Inspired by the popular success of Triumph's
pre-war Speed Twin and aware that other factories
were working on their own versions, Norton realised
that if they were to have any future after World War
2, they too needed a twin engine.
The job was undertaken by Bert Hopwood, who had worked
on the development of Edward Turner's original Speed
Twin design and had vast experience in the insustry.
In 1947 Hopwood laid out his design, which aimed to
improve on the Triumpg's weakness, such as poor cooling
and also incorporated some ideas of his own. Chief
among these was the use of only a single camshaft
for inlet and exhaust valves, in place of the two
used by Triumph and all the other factories.
The design had to work within the constraints of
Norton's antiquated manufacturing machinery as well
as running on the poor quality post-war petrol. And
for reasons of economy, it had to fit into the existing
single cylinder model's frame. Such thoughts as these
were behind the choice of a single carburettor, with
close inlet ports and aplayed exhausts.
Fited into plunger cycle parts from the range-leading
ES2 single, with some cosmetic changes including a
special tank and mudguards, this became the Norton
Model 7 Dominator, launched in 1949.
With soft tuning, it offered little real challenge
to Triumph's twin - but it could still reach 90mph
and offered excellent reliability and handling in
the Norton tradition. It was phased out in 1956, having
long been overshadowed by its replacement, the De-Luxe,
or Dominator 88, which first appeared in 1953. What
made the 88 special was its frame, a close copy of
the successful Featherbed used on the works Manx Norton
racers. Weighing some 40lb less than the Model 7,
it handled and went rather better than its predecessor.
In 1956 the 88 Dominator's engine received the benefit
of some serious performance development. The engine
was resized by enlarging both bore and stoke to give
a new capacity of 600cc. Its power output went up
from 29 to 31bhp and the new model was given a new
name, the Dominator 99. With a hotter camshaft and
higher compression ratio, plus new carburettor, the
model's number roughly equated to its top speed. There
were also frame refinements to match the performance.
The next important change was in 1961-61, when a
new 49bhp 650cc model was announced and both the Dominator
88 and 99 came out in SS (Super Sports) versions.
The 600s were soon discontinued and in 1964 the first
of a series of 750 models, the Atlas appeared.
- Years in production - 1956-62 (Dominator 99)
- Engine type - parallel twin ohv four-stroke
- Capacity - 596cc
- Bore and Stroke - 68 x 82mm
- Compression ratio - 7.4:1
- Power - 31 bph @ 6500rpm
- Carburettors - 1 1/16in Amal 376
- Ignition - coil
- Wheelbase - 56.5in
- Top Speed - 101mph