Seventy years ago, the Vincent Black Shadow became the world’s first 125mph production motorcycle. Designer Philip Vincent achieved his masterpiece by rejecting conventional thinking
Celebrating 70 years of the Vincent Black Shadow, the world’s first 125mph bike
No other motorcycle in the post-war years has ever made such a performance leap over the opposition as the 1948 Vincent Black Shadow. Seventy years ago this September, the 998cc V-twin became the world’s first 125mph road bike when it was launched at the Earls Court show in London. Motor Cycling magazine in England tested it at 122mph, while in France Moto Revue achieved 128mph.
Vincent produced this astonishing machine at a time when other British factories hadn’t even got around to making 650s. BSA’S 1948 range-leader was the 500cc A7 Star Twin, which peaked at 84mph in a Motor Cycle road test. Norton’s Model 7 500cc twin would do around 90mph, and Triumph’s Tiger 100 about the same. Ariel offered a 1000cc bike, but the 4G Square Four was more of a sidecar-puller or gentleman’s tourer. In the USA Harley-davidson had the 74 cubic inch (1207cc) Panhead, but that too was a 90mph-ish bike. The Black Shadow was 25-35% faster than any other motorcycle you could buy – a feat unmatched by any other bike since – from Honda CB750 to Suzuki GSX1100, Laverda Jota, Kawasaki Z1 and Ducati 916.
“One hundred miles per hour doesn’t sound like much now, but back in the day most vehicles would go 80, 90, 91, and then you’re out of road,” says American TV star and Vincent enthusiast Jay Leno. “The Vincent could do it quite easily. You’d read stories about guys racing a Harley or an Indian, and then the Vincent guy would just click into fourth gear and pull away. All those tales make it a very exciting vehicle.”
“The Black Shadow must have been amazing in 1948,” says film-maker David Lancaster, who is making a documentary – Speed is expensive: The Untold Story of the Vincent Motorcycle. “You were on the fastest vehicle on the road. For fast touring, it would sit comfortably at 85-90mph, and the factory road testers would regularly do 120mph on the open road.”
Road conditions in Britain’s post-war era have to be considered to fully appreciate the Black Shadow’s impact. There were no motorways, few speed limits outside
30mph urban areas, and main roads were mainly two lanes. The Morris Minor – an exciting new family car for its time – had a 918cc side-valve engine, a top speed of 64mph and a 0-60mph time of 50-plus seconds.
In this landscape, the Motor Cycle magazine couldn’t find a space big enough to explore the limits of its Black Shadow. “No airfield or stretch of road could be found which would allow maximum speed to be obtained,” it intoned. It added: “It is difficult to visualise a route on which the Black Shadow could be driven for any length of time at or near its limit.”
The Shadow’s designers, Philip Vincent and his chief engineer Phil Irving, had created a motorcycle that was greater than Britain’s road system. It would be a quarter of a century or more before other manufacturers produced bikes such as the Z1, Jota and Ducati 900SS that could match the Black Shadow’s top end.
Just how did Vincent and Irving achieve such prodigious performance in a post-war Britain hollowed out by war, and strangled by materials shortages and money? They did it by dreaming big, and by rejecting accepted methods of achieving high speed. For more power and speed, most designers chase higher revs via radical tuning, more cylinders, more valves and exotic valve gear. Four cylinders, overhead camshafts and multi-valve cylinder heads were all familiar concepts by the time the Black Shadow was conceived.
But Vincent coveted none of that. He wanted just two cylinders (crucially, in a V-twin formation), two valves per cylinder and no overhead camshafts. He argued that his high-camshaft pushrod design avoided excessive engine height and improved cylinder-head cooling. Even the petrol he had to work with was a thin 72-octane gruel, which limited the Black Shadow’s compression ratio to 7.3:1.
Vincent was, however, early to adopt short-stroke cylinder dimensions. The first engine that he and Irving designed, a 500cc single in 1935, had an 84mm bore x 90mm stroke. That was short-stroke in an era when most manufacturers had not dared to budge from long stroke convention. The 84 x 90mm configuration was
retained in every Vincent engine made subsequently.
“We set out to get good low-speed torque on all our engine designs,” Vincent said in an interview. “There is too much of a tendency nowadays to sacrifice low-end performance, which is used nearly all the time the machine is ridden, for a very slight gain in top-end performance, which forms but a small part of the machine’s working life.
“Better torque characteristics also improve hillclimbing and provide a sweeter-running engine than where the valve timing and other features are designed for maximum power at very high revs.”
Add to that formula Vincent’s preference for tall gearing, and you had the basis for a motorcycle that was just loafing when others were screaming at flat-out revs. The Shadow’s 150mph speedometer became a design icon that everyone wanted to see just once, even if they could never dream of owning a Shadow.
It could be argued that Vincent and Irving didn’t have the resources to create a new exotic engine and that they had to rely on a development of their 1936 Rapide. But when they conceived that early Series A Rapide they did it using exactly the same design criteria outlined above – modest tune, tall gearing, mighty torque.
Vincent even foresaw the blind alley the parallel twin represented. Edward Turner’s 500cc Triumph Speed Twin was launched in 1936 to great acclaim. But Vincent wrote: “The V-twin’s slightly off-beat firing order gives an immense impression of effortless running that is so much more attractive than the fiendishly busy buzz of parallel twins which always seem to be working so hard that they cause fatigue in the rider.”
Vertical twins fatigued components as well, as riders in the ’60s and ’70s came to know only so well. British factories were bloating the capacities of their parallel twins and pushing increasing power outputs through them. They’d backed the wrong horse: they should have noted Philip Vincent’s prescient words. The parallel twin both opened the doors to a period of prosperity for British factories – and the creation of some memorable motorcycles – but also doomed it to eventual collapse. Philip Vincent was only 40 when the Black Shadow was launched. He was a visionary – he had designed his cantilever rear suspension system as a 14-year-old schoolboy in 1922. He used it on the first bike that he manufactured, a single-cylinder Jap-engined machine in 1928, when he was 20. He employed the cantilever system (adopted by the Japanese years later) on every machine he made, yet at the Black Shadow’s launch in 1948 other makers’ basic models still had rigid frames.
Vincent was an enigmatic figure. Bike production ceased in 1955 due to financial problems – he admitted he was more interested in engineering than money. He was 47, an age when most people are in their creative
prime. But after designing the world’s fastest bikes he never made another two-wheeler, and died at the age of 71 in relative poverty and obscurity in a council flat in West London, in 1979.
What happened? Why didn’t Vincent bounce back with another business, as creative types so often do? Why didn’t other British motorcycle makers employ him or use him as a consultant? Why didn’t someone help to ‘productionise’ his expensive bikes – lower the price while maintaining the core concept?
The rise of the Japanese bike industry was based on the cult of the across-the-frame four. These bikes were based on exactly the principles Vincent derided in a road bike – unnecessary complexity (as he would have seen it) and loadsa revs. These bikes are often criticised for offering a fussy, jangling, nervy riding experience, with poor, snatchy drivetrains (early examples, at least).
Again, it took a quarter of a century after the Vincent’s demise before Ducati saw the potential of the performance V-twin (I’m not including Harleydavidson in the category) and created a cult brand from it. It was all there in the world’s first 125mph road bike – but no one capitalised on Philip Vincent’s genius.
The Vincent team at Montlhéry in 1952, where Black Shadows set eight world records (Phil Vincent on right in suit and tie)
Right-hand profile reveals the full brutal beauty of the engine
Vincent’s famous five-inch 150mph speedo
A pair of Amal carbs feed the big V-twin
Phil Vincent had designed his first cantilever suspension system at the age of 14.
Brake light is as distinctive as the speedometer
Brakes were the best on the market at the time
Triplex primary chain and Vincent’s own clutch handled the power
Rollie Free (left) made his name on a Black Shadow
LEFT: Imagine being prone on the tank, as the needle passes 120...
ABOVE: Power, handling and craftsmanship make riding experience unique