Vincent Rapide
Vincent Rapide Background & History
The Vincent Rapide was a 1000cc (998cc actual displacement) V-twin, high-performance motorcycle built from 1936 through 1955, with a break in the middle for World War 2. It was built in 4 ‘series’, A through D. Series A was everything built prior to the suspension of civilian production in 1940, so 1936 through the 1939 model year. Series B was substantially redesigned and ran from 1946 through 1947. Series C further revised was produced from 1948 through 1953. The Series D ran from 1954 to Vincent’s final year in business, 1955.
LEFT: The Vincent Comet engine was a 499cc single. Check out the shape of the timing cover. RIGHT: The Vincent Rapide engine was exactly double that, at 998cc. Compare the shape of the timing covers. They're the same! It's practically the same engine with one more cylinder added in back. Brilliant!
From a Single to a Twin
Prior to the war, Phil Irving, Vincent's chief engineer, was sitting at the drawing board with two tracings of the Vincent 499cc single-cylinder engine. As things got moved around, the top tracing roughly lined up withj the bottom one such that it made it look like a V-twin. With a little cajoling, he lined it all up and the Vincent V-twin was born. The likeness is so uncanny that the single looks the same as the V-twin except that it's missing the rear cylinder. The new 998cc V-twin was introduced in the 1936 Vincent Series A Rapide. It made 45 hp and was good for 100 mph, stellar at the time. It was produced in small numbers prior to World War 2. When it was reintroduced after the war in 1946, it had been completely reengineered and it was a monster. This in turn led to the Vincent Black Shadow, which was the hot rod version of the Rapide. But it all started with the lowly 499cc Vincent Comet single.
This 1938 Vincent Rapide is a fine example of a Series A.
Series A Vincent Rapide, 1936-1939
The Series A Vincent Rapide was their first-ever V-twin, and it was built on the platform of the Vincent Comet. They shared frame, wheels, brakes, suspension and some bodywork. The frame incorporated Vincent’s own ‘cantilever rear suspension’ that functioned very much like Harley’s Softail. Both bikes replace the conventional swing arm with a floating rear frame section called the ‘rear frame member’ or RFM for short, whose pivot point bolted to the back of the gearbox. The whole rear of the frame moved and was suspended by two shock absorber-like ‘spring boxes’ and a friction damper positioned almost horizontally under the seat. It was a brilliant system in a day when almost everyone else was running rigid frames. As the result, the Vincent Rapide rode better than just about anything else on the market, but they were prone to flexing during hard cornering.
The front suspension of the Series A Vincent Rapide was the same Brampton girder front fork with friction damping that was used on the Vincent Comet. However, the Comet had an external oil tank to support its dry sump lubrication system, and the bigger engine took up the space in the frame where the oil tank used to live. So the Series A got a fuel tank with two filler caps, one for gas and one for oil. The brakes were Vincent’s unique dual (2-sided) 7-inch single-leading shoe (SLS) drum brakes front and rear, and the wheels were interchangeable. Vincent worked hard to keep the weight down on all their bikes, and it paid off. The Series A Vincent Rapide weighed just 430 lbs. and had a wheelbase of 58 inches.
This Series A 1938 Vincent Rapide shows what a Series A engine looked like from the timing side. Check out all those chromed oil lines running to the top end. Also note the exposed 'hairpin' valve springs. Those were gone in the Series B.
The 998cc V-twin engine of the Vincent Rapide was unique with a 47-degree V-angle. The overhead valve (OHV) setup placed two gear-driven cams high in the crankcase, one for each cylinder, operating short pushrods that in turn worked the rocker arms which were also quite unique. In the 1930s valve stability at high rpms, and the poor metallurgy available then to make valve guides were limiting factors on performance and durability. Vincent solved the problem by installing two valve guides on each valve, one high and one low. The ‘hairpin’ valve springs were at the end of the valve stem, exposed on top of the cylinder head. The rocker arms were forked and worked the valves from between the two guides. It was a complex system but it worked quite well. The bore and stroke were 84mm X 90mm, very nearly square. Fuel was handled by two Amal 1-1/16” carburetors, and with a compression ratio of just 6.8:1 the Series A Vincent Rapide produced 45 hp at 5500 rpm, good for 110 mph top speed. That was stellar in 1936. All Series A Vincent Rapides used a separate gearbox, just like the Comet, which was a 4-speed Burman unit driven by a triplex primary chain, with a multi-plate wet clutch. The dry sump lubrication system pressure fed oil to the connecting rod big ends, and the cam bushings, then via a wild set up oil lines oiled the top end as well, which were known as ‘a plumbers’ nightmare.
The Series A Vincent Rapide listed for just £142, the equivalent of around $200 USD. That seems impossibly low, but that’s the power of 90 years of inflation. Series A Vincent Rapide production ended in 1939, just as civilian production was curtailed in favor of war production during World War 2. The Series B would have to wait until after the war, in 1946.
This Series C Vincent Rapide engine shows how cleaner they were than the Series A machines. They just look fast, and they were!
Series B Vincent Rapide, 1946-1947
While Vincent didn’t make any motorcycles for the war effort, they made lots of other stuff including a very cool lifeboat motor. During the 5 years of wartime production, Vincent redesigned the Rapide. The Series B Vincent Rapide would have unitized construction, joining the engine and gearbox in a single housing, more than 10 years ahead of BSA and Triumph, and 6 years ahead of Harley-Davidson's unit-construction Model K. The V-angle of the cylinders was changed from 47 degrees to 50 degrees. This was done to better package the engine as a stressed member of the frame. In other words, the engine itself acted like a frame member, eliminating the front down tube and engine cradle of most motorcycles. Phil Vincent is quoted as saying “What isn’t present takes up no space, cannot bend, and weighs nothing”. So, why not eliminate that part of the frame, right? This left only an upper frame section that was pressed out of sheet steel, creating a hollow space inside that doubled as the external oil tank for the engine’s dry sump lubrication system. Gone were that gaggle of oil lines running up to the top end, all top end oil lines were now internal, cleaning up the looks and the oil leaks. Cantilever rear suspension continued but with shock absorbers to replace the Series A’s spring boxes and friction damper. The rear wheel on the Series B Vincent Rapide was reversible, with a sprocket on both sides. It was possible to run different sized sprockets on the two sides and change ratios by turning the wheel around.
The Vincent Rapide, and all Vincents used a unique 2-sided brake, front and rear. This image shows both sides of the front brakes on this 1948 Series C. Note that by Series C they had become twin-leading shoe (TLS) brakes with 7-inch finned iron drums. The wheels could be turned around and also swapped front to back.
Series C Vincent Rapide, 1948-1953
The Series C Vincent Rapide launched in 1948 with its primary improvement over the Series B being new front suspension. The old Brampton girder was replaced by Vincent’s own Girdraulic front suspension, which adopted blade-like fork legs instead of the welded tubes of the prior design. They had two springs and a damper. The Korean War caused a shortage of nickel chrome so some motorcycles built during this time (1950 through 1953) had black rims instead of chrome. In 1950 the ‘HRD’ monogram was dropped and from then on the logo said ‘The Vincent’.
Series D Vincent Rapide, 1954-1955
The Series D Vincent Rapide appeared in 1954, just one year before the demise of the company. While the factory never used the designation ‘Series D’ for the bike, there were so many changes and improvements made on the 1954 Vincent Rapide that it was viewed as another bike, and so the public adopted the Series D moniker. A combination of moving the shock absorber mounting lugs and adopting a single Armstrong damper unit increased rear travel by 30%. For the Series D, the engine had been converted from dry sump lubrication, which required an external oil tank, to wet sump which carried all its oil within the engine. So, the box section/integral oil tank of the original chassis was no longer necessary Vincent redesigned the upper frame out of welded steel tubing. Tire sizes increased in width and decreased in rim size from 3.00-20 fronts and 3.50-19 rear tires to 3.25-19 front and 4.00-18 rear. The magneto was replaced by a more modern coil ignition system.
Unfortunately, the lights went out at Vincent Motorcycles in December of 1955.
This is a 1955 Series D Vincent Rapide, the final year of production.
Vincent Rapide Motorcycle Books
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"Illustrated Vincent Motorcycle Buyer's Guide" Loaded with all the info you need before you buy a Vincent, or bid on one in auction, illustrated. |
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"Vincent Gold Portfolio, 1945-1980" By R M Clarke, 172 pagesReprints of motorcycle magazine articles, road tests, new model introductions, history, specs & more. |
More Vincent Motorcycle Pages
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