Blackburn Cirrus Minor
The Blackburn Cirrus Minor was a general aviation piston aircraft engine made by the British manufacturer Blackburn Aircraft . The engine was derived from the ADC Cirrus , which was produced by the predecessor company Cirrus Engines Ltd. was produced from 1925. The company first presented the four-cylinder OHV engine in 1933, initially with a bore of 95 mm and a stroke of 127 mm. Series production began in the same year. Blackburn took over Cirrus Engines Ltd. in 1934. and continued the series production of the engine. It was then widely used in several versions. In 1937 the compression was increased and thus the performance increased accordingly.
An essential design feature of the engine were the suspended air-cooled cylinders made of high-alloy steel, which were turned out of solid material with their cooling fins. The individual cylinders were attached to the crankcase with short anchor bolts. There was one inlet and one outlet valve per cylinder. The cylinder heads made of aluminum were connected to the cylinders by eight bolts. The rocker arms were protected by an electronic cover. The aluminum slipper pistons had two compression rings and an oil control ring. The connecting rods were made of forged hiduminium. The forged crankshaft, machined on all sides, consisted of a high-strength steel alloy. It was mounted in plain bearings made of white metal. The tensile forces of the directly driven propeller were absorbed by a radial ball bearing in the front part of the crankcase. Like the upper housing cover, this was made of electron. The camshaft ran directly in the cast part of the crankcase and was driven by a spur gear. A circulation system with a piston pump provided lubrication. A downdraft carburetor from Claudel-Hobson with mixture adjustment and flame screen was used to supply the mixture. Fuel was supplied by Amal fuel pumps powered by a shaft on the rear cover of the unit. For the ignition, two shielded systems from BTH were available, whose magnets were also attached to the rear cover. In addition, an electric starter and a filter device could be installed.
The Cirrus Minor II, introduced in 1945, had a bore that was enlarged to 100 mm, and the compression had now been increased to 6.5: 1. This made the use of 77 octane fuel necessary. Leaded petrol was also allowed. In order to improve the lubrication of the rocker arms, the cylinder covers were changed. The outlet valves were filled with a Stellite , which increased their service life. A Zenith version with automatic preheating was used as the carburetor .
The Cirrus Minor has been incorporated into a number of General Aviation, Taylorcraft, and Miles models.
Technical specifications
Minor Minor I Minor II Bohrung mm 95 95 100 Hub mm 127 127 127 Hubraum l 3,6 3,6 3,99 Verdichtung 5,1:1 5,8:1 6,5:1 Länge mm 960 1013 Breite mm 440 455 Höhe mm 636 650 Gewicht kg 95 108 113 Startleistung PS/min-1 80/2400 90/2600 100/2600 Reiseleistung PS/min-1 70/2200 80/2300 90/2300
literature
- "British Piston Aero Engines and their Aircraft," Alec Lumsden, ISBN 1-85310-294-6 .
- Jane's all the world's aircraft , 1945.
- Piston aircraft engines, Hans Giger, ISBN 3-613-01089-5 .
- Encyclopedia of Aero Engines ”, Bill Gunston, ISBN 3-613-01422-X .
