British 350cc twins that broke the mould
Pete Kelly takes another look into the bound volumes in Mortons Archive to see what the road testers of the day thought about three sensational homespun 350cc twins – the Douglas Dragonfly, Triumph Twenty-One and Norton Navigator.
While many might still imagine a typical British three-fifty as an iron-barrel ‘single,’ this certainly wasn’t always the case. So, instead of going straight for the revered ‘singles’ from the likes of Velocette, Ariel, Norton, Royal Enfield, Matchless and BSA, this month I’ve chosen three very different 350cc home-grown ‘twins’ – the 1955 Douglas Dragonfly, 1957 Triumph Twenty-One and 1961 Norton Navigator – to see what the road testers of the day thought about them.
Powered by a breathed-on 348cc version of a transverse horizontal twin engine that originated in a Second World War generator engine, the 1955 Dragonfly, with its brandnew Reynolds open duplex frame, Earles front fork and conventional Girling damped suspension units all round, handled like a dream, and had similar sturdy looks to BMWs of the day. Styling of the fuel tank and headlamp nacelle gave the model notably flowing lines, but the headlamp was now fixed and did not swivel with the handlebars.
While the engine had been fitted to previous models, it now looked tidier than ever and boasted modern coil ignition, an AC generator and distributor, bolt-through cast iron cylinders and heads and duralumin pushrods. But sadly none of these improvements could hide the fact that the Dragonfly had become heavier and slower than its predecessors because it had completely outgrown the engine’s measly swept volume of 348cc – a fact that was confirmed in a Motor Cycling road test that also went to great lengths to praise its comfort and handling.
Douglas’s fame was built upon its legendary fore-and-aft twins and its huge contribution to the 1914-18 war effort, and the marque reached the height of its achievements in the 1920s and 30s. Founded by brothers William and Edwin in the 1880s, the business began as a blacksmiths’ shop before becoming an iron foundry, and, by 1905, the Douglas Engineering Company was building a prototype Joseph Barter-designed engine that was developed to form the basis of the Fairy motorcycle in 1907.
The first of Douglas’s 2.75hp horizontally opposed engines followed soon afterwards, and later, when the firm became preoccupied with wartime production, these were developed into 3.5 and 4hp models.
Until the Wall Street Crash of 1929, the Roaring Twenties were a golden age for the Bristol firm, with an expanding range of motorcycles including the 350cc EW, 500cc and 600SS models and successes in both road racing and speedway, but the family decided to sell the business in 1931.
Although various efforts were made to resurrect Douglas’s fortunes both before and after the Second World War (and not only in regard to the manufacture of motorcycles), the sell-off marked the beginning of a steady but unstoppable decline, with several more takeovers and continuing financial headaches.
The last chance to turn the motorcycle sales around was the Douglas Dragonfly that made its debut at the 1954 Earls Court Show. It aroused plenty of attention, but a continuing lack of funding meant that it would never be developed into the high-performance roadburner that it could – and should – have been.
The first across-the-frame horizontal twin to have been built using the Douglas name had been a 495cc shaft-drive prototype called the Endeavour that was unveiled in 1934, but just a year later the parent company was voluntarily liquidated. After this, the Douglas factory was taken over by Aero Engines, which intended to end motorcycle production at the works altogether and start building aircraft engines instead – but that plan was scuppered when an anticipated contract to produce Hispano-Suiza engines failed to materialise.
With war clouds gathering across Europe once again, the firm was awarded a government contract for portable generators using a 348cc overhead-valve flat-twin engine, and it was this that eventually formed the basis of the postwar motorcycle designs.
Aero Engines changed its name to Douglas (Kingswood) Ltd in 1946, raising capital from a shares issue, and the first model to use the generator-based engine was the T35 (transverse 350) Mk I featuring a torsion-bar sprung frame and leading-link Radiadraulic front fork. The undamped torsion-bar arrangement worked well, but could give a light solo rider quite a bouncy ride and needed plenty of attention from the grease gun, too.
It soon became apparent that the 348cc engine, which, after all, had been designed specifically to perform best in its generator application at a constant speed, was noisy, relatively slow and at times unhappy with the ever-changing throttle demands of motorcycle use.
It became more user-friendly after Sunbeam S7 designer Erling Poppe and racing star Freddie Dixon got their heads around the problem and improved the gas flow by redesigning the cylinder heads, pistons and combustion chambers. In 1949 the improved Mk 3 models emerged – a normal roadster and a high-level-exhaust sports version – and these were followed in the early 1950s by the Mk 5 and the Competition and Plus series.
A road test of the final Dragonfly model in The Motor Cycle of September 29, 1955 began with both positives and negatives. “Pivoted suspension systems front and rear, a redesigned 348cc horizontally opposed transverse twin-cylinder engine and an all-welded duplex frame are among the up-to-theminute features of the Douglas Dragonfly. At its London Show debut last November the new model was widely acclaimed, but production delays resulted in its lapsing into relative obscurity. Only comparatively recently have the machines been reaching the public in worthwhile quantities.
“The Dragonfly is now the sole Douglas motorcycle listed and represents an attempt at combining in one machine a clean, homogenous power unit with the latest type of frame and suspension. Engine and gearbox are constructed as an integral unit in which the generator and distributor are enclosed.
The steering head is embraced by a pressed-steel cowling which blends at the rear with the nose of the 5½-gallon fuel tank and houses the headlamp, speedometer, ammeter and ignition and lighting switch.” The reporter also noted: “A first reaction to a fuel tank of so great a capacity is that it must inevitably be wide, and hence be likely to impair riding comfort. In the case of the Dragonfly, however, that criticism does not arise. Tank width at the rear (measured across the wafer-type knee grips) is no greater than 12½ inches, and for riders of average stature the riding position is first class, combining comfort and control in excellent measure.”
As the machine’s specification suggested, the handling was exceptional, and even on greasy surfaces the Dragonfly displayed a high degree of inherent stability. The road test rider recorded: “There was no tendency for the machine to snake on a short section of road noted for the atrocity of its surface when wet, and straight-ahead steering at high speed was in the best hands-off tradition.”
Low-speed stability was such that the Douglas could be ridden feet-up to a stop without recourse to body lean, and, just for the fun of it, the motorcycle was ridden over undulating heathland in a downpour. “The muddy, rutted tracks were negotiated nonchalantly, and minor trials hills served further to emphasise the model’s high degree of controllability.”
In these days of push-button starting, the rigmaroles that were involved in kick-starting, and which were described in infinite detail by the reporters of the day, always bring a wry smile to my face, especially as I remember a particularly savage kickback from a Velocette Venom Veeline that all but broke my leg! Perhaps because of its smaller engine, and the fact that it was a twin, the drill required to bring the Dragonfly to life was simplicity itself, whether the engine was hot or cold.
The tester wrote: “When the engine was warm, there was no need for the rider to raise himself from the seat to operate the kick-starter. No exhaustvalve lifter or decompressor is fitted, and none is required. The muscular effort demanded in spinning the engine is negligible, and the air lever could be opened almost immediately after a cold start.
Piston slap was apparent from both cylinders and persisted even when the engine was hot.”
The extent of exhaust blueing was reported in most road tests, but, after 1000 miles of running, the twin exhaust pipes of the Douglas were no more than straw-coloured near the ports. Other than slight stains on the gearbox below the kick-starter and around the cylinder base joints, the power unit remained oil tight.
Although the Dragonfly suffered with roughness while pulling hard at low and medium revolutions, it smoothed out at higher speeds, and 55 to 60mph could be held for long periods. Acceleration was moderately brisk rather than zestful.
The poorest aspect of Douglas’s final model was its brakes, the test machine requiring a massive 43ft stopping distance from 30mph. The headlamp was entirely adequate for 60mph running, and, although only a centre stand was fitted, no undue effort was needed to lift the rear wheel well clear of the ground.
Mean maximum speeds through the four gears, with valve-float occurring in the first three, were 30, 49, 67 and 72mph, with a highest one-way speed with a following wind of 75mph. Finish was in black and silver enamel, and in 1955 the Douglas Dragonfly cost £217 16s including UK purchase tax.
Like the primordial aerial wonders that inspired its name, the Dragonfly remains a sight to behold, yet just over 1450 were ever produced. After the ownership of Douglas changed yet again in 1956 (this time to the Westinghouse Brake & Signal Company), the very last Dragonfly left the works the following year. What a difference a highperformance 500 or 650cc engine, along with the brakes to match, might have made!
Douglas Vespa scooters continued to be built at Bristol for a time, but as far as the motorcycle story was concerned, it was over, and the final Dragonflies were sold at discount by Pride & Clarke of Stockwell Road in London.
Introduced just two years after the Dragonfly, the Triumph Twenty-One was an Edward Turner classic, and a different kettle of fish altogether. In the April 30, 1959 issue of Motor Cycling, it was described as “one of the swiftest standard British-made 350cc roadsters the magazine had ever tested, combining an untiring zest for high-speed cruising with safe handling and a remarkably economical fuel consumption.”
The name ‘Twenty-One’ reflected the fact that it was launched in the 21st year of the then-present Triumph company’s trading history, and partly because, to the enthusiasts in America for whom the early batches were produced, its engine capacity was 21 cubic inches.
The Motor Cycle’s late lamented Dublin-born scribe David Dixon, identifiable in the old photos by his shamrock-decorated helmet, wrote a beautifully scripted road test report on the Triumph Twenty-One in the July 26, 1962 issue. It began: “Let’s dissect the model – the engine for a start.
It is as cleanly styled and homogenous a unit as will be found anywhere. Good styling, yes, and very functional. You want to meander at 20mph in top gear? Fine, there’s no trace of transmission snatch, and barely a whisper from the engine.
“But you would prefer to cruise at an effortless 70mph-plus? No bother at all. And as for hill-climbing, the unit just revels in levelling even the steepest gradients. Its bottom-end power was amply demonstrated by a standing start on a 1-in-6 gradient in the 9.32 to 1 second gear.
“So you want a smart getaway? Characteristically Triumph, the Twenty-One answered the throttle crisply and cleanly, with a rapid build-up of power throughout the range – and the exceptionally quiet exhaust allowed this power to be used whenever possible.”
David noted that up to 55mph the unit was delightfully smooth. A patch of vibration was then felt through the footrests but gradually lessening as the speed approached 60. Above that, right to the maximum, just a barely perceptible tremor was present.
The Triumph’s ease of starting was outstanding. With the carburettor lightly flooded and the air control fully open, one prod on the kickstarter invariably brought the engine to life, and, within a minute or so, it would settle down to a slow and reasonably reliable tickover.
“So easily could the pedal be operated,” remarked David, “that the kick-starter could be depressed with the rider remaining seated,” but for the first start of the day it was best to first free the clutch plates by depressing the kick-starter with the clutch withdrawn.
Light and positive in action, the clutch engaged the drive sweetly and without snatch, and wasn’t even affected by deliberate abuse inflicted during the full throttle getaways for standing-start performance figures.
David found the steering light and utterly positive, but on an 80mph downhill stretch with a rather bumpy surface “the handlebar began to feel a trifle lively and a steering damper might have been welcome.” Soft but well-balanced, front and rear springing provided a comfortable, pitch-free ride, and neither suspension topped nor bottomed over bumps.
A low centre of gravity allowed effortless cornering and called for negligible effort when rapid changes of direction were made, although when the machine was cranked well over to the left the centre stand extension and footrest grounded, and the centre stand leg limited the angle of lean to the right. Impressed by the Triumph’s braking, David wrote: “Both tyres could be made to squeal at 60mph without locking the wheels, and maximum-effort braking from 80mph produced remarkably rapid stopping without any trace of fade.” However, a slight juddering from the front wheel, caused by a touch of ovality in the brake drum, was apparent during hard braking above 40mph.
With a seat height of just 28½ inches, the Twenty-One offered a compact riding position, but the relationship between handlebar, footrests and seat was such that riders of all heights found themselves adopting a marked forward lean that was ideal for combating wind pressure above 65mph.
Wide and softly padded, the seat gave comfortable support for rider and passenger alike, and David observed: “Even after a 200-mile trip, no trace of discomfort was felt, and the seat is low enough to allow both feet to be planted firmly on the ground.”
Although all the controls were well situated and light in operation, with finger adjusters for the front brake and clutch along with a finger-adjusted friction screw for the twistgrip, it was something of a chore to reach the adjusting bolt that altered the level of the rear brake pedal because it necessitated detaching half of the rear ‘Bathtub’ cowling. The headlamp offered a deep spread of light and penetrating beam that allowed a comfortable cruising speed of 55-60mph, and the alternator balanced the full lamp and coil load at 25mph.
Over 900 hard-ridden miles, the model averaged 66mph and consumed two pints of oil. Top speeds obtained were 35mph in first gear, 51mph in second, 74mph in third and 82mph in top, and the 7in diameter drum brakes gave a best stopping distance from 30mph of just 29ft 6in. In 1962 the model cost £253 19s 3d including UK purchase tax.
During the single-cylinder era, most three-fifties utilised the same frames and cycle parts of the 500cc versions, but it gradually dawned on some manufacturers that squeezing a 350cc engine into a 250cc frame might result in much better performance and handling all round.
Norton’s answer to the Twenty-One was the ‘over-square’ 349cc Navigator parallel twin based around its smaller sibling, the 249cc Jubilee of 1958, and we’ll turn to the November 17, 1960 issue of Motor Cycling for our final road test on the De Luxe model of the 349cc Norton Navigator parallel twin that made quite a splash when it first appeared in 1960.
The term ‘race-bred’ was often applied when Norton machines were tested, and the Navigator, which recorded a best one-way speed of 89.2mph, certainly deserved the acclaim. Distinguished by its pressed steel fabricated and tubular cradle-type frame, it combined impeccable handling, brisk acceleration and pin-sharp braking from its full-width 8in front and 6in rear drum stoppers that brought it to rest from 30mph in a scorching 28½ feet.
Even though the test took place in appalling weather conditions, the report went: “It is the fastest British standard roadster of its kind and also one of the safest, for the design team at Bracebridge Street have put into the Navigator all the experience of braking and steering that they have won on the Grand Prix circuits of Europe. The high-revving engine has a usable ceiling of 7000rpm, with an acceleration curve that just a few years earlier would have done credit to a sports five-hundred.”
To make the best use of the available power at all speeds, 100-octane fuel was recommended by the makers, and suited the
8.8:1 compression ratio admirably although, observed the test rider, “the utterly pink-free behaviour of the unit encouraged screwing open the twist-grip – the engine gulping in quantities of expensive petrol – when a change-down might have achieved the same result more economically.” This combination of a high-revving peak output with slogging side-valve characteristics at the other end of the scale gave the Navigator a really flexible top gear range.
Adding to the rocket-like performance of the twin was handling and steering that almost put it into the racing category. A modified steering head angle, together with the famous Norton Roadholder forks (resprung to suit the Navigator’s weight distribution and wheelbase just an inch shorter than the Jubilee’s) produced absolutely precise navigation no matter the conditions.
“One exhilarating experience,” the tester wrote, “was to swing around the MIRA circuit at full bore. Another was to fling back mile after mile of main road at a 55-60mph cruising speed and feel the machine with you at the slightest change of course, the whole rock steady as if part of the rider, and almost thinking with him. Adverse cambers, wet leaves… the conditions never seemed to matter.”
Gear selection was commendably quiet. The four-plate clutch freed to give a slick first-gear engagement every time, and there was never any difficulty in finding neutral. The report continued: “The brakes were a revelation of how safe a fast middleweight could be. Norton’s have never been content with minimum lining areas that will just do the job, and instead they have given the Navigator the best they make.
“The lightest touch would bring the powerful front stopper into action, slowing the machine without the slightest hint of grab or fade – and this after the test model had been out for a day on flooded roads.
“Equally effective was the smaller but efficient rear brake, and the two, applied with determination, gave a safe, reliable pull-up in much less than the classical datum distance of 30ft from 30mph without streaks of rubber left on the road, or the alarm that accompanies a sudden wheel lock.”
The deep front guard checked throwback from the wet weather, and the rear enclosure of the
De Luxe test machine gave very effective protection against water flung from the tyre.
“At the conclusion of the test, the chain condition indicated the results of a wet life,” wrote our lucky scribe, “and the chaincase that’s available as an extra for £3 15s would be a good investment.”
He found the seat and handlebars well-positioned for a rider of average stature and, although rotating the bars gave some measure of adjustment, this was limited by the clutch and brake levers that were integral with the bars.
Weighing less than 360lb with two gallons of petrol in the tank, the Navigator De Luxe (distinguished from the normal Navigator mainly by the rear enclosure) was no trouble to manhandle and could be lifted easily on to its centre stand.
Highest speeds obtained from the unit-construction four-speed gearbox were 49mph in second, 71mph in third and a sizzling 91mph in top. No first-gear speed was given. In 1960, the Norton Navigator De Luxe cost £237 12s 7d including UK purchase tax.
“If a motorcycle will sell on safety as well as speed,” the writer concluded, “there is no doubt about the future of the Norton Navigator.” But, unfortunately, the demise of the British three-fifty was just around the corner with the emergence of machines such as Honda’s CB77 which, with an engine capacity of just 305cc, had a genuine top speed of 100mph with a top-notch specification to match.