Swiss engineer Arnold Zoller, who lived in Berlin, had been a designer for Horch before setting-up on his own company
for building superchargers. Used on the victorious DKW and BMW motorcycles Zoller superchargers would later also be known
to automobile racing fans as they appered on the ERA voiturettes.|
Zoller decided to attack the problem of producing a high-performance two-stroke racing car to be run in 1500cc Voiturette class events. Zoller was also reported to be developing a similar smaller 750 cc engine for smaller class events.
For the chassis Zoller turned to Röhr Automobilwerke AG, a firm that had been established at Ober-Ramstadt in 1928 by fellow Swiss Hans-Georg Röhr, an ex-aviation engineer. Röhr had produced a swing-axled car, the Röhr type R, with a 2.5 litre 8-cylinder engine. The car had proved to handle very well. In 1930 Röhr had to go to Adler and a Swiss finance house took it over. Zoller decided that he should adopt Röhr suspension layout in his new car.
The Zoller racing car was a neat construction looking very much like a mini version of the Mercedes-Benz W25. Three cars were ready for the Voiturette class of the 1934 AVUS rennen to be raced by von Delius, Macher and Wimmer, but they suffered from technical difficulties and had all to retire. Two cars ran well in the 1934 Eifelrennen before suffering from overheating. Then the project suddenly came to an end as Arnold Zoller collapsed and died. Gerhard Macher attempted to carry on the project constructing a sports car with Zoller engine but the project advanced slowly and was finally interrupted by the war.
The two stroke engine had an aluminium alloy crankcase and cylinder block, cast in one piece with twelve cylinders in two rows. The detachable head casting carried common combustion chambers for each pair of cylinders. The left side of the engine carried the inlet ports and the right side the exhausts. The exhaust-side pistons had the "master" con-rods, and the inlet bank had shorter "slave" rods. The exhaust pistons opened and closed their ports earlier than the inlet pistons. Zoller's crankshaft ran in roller-bearing mains, with needle-rollers at the big-ends.
The two Zoller superchargers were arranged horizontally one above the other, and they took air from a dual-stroke Solex carburettor. Boost pressure was 21 psi.
It was clamed that the dual cylinder arrangement made the 1.5 litre two stroke engine enable to consume a volume of gas equal to that of a conventional 6 litre engine.
The chassis was a sheet-steel platform construction with twin transverse leaf springs suspending the front wheels and outboard semi-elliptics at the rear springing swing-axles.
Info supplied by Richard Armstrong and Felix Muelas
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