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Aviation History
1943
1943 - 0388.PDF
156 FLIGHT FEBRUARY IITH, 1943 Wright Double-row Cyclone An American 14-cyL 1,600 h.p. Radial of 2,603 cu. in* Capacity : Single-speed or Two~speed Blowers AS early as 1930 the engineers of the Curtiss-Wright A% Corporation of America had developed a double-row •*• -* radial engine of moderate displacement on which wide experience was gained through extensive tests and flight operations. Subsequent modifications increased its output to approximately 900 h.p., and a basic design was established which eliminated many of the disadvantages previously associated with double-row engines. This engine, however, fell in the same power class as the single- row Cyclone of that time, and development was held in abeyance until such time as a really great increase in power should be needed. The year 1938 saw the introduction, on a production scale, of an aircraft engine 30 per cent, more powerful than any then available. This engine was the Wright double-row Cyclone 14, of 1,500 h.p., which made possible the design of the Pan American Airways 41-ton Boeing Clippers. These, with the British Short Bristol-engined commercial flying boats, paved the way for the trans- atlantic operations. Although put to immediate commer- cial use, the double-row Cyclone 14 remained under U.S. Government restriction and was adopted by the U.S. Navy for its Martin patrol boats and by the U.S. Army for various types of attack and bomber aircraft. Due to these restrictions little became known of the engine except that it was obviously a development of the single-row Cyclone. The engine was remarkably successful from its inception, having passed all its tests in a very short time and emerging as a production engine with practically no change from the original design. It was conservatively rated at 1,500 h.p., which was later increased to 1,600 h.p. for take-off, with 1,350 h.p. available for normal operation. Many parts of the double-row Cyclone 14 are similar to those of the single-row Cyclone. With the exception of the crankshaft and the crankcase, the basic design remains unchanged from that of the engines on which over 500,000,000 operating miles of experience have been gained. Refinements have, however, been incorporated. The cylinders, for example, though similar in appearance to previous Cyclone types, have much greater cooling area. CYCLONE 14 C14A and C14BA Engine Model 579C14AC1 (-A2A) GR2600-A2B GR2600-A5A ... GR2000-A5B 585C14BA 586C14BA Dry Wt la. 1,935 1,935 1,950 1,050 l.Ofia 1.H80 Blower Ratio 7.00 7.00 7.14 10 ; 7.14 K) : 7.30 7.0(5 an< 10.02 1 1 1 1 1 1 1> 1 Take-off r.p.m. h.p. 2400 2400 2400 2400 2"ion 2500 1600 1800 1600 lfiOO 1700 1700 Sear.p.m. 2300 2300 2300 2300 240(1 2400 Level h.p. 1350 1350 1350 1350 1500 .1500 Low Blowerr.p.m. h.p. ft 2300 2300 2300 2300 2400 2400 1350 1350 1350 1350 1500 1500 6200 5800 5000 5000 C.700 f"»7()() High Blower r.p.m. h.p. ft. 2300 2300 2400 1275 12000 1275 11500 1350 1500C The first four models have an airscrew reduction gear ratio of 0.5625. The 585C14BA modelhas a ratio of 0.4375, and the last model in the table may have O«6625 or 0.4375. The C14A model has a diameter of 55in. and a length of 62.06 in. The corresponding figurestor the C14B are 54.25 in. and 6H.40in. respectively. Both models have a bore of 6.125in-. and a stroke of 6.312in. The cylinders of the Double-row Cyclone are similar to those of the single-row engine, but have larger cooling area. The engine is a staggered radial of 14 cylinders, having a total displacement of 2,603 cu- m- Cylinder bore is the standard 6.125m. of the single-row Cyclone, but the stroke is slightly shorter, being 6.312m. instead of 6.875m. The diameter of 55m. is the same as that of previous Cyclones, but so compact is the construction that the additional row of cylinders has been accommodated in little more than a foot extra in length, which includes an extension of the accessory section to provide a more streamlined passage for the mixture between carburettor and supercharger. Cylinders follow usual Cyclone construction of cast alu- minium' alloy heads shrunk on forged nitralloy steel barrels. Head finning is deeper than usual, and intake and exhaust ports are at the rear on all cylinders. Valves are inclined to the centre line of the cylinder at an angle which enables a hemispherical combustion chamber to be used. Valve guides, seats, intake pipe and push rod housing connec- tions are shrunk into the head. Sparking Plug Cooling Two bronze sparking plug bushings, just above the main horizontal cooling fins of the head, are located at 90 deg. of each other and surrounded by deep vertical cooling fins arranged to permit a free flow of air over the finned spark- ing plug. The inside of the forged steel cylinder barrel is nitrided to the hardness of glass and given a micro-finish that leaves no point of roughness greater than two mil- lionths of an inch. Cooling .fins are machined on the out- side for heat dissipation, and improved attachment of the head is provided by ground threads. The main section of the crankcase consists of three aluminium forging;, divided along planes through the centre of the cylinder locations. They are bolted together between the cylinders of each bank. These com- bined main sections contain the three main crankshaft roller bearings and support the front and rear cam drive gear assemblies, the cams, and the tappet and guide assemblies. The nose section provides for vertical mounting of a constant-speed airscrew governor and is machined from an alumipium
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