SBC-4 Wright R-1820 Cyclone engine
The R-1820 Cyclone series, specifically the F model, marked a significant evolution in radial engine design by Wright Aeronautical. Initially developed in the early 1920s, the R-1820 evolved through several iterations, reaching a sophisticated design by World War II.
F Model Cyclone
- Design and Construction: The F model featured a forged aluminum crankcase split on the cylinder centerline. The cylinders were constructed using a steel barrel with integrally machined cooling fins, and the cast aluminum cylinder heads were screwed-and-shrunk onto these barrels. The hemispherical combustion chambers housed two valves, with the exhaust valve using Heron’s sodium-cooling technique to manage high temperatures.
- Crankshaft and Rods: The engine utilized a two-piece crankshaft supported by two roller bearings. A one-piece master connecting rod connected to a steel-backed lead-indium-silver bearing. The crankshaft assembly included counterweights, one of which was a pendulum-style dynamic counterweight.
- Supercharging and Carburetion: The supercharger, designed by General Electric, had limitations with an efficiency below 60%. Carburetion was provided by a two-barrel downdraft Holley carburetor. The engine typically produced between 575 and 890 horsepower at 1900 RPM, with a weight around 1000 pounds.
- Ignition and Lubrication: Ignition was handled by two Scintilla magnetos mounted on the rear cover, firing two spark plugs per cylinder. The lubrication system used a dry sump with one pressure pump and one scavenge pump.
G Series Enhancements
- Cooling and Supercharging: The G series introduced significant improvements, particularly in cooling and supercharging. Additional cooling fin area brought the total to 2800 square inches per cylinder. The original General Electric supercharger was replaced by a more efficient single-speed supercharger developed under Kenneth Campbell, which improved efficiency from around 60% to over 75% by the end of production.
- Crankcase and Performance: The crankcase was redesigned using a steel forging to enhance mechanical properties while minimizing weight. The G series also retained many design features of the F series but offered considerably improved performance, reaching up to 1200 horsepower at 2500 RPM.
Manufacturing and Production
- With the onset of World War II, the G-series engines became the primary production model, phasing out the F series. The Studebaker Corporation played a significant role in manufacturing the G series, establishing three facilities: the main assembly plant in South Bend, Indiana, a gear and connecting rod plant in Fort Wayne, Indiana, and a precision parts plant in Chicago, Illinois.
These developments positioned the R-1820 as a crucial engine for various aircraft during World War II, demonstrating significant advancements in radial engine technology.