DKW ULD 250

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DKW US 250 from 1939
Further development of the ULD with multi-cell compressor
DKW UL 250 with charge pump (1935–1937)

The DKW ULD 250 was a racing motorcycle of DKW , the 1937-1939 very successful in motorcycle racing was used. The DKW ULD 250 with dual pistons - two-stroke engine and charging pump was valid until World War II when racing in their class to be unbeatable.

History and technology

As early as 1932, the DKW racing department was developing two-stroke racing engines with double pistons based on the Zoller system . A secondary connecting rod for the second piston was linked to the main connecting rod in order to reduce flushing losses. The two-stroke piston piston engines used up to now have become less and less competitive as racing engines. In 1935 a water-cooled 250 series with a double piston engine and charge pump appeared. The charge pump used the crankcase for pre-compression. The piston of the pump was driven by the crankshaft by eccentric connecting rods, the inlet was controlled by diaphragm plates. This engine (URe 250) last developed 17.6  kW (23.9  hp ) at 4500 rpm. The engine was continuously developed, experimenting with the position of the charge pump. However, the membrane control did not allow speeds above 4800 rpm.

The ULD 250 was introduced in 1937. The double-piston engine with charge pump was now controlled by a rotary valve, the charge pump had its own crankshaft, which was driven by the crankshaft of the engine via gears. This stable engine achieved an output of 22 kW (30 hp) at 6000 rpm. The fuel consumption of the 183 km / h machine was 15.68 liters per 100 km (15  mpg ).

The last expansion stage was the DKW US 250 with two cylinders (double piston, a total of four pistons) and rotary compressor (multi-cell compressor) from 1939. The US 250 is said to have achieved 29.4 kW (40 hp) at 7000 rpm, but only in the Training and not being used in races.

Races and other models

With the DKW ULD 250, Ewald Kluge became European and German champions in the class up to 250 cm³ in 1938 and 1939 . In 1938 Kluge also succeeded in becoming the first German TT winner in the class up to 250 cm³ (lightweight) . Bernhard Petruschke was the 250 runner-up European champion behind Kluge in 1938 and 1939.

A 350cc racing machine with a double piston engine and charge pump developed 40 hp at 5500 rpm, but never came close to the great successes of the ULD 250. Siegfried Wünsche achieved third place in the class up to 350 cm³ at the European Motorcycle Championship in 1938 behind the British Ted Mellors ( Velocette ) and "Crasher" White ( Norton ).

With a 350 series UL 350 racing machine (two-cylinder, double piston, piston charging pump) Heiner Fleischmann was able to "clearly eliminate all English competition in 1939 and won the European championship in its class".

A sidecar version with 598 cm³ displacement and 48 hp was successful at the European motorcycle championship in 1937 with the duo Karl Braun / Ernst Badsching. They won the European Championship run in Bremgarten as part of the Swiss Grand Prix, ahead of the locals Ferdinand Aubert / Rudi Grob and Max Hunziker (both Norton).

References

literature

  • John Griffith, Siegfried Rauch: The famous racing motorcycles . A type book. 2nd Edition. Motorbuch Verlag, Stuttgart 1965, p. 44-45 .
  • Frank Rönicke: DKW racing machines 1921–1956 . About people, machines and DKW victories. 1st edition. Schrader Verlag, Stuttgart 2003, ISBN 3-613-87256-0 , p. 43-45 .

Web links

Individual evidence

  1. ↑ a b Siegfried Rauch: Famous racing motorcycles . 2nd Edition. Motorbuch Verlag. Stuttgart (1980). ISBN 3-87943-590-1 , pp. 58, 59
  2. ↑ a b c Erwin Tragatsch : Famous Motorcycles. Motorbuch Verlag Stuttgart, 1st edition 2000, ISBN 3-613-02038-6 , p. 46 ff
  3. ↑ ULD 250 construction drawing (accessed April 12, 2012)
  4. ^ LJK Setright: The Guinness Book of Motorcycling. Facts and Feats. 1982, ISBN 0-85112-255-8 , p. 97
  5. ^ Christian Bartsch (ed.): A century of motorcycle technology. VDI Verlag, 1987, ISBN 3-18-400757-X , p. 146
  6. ↑ Helmut Krackowizer: Milestones in motorcycle history. Motorbuch Verlag, 1st edition 1987, ISBN 3-613-01141-7 , p. 117
  7. ^ Siegfried Rauch: DKW. History of a global brand. Motorbuch Verlag, 1st edition 2007, ISBN 978-3-613-02815-9 [based on the first edition from 1981], p. 85: “What was in terms of performance in the new four-piston engine was demonstrated by Heiner Fleischmann in 1939 at the Hamburg city park race, the lap times that came close to the 500cc supercharged BMWs. The compressor lasted this relatively short race - the fact that the DKW only came in second was due to ignition difficulties and a crankshaft seal that was blowing through. ”- Rauch mentions the power output“ just under 40 hp ”at 7000 rpm for 1941 when the engine was stable had become. A version intended for record attempts achieved 50 hp with alcohol fuel.
  8. ^ Rauch, page 93