A Light‐Weight Radial Engine: Some Particulars of the 80 h.p. Seven Cylinder Pobjoy Air‐Cooled Radial

THE 80 h.p. seven‐cylinder Pobjoy “R” engine, fitted as standard to the twin‐engined Monospar monoplane, is of the radial air‐cooled, geared, dry sump type. The cylinder bore is 77 mm. (31/32 in.) with a stroke of 87 mm. (3 27/24 in.), the total volume being 2,835 cu. cm. The power at normal revolutions, 3,000 r.p.m., is 75 rated and 77–79 actual b.h.p., while at the maximum of 3,300 r.p.m. it develops 85 b.h.p. The weight, complete with airscrew hub, is 135–140 lb. At normal horse‐power the power‐weight ratio is, therefore, 1·87 lb./h.p. At full throttle the fuel consumption is 0·62 pints/b.h.p., or 6 gallons per hour; the oil consumption being 1¼ pints per hour.