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54-449: The BSA A10 series was a range of 646 cc (39.4 cu in) air-cooled parallel twin motorcycles designed by Bert Hopwood and produced by Birmingham Small Arms Company at Small Heath, Birmingham from 1950 to 1963. The series was succeeded by the A65 unit construction models. BSA, then the largest UK motorcycle manufacturer, was falling behind in the parallel-twin race after

108-412: A closed circuit carrying liquid coolant through channels in the engine block and cylinder head. A fluid in these channels absorbs heat and then flows to a heat exchanger or radiator where the coolant releases heat into the air (or raw water , in the case of marine engines ). Thus, while they are not ultimately cooled by the liquid, as the heat is exchanged with some other fluid like air, because of

162-626: A fact-finding tour to America and talked to dealers and riders. The feedback he got from the tour was that a more powerful motorcycle would sell well in America. The swinging arm frame and alloy head Road Rocket were planning stages but some way off production. The BSA competitions department had experience of tuning the existing models. They had turned versions of the 500 for the Daytona 200 race. Works rider Fred Rist has an A10 dessert racer capable of 140 mph, and Gene Thiessen set an AMA class 'B' record at

216-430: A fluid is a function of its capacity and the difference in input and output temperatures. As the boiling point of water is reduced with lower pressure, and the water could not be efficiently pumped as steam, radiators had to have enough cooling power to account for the loss in cooling power as the aircraft climbed. The resulting radiators were quite large and caused a significant amount of aerodynamic drag . This placed

270-486: A great percentage of the heat generated, around 44%, escapes through the exhaust. Another 8% or so ends up in the oil , which itself has to be cooled in an oil cooler . This means less than half of the heat has to be removed through other systems. In an air-cooled engine, only about 12% of the heat flows out through the metal fins. Air cooled engines usually run noisier, however it provides more simplicity which gives benefits when it comes to servicing and part replacement and

324-440: A horizontal fashion as a Flat engine , while vertical Straight-four engine have been used. Examples of past air-cooled road vehicles, in roughly chronological order, include: During the 1920s and 30s there was a great debate in the aviation industry about the merits of air-cooled vs. liquid-cooled designs. At the beginning of this period, the liquid used for cooling was water at ambient pressure. The amount of heat carried away by

378-552: A second link between the rear drive and transmission to allow the driveshaft to pivot along the same axis as the sprung rear frame. Moto Guzzi patented its Compact Reactive Drive Shaft system (Ca.R.C.), where the driveshaft is free to float into its structure, providing much softer feedback from transmission. An upper arm serves as a guide to close the geometry of the suspension. Extended swingarms - are often used by drag racing motorcycles (called dragbikes) to keep their center of gravity as forward as possible, which reduces

432-486: A separate "pre-unit" item. The new design had a modified clutch , new gearbox internals and a single row primary chain. The primary chain was adjusted by moving the gearbox, which caused the rear chain to requiring re-tensioning. An alloy head was introduced with the Road Rocket in 1955. The RR also featured a thicker cylinder base flange (1/2" instead of 3/8") and these cylinders became known as "thick flange". The big end

486-551: A single mounting point guarantees proper wheel alignment. Single-sided swingarms date from at least the late 1940s. In 1948, the Imme R100 produced by Norbert Riedel of Germany had both a single-sided front wheel suspension as well as a single-sided rear swingarm that doubled as the exhaust pipe. In 1950 Moto Guzzi introduced the Galletto, a large-wheel step-through scooter. In 1980, BMW introduced its first single-sided swingarm on

540-471: A standing quarter mile (400 m) in under 16 seconds. Its gold colour proved a marketing success, outselling Triumph's Speed Twin and 6T Thunderbird . It received updates throughout its model life. In 1960 it was renamed the "Royal Tourist" in the US. An alternator was offered as an alternative to the dynamo from 1961 to 1963, the last three years of production. In 1951, BSA Chief designer, Bert Hopwood, went on

594-573: A subsidiary of BSA in 1951. Although they already had a 500cc twin, the Val Page designed model KH500, the management did not want the expense of developing a 650cc machine. In 1954 an A10 Golden Flash enginge, with different outer casings, was fitted to the Ariel frame to create the Ariel Huntmaster. The machine continued until 1959 when all 4-stroke Ariel motorcycles were discontinued. A sporting version of

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648-495: A swing fork or pivoted fork, is a single or double sided mechanical device which attaches the rear wheel of a motorcycle to its body, allowing it to pivot vertically. The main component of the rear suspension of most modern motorbikes and ATVs , it holds the rear axle firmly, while pivoting to absorb bumps and suspension loads induced by the rider, acceleration, and braking. Originally motorcycles had no rear suspension, as their frames were little more than stronger versions of

702-490: A tuned Super Rocket engine a Gold Star frame. Gold Star tuner and dealer, Eddie Dow, had a customer that wanted to be supplied with a Gold Star fitted with a Super Rocket engine. BSA supplied a Gold Star less engine and a separate Super Rocket engine. Dow assembled the special. The special was well received and the BSA management decided to put the concept into limited production. The later (1961-1963) 9:1 compression Super Rocket engine

756-495: A variety of geometries. Many single-sided also incorporate the driveshaft. Swinging fork - the original version consisting of a pair of parallel pipes holding the rear axle at one end and pivoting at the other. A pair of shock absorbers are mounted just before the rear axle and attached to the frame, below the seat rail. Cantilever - An extension of the swinging fork where a triangulated frame transfers swingarm movement to compress shock absorber/s generally mounted in front of

810-418: Is usually cheaper to be maintained. Many motorcycles use air cooling for the sake of reducing weight and complexity. Few current production automobiles have air-cooled engines (such as Tatra 815 ), but historically it was common for many high-volume vehicles. The orientation of the engine cylinders is commonly found in either single-cylinder or coupled in groups of two, and cylinders are commonly oriented in

864-571: The R80G/S , the "Mono-lever", which was superseded by the "Para-lever" used currently. Honda currently features this style of swingarm on the Honda VFR . Ducati has created several models featuring single swingarms, most notably the Massimo Tamburini -designed 916 series . While Ducati abandoned this style for the 999 , the company returned to it for the 1098 superbike in 2007, and it survives in

918-579: The parallel twin engine layout for British motorcycles in the 1950s and 1960s. In April 1947 Hopwood joined Norton to design the Norton Dominator engine. In May 1948, the factory enticed Hopwood after only a year at Norton, and he was commissioned to create a competitive BSA 650cc parallel-twin. Launched in October 1949, Hopwood's A10 Golden Flash drew heavily from the A7 design by Page and Bert Perkins. The A10

972-604: The 'big valve' head which was also fitted to the newly launched Super Rocket. A shorter seat was fitted in 1959 and the exhausts were high level on the left hand side. This configuration continued until production ended in 1963. In 1963 the model again used the Gold Star cycle parts after being merged with the Road Gold Star Scrambler and renamed the Gold Star Spitfire Scrambler. Ariel Motorcycles became

1026-645: The 1900s. The first commercial production was by the New Way Motor Company of Lansing, Michigan, US. The company produced air-cooled engines in single and twin cylinders in both horizontal and vertical cylinder format. Subsequent to their initial production which was exported worldwide, other companies took up the advantages of this cooling method, especially in small portable engines. Applications include mowers, generators, outboard motors, pump sets, saw benches and auxiliary power plants and more. Swingarm A swingarm ( or swinging arm), originally known as

1080-456: The 356 "sports" profile, were also fitted. These engine modifications raised the power output to 40 bhp (30 kW) and a top speed of 109 mph (175 km/h). The model was launched with chrome mudguards and stays and a half-chrome petrol tank. A tachometer was an optional extra. The Road Rocket was discontinued in 1958 when it was replaced by the Super Rocket. The Super Rocket

1134-497: The Bonneville salt flats of 151 mph in October 1951. Hopwood decided to make a faster odel by bolting on performance parts to the existing model. Engine modifications included a 356 race camshaft and an Amal TT carburettor. Power output was 40 bhp (30 kW). The TT carburettor required a kink to be put in the frame's seat post for clearance. The frame also had welded on lugs for rearset footrests. A 2.5 gallon Gold Star tank

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1188-701: The Gold Flash, was the first of the series to be launched in 1950. Painted in a new gold colour, 80% of production was destined for the United States. This resulted in long delivery times for British customers, who were offered the model only in black. Although never designed as a sport motorcycle , the Golden Flash was nonetheless fast for its time and competitive with the Triumph Tiger 100 , achieving over 100 miles per hour (160 km/h) in tests in 1950, and covering

1242-407: The Golden Flash, the inlet manifold was separate to the cylinder head enabling twin carburettors to be fitted if required. Standard fitment was an Amal TT carburettor. New "thick flange" cylinders were introduced. (The bottom flange was increased from 3/8" to 1/2" for improved rigidity and reliability.). Big end size was increased from 1.48" to 1.68". High compression pistons and a higher lift camshaft,

1296-935: The Huntmaster, the Cyclone was also produced. This used the 40 bhp (30 kW) Super Flash engine, albeit with an Amal Monobloc carburettor fitted instead of the Super Flash's Amal TT version. Air cooled Air-cooled engines are widely seen in applications where weight or simplicity is the primary goal. Their simplicity makes them suited for uses in small applications like chainsaws and lawn mowers , as well as small generators and similar roles. These qualities also make them highly suitable for aviation use, where they are widely used in general aviation aircraft and as auxiliary power units on larger aircraft. Their simplicity, in particular, also makes them common on motorcycles . Most modern internal combustion engines are cooled by

1350-677: The Light-Sport Aircraft ( LSA ) and ultralight aircraft market. Rotax uses a combination of air-cooled cylinders and liquid-cooled cylinder heads. Some small diesel engines, e.g. those made by Deutz AG and Lister Petter are air-cooled. Probably the only big Euro 5 truck air-cooled engine (V8 320 kW power 2100 N·m torque one) is being produced by Tatra . BOMAG part of the FAYAT group also utilizes an air cooled inline 6 cylinder motor, in many of their construction vehicles. Stationary or portable engines were commercially introduced early in

1404-565: The Navy underwriting air-cooled engine development at Pratt & Whitney and Wright Aeronautical . Most other groups, especially in Europe where aircraft performance was rapidly improving, were more concerned with the issue of drag. While air-cooled designs were common on light aircraft and trainers, as well as some transport aircraft and bombers , liquid-cooled designs remained much more common for fighters and high-performance bombers. The drag issue

1458-476: The classic diamond frame of a bicycle. Many types of suspension were tried, including Indian 's leaf spring suspended swingarm, and Matchless 's cantilevered coiled-spring swingarm. Immediately before and after World War II, the plunger suspension , in which the axle moved up and down two vertical posts, became commonplace. In the latter, the movement in each direction was against coiled springs. Some manufacturers, such as Greeves, used swingarm designs for

1512-494: The current Ducati 1199 . The Triumph Sprint ST and Speed Triple also feature single-sided swingarms. "Squat" occurs because the top of the final drive chain run pulls the swingarm upwards; "shaft-jacking" occurs because the shaft drive bevel gear tries to "climb up" the large bevel gear in the wheel hub, thereby pushing the swingarm downwards and away from the frame. Shaft-jacking can be minimised by devices such as parallelogram swingarms. A practical way to minimise squat on

1566-407: The duplex primary chain was adjustable via a slipper tensioner within the primary chain case. The A10 was so closely based on the A7 that it used many of its well-proven components, and this large carry-over of parts from the A7 promised greater reliability, with minimal risk of new technical problems. With the introduction of a swinging arm frame in 1954, the semi-unit gearbox was abandoned for

1620-854: The factory adopted a swinging arm , and the hinged mudguard was deleted. Plunger frames remained an option on the Gold Flash until 1957. Brakes were initially an 8" single side front brake and a 7" rear. Full width brake of the same size were fitted to the higher performance models from 1958. Some of the Spitfire Scramblers and the Rocket Gold Star used a Gold Star 190mm front brake. The Rocket Gold Star used Gold Star cycle parts (Frame numbers beginning with A10, all other A10 models had frames starting with A7) Spitfire Scramblers also used Gold Star Catalina cycle parts in 1957 and 1963. All models are swinging arm frame unless otherwise indicated. Notes The BSA Golden Flash, commonly referred to as

1674-504: The front forks, which were more robust than telescopic forks . In particular, sidecar motocross outfits frequently use swingarm front forks. The swingarm has also been used for the front suspension of scooters . In this case it aids in simplifying maintenance. In motorcycles with shaft drive, such as the Yamaha XJ650 Maxim , the shaft housing forms the left side swingarm. Swingarms can be single or double sided, and have appeared in

BSA A10 series - Misplaced Pages Continue

1728-450: The introduction of the 650cc Triumph Thunderbird . Although BSA had a 500cc parallel-twin, the BSA A7 , they needed to develop a 650 to remain competitive. Bert Hopwood served an apprenticeship under designer Val Page at Ariel . In 1936, Hopwood moved to Triumph , where he worked under Edward Turner to develop the 1937 Triumph Speed Twin . The innovative Speed Twin became the exemplar of

1782-420: The line. New brakes were fitted to the model, full width hubs instead of the previous half width items. The front brake was 8" and the rear 7". Both were operated by cables. The 357 race camshaft was fitted in 1960 and the clutch was improved. A larger 1 5/32" bore Monoblock carburettor fitted in 1962. These raised the power output to 46 bhp (34 kW). The Rocket Gold Star was introduced in 1962, using

1836-568: The liquid-coolant circuit they are known as liquid-cooled . In contrast, heat generated by an air-cooled engine is released directly into the air. Typically this is facilitated with metal fins covering the outside of the Cylinder Head and cylinders which increase the surface area that air can act on. Air may be force fed with the use of a fan and shroud to achieve efficient cooling with high volumes of air or simply by natural air flow with well designed and angled fins. In all combustion engines,

1890-506: The much smaller radiators and less fluid in the system, the weight and drag of these designs was well below contemporary air-cooled designs. On a weight basis, these liquid-cooled designs offered as much as 30% better performance. In the late- and post-war era, the high-performance field quickly moved to jet engines . This took away the primary market for late-model liquid-cooled engines. Those roles that remained with piston power were mostly slower designs and civilian aircraft. In these roles,

1944-437: The production models, with another available as an accessory for racing only. Five different Amal carburettors were fitted to the range. The frame was available in rear rigid format, but the more common option was plunger suspension, adopted for the export market. The A10 featured a hinged rear mudguard to ease rear wheel removal. BSA were concerned that wear in the plunger suspension was leading to uncertain handling. In 1954

1998-464: The race cam proved to be suitable. The gearbox had wider, scrambles ratios. The frame, forks and wheels initially used were from the Gold Star Catalina, but halfway through 1957 this was changed to an A10 frame. A skid-plate and 2 US gallon petrol tank were fitted. No lights were fitted and the exhausts had no silencers. A Lucas competition magneto was used on this model. In 1958 the engine gained

2052-481: The radiator size by 50% compared to water cooled designs. The experiments were extremely successful and by 1932 the company had switched all future designs to this coolant. At the time, Union Carbide held a monopoly on the industrial process to make glycol, so it was initially used only in the US, with Allison Engines picking it up soon after. It was not until the mid-1930s that Rolls-Royce adopted it as supplies improved, converting all of their engines to glycol. With

2106-454: The simplicity and reduction in servicing needs is far more important than drag, and from the end of the war on almost all piston aviation engines have been air-cooled, with few exceptions. As of 2020 , most of the engines manufactured by Lycoming and Continental are used by major manufacturers of light aircraft Cirrus , Cessna and so on. Other engine manufactures using air-cooled engine technology are ULPower and Jabiru , more active in

2160-458: The steam through tubes located just under the skin of the wings and fuselage, where the fast moving outside air condensed it back to water. While this concept was used on a number of record-setting aircraft in the late 1930s, it always proved impractical for production aircraft for a wide variety of reasons. In 1929, Curtiss began experiments replacing water with ethylene glycol in a Curtiss D-12 engine. Glycol could run up to 250 C and reduced

2214-458: The swingarm. The HRD- Vincent Motorcycle is a famous early form of this type of swingarm, though Matchless used it earlier, and Yamaha subsequently. The Harley-Davidson Softail is another form of this swingarm, though working in reverse, with the shock absorbers being extended rather than compressed. Parallelogram - Was first introduced commercially in 1985 on the Magni "Le Mans". Magni called

BSA A10 series - Misplaced Pages Continue

2268-597: The system Parallelogrammo . Various parallelogram systems have been developed by other manufacturers. Whereas downward generated mechanical forces would cause a chain-driven bike to "squat" at the rear under acceleration, the torque reaction of a shaft drive machine would induce the opposite, causing the seat (and rider) to rise upwards, a phenomenon known as "shaft-jacking" . This anti-intuitive sensation can be disconcerting to riders, which parallelogram suspensions seek to neutralize. BMW introduced its Paralever system on its 1988 R80GS and R100GS motorcycles, which adds

2322-429: The tendency to wheelie at the start. Single-sided swingarm - a suspension lying along only one side of the rear wheel, allowing it to be mounted to a hub like a car wheel. Also found on scooters , where a robust chain case doubles as the swingarm linking the engine and rear wheel, single-sided swingarms need to be much stiffer and more heavily built than double-sided, to accommodate the extra torsional forces. Having

2376-454: The two designs roughly equal in terms of power to drag, but the air-cooled designs were almost always lighter and simpler. In 1921, the US Navy , largely due to the efforts of Commander Bruce G. Leighton , decided that the simplicity of the air-cooled design would result in less maintenance workload, which was paramount given the limited working area of aircraft carriers . Leighton's efforts led to

2430-578: The volume of water required and the size of the radiator by as much as 30%, which opened the way to a new generation of high-powered, relatively low-drag liquid cooled inline engines such as the Rolls-Royce Merlin and Daimler-Benz DB601 , which had an advantage over the unpressurized early versions of the Jumo 211 . This also led to development work attempting to eliminate the radiator entirely using evaporative cooling , allowing it to turn to steam and running

2484-591: Was $ 975 in the US and £325 in Australia. Production stopped in 1954 with the Road Rocket about to go into production. In total about 700 machines were made. The engine from the Super Flash later powered the Ariel Cyclone. The Road Rocket was a sports motorcycle developed from the Golden Flash. Launched as the top of BSA's range in 1954 the BSA Road Rocket was the first A10 engine with an alloy cylinder head. Unlike

2538-571: Was an improved sports model that replaced the Road Rocket in 1958. It retained the Amal TT carburettor and 356 sports cam of the Road Rocket. Compression ratio was raised to 8.5:1 and a new alloy cylinder head fitted. The cylinder head had a cast in inlet manifold and larger ports and valves. The inlet valve was increased from 1.455" to 1.5". The crankshaft was stiffened compared to the previous models. These modifications increased power output to 43 bhp. A lower 1st gear ratio gave increased acceleration off

2592-638: Was fitted and chrome mudguards and stays. The first Super Flash was shipped to America in February 1953 and American Motorcycling magazine give it 'Motor of the Month'. The bike was in American showrooms in April that year. Most of the production went to the US, but later in the year models were shipped to Europe, Africa and Australia.. Production continued into 1954, and some swinging arm versions were made in that year. The price

2646-433: Was increased in diameter from 1.46" to 1.68". Crankshafts and conrods with the bigger bid ends became known as "big journal". These changes continued on subsequent sports models. "Thick flange" cylinders and "big journal" big ends were fitted to the Gold Flash in 1958. In 1957 an improved clutch was introduced on all models, using 4 springs instead of six and improved friction material. Three different camshafts were used on

2700-445: Was increased to 650 cc (40 cu in) by using a 70mm bore and 84mm stroke. It had a revised alloy rocker box and cast-iron cylinder head, plus an integral manifold for the single Amal carburettor . A single camshaft behind the cylinders operated the valves via pushrods passing through a tunnel in the cast iron block. A magneto was located behind the cylinders, driven by a train of gears, to provide ignition. A dynamo

2754-432: Was introduced in 1957 at the request of BSA's West Coast distributor, Hap Alzina, to meet a need in US desert racing to deat the dominant Triumph twins. The engine was a modified Road Rocket unit. The head was modified to allow a 1 1/16" Amal Monoblock carburettor to be fitted. Compression was raised to 9:1 and a 357 "race" camshaft was fitted. Initially it was thought a special scrambles cam would need to be developed, but

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2808-489: Was positioned in front of the cylinders, driven by a chain. Lubrication was dry sump with oil being distributed by a mechanical pump located inside the timing cover. The crankshaft was a bolt-up 360-degree item (both pistons went up and down at the same time). Main bearings were roller drive-side and a white metal plain bush on the timing side. The conrods were of the split type with shell type big ends . The crank-cases were vertically split. A semi-unit gearbox meant

2862-489: Was upset by the 1929 introduction of the NACA cowl , which greatly reduced the drag of air-cooled engines in spite of their larger frontal area, and the drag related to cooling was at this point largely even. In the late 1920s into the 1930s, a number of European companies introduced cooling system that kept the water under pressure allowed it to reach much higher temperatures without boiling, carrying away more heat and thus reducing

2916-482: Was used with a 357 Spitfire camshaft and a 1 5/32" bore Amal Monobloc carburettor which gave 46 bhp (34 kW) as standard. Options such as an Amal GP 2 carburettor, siamesed exhaust pipes and a close-ratio RRT2 gearbox could increase this to 50 bhp (37 kW) – and add 30% to the price. The model was also known as the Gold Star Twin. Rocket Gold Star production ended in 1963. The Spitfire Scrambler

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