Hermann Reeb, a very talented designer, began developing twin-cylinder engines and presented the results to Fritz Kleemann, his superior at Horex, in late 1932.
The engine was an OHC parallel twin which preceded Edward Turner's Triumph Speed Twin by some five years.
The twin was marketed in two versions: the S6 (600cc, 24 hp) and the S8 (800cc, 30 hp). Both engines had the same stroke: 90 mm, with a cylinder bore of 65 mm for the 600 cc version and 75 mm for the 800.
The alloy crankcase supported two cast iron cylinders, with considerablee space between them allowing for superior air-flow. The crankshaft had three main bearings with support on both sides and centrally.
The overhead camshaft was driven by a chain within an aluminum housing. The machine used four chains - one for the valve drive, one for the magneto, a dual-row chain for the primary drive to the Hürth four-speed gearbox, and a chain for final-drive to the rear wheel.
The engine had dry-sump lubrication with the 2¼ litre oil tank situated within the crankcase. Fuel was delivered via Amal carburettors.
A competition version was developed for sidecar racing, with displacement increased to 995cc. This engine had aluminum alloy cylinders and bronze cylinder heads, and developed 58 hp at 7,500 rpm. Karl Braun won the 1935 German Sidecar Championship with a supercharged 1000cc S8.
The Horex-Columbus engine powered Tornax Tornado model.
With the economy still in recovery mode, the high price of the S6/S8 led to limited demand. Production was discontinued after two years, with 82 of the S6 and 96 of the S8 sold.
Source: Sergio Scalerandi
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