The Legendary Vincent Series A Rapide

Was Philip Vincent driven by a restless pursuit of something better, or just a need to do things differently? Whichever theory you subscribe to, he always swam against the tide. Having acquired, with the help of family money, the name and intellectual property of HRD Motors Ltd. in 1928, he set out to revolutionize motorcycle design.

The first Vincent-HRDs used bought-in, off-the-shelf engines housed in a cleverly triangulated frame using straight tubes and, of course, Vincent’s own rear suspension. Unfortunately, Nigel Motorbike-Buyer had a fixed idea of how a proper British motorcycle should be. Previous attempts at rear suspension by other makers had been unsatisfactory and simply added to the cost. And the straight-tube frame, whatever its merits, was also regarded with suspicion. Vincent-HRD sales were disappointing.

By 1931, Phil Irving had joined Vincent-HRD, and his first tasks were to design a semi-sprung passenger pad (something he no doubt had an opinion on after the trip from Australia!), and to create a steel tube diamond frame to appeal to the conservative British buyer. The rear suspension stayed, albeit with the spring boxes hidden under the seat.

Vincent’s preferred engine was the 500cc Python OHV engine from the Rudge-Whitworth company of Coventry, though JAP engines from John Prestwich & Sons of Tottenham, London, were also used in both side- and overhead-valve forms. With Rudge winding down its proprietary engine division, JAP became the default option. However, when the JAP racing engines fitted to all three Vincent-HRD entries in the 1934 Isle of Man TT expired, Vincent decided it was time to make his own engine.

The Vincent Series A Rapide in the making: The Vincent-HRD single

The resulting power unit was an overhead valve design incorporating many innovations. Steel crankcase inserts supported the main bearings, while a high camshaft, driven by a bronze idler gear, operated short, widely splayed pushrods. These in turn operated forked rocker arms, which actuated the valves by means of collars fitted in the middle of the valve stems. This kept the valve train light, while minimizing side loads on the valves. Without rockers above the valves, there was room for race-style hairpin valve springs while still keeping the overall height of the engine at a minimum.

The first Vincent-HRD singles — the touring Meteor and sportier Comet — used a cast iron cylinder and head, and established the 84mm x 90mm bore and stroke dimensions used on all subsequent Vincent motorcycles. It was a compact engine with considerable tuning potential, a fact confirmed by the success of Vincent-HRD singles in the 1935 Senior TT, with Jack Williams and Noel Christmas finishing seventh and ninth, respectively. Jock West placed eighth in the 1936 race against the full factory-supported Norton and Velocette teams with their OHC racers. The Vincent-HRD became the little engine that could.

To celebrate its TT success, the factory released a limited run of TT Replica singles with iron-lined aluminum cylinders, bronze cylinder heads, higher compression, close ratio gearboxes and cast alloy brake drums. The gas tank was made of stainless steel, and light alloy blades replaced steel fenders.

Single times two: The twin

Whether through luck or inspiration, legend has it that Irving’s twin-cylnder design came about when he superimposed one single drawing over another. In engineering and production terms, the twin made perfect sense. The second cylinder’s camshaft could be driven from the same idler gear that drove the first, with the added camshaft going almost exactly where the magneto drive was on the single. The twin used new crankcases for the extra cylinder and a wider crank with side-by-side con rods, but from the cylinder up the rest of the engine used the same parts as the single. This meant both exhausts exited toward the front, unlike most V-twins of the era, where the rear cylinder exhausted rearwards. This made sense, with fresh cooling air flowing over both exhausts.

Much of the rest of the Rapide, as the new twin was called, also came from the singles, though the frame was stretched by 3 inches. Other changes included repositioning the magdyno in front of the engine, a larger fuel tank with two compartments (one for fuel and one for oil), and the addition of an elegant Smith’s eight-day clock pairing the speedometer. Most Rapides came with the iron-lined light alloy cylinder option and most came with iron drum brakes, though a few borrowed the composite front brake drums from the TT Replica. All Vincent-HRDs from 1933-on used dual-drum brakes on each wheel.

The Rapide’s weak spot was its transmission, also borrowed from the singles. The Burman clutch and gearbox were under-engineered to handle almost twice the torque they were used to. Typically, the clutch slipped, which was just as well. If the clutch was made to work without slipping, the gearbox often let go.

Just 79 Vincent Series A Rapides were built between 1937 and 1939 (though two numbers were duplicated and a couple more were missing from the sequence), and there’s little doubt Irving and Vincent saw it as a stepping stone to the next model: the Series B Rapide.

Robert Watson’s 1939 Rapide

Robert Watson admits to a bad Vincent-HRD habit. He owns six of the Stevenage scions, including three post-war Rapides and a Comet, plus two “A” models: a TT Replica single and our feature 1939 Rapide twin. “It’s like the club T-shirt,” he says of his addiction: “HRD Positive: No Known Cure.”

The idea to restore a pre-WWII twin came as Watson contemplated retirement. “I know what happens to guys who retire with nothing to do,” he says, “so I thought, ‘what would be fun?’ I was figuring it would take two or three years to find enough parts to start building one.”

Watson contacted Canadian Guy Stanford, who had owned a Vincent Series A Rapide in Toronto before moving to the West Coast. Stanford thought the Twin was still in Toronto. It was, and the owner turned out to be … well, we will call him John Doe. Stanford thought it was unlikely the bike would be for sale — John Doe reputedly never sold anything — but it was worth asking. So Stanford emailed a mutual friend. A reply came back five weeks later.

Yes, John Doe would sell the A twin, but an A single would be included in the deal, and the price? Let’s just say an apartment might have been cheaper.

“I just about collapsed on the floor,” Watson says. “I’d been figuring on spending maybe half of that. So I phoned him and we talked and talked. Finally he said, ‘now about the A single: the engine number is TTR121.’ And I just went: ‘TT Replica. It’s done. This is a done deal, right here, right now.'”

It took John Doe a few months to round up all the parts of the two bikes, which were both completely dismantled and spread over a number of warehouses. In the meantime, Watson found a van for sale in Toronto and flew out from the Vancouver area to collect the two bikes.

The deal required payment in cash. “It was April 1, 2006,” Watson says. “I was sitting in the back of the van outside [John Doe’s] bank with a briefcase full of cash, counting it out, and I said, ‘isn’t this an appropriate day!’ and he couldn’t see the humor in it, never even cracked a smile.”

The two bikes (except for the frames and other large parts) were packed into Rubbermaid containers and stacked in the van. The only assembled parts were the two halves of the twin’s crankcase.

Restoration

It took Watson another five years to finish restoring and reassembling the Vincent Series A Rapide, and he showed it for the first time in 2011. The rebuild was complicated by the fact that it had been crashed in the 1950s, breaking the frame. It had been repaired by the time-honored method of ramming a smaller tube inside and welding up the join. Watson replaced the tube and then re-jigged the frame to straighten it. The engine, always a tight fit, was then found to interfere with the seat pillar, requiring more heating and bending.

The engine’s bottom end has been modified to bring it closer to post-war spec with improved location and sealing, and it gained a splined primary drive sprocket. Much of this work was done by Vincent guru and AJS V-4 builder Dan Smith (Motorcycle Classics, January/February 2011). Big end bearings came from Alpha Bearings, and the connecting rods were magnafluxed. The pistons are the post-war type made by Omega for the Vincent Owners’ Club spares scheme, with Honda piston rings meant for a 350 dirt bike. New rear suspension spring boxes in stainless steel are by Overlander in Australia. The front brake alloy ribs were damaged in the earlier-mentioned crash, so Watson turned up a new set from alloy billet, then shrunk and screwed them to the drums.

Provenance

Vincent purists have noted that Watson’s A twin doesn’t seem to be completely “stock.” Some of the plated parts, for example, are chromed (Phil Vincent is said to have despised chrome), and the large tubular cable splitters for the throttle and choke controls seem to be an afterthought. But Watson has dated, period photographs of his twin from the early 1940s showing these features. Watson has also traced the bike’s ownership lineage.

According to the factory records, the twin was originally sold to a Mr. R. Smith in England. Noted on the build sheets was the fact that the cylinder heads had been prepared by none other than George “Gunga Din” Brown, the famous Vincent factory tuner and racer (Motorcycle Classics, May/June 2010). The next owner was a Major Johnston, who sold it to George Rampling, the Vincent factory test house supervisor. Rampling emigrated, with the Vincent, from the U.K. to Canada in 1948.

“I know that because one day I got on the Ontario white pages, and I found a Rampling and phoned them,” Watson recalls. “I said, ‘Sir, this is not a crank call. I’m a motorcycle guy, and I’m looking for anybody that might be a relative of George Rampling.” It turned out to be Rampling’s stepson. George Rampling married his mother after her husband had been killed in WWII, adopted their children and moved to Canada. “He said, ‘I always wondered what happened to Dad’s bikes.'”

Guy Stanford later discovered the Vincent in a chicken barn in Toronto when he was 15. He managed to get it running, but it didn’t prove too reliable. Watson has pictures of the bike from that era, and also of the group of Vincent owners, including John Doe, that Stanford belonged to. Stanford sold the bike, and it was passed around the group before landing in the hands of John Doe. The bike remained in storage from that time on while John Doe accumulated parts for it.

Riding the Vincent Series A Rapide

So how does the A twin compare with the later B series? “They’re lower,” Watson says. “It’s a much smaller bike to sit on. And you have to deal with the Burman gearbox. Post-war gearboxes were not particularly slick, but this is a bit clunky.” In order to alleviate overloading problems in the gearbox, Watson has changed to a taller primary drive ratio, made possible by the use of a modified Honda clutch supplied by Conway Motors.

“The forks are quite similar to post-war Brampton forks. They’re very light-feeling, and the bike is very light to ride, quite different from the [Vincent C series] Girdraulics,” Watson says.

When it comes to comparing the A’s performance with later twins, Watson says it’s “very similar,” noting that his A twin has a higher compression ratio than stock, estimated at about 8:1 versus the standard 6.8:1.

“It motors right along,” says Watson. “There’s a little vibration between 65 and 75mph, but at 85 it’s quite smooth again. It’s a fun bike. I really enjoyed building it.” Overall, he says, the experience of owning the Series A twin is every bit what you’d expect — legendary. MC

Want more information on Vincent motorcycles? Check out Build a Vincent Rapide A Twin and In Pursuit of the Vincent Series B Rapide.