Today in Motorcycle History

Jack Moore

In 1945, Jack Moore had been asked to design an engine to compete with the Triumph 500. He delivered two prototypes, the first of which was a shaft-drive engine mounted in a modified Norton 16H frame. His second design was more conventional, with a chain driven rear wheel. This engine was destined to go into production during 1948 mounted in a modified ES2 frame.

Bert Hopwood joined the firm in 1947 as Chief Designer and decided that Moore's engine was too complex to produce economically, besides which it leaked oil and the similar appearance to the Triumph twin could well cause copyright issues. It had twin camshafts with front and rear pushrod tubes, gear driven timing wheels and detachable rocker boxes.

Joe Craig had the position of Chief Engineer at Bracebridge. Craig and Hopwood battled for more funding for each of their respective projects.

Phil Hannam writes:

The other major problem that probably condemned this engine as a non-starter is the number of oil seals required in the barrels and cylinder head. There are individual sets of three for each valve plus two external pushrod tubes all fighting to keep the motor oil-tight - the combination of steel, iron and aluminium plus heat making this near impossible.

Hopwood's solution was easier and cheaper to manufacture, and almost oil tight.

However, the Moore design was not wasted as modified variations of his crankshaft, conrods, pistons, timing cover and oil pump were incorporated in the Model 7 Dominator engine, with which it also shared very similar bore and stroke dimensions. Other features of the Moore design were used in the Jubilee and Navigator engines over a decade later.

Source: Phil Hannam of the Surrey Norton Owners Club. More here: Jack Moore at

1. There was another Jack Moore. Born in Cheadle, he died riding a Norton at Ramsay on the Isle of Man during the TT on June 13th 1938.
2. Walter Moore was another Norton designer, famed for the CS1.

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