 1.5 HP Swiss-built Zedel engine
(another copy of the DeDion-Buton) clip-mounted on the downtube next to the
crank assembly of one of their standard bicycles. Final drive was accomplished
via a flat leather belt that connect a pulley on the crankshaft to a pulley on
the rear wheel.
Not satisfied with the Zedel, NSU introduced their own singles and V-twins in
1903. This rapid pace of development continued, and the factory introduced a
liquid-cooled single in 1905, and a revolutionary swing-arm rear suspension
motorcycle in 1914 (still belt-drive, though).
The NSU V-Twin engine, circa 1905. Note the "atmospheric"
intake valves, opened by the suction of the piston going down. Photo by W.
Conway Link, Deutsches Motorrad Register.
During this period, racing success for the NSU factory led to fame and a
greatly-increased export market. It's likely that the unpronounceable name lead
to the reduction of the tank emblem to the initials "NSU," or perhaps there was
a paint shortage.
NSU was heavily involved in war production during W.W.I. After
the-war-to-end-all-wars, demand was very high for motorcycles and they responded
with a wide range of models. These included sidevalve and OHC 250's, sidevalve
500 singles, and V-twins of 500, 750, and 1000cc displacements.
In 1929, NSU hired Walter William Moore away from Norton, where he had recently
completed the design of the CS1, a towershaft-driven OHC 500cc single (also
known as a "bevel drive," as in bevel-drive Ducatis -- a bevel gear on the
crankshaft drives another bevel gear on a driveshaft that parallels the
cylinder. At the top of the cylinder, another bevel gear drives a fourth bevel
gear on the overhead camshaft), the forerunner of the fabulous Norton Manx. By
1931, NSU was producing excellent towershaft-driven OHC singles that were highly
successful. NSU became one of the largest producers of motorcycles in the world
in the 1930s. Starting in 1937, Moore and Albert Roeder designed supercharged
DOHC GP twins in 350cc and 500cc flavors. These bikes were unsuccessful before
the war due to reliability problems, but performed well after the war when the
bugs were worked out.
Unlike the Allies, the German Army had a great deal of faith in motorcycles as
weapons of war. Motorized rifle regiments equipped with heavy BMW and Zundapp
sidecar rigs were present in every armored division. Meanwhile, NSU produced one
of the weirdest military vehicles ever conceived.
The Sd. Kfz 2 Kleines Kettenkraftrad half-track-- Who thought
this up, anyway?
The Sd. Kfz 2 Kleines Kettenkraftrad (Small-Tracked Motorcycle) was a light
armored vehicle with the front end of a motorcycle attached to the rear end of a
half-track. The handlebars operated differential brakes on the tracks as well as
turning the front wheel. Powered by an 1500cc 4-cylinder Opel engine, it was
produced by the thousands to equip Wehrmacht Panzer units.
More-or-less undamaged in the war, NSU immediately switched back producing
consumer motorcycles. In 1950, a towershaft DOHC 4-cylinder 500 was designed for
the GP circuit, but it was decided to campaign 125 and 250cc machines based on
single- and two-cylinder slices of the 500. These smaller machines, the Rennfox
and Rennmax (the Fox and the Max were NSU's 125 and 250 streetbikes) were
world-beaters, repeatedly winning world championships until NSU officially
withdrew from racing in 1954. The streetbikes weren't exactly slouches either.
The Fox and the Max were SOHC singles of moderate output, high durability, and
excellent fit and finish. The engines had a unique cam-drive system consisting
of two reciprocating connecting rods driven by eccentrics on a reduction gear,
and driving eccentrics on the end of the camshaft. If you can picture the
driving wheels on a steam locomotive, or the pedal rods in a kiddie car, you can
almost get the picture. This system was silent, efficient, trouble-free, and so
compact that the top end of the engine can easily be mistaken for a two-stroke.
The motor could spin to then-astronomical revolutions that destroyed chains and
formerly could only be achieved by towershaft drives.
This fact was not lost on the racing department, who fiddled with a Max engine
until it produced nearly the same power as the DOHC twin: 30 hp at over 9000
rpm.
In spite of having officially withdrawn from racing, the engine was installed in
a Max streetbike frame, fitted with aluminum bodywork and a dustbin fairing, and
given to Herman-Peter Mueller, the 1954 250cc World Champion. Named the Sportmax,
the bike was ridden by Mueller to another World Championship in 1955, making it
the only streetbike-based motorcycle to ever win a world GP title.
During the 1950s, NSU also produced vast quantities of 50 and 100cc Quicks and
Quicklys, as well as Lambretta scooters under license and their own Prima
scooter. But motorcycle production was doomed by the success of their small car,
powered by a 4-cylinder engine based on the Max design, still with the
eccentric/pushrod cam drive system. In 1957, NSU sold the entire motorcycle
facility to the Yugoslavians, who moved it all to Sarajevo.
In the 60's, NSU obtained the sole license for Germany to the Wankel rotary
engine. They developed a highly successful version of it, and produced large
numbers of compact cars with it. For this reason, they were absorbed by VW-Porsche-Audi.
Although NSU no longer produces cars, they still manufacture a fair number of
small Wankel engines for utility applications.
Today, the former NSU motorcycle factory in Neckarsulm is now a museum housing
one of the finest collections of bikes on the planet.
Source
home.cogeco.ca
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