Ariel Square Four (1952) Specificaion, Review, Photos

                              Ariel Square Four

                                              The Square Four 4G Mkl was a 997cc machine that provided plenty of smoothness and comfort, if not outstanding performance. This bike dates from 1952, the year before this model ‘Squariel’ was replaced by the Mkll version, which featured more power and improved cooling, and was distinguishable by its two pairs of exhaust downpipes.

                                                ‘Ten to a hundred in top gear’ was the proud boast that Ariel used in its IBtf advertising for the Square Four during the 1950s, emphasizing the machine’s low-rev refinement as well as its top speed of over 1 OOmph (161km/h). In fact, even the final version of the Square Four was not as fast as its impressive specification and high price suggested. It was more of a luxurious - if rather unreliable - grand tourer than a sports machine. But for many years Ariel’s flagship was one of the most glamorous bikes on the road.

                                                  The Square Four went through numerous redesigns during its long life, which lasted from 1931 to 1958. During that 27-year period, the Ariel’s engine capacity doubled, and its chassis and styling were transformed. Yet the air-cooled square four engine layout's advantages of power, smoothness and compact size remained throughout - as did its drawbacks of high production cost and the difficulty of providing sufficient cooling for the sheltered rear cylinders.

Cigarette packet sketch

                                                  Legend has it that this most exotic of motorcycles was born after a gifted young engineer, Edward Turner, had drawn up a novel square four engine layout on the back of a cigarette packet and tried unsuccessfully to sell the idea to a succession of bike manufacturers. Turner, later to find lasting fame at Triumph, eventually convinced Ariel chief Jack Sangster that the square four concept was sound, and was hired to put it into production.

                                                   Turner’s design was basically a pair of parallel twins, sharing the same cylinder head, block and crankcase, with their crankshafts geared together. This gave a naturally smooth-running engine, and was so compact that the original 497cc unit could be fitted into a frame very similar to that of Ariel's current 500cc single. That first Square Four, introduced in 1931, featured a chain-driven overhead camshaft and exhaust manifolds integral with the cylinder head, so that only two exhaust pipes emerged from the engine. Turner’s original design had used an integral three-speed gearbox, but the production bike had chain primary drive to a separate four-speed Burman box.

                                               After one year of production the engine was enlarged to 597cc, giving extra power that was particularly welcomed by sidecar owners. In this form the Square Four produced 24bhp at 6000rpm, and stayed smooth to its top speed of 85mph (137km/h). But the ‘Squariel’ suffered from cooling and other problems. In 1937, after Turner had left for Triumph, Ariel introduced revised 597cc and 997cc models, known as the 4F and 4G, designed by new chief engineer Val Page.

                                                     The new engines featured more cylinder head finning plus a tunnel between the cylinders to allow cooling air to the rear of the block. Other changes included pushrod valve operation and longer-stroke dimensions. The larger 4G produced 34bhp with plenty of low-down torque. But as well as some unreliability it also suffered from mediocre handling, being too heavy for the plunger rear suspension system that had been adopted along with telescopic forks.

                                         In 1953 Ariel introduced an uprated version, the 4G Mkll. incorporating a new cylinder head complete with four instead of two downpipes. Cooling was improved by the air that now ran over the exhaust ports. Reshaped pistons helped raise power to 40bhp at 5000rpm, increasing top speed to over 105mph (169km/h). But Ariel never got round to introducing the liquid-cooled engine that might have solved the longstanding overheating problem for good.

                                               The reason for lack of further development was simple: Ariel, by now part of the BSA group, had made its controversial decision to abandon four-stroke production in favour of the two-stroke Leader commuter bike. In 1958, the year the Leader was launched, the four-cylinder bike was dropped from the range, and an era that had lasted for almost 30 years came to an end. No rider who had experienced the Square Four’s unique blend of performance, smoothness and sophistication would forget it.

                                                  Handling of the plunger-framed Square Four 4G Mkl was not a strong point, partly due to the bike's substantial weight, but the Ariel provided a comfortable ride.

                                                    Twin downpipes gave the square four engine a deceptively ordinary look. Despite heavy finning, cooling of the rear cylinders remained a problem throughout the model’s life.

                                                    The Square Four’s good looks added to its glamour and appeal, and when the bike was running well there were few machines of the early 1950s that were more refined.

        Specification Ariel Square Four 4G Mkl                                            (1952)

• Engine Air-cooled ohv eight-valve pushrod square-four
• Capacity 997cc (65 x 75mm)
• Maximum power 34bhp @ 5400rpm
• Transmission Four-speed, chain final drive
• Frame Steel twin downtube
• Suspension Telescopic front; plunger rear
• Brakes Drum front and rear
• Weight 433lb (196kg)
• Top speed 100mph (161km/h)

Ariel Huntmaster (1955) Colors, HD Wallpapers, Specification

                              Ariel Huntmaster

                                      Ariel’s 646ccparallel twin engine was essentially the unit from BSA’s Golden Flash, modified with a new gearbox, clutch and engine covers.

                                      The Huntmaster was a reasonably stylish machine that combined Ariel’s traditional paint scheme with a high standard of finish. The marque was unique in producing models with one, two and four cylinders.

                                             Ariel’s variation on the familiar 650cc parallel twin theme was one of the more successful examples of the badge engineering common in the British motorcycle industry of the 1950s. The Huntmaster, produced when Ariel was a subsidiary of BSA, was a modified version of BSA’s Golden Flash model.

                                              But there were sufficient differences between the two bikes to give them distinctly different appearances and personalities.

                                     Most of Ariel’s effort went into the Huntmaster’s chassis. Its twin-downtube frame was widely regarded as stronger than that of the Golden Flash. Front forks were similar, as BSA had been using Ariel units for years, but the Huntmaster was fitted with rear shock units from Armstrong instead of Girling. The Ariel was finished to the firm’s usual high standard and looked smart in its traditional deep red paintwork.

                                              There were fewer differences in the two models’ 646cc air-cooled, pushrod-operated, single­camshaft engines. Ariel fitted a new Burman four- speed gearbox and a dry clutch, and made some changes simply to disguise the unit’s BSA origins. The right engine cover was reshaped into a triangular, rather than Y-shaped, form, and the rocker-box and its covers were redesigned. But peak output remained 35bhp at 5600rpm.

Cracking the ton

                                     By the standards of 1954, when the Huntmaster was introduced, that gave good if not outstanding straight-line performance. Top speed was initially just under lOOmph (161km/h), hindered slightly by tall gearing. Ariel lowered the final gear ratio slightly in 1956, after which the bike could just about ‘crack the ton’. The Huntmaster also gave good acceleration through the range, though it was handicapped by typical parallel-twin vibration at high revs.

                                            Handling was good, and combined with the new gearbox to give the Ariel a distinctly different feel to that of its BSA sibling. At 4101b (186kg) the Huntmaster was not particularly light, but it was stable, steered well and was comfortable, especially after Ariel redesigned the seat in 1956. Its drum brakes were reasonably powerful too, and owners soon grew to appreciate the bike’s excellent fuel economy, even when fitted with a sidecar.

                                           The Huntmaster was also impressively reliable. Later versions, especially, had numerous rider- friendly features such as an easily adjusted headlamp and brakes, enclosed final drive chain, plus a rear mudguard that hinged to facilitate rear wheel removal. The bike’s practicality could also be increased by fitting factory-made accessories, which included a tall windscreen, crash-bars, luggage rack and panniers.

                                              The Huntmaster’s performance and versatility were enough to make it reasonably successful, and highly regarded by most who rode one. But thoseassets were not enough to save the model, or to keep Ariel from disaster once the firm undertook a controversial and ultimately suicidal decision to abandon four-stroke production completely.

                                             The company had a proud if occasionally troubled history, having begun building motorbikes around the turn of the century. Ariel had been one of Britain's most important bike manufacturers in the 1930s, and had produced a succession of successful four-strokes, notably the Red Hunter range of singles. The Red Hunter name had also been used for a 500cc twin produced from 1948; and then there was the famous Square Four...

                                           But in 1959, Ariel dropped the Huntmaster and all other four-stroke models to make way for the Leader, a 250cc two-stroke scooter with which the firm’s bosses aimed to change the face of motorcycling. When the Leader failed to win sufficient converts, the firm had nothing to fall back on. In 1963 Ariel production was moved to BSA’s factory, and a few years later ceased for good.

                                                  Although the Huntmaster had enough unique features to qualify as a new model, it was essentially an example of the ‘badge engineering ’ that was popular with British manufacturers in the 1950s. Ariel had been part of the giant BSA group.

                                             The Huntmaster's new twin-downtube frame and Armstrong rear shocks gave handling that at least matched that of the BSA Gold Flash on which the Ariel was based. Braking power from the front and rear drums was good by mid-1950s standards, too.

         SpecificationAriel FH Huntmaster 650                                            (1955)

• Engine Air-cooled ohv pushrod four-valve parallel twin
• Capacity 646cc (70 x 84mm)
• Maximum power 35bhp @ 5600rpm
• Transmission Four-speed, chain final drive
• Frame Steel twin downtube
• Suspension Telescopic front; twin shocks rear
• Brakes Drum front and rear
• Weight 4101b (186kg)
• Top speed 100mph (161 km/h)