The Dominator is a twin cylinder motorcycle developed by Norton to compete against the Triumph Speed Twin. The original Dominator was designed in 1947 and 1948 by Bert Hopwood, who had been on the Speed Twin design team at Triumph. This design set the pattern for Norton twins for the next 30 years.
The first Dominator, the Model 7, had a 497 cc parallel twin engine with iron cylinders and cylinder head and a Lucas K2F magneto. The crankshaft was of 360-degree layout. A single camshaft at the front of the engine was driven by gears and chain. The rocker box was integral with the head, so there were fewer gasket faces to leak and less valve noise. The engine was a long stroke design with 66.0 mm × 72.6 mm (2.60 in × 2.86 in) bore and stroke and mild tuning, resulting in more torque low down. For the first few years a plunger frame was used, but in 1953 the Model 7 was upgraded with a single downtube swinging arm frame, 19-inch front wheel and ‘pear shaped’ silencers, still known as a Model 7. The Model 7 continued in production through to 1955 and was often used with a sidecar, which could not be fitted to the later Featherbed frame Dominators.
The Featherbed frame was designed for Norton by the McCandless brothers and made by the Reynolds company because the Norton works did not have the necessary welding capacity for its manufacture. The Featherbed frame led to the Model 88 Dominator, also called the Dominator De Luxe, which used the same 497 cc engine and was developed in 1951. Originally developed for export it was sold on the home market from 1953. The 88 suffered from oil leaks from the primary chain case but it was the outdated and inefficient Norton works that resulted in quality control problems for the 200 Model 88′s produced each week.
The 597cc featherbed framed Model 99 Dominator was introduced in 1956, as a larger capacity version alongside the 500 cc Model 88 version. Due to the increased engine capacity, the 99 had a power output of 31 bhp, partly due also to a higher compression ratio possible with the alloy head introduced a year earlier. Full width alloy hubs with improved brakes had also been introduced a year earlier, preparatory for the capacity increase from 500 cc to 600 cc
The first Model 77 was a rigid framed telescopic forked Dominator version of 500 cc produced from 1950, and supplied to the Australian market only. Only a few hundred were made, from 1950 to 1952. This used the all iron Dominator 500 cc twin engine, with an oil pressure gauge in the ES2 style but flat bottomed petrol tank.
The 596 cc Model 77 Dominator was introduced in late 1956. Essentially a swinging arm, single downtube ES2 chassis with a 600 cc Dominator 99 engine, it was in production at the same time as the Dominator 99 as a sidecar motorcycle but was dropped from production after 1957, when sidecar Featherbeds were introduced.
A new 650 cc model was added to the lineup late in 1960. The frame was altered so that the top rails were closer together at the front of the seat area to create what became known as the ‘slimline’ featherbed. A 650 cc engine was installed to create the Norton Manxman. First built from 7 November 1960 to September 1961, these machines were a Limited Edition for the USA only, in custom-cruiser style – with high handlebars, all polychromatic blue paint and bright red seat with white piping round the edge. In September 1961 the 650SS was introduced. It had USA cafe bar style and twin carburettors. The SS stood for Super Sports and the 600 cc models were discontinued to concentrate on production of the 650SS, which quickly earned a reputation as the “best of the Dommies”.
The Norton factory racing team briefly used race-tuned Dominators from circa 1960, but they were still outclassed by the Norton Manx. Doug Hele wanted to see the Dominator developed and produced a 55 bhp (41 kW) “Domiracer” that revved to 8,000 rpm. The Domiracer weighed 35 lb (16 kg) less than the Manx. Dennis Greenfield and Fred Swift won the 500 cc class in theThruxton 500 event in 1960. In the 1961 Isle of Man TT Tom Phillis took the bike to third place and lapped at over 100 mph (161 km/h), a first for a pushrod engine and a first for any twin. Norton abandoned the Domiracer project a year later when the Bracebridge Street race shop closed and the Domiracer and factory spares were sold to Paul Dunstall, who continued with development and began producing Norton performance parts, eventually selling complete Norton Dunstall bikes to customers including Steve McQueen.