DkW 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 week—though not in a practice period—the 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
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
design—if 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 normal—more or
less—three-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.
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.