The Alvis Pelides was an unflown British air-cooled radial aero engine first developed in 1936. The Pelides Major was a projected but unbuilt development as were the Alcides, Alcides Major and the Maeonides Major, the Alvis aircraft engine range taking their names from Greek mythology.
The Pelides was the first aero engine of Alvis design, the company had previously built the French Gnome-Rhône Mistral Major under license. With the two companies working closely together the 14 cylinder radial layout of this engine retained metric dimensions but substituted metric screw threads with British fasteners such as BSF and Whitworth. Material specifications were different as were the detail design of internal parts such as the crankpin. The Pelides passed a 50 hour Air Ministry type test in 1937 where it produced 1,065 hp (794 kW) but no aircraft application was found and only 15 engines were built. The onset of the Second World War caused the abandonment of any further development of the Pelides and its related designs.
The Pelides Major was a projected but unbuilt version retaining the same dimensions as the Pelides but with improvements to the supercharger.
Alcides and Alcides Major
The Alcides of 1937 was another projected medium supercharged two row radial engine but was planned to have 18 cylinders with a displacement of 3,314 cu in (54.24 L) and a power output of 1,300 hp (969 kW). Again the Alcides Major was an improved fully supercharged version.
Also designed in 1937 was the unbuilt supercharged Maeonides Major, effectively a smaller version of the Pelides with a displacement of 1,158 cu in (19 L) and a power output of 650 hp (485 kW).
Type: 14-cylinder, 2 row, supercharged air-cooled radial piston engine.
Bore: 5.75 inch (146 mm)
Stroke: 6.5 inch (165 mm)
Displacement: 2,359.8 cu in (38.7 L)
Diameter: 52 in (1321 mm)
Dry weight: 1,190 lb (540 kg)
Valvetrain: Two pushrod-actuated poppet valves per cylinder with sodium-cooled exhaust valve.
Supercharger: Single speed, single stage.
Fuel system: Heated Zenith carburettor
Fuel type: Petrol, 87 Octane
Oil system: Dry sump
Cooling system: Air-cooled.
Power output: 1,000 hp (746 kW) at 2,400 rpm (rated power)
Compression ratio: 5.5:1
Power-to-weight ratio: 0.84 hp/lb (1.4 kW/kg)