The Triumph brand dates to the very beginning of the motor-car and -cycle era. Until World War 2, production was based in Coventry, being forced to a new facility at Meriden by the destruction of the City. By then the company had already gone to the brink, with the motorcycle company being bought out by Ariel Motorcycles in 1936, and the car company eventually being bought out by the Standard Car Company.
Edward Turner launched the Triumph Speed Twin motorcycle at the 1937 National Motorcycle Show. It was a standard ‘touring’ motorcycle, and debuted 500cc overhead valve vertical twin giving about 27hp in standard trim and set the standard for many twins to follow. Although a twin-cylinder, and originally mainly cast iron, it was impressively light in comparison to the singles it would have to battle on the circuits.
The Speed Twin engine had a vertically split crankcase housing a single, central flywheel, crankpins are “in line”, allowing both pistons to rise and fall simultaneously and the cylinders fire alternately with power impulses spaced evenly at 360 degrees. Early Twins are fitted with a six-stud cast iron barrel and cylinder head, with separate alloy boxes housing both the rockers and valve adjusters. Camshafts are situated high in the crankcase, gear driven through an idler gear by the right side of the crankshaft. Separate pushrod tubes run fore and aft of the cylinders. With separate magneto and dynamo, the engine also gained the distinctive V-cover on the right hand side (in comparison to most other engines of the time)
The Speed Twin motorcycle effectively saved the company through exports to America and sales to the police and the engine formed the basis of a whole generation of motorcycle engines.
Turner already had a policy of delaying the sport model of a motorcycle, so the problems could be worked out on the less-stressed touring model. So in 1939, Turner launched the Tiger T100 – the sport model (read that as clubman racer model) of the Speed Twin. The revised engine ran with forged alloy pistons and a higher compression ration of 8:1. The cylinders were forged in a single casting and held in place by eight studs giving around 30 hp. Ignition came from Joe Lucas and a single Amal carb fed though a revised manifold. The result was the Tiger 100, capable of 100 mph. As an indication of the intended purpose of the Tiger, the production exhaust featured a novel end cap and baffle assembly that could be easily removed, leaving a pair of full-race megaphones…
The Tiger 100 responded well to tuning and Triumph offered a Racing Kit with either 8.25:1 or 9.5:1 compression ratio pistons, profiled camshafts, valve springs, twin Amal Type 6 carbs with remote float and dual throttle cables, Smiths tachometer and megaphone exhausts. 42hp was the result, still not quite on par with the JAP but a compact design and flexible power delivery helped offset the 5hp disadvantage.
In 1951 the engine gained an alloy cylinder barrel & head, followed by revised head finning in 1954 to improve cooling. Then in 1956 Triumph introduced the Delta-head variant. This splayed the inlet ports, making space for a pair of Amal TT carbs and better breathing.
It was probably this last point that explains why the Triumph engine never quite ‘broke through’. Always developed as the clubman’s racer, the Twin had an efficient hemispherical combustion chamber – which was great for the petrol engine, but once the piston was domed to up the compression ratio for methanol, efficiency ran down. On top of this, the high-revving you would hope for from a Twin (compared to the Norton and JAP thumpers) was compromised by having to continue with a single carburettor. Developments of both might have come through earlier, but in 1951 Triumph had been sold to the BSA group, and there was never the interest or funds to develop a methanol special (where Norton’s ‘win at any cost’ approach had produced specialists like Francis Beart and Steve Lancefield).
The Grand Prix engine was derived from a war time portable generator unit (which, unlike the contemporary versions of the Tiger and Speed Twin, had an alloy head), though still based on the basic Speed Twin design. In effect it was like the Tiger engine, but with all of the road elements (such as the dynamo & mounting) eliminated. It first appeared in 1946 helping to win the Senior TT on the Isle of Man and eventually became available in a limited production machine in 1948. Production was very limited, and it was phased out in 1950, replaced by the race-spec version of the Tiger 100.
Known Triumph Twin powered cars include: Aikens, ASA, Cooper T4 sports car, Deslandes, Dane, Flash Special, Jason, JLR, Keller, Mackay, Marshall, Marwyn, Snipe, Tiger Cub, Tiger Special, WHD, Whitfill The most high profile victory for a Triumph was when Frank Aikens won the 1950 British Grand Prix support race in his Iota P1.
Triumph In America
Triumph’s range of 650cc engines provided the simplest way of boosting the power of standard Formula III car, which even into the early 1960s offered light weight and impressive roadholding. The Twins also provided better reliability than the JAP, better accessibility to spares, and the opportunity to revert to petrol, all rather useful in some of the more obscure places that 500s reached.