Ariel Square Four

The Ariel Square Four is a motorcycle of the British manufacturer Ariel with an air-cooled four-cylinder four -stroke engine and two crankshafts.

Development

The engine was designed by Edward Turner and tested in late 1929 for the first time. The two crankshafts with two 180 ° offset crank pins, recorded the cantilevered rods, were installed across the vehicle and connected via a helical gear the centrally disposed flywheel together so that they circulated in opposite directions. This resulted in a cylinder arrangement in a square from which was derived the name. From the teeth of the rear crankshaft the force was first routed directly into the integrated three-speed gearbox. In the series, however, a separate transmission Burman was used and built another camp before the primary chain sprocket. The gas exchange was accomplished by overhead parallel valves were actuated by an overhead camshaft. Cylinder block and the cylinder head were each a cast iron piece. The gas outlet of the cylinders lying on both sides of the outside of the head, the fresh gas channels on the inside. While the valve gear and the crankshaft gear was equipped with a dry sump forced lubrication with one gear pump for oil pressure and return flow, was lubricating the crank mechanism by spin oil.

Ariel 4F

The idea of officially Ariel 4F -31 type mentioned with 498 cc and 20 hp first took place in November 1930 in the Olympia Motor Show in London. In 1932, a 599 cc version with 24 hp (Type Ariel 4F / 6) to do so. This year, Ariel first went into bankruptcy. The production facility but was bought by Jack Sangster, who had to continue production. 1933, the 500 - cc - type has been set. The dry sump lubrication system was replaced by a wet sump lubrication system with piston oil pump and the gears of the crankshafts were straight teeth. 1935, the motor housing has been reinforced.

Ariel 4G/4H

The production costs could not be covered by an appropriate selling price to the motorcycle market. Sangster therefore decided to develop a completely new square four engine with 1000 cm ³, which should only have in common the cylinder assembly to the output type. It was constructed an OHV engine. The crankshafts were separate for power transmission gears on the left side of engine. They were conventionally performed in two outer bearings, which were mounted in a vertically split crankcase. The engine made ​​36 hp and was first delivered in September 1936, the model identifier Ariel 4G. 1939, added a simple equipped Ariel 4H. Similarly, there was a reduction in the bore 601 cc version otherwise corresponded to the 4H.

After World War II, production continued. A telescopic fork replaced the previous 1946 Keystone fork.

Ariel Square Four Mark I

After successful exports to the United States, there were increasing complaints there by overheating of the rear cylinder by prolonged exposure and in the UK by knocking due to decreased after the war octane number of available fuels of partially only 70 octane.

Val Page designed so 1949 cylinder head and cylinder block made ​​of light metal new. In the cylinder head rocker box has been integrated. Other changes included the mounting of cylinder block and cylinder head and the replacement of the light Magneto by a DC alternator and coil ignition. By design measures the weight has been reduced by 15 kg. This version was built until 1953.

Ariel Square Four Mark II

1952, the cylinder head was changed again. The exhaust gases flow now to reduce by four individual manifolds to the heat load of the cylinder head. Two single rocker box allowed for a more favorable fresh gas management. The engine made ​​40 hp so, in a version with 7.2: 1 compression also increased 42 hp. In 1956 the model full hub brakes and a larger oil supply was provided. This version was built until the end of production in 1958.

Ariel Square Four Mark III Royal Hunter

This variant should replace the Mark II in 1954. The main design difference was a long arm instead of the telescopic fork. There were only prototypes.

Ariel Square Four Mark IV

The Mark IV should replace the 1958 Mark II and had rear swing arm. Due to the change of business policy and the setting of all motorcycles with a 4- stroke engine with Ariel, it remained in the design.

Production figures

Specifications ( Mark II 1958)

  • Displacement: 998 cm ³
  • Bore: 65 mm
  • Stroke: 75 mm
  • Compression ratio: 7.2:1
  • Power: 42 hp at 5800 min-1
  • Transmission: 4-speed foot control
  • Wheelbase: 1422 mm
  • Seat Height: 787 mm
  • Fuel tank capacity: 23 liters
  • Weight: 197 kg

Swell

  • English article from January 27, 2007
  • Motorcycle Classic, 1/95
  • Patent CH150402 1931
Ariel (vehicle) Olympia (London) Engine knocking Rocker arm Drum brake
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