1955 Vincent Black Prince

A few years ago, Jim Balestrieri of the Throttlestop Collection in Wisconsin was reading up on Vincent machines. He first fell in love with a Godet Vincent, which was added to the collection (Egli-Vincent: the Café Racer built by Godet). “To me, all Vincents are special because of the V-twin motor,” Jim says. Then, he missed an opportunity to purchase a highly original example of a Series C Vincent Black Shadow. While researching the Black Shadow, he learned of the fully-fired Series D Black Prince and Black Knight machines, and then began a serious search for one.

“I’m a fairing guy, and have been since my earliest riding days,” Jim explains. “And here’s an all-weather Vincent, with all that raw Vincent power underneath it. I read the bikes had been used in the movie ‘1984’, and that added something to it for me as well.”

In 2022, from Geert Versleyen at Yesterdays Antique Motorcycles in the Netherlands, Jim bought and had shipped to Wisconsin this 1955 Series D Black Prince. The machine is on static display at Throttlestop. Jim says it’s an earlier restoration and shows just 110 miles on the Smiths chronometric speedometer. It was sold as a runner, and although Jim has not fired it up, he’s contemplating doing that this fall to prepare a riding video of the clad Vincent.

This story really began at the end, so for some history, let’s go back to Vincent’s own beginning. Philip Conrad Vincent was born in 1908 in Fulham, England. His British family operated a cattle ranch in Argentina. To ensure her son had English citizenship, Mrs. Vincent traveled back to the home country as her due date approached. Although Philip was raised and began his schooling in South America, he moved to England as a teenager to live with his uncle and continue his education. He eventually attended boarding school, where Philip became entranced by motorcycles. After some persuading, in 1924 his mother bought him a used 1923 BSA powered by a 350cc side valve engine.

In Roy Harper’s excellent book, The Vincent H.R.D. Story, Philip shared firsthand accounts of his early life and many of his motorcycle endeavors. He was clearly not impressed by the BSA and is quoted in Harper’s book, saying, “… it incorporated so many horrible mistakes in its design and manufacture that it created in me the desire to become a motor-cycle manufacturer in order to make better quality machines.” He felt improvements could be made in both frame and fork design, and it is thought he drew some of his first sketches at his uncle’s house.

Philip enrolled in Mechanical Sciences at Cambridge in 1926, but he was already at work constructing a Vincent Special. While unorthodox at the time, his first motorcycle incorporated rear suspension, featuring a triangulated swingarm on roller bearings. Twin springs were mounted below the saddle while a Webb girder fork suspended the front. Powering the machine was a 350cc Swiss-built M.A.G. engine. In short order, Philip left Cambridge prior to completing his studies and was in business, backed by his father. Instead of starting from scratch, in 1928 the name and assets of motorcycle manufacturer Howard Raymond Davies, or H.R.D., were purchased and renamed the Vincent H.R.D. Company.

Vincent senior put his friend, Frank Walker, in place as managing director and a small garage in Stevenage became the home of the fledgling company, and that’s where it remained to the very end. First, Philip built motorcycles powered by J.A.P. single-cylinder engines, and all featured his triangulated rear suspension. Through the late 1920s and into the early 1930s, all Vincent H.R.D. machines relied on engines produced by other manufacturers, including J.A.P. and Rudge.

Enter Phil Irving in 1931. An Australian engineer, Irving helped design Vincent’s first proprietary engine, a 499cc short-stroke single cylinder. Launched in 1935, the singles were dubbed the sports-oriented Comet and for touring, the Meteor. In 1936, the singles were joined by the new Series A Rapide. The Rapide was powered by Vincent’s own 998cc V-twin engine, and the motorcycle was fast and powerful. On the famed Brooklands circuit, the Rapide reached 112mph.

However, problems with clutches and transmissions were discovered, as they were ill-equipped to transmit the power made by the V-twin powerplant to the rear wheel. Vincent was at work solving the issue when all production was halted by the advent of war in 1939. While occupied manufacturing wartime goods for the duration, fully redesigned single and twin-cylinder engines were in the works.

The new motors featured unit construction and incorporated the transmission. Clutches were new, the wheelbase was shortened 3-inches, the gas tank was revised and the new Series B Rapide, launched in 1946, weighed less than its predecessor. Most importantly, the Series B Vincents featured a unique new frame, which departed from conventional thinking.

Vincent designed what is referred to as the Upper Frame Member. This is essentially an oil-bearing spine that attached securely to the front and rear cylinder heads. This backbone encapsulated the neck and rear spring mounting points, while the triangulated swingarm pivoted off the rear of the engine cases.

Speed-related modifications made to a Series B Rapide were incorporated in a new model launched in 1948, the sports-oriented Series C Black Shadow. A well-tuned Black Shadow was the basis for Rollie Free’s speed bike, which he rode across the Bonneville Salt Flats in nothing more than swimming trunks, stretched out prone to a record-setting 150.313mph run.

The Series C Vincents also featured the new Girdraulic fork. Instead of moving toward telescopic front ends, Vincent’s Girdraulic combined the lateral strength and rigidity of a girder fork with the long travel attributes of a hydraulically damped shock. According to a period Vincent brochure, the blade and links of the Girdraulic were made from, “high grade aircraft quality light alloy forgings.”

The Series C machines with Girdraulic forks were built until 1954, when Philip Vincent had been considering how to increase buyer interest in his motorcycles. In Roy Harper’s The Vincent H.R.D. Story, Philip spoke about how he needed to, “think up some new sales-appeal features,” and continues, “After considering the position I realized that any new model for 1955 would have to embody strictly limited changes to the basic design because the firm’s financial position could not possibly endure any substantial period of change and the inevitable loss of production entailed.”

He goes on to say he’d worked out moving to coil ignition, a new single-shock rear suspension — still with triangulated swingarm — and a revised top tube frame that no longer carried oil. The engine continued to be a stressed member, however, and an external oil tank was added. The frame member was altered to increase fuel capacity to 4 imperial gallons. But here’s the clincher. Philip said, “To obtain a striking alteration to the superficial appearance I decided to seek to embody a series of plastic [fiberglass] cladding which would enclose beneath its skin the whole of the existing works of the motorcycle, rendering the machine cleaner to ride and more silent in operation.”

Philip continued, “This plastic cladding, by slight design dodges, could be made to incorporate efficient leg shielding to keep the rider clean and dry, and could also incorporate a central tower round the steering column, which would carry a rigid curved windscreen made of Perspex and a dashboard in which we could mount all the instruments. Two cup-shaped rigid extensions could be arranged to shield the rider’s hands from the elements.”

Such were the details of the machines that became the Series D Black Prince, based on the running gear of the Black Shadow, and the Black Knight, essentially a clad Rapide. There was a Victor, too, based on the single-cylinder Comet, but of two produced only one sold fully clad — the other had its bodywork removed to become a Series D Comet.

The rear enclosure was hinged and could easily be released to enable access to the rear wheel. According to an article by Vaughn Greene in the February 1965 issue of Cycle World, other upgrades included a lever-operated center stand that a rider could engage from the saddle. In addition, the electrics were improved, clutch and brake friction materials were upgraded, new Amal Monobloc carburetors went on the intakes and several changes were made to the primary drive side of the machine.

However, Philip found fault with the finish on the fiberglass bodywork, resulting in a delay of four months before a new supplier of fiberglass body pieces could provide the quality he desired. While interest initially had been quite high, this unfortunate delay in clad machines fed rumors that the fully faired Vincents were ill-handling machines and could not handle a crosswind. This wasn’t the case, and in fact, period testers found the motorcycles eminently stable and a pleasure to ride. Philip said, “Looking back with the benefit of hindsight I can see that we must have lost at least 600 sales during the 1955 season caused primarily by the four-month delay after the Show before any Series D appeared on the road.”

To fill the gap, Philip released several unclad Series D Vincents which included all of the mechanical upgrades, and even the mounting points for the cladding, should a buyer wish to add the enclosures at a later date. According to the book Know Thy Beast by E.M.G. Stevens, only 235 of the enclosed Series D Black Knight, Black Prince, and the single 500cc Victor, left the factory prior to the doors closing on December 16, 1955.

“Vincent was about 15 years ahead of its time with the enclosed models,” Jim at Throttlestop figures. “But they weren’t alone in enclosures because scooters were on the scene, and Triumph came up with the bathtub in 1957. Ariel also launched its enclosed 2-stroke Leader in the late 1950s. And then in the mid-1960s, Craig Vetter was launching his fairing company, and eventually transformed the motorcycle industry with his Windjammer products.”

He concludes, “It would seem Vincent wasn’t all about increasing the aerodynamics of its machines, which Vetter was, but more about keeping the rider clean and dry, and the Black Prince certainly fashionably, and somewhat ominously, did that.” MC