The BSA Rocket 3/Triumph Trident was
the last major motorcycle developed by Triumph Engineering at Meriden, West
Midlands. It was a 750 cc air-cooled unit construction pushrod triple with four
gears and a conventional chassis and suspension. The motorcycle was
badge-engineered to be sold under both the Triumph and BSA marques. The Rocket
3/Trident was part of Triumph's plan to extend the model range beyond their 650
cc parallel twins.
Created to meet the demands of the
US market, the smooth 750 cc three-cylinder engine had less vibration than the
existing 360° twins. Although BSA experienced serious financial difficulties, 27
480 Rocket 3/Tridents were produced during its seven-year history.
Although designed during the mid-1960s, the BSA Rocket 3/Triumph
Trident engine originated in a 1937 parallel twin: the 500 cc
Triumph Speed Twin, designed by Edward Turner. The 1938 Tiger
100 was a sports version of the Speed Twin; the Trident
three-cylinder engine is a larger version (although the triple
has a longer stroke than the Tiger 100 engine). Following
Triumph tradition, the OHV Trident engine has separate camshafts
for the inlet and exhaust valves.
The three-cylinder design was developed in 1962 by Bert Hopwood
and Doug Hele. Test engineers developed the chassis' handling
characteristics by affixing lead weights on a standard 650
Bonneville. The first prototype (P1) was running by 1965, and it
seemed that Triumph might have a machine in production by 1967.
However, the decision to produce a BSA version with sloping
cylinders and employ Ogle Design to give the early
Tridents/Rocket 3s their "square tank" added bulk and 40 lb (18
kg) of weight, delaying production by 18 months.
In 1966 a P2 prototype was produced with a more production-based
Trident engine, different bore and stroke dimensions and
improved cooling. Hele got 90 bhp (67 kW) from a Trident engine,
leading to speculation that if development had quickened in 1964
a 140 mph (230 km/h) British superbike could have been produced
by 1972.
Although most British motorcycles used a wet multiplate clutch,
this triple had a dry single-plate clutch in a housing between
the primary chaincase and the gearbox. Mounted on the end of the
gearbox mainshaft (where the clutch would be expected) was a
large transmission shock-absorber.
All the three-cylinder engines (and the Rocket 3 motorcycles)
were produced at BSA's Small Heath site, but final assembly of
the Triumph Trident model was carried out at Meriden in
Coventry. The major differences were the engine and frame: the
BSA had an A65-style double-loop cradle frame (with engine
mounted at a slant), while the Triumph had a Bonneville-style
single downtube frame with vertical cylinders. Other differences
were cosmetic. Triumphs sold better in the US, despite BSA's
Daytona racing successes during the early 1970s. Sales did not
meet expectations; for the 1971 model year a fifth gear was
added, creating the BSA A75RV and Triumph T150V. BSA were having
financial difficulties, and only some 205 five-speed Rocket 3s
were built before production of the BSA variant ceased.
Any corrections or more information on these motorcycles will be kindly appreciated.