Rapp Motorenwerke - Early Engines

Early Engines

Karl Rapp and Julius Auspitzer founded Karl Rapp Motorenwerke GmbH (Rapp Motorenwerke) with a capital stock of RM 200,000 on 28 October 1913 on the site of Flugwerke Deutschland GmbH (after the company went into liquidation). General Consul Auspitzer was the company's sole shareholder, with the operational side of the company managed by Karl Rapp. The idea was for the new company to build and sell "engines of all types, in particular internal combustion engines for aircraft and motor vehicles", in addition to building an engine for the second Kaiserpreis (Kaiser's Trophy) rally, but it was not ready in time.

Before World War I, Rapp produced both in-line 6-cylinder and V8 cylinder water-cooled aeroengines. The in-line 6-cylinder produced 125 hp @ 215 kg (474 lb); with a 901 cu in (14.8-litre) displacement. Soon, the company made the Rapp II, which increased the power output to 150 hp @ 260 kg (573 lb). Shortly thereafter, early into World War I, the Rapp III 175 hp (actual 162 hp @ 1400 rpm) 295 kg (651 lb) six-cylinder aeroengine was manufactured. The V8 they developed was 1201 cu in (19.7-litre), producing 200 hp @ 300 kg (661 lb).

All of Rapp's designs were overhead cam, with forged steel liners screwed to cast steel heads. The aeroengines produced by Rapp were easily distinguished from the other aeroengines (Mercedes, Benz, Basse, Selve, etc.), because the vertical shaft that drove the overhead camshaft came up between cylinders #4 and #5, instead of at the rear. Additionally, all the cylinders were in pairs.

When World War I broke out, German military authorities placed orders with Rapp Motorenwerke. With the influx of capital, the company expanded rapidly and employed 370 workers by 1915. In response to a commission from the German military authorities, Karl Rapp increased the output of his Rapp III engine from 150 to 175 horsepower. However, the strengthening which this called for made the engine extremely heavy, and the engines developed severe vibrations; so much so, that it achieved no commercial success. Even a revised version with four valves per cylinder, the Rapp IIIa, was unable to rectify this situation: the name Rapp had suffered to such an extent that the military departments no longer purchased engines from his company.