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

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