Wright R-3350 Duplex Cyclone technical specification

    Wright R-3350 Duplex Cyclone technical specification

    The huge Wright R-3350 Duplex Cyclone was an air-cooled, 2,200-horsepower, twin-row, eighteen-cylinder engine. With a displacement of 3,350 cubic inches, it was one of the most powerful radial aircraft engines produced by the United States. Wright Aeronautical Division of the Curtiss-Wright Company of Paterson, NJ developed it in the ’30s before World War 2.

    The R-3550 main military application was the Boeing B-29 Superfortress. Due to the war, the US rushed it into combat with severe consequences. After it, the R-3550 remained in production and it was mature enough to bed used in civilian aircraft.

    R-3350 engines during World War 2
    Some R-3350 engines in the Burma-India theater during World War 2 (NARA)

    The list of applications includes the Boeing B-29, Consolidated B-32, Lockheed C-69, Boeing C-97, Fairchild C-119, Lockheed C-121, and Douglas A-1 Skyraider.

    The main parameters of the R-3350 (-35 variant) were:

    Military ModelR-3550 -35
    WAD Model711C18BA2 (B series)
    Type18 cylinders, 2-row radial, air-cooled, geared drive, Supercharged, 4-cycle
    Construction3-piece steel crankcase, Cylinders with steel barrels with W-type aluminum alloy fins and cast aluminum alloy heads, one inlet valve and one exhaust valve (sodium cooled) per cylinder actuated by push rods, 2-throw 3-piece counterbalanced crankshaft supported in 3 roller bearings, Planetary reduction gear, ratio 0.44:1 or 0.56:1
    SuperchargerG.E. Gear-driven, 2-speed supercharger, ratio 6.61:1 and 8.81:1
    CarburationOne Chandler-Evans 58CPB4 variable venturi pressure- type down-draft carburetor with automatic mixture control
    IgnitionOne Bendix-Scintilla DF18LN-1 dual magneto and one 18-point distributor. Two 28mm long reach spark plugs per cylinder. Shielded ignition system
    LubricationPressure feed, 60-70 lb./sq.in. (4,2-4,9 kg/cm2). Dry sump.
    StarterOptional. Eclipse E-160 or 1416 direct cranking or Series 48 inertia and direct cranking, starter
    Bore6.125 in.155 mm
    Stroke6.3125 in.160 mm
    Displacement3.347cuin54,9 lit
    Compression Ratio6.85:16,85:1
    Diameter55.8 in.1 417 mm
    Length55.8 in.1 935 mm
    Frontal area17.0 sq.ft.1,57 m2
    Weight2,670 lb.1 211 kg
    Weight/hp1.21 lb./h.p.0,55 kg/hp
    Fuel consumption (cr)0.46 lb./h.p./hr.210 g/hp/hr
    Oil consumption (cr)0.020 lb/h.p./hr.9 g/hp/hr
    Gasoline grade100/130 octane100/130 octane
    Oil grade (viscosity)120 S.U. secs25,1 cs
    Output/displacement0.66hp/cuin40,1 hp/lit
    Output/piston area4.15 hp/sqin0,64 hp/cm2
    Piston speed (max.)2,946 ft/min14,9 m/sec
    B.m.e.p. (max.)187 lb./sq.in.13,1 kg/cm2
    Rating (take off)2,200 h.p./2,800 r.p.m. at sea level
    Rating (normal, low)2,000 h.p./2,400 r.p.m./4,500 ft. (1 400 m)
    Rating (normal, high)1,800 h.p./2,400 r.p.m./14,000 ft. (4 300 m)
    Rating (cruising)1,300 h.p./2,100 r.p.m./no specified altitude
    Military2,200 h.p./2,600 r.p.m/25,000ft (for maximum of 5 minutes)
    Temperature Limits (Degrees F)
    ConditionsCylinder HeadOil
    Ground Operation500F203F
    Take Off Power 500F203F
    Military Power 500F203F
    Rated Power (1hr)478F185F
    Rated Power (continuous)450F185F
    70% Rated Power (cont.)450F185F

    Further reading

    Bibliography and source

    • Aircraft Engines of the World 1945 by Paul Howard Wilkinson
    • Boeing B-29 Superfortress: The Ultimate Look: From Drawing Board to VJ-Day by William Wolf
    Javier is the editor @ Nuclear Companion and loves to investigate and write about the cold war. He lives in Montevideo, Uruguay.

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