When it first appeared, in August 1918, the Condor followed very closely the pattern of the Falcon and Eagle, though it was of larger (35 litres) capacity. The Condor Series I was designed for 550/600 h.p., and the larger cylinders necessitated four valves per cylinder instead of two. The valves on each bank were operated by a single camshaft. There were only two carburettors and these were mounted low down on each side of the crankcase in line with the centre bearing. The water pump was transferred to the centre of the engine and an electric starter could be provided.
In succession to the Series I came the IA, wherein the normal output was raised to 650 h.p. at 1,900 r.p.m. There is no record of the Condor II but the Series III, which differed considerably from its predecessors, developed 650 h.p. at 1,900 r.p.m., though it weighed nearly 300 lb less. The Series III was fitted with a single-spur reduction gear, carried in a housing bolted to the front end of the crankcase. This changed the outline of the engine and made for improved cowling lines. The makers nevertheless recognized that higher stresses were set up in the crankcase than with the old epicyclic type. In the new gear a flange was formed on the front end of the camshaft and to this was bolted an internally toothed ring, the teeth of which engaged with similar teeth on the end of a short hollow shaft. The opposite end of the shaft was formed with splines to transmit the torque to a hollow pinion mounted in roller bearings. Thus, any transverse loads were prevented from being transmitted to the crankshaft from the gearing. The pinion engaged with a toothed wheel mounted on, and keyed to, the airscrew shaft, which was supported on roller bearings and was fitted with a ball-and-thrust bearing to take the thrust of the airscrew. The engine was cleared to use a metal airscrew and an efficient diameter was about 16ft.
Another point of difference between the Condor and the earlier Rolls-Royce engines was in the design of the connecting rod assembly: in the former engines articulated rods had been used, the Condor had forked rods.
Engines of the Condor III series varied from one another in certain respects, but an Air Ministry description in a publication of 1926 remarks that the various pumps serving the engine had been built into a single unit bolted beneath the crankcase lower half. This unit comprised three oil pumps, a water pump and a petrol pump, the last-named being a unit not previously fitted to any Rolls-Royce engine as a standard component. The description went on: "the carburettor has been redesigned and the altitude control valve is of an entirely new design. Owing to the desire to reduce weight, no hand starting device has been provided, but provision has been made for starting by means of the Bristol gas starter. To this end a gas distributor is provided and is driven from the mechanism contained in the wheelcase."
The Condor IV was a direct-drive engine intended for fighters, and was extensively flown in the Hawker Hornbill, the fastest fighter of its day. The absence of the reduction gearing saved about 80 lb in weight. Normal output was 650 h.p. at 1,900 r.p.m., and dry weight 1,250 lb.
An experimental Condor was fitted with a turbo supercharger running at 26,000 r.p.m., and giving an induction pipe pressure of 13.5 lb/sq in at a height of 2,000 ft. It was never flight tested. The Series VIII, specially designed for internal installation in a projected Supermarine flying-boat, was another development which was not air-tested.
During 1932 it was announced that a compression-ignition version of the Condor had passed the Air Ministry's civil-engine type test of 50 hr and that flight trials were then under way at Farnborough in a Hawker Horsley. The C.I. Condor gave 500 h.p. and weighed, with spares and accessories, 1,504 lb. Conversion was initiated by the Air Ministry and the engine was developed at the Royal Aircraft Establishment with the co-operation of Rolls-Royce, Ltd.
British aircraft powered with the Condor included the Beardmore Inflexible, Avro Aldershot, Ava and Andover, Blackburn Iris I. II and III, D.H. Derby, Fairey Atalanta, Titania and Fremantle, Handley Page Handcross, Hawker Horsley, SauridersRoe Valkyrie, Short Cromarty and Singapore, Vickers Vixen and Vanguard, and Westland Yeovil.
A total of 327 engines were recorded as being built.
In 1932 the Air Ministry initiated a conversion of the Condor petrol engine to the compression ignition system. The conversion was developed at the Royal Aircraft Establishment, Farnborough, with the co-operation of Rolls-Royce Ltd. Engine layout, bore, and stroke remained the same as for the petrol version; the compression ratio increased to 12.5:1. The more robust construction required to withstand the increased stresses increased the engine weight to 1,504 lbs (682 kg). At its maximum 2,000 rpm the engine developed 500 hp (373 Kw), giving a power/weight ratio of 0.33 hp/lb.
The engine passed the 50-hour civil type test for compression ignition engines, being only the second British engine to do so. The only previous engine to pass this test was the much larger Beardmore Tornado fitted to the R101 airship. The diesel Condor was experimentally flown in a Hawker Horsley to explore the practical operation of a diesel engine in flight.
(1920-1921) 600 hp, 72 built at Derby.
Alternative designation for Condor II.
(1921) 650 hp, revised propeller reduction gear ratio, increased compression ratio (5.17:1). 34 built at Derby.
(1923-1927) 650/670 hp, compression ratio 6.5:1, Re-designed connecting rods. 196 built at Derby.
(1925) 650/665 hp. Improved main bearing design and material.
(1930) 650 hp, 0.477:1 reduction gear, re-designed crankcase and crankshaft.
(1925) 750 hp. Direct-drive, modified engine mounting. 13 built at Derby.
(1927) 750 hp. Nine built at Derby.
(1925) As Condor IIIA with two-stage turbocharger. Run but not flown, one built at Derby.
Direct-drive Condor IIIA, two built at Derby.
(1932) 480 hp, compression ignition (diesel), two engines tested and flown.
de Havilland DH.27 Derby
de Havilland DH.54 Highclere
de Havilland DH.14 Okapi
Handley Page Handcross
Rohrbach Ro V Rocco
Type: 12-cylinder liquid-cooled 60 deg. Vee aircraft piston engine
Bore: 5.5 in (139.7 mm)
Stroke: 7.5 in (190.5 mm)
Displacement: 2,137.5 in³ (35.03 L)
Length: 69.3 in (1,760 mm)
Width: 41.1 in (1,044 mm)
Height: 43.2 in (1,097 mm)
Dry weight: 1,380 lb (628 kg)
Valvetrain: Overhead camshaft
Fuel system: 2 x Claudel-Hobson carburettors
Fuel type: Petrol
Cooling system: Liquid-cooled
Power output: 670 bhp (500 kW) at 1,900 rpm
Compression ratio: 5.1:1