The TRW wasn’t Triumph’s first military twin. The Edward Turner-designed 350cc 3TW ohv lightweight twin had just commenced production when bombs destroyed the Coventry factory in 1940. When the new Meriden factory opened in 1942, building thousands of 350cc 3HW ohv singles was the priority. Turner returned to Triumph from a brief stint at the rival BSA factory, having reportedly designed a 500cc side-valve military twin while there – but Triumph resolved to trump the BSA twin and was first to have a prototype running, in 1943. Coded 5TW, it was pitted against the BSA and a 600cc Douglas side-valve flat-twin in post-war Ministry of Supply comparison tests.
The 5TW had the factory’s first telescopic forks and a crankshaft similar to the Speed Twin’s, but camshaft drive was by chain instead of gears. To help meet a 300lb maximum weight stipulation, the crankcase was of magnesium alloy.
The MOS, which would have subsidised tooling and production, cancelled trials in 1948. A special military machine would be too costly, so the policy instead would be to adapt an existing production model to military trim, should the necessity arise. Seeing future orders likely, Meriden revised the design so as to share 80% of components with existing models. The frame and other cycle parts came from the TR5 Trophy trials iron, while the engine used a crankshaft like that in the 350cc 3T commuter ohv twin, with one-piece conrods on crankpins clamped with cotters in a central flywheel. Meriden could then offer a military bike at a keen price and did not rule out a possible civilian version. The TRW, known at the factory as the Hybrid, appeared at the 1949 Scottish Six Days Trial in the hands of MOS rider WA Randall, who also rode one to a Gold Medal in that year’s ISDT. Production batches began in 1950, the biggest by far being more than 2000 in 1957. While the British Army stuck with BSA’S M20 side-valve single as its standard issue for low-ranking soldiers, it ordered some TRWS, including for the Royal Signals White Helmets display team, who famously carried 22 soldiers on one bike. Triumph found several other buyers including NATO forces and authorities as far afield as South Africa and Pakistan. Nearly 16,000 were built in batches until 1964, one leaving the factory with a swingarm frame. Little-used TRWS can now fetch £10,000 and caches of NOS parts have popped up (see burtonbikebits.net). As Chris Evans discovered, the TRW is no longer scorned for its utilitarian character. Modest performance does not preclude it from being a cool urban ride that can be made more glamorous with a period civilian finish.
Triumph TRWS about to be testridden at Meriden
Cutaway engine shows gear-driven camshaft