Designed during the Second World War, the Triumph TRW 500 is still a reliable mount for a peaceful country ride.
Story and photos by Graham Clayton
Over the past hundred years or so, many motorcycle manufacturers have built special models for use by the military, police departments and other government ministries. The original Triumph company was one such concern, building military models during both World Wars, as well for peacetime use.
The TRW 500 side-valve vertical-twin was one of these machines. Typically, such bikes had to be capable of off-road running in various adverse conditions, including the ability to climb relatively steep grades and to traverse a stream with 38 cm (15 in.) of water. Hence, ruggedness of build, durability and reliability were essential attributes of such machines.
So too were simplicity of design, ease of maintenance and repair in the field, and such things as a quiet exhaust, so as not to draw the attention of the enemy or to aid them in locating the source of any noise. Part of the original design specifications for what became the TRW 500 was that it was not to be audible at a distance of 0.8 km (half a mile).
The original design work on the bike was started in 1942 by Bert Hopwood to meet the British military’s need for a side-valve 500 for the war effort. These bikes were meant for use in couriering dispatches, staff car and convoy escort, military police security work, patrolling, reconnaissance and so on. At that time, Triumph was already building a 350 OHV single for the military.
So what really led Triumph to the build their side-valve 500 twin? Some say a huge shouting match between then Triumph-owner Jack Sangster and his chief designer, Edward Turner, who promptly quit, jumped ship and became chief designer at rival firm BSA.
When Sangster heard that Turner was designing a new side-valve 500 BSA twin for a military contract, he immediately ordered Hopwood to do the same thing, and to get it finished before Turner. Hopwood completed the 500 twin by February 1943.
For various reasons, Triumph’s side-valve 500 prototype never made it into wartime production, even though it met all of the required design brief specifications, including a dry weight of just 127 kg (280 lb.).