Norton Motorcycles Dominator 7 1951
In 1947, Bert Hopwood, who had worked on the development of Edward Turner’s original Triumph Speed Twin design, moved to Norton and laid out plans for a vertical twin to compete with the landmark Triumph and other similar machines that were being developed by the competition.
Hopwood used a single camshaft whereas the competitors used two and, for reasons of economy, the 497cc engine and its separate four-speed gearbox had to be accommodated in the existing single-cylinder ES2 model’s plunger frame. Continuing the economy theme, a single carburettor was used with the inlet ports close together and the manifold cast into the iron cylinder head although that arrangement was soon replaced with a bolt-on alloy manifold. The exhaust ports were splayed to improve cooling, which was an issue on the Speed Twin.
With newly designed fuel tank and mudguards, the Model 7 Dominator was launched in 1949 with an advertised top speed of 92mph (148kph). The Model 7 remained in production until 1956 despite being considerably overshadowed in 1951 by the launch of the Model 88 that featured the Featherbed frame. Its engine remained the basis of Norton twins for around 30 years.