Difference between revisions of "DKW SS350 Three Cylinder"
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Wiinsche, retired at Ramsey on the second lap of the Junior T.T. after lying | Wiinsche, retired at Ramsey on the second lap of the Junior T.T. after lying | ||
about fifteenth on lap 1. | about fifteenth on lap 1. | ||
The machine did, however, achieve some degree of | The machine did, however, achieve some degree of | ||
success on the Continent and became almost legendary for its fantastic rate of | success on the Continent and became almost legendary for its fantastic rate of | ||
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six-cylinder Bosch magneto was used, running at half engine speed and driven by | six-cylinder Bosch magneto was used, running at half engine speed and driven by | ||
bevels from the offside crankshaft end. | bevels from the offside crankshaft end. | ||
SPECIFICATION | SPECIFICATION | ||
Engine: three-cylinder 350 c.c. two-stroke with 1200 firing intervals; | Engine: three-cylinder 350 c.c. two-stroke with 1200 firing intervals; |
Revision as of 21:17, 14 June 2019
Class | Classic |
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Overview
DKW SS 350 Three Cylinder
DKW SS 350 1953 HREE-CYLINDER DkW. Possibly the only three-cylinder machine to have been raced in the I.o.M. T.T. events since they began 'way back in 1907, the 1953 German 350 c.c. D.K.W. design was not destined to achieve distinction in that series for, after one rider had had an accident during practice weekthough not in a practice periodthe other, Siegfried Wiinsche, retired at Ramsey on the second lap of the Junior T.T. after lying about fifteenth on lap 1.
The machine did, however, achieve some degree of
success on the Continent and became almost legendary for its fantastic rate of
acceleration.
This feature came about not only because of an excellent power output, but
because the machine had been designed from the start, by Ing. Wolf, as a
lightweight. Light alloy was used for almost everything and the factory had a
set of four interchangeable tanks made, in capacities from 2 to 7 gallons, for
each machine, so that weight could be saved according to race length. This
policy paid off, for the dry weight of the complete machine was a mere 180 lb.!
Weight is the start of a vicious circle in
designif a machine is heavy it needs more powerful (and so, generally, heavier)
brakes to stop it which puts the weight up further. The better brakes need
stiffer forks to cope with the increased load . . .
But what of the power unit, with its triple
crankcase in unit with a four-speed box? Each light-alloy barrel, with cast-in
liner, and its head, with hemispherical combustion chamber and central plug, was
held to the crankcase by four through-bolts. Although the factory's 250 c.c.
twins employed a rotary inlet valve, the "350" had a normalmore or
lessthree-port inlet, transfer and exhaust system. The outer cylinders were
parallel, but the centre one lay horizontal (6o° from the others) and a 120°,
three-throw crankshaft was used, running in five roller bearings.
Each crank compartment was, of course, sealed from its neighbours.
One float chamber was shared by the 28 mm. bore
carburetters for "rear" pots and, to cope with the unit's 12,000 r.p.m., a
six-cylinder Bosch magneto was used, running at half engine speed and driven by
bevels from the offside crankshaft end.
SPECIFICATION
Engine: three-cylinder 350 c.c. two-stroke with 1200 firing intervals;
light-alloy barrels with cast-in liners; claimed maximum r.p.m. 12,000.
Ignition: six-cylinder Bosch magneto driven at half engine speed by bevel gears.
Transmission: four-speed gearbox in unit with engine, chain final drive.
Frame: ultra-light duplex cradle with swinging-fork rear suspension.
Forks: telescopic.
DKW SS 350 Three-cylinder 1955
Though World War II brought a lot of changes everywhere, the
designers at DkW persisted in maintaining the racing possibilities of the
two-stroke engine. After the war Zschopau in Saxony became part of East Germany
and DkW relocated in Ingolstadt, where it went back into motorcycle
manufacturing. Two new designers, Wolf and Jacob, succeeded Zoller at DkW, but
they shared his general views.
Wolf and Jacob built a new two-stroke engine with three
cylinders arranged in V form. Two cylinders were parallel and slightly tipped
forward. The cylinder between them was horizontal.
The engine was quite different from
the older supercharged models. But if one looked at the cylinder pump of the URe,
in effect a kind of atrophied engine cylinder, one might argue that the URe also
had a three-cylinder V engine, aside from the fact that the upper two cylinders,
although parallel, were set longitudinally.
The new two-wheeler made its debut at the 1952 Swiss Grand
Prix, but the DkW 350 three-cylinder did not look as promising as its
predecessors. All it had in common with them was the large fuel tank, which gave
it a very heavy look.
Throughout 1953 and 1954 the DkW 350 never started a race as a
favorite. The 350's lack of success only spurred the DkW designers to try
harder. Late in 1954 the three-cylinder vehicle was generating 42 h.p. in tests,
a record for its displacement.
To compensate for the almost total lack of engine-braking (due to the two-stroke
cycle), the designers gave this DkW a new suspension system and a large front
and rear brake.
The chassis was extensively modified and the cylinder exhaust
system was redesigned. Thus appeared the first expansion chambers, which are now
standard on all two-cylinder racing motorcycles.
In 1956 the DkW 350 seemed really competitive; indeed, it was
faster and more powerful than the competition. The DkW's rivals that year were
the Italian four-cylinder Gilera and the Moto Guzzi single-cylinder. Although
the Guzzi was less powerful than the DkW, it was also considerably lighter in
weight than its German rival.
The DkW showed its unusually high speed when it won at Hockenheim, the fastest
circuit in Europe. Subsequently it had disappointing losses, and late in 1956 it
was withdrawn from racing.
Motorcycle: DkW 350 Three-cylinder Manufacturer: Auto Union
DkW, Ingolstadt Type: Racing Year: 1955
Engine: DkW three-cylinder, two-stroke, V (two vertical cylinders and one
horizontal cylinder) with cross-port distribution. Displacement 349.4 cc. (53
mm. x 52.8 mm.)
Cooling: Air
Transmission: Five-speed block
Power: Over 42 h.p. at 10,500 r.p.m.
Maximum speed: 130 m.p.h.
Chassis: Continuous double cradle with tubular elements. Front, swinging-trigger
suspension; rear, telescopic shock absorbers
Brakes: Front, central drum with four hydraulic shoes; rear, central drum with
hydraulic controls and supplementary hand control
For a complete DKW racing history click
External Links
http://www.odd-bike.com/2014/02/dkw-supercharged-two-strokes-force-fed.html