FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1954
1954 - 1292.PDF
FLIGHT, 7 May 1954 THE TWO Rs . F.10 (later Kestrel). During 1930 the "F" type engine was named the Kestrel, and yet another system of designation was introduced. The name was followed by the series number I, II or III, indicating 0.632, 0.552 and 0.475 reduction gear ratios respectively; then followed the letters A, B, MS, or S, indicating 6:1 compression, 7:1 compression, medium supercharger, or full supercharger. As we have said, the most notable design feature of the Kestrel was the adoption of the monobloc principle, and this resulted in a very light and rigid engine. The blocks were set at an angle of 60 deg, the cylinder heads, with the necessary inlet and exhaust passages, being cast integrally with the walls form ing the water-jackets. Renewable valve-seating rings were screwed into the heads and the valve-guide bushes were of cast iron. The flanged joint between the upper end of the carbon- steel cylinder liner and the head was made gas-tight by a soft aluminium ring, and near the lower end of the liner a sliding watertight joint was formed by means of a rubber ring fitted into a groove in the liner. Just below this joint a flange formed on the liner abutted on the crankcase and the whole assembly was held in position by long bolts. Where these bolts passed through the water space between the liners they were enclosed in aluminium tubes, swaged at the ends to make a watertight joint with the jacket casting. The two inlet and two exhaust valves per cylinder were operated by an overhead camshaft, through a separate rocker for each valve. The three oil pumps were of the gear type and were driven by spur gearing from the vertical shaft which drove the water pump. Lubrication was on the dry-sump principle. The engine was fitted with hand-starting gear, comprising a worm wheel incorporating a multi-plate clutch mounted on the sleeve carrying the main bevel wheel for the auxiliary drive; the clutch was set to slip when a predetermined torque was exceeded. In the event of backfire also the clutch would slip, thus saving the gears from damage. In Kestrel engines of the types A and B, two Rolls-Royce Duplex carburettors were mounted between the cylinder blocks. The two throttles of each carburettor were connected by a pair of toothed quadrants, and one quadrant of each pair was mounted on the end of a longitudinal shaft so that all four throttles were opened and closed simultaneously and to the same extent. The carburettors were fitted with a device by which the flow of petrol from the float chamber to the jet was automatically regulated in accordance with altitude. The supercharger consisted of a high-speed centrifugal fan mounted co-axially with the crankshaft at the rear of the engine and drawing air through the carburettors. The aluminium-alloy impeller, with radial blades, was driven through a speed-multi plying gear comprising a system of three planets. These were frictibnally driven from a pinion on the crankshaft by means of slippers, held in engagement with the insides of the gear rims by light springs. As the speed of rotation of the crankshaft—and therefore of the slippers—increased, the radial pressure of these springs was augmented by centrifugal force, and consequendy the torque which the planets could transmit increased as the square of the speed. As the torque required to drive the im peller increased at a like rate, the gear was capable of driving the impeller with a predetermined margin of torque above that causing slip, which was constant throughout the working range of speed. The object of this special friction drive was to protect the gearing against damage on sudden acceleration or deceleration of the crankshaft due to the inertia of the impeller. The impeller 575 inertia, however, in combination with the friction drive, served to damp out torsional oscillations of the shaft which drove the camshaft and auxiliaries, including the supercharger itself. For all the varieties of Kestrel so far mentioned the normal crankshaft speed was 2,250 r.p.m. and at this speed the un- supercharged low-compression engine developed 490 h.p. at sea level. The unblown high-compression types gave 480 h.p. up to 3,000ft, the medium-supercharged models 525 h.p. at sea level Kestrel XVI. and 500 h.p. at 3,000ft, and the fully supercharged versions 480 h.p. at 11,400ft. The next series of Kestrels bore the series numbers IV, V, VI, VII, VIII, IX, X, XI and XII. Of these the IV, V and VI were fully supercharged, with 0.632, 0.553 or 0.477 reduction gear; the VII, VIII and IX were medium supercharged, with the same sequence of gear ratios; and the X, XI and XII were unsuper- charged, with a compression ratio of 7:1. The fully super charged engines were rated at 600 h.p. at 11,000ft, and the medium supercharged and unsupercharged versions at 630 h.p. at 3,000ft and 575 h.p. at sea level respectively. The ultimate in Kestrel development were the Series XIV, XV and XVI, fully supercharged, but more highly rated than the IV, V and VI. The supercharger ran at 9.4 times the crankshaft speed, whereas on the IV, V and VI it ran at 8.8 times that speed. The rating was 690 h.p. at 2,600 r.p.m. (an increase of 100 r.p.m. over the earlier engines) at 11,000ft, and at 3,000 r.p.m. the output was 745 h.p. at 14,500ft. The weight was 975 lb. The Kestrel XXX was a later development for training air craft, and had a rated power of 535 h.p. at 12,500ft. Kestrels were installed in numerous types of British and foreign aircraft—military and civil. British military applications included the Avro Antelope, Blackburn Nautilus and Sydney, Fairey Fox I, II, III and IV, IIIF, Firefly II and III, Fleetwing, Hendon II and S.9/30, Gloster C.16/28 and Gnatsnapper III, Handley Page Heyford, Hawker Hart, Demon, Fury, Osprey, Nimrod, Audax, High-Speed Fury, Hardy, Hartebeeste and Hind, Miles Master, Parnall Pipit, Saunders-Roe A.10, Short Singapore II and III and Gurnard, Supermarine Southampton, Vickers 141, B.19/27 and 163, and Westland Wizard. Ruzzard THE BUZZARD Originally known as the "H" engine, the Buzzard was larger and more powerful than the Kestrel, but very similar in design. In fact, it bore the same relationship to the Kestrel as did the Eagle to the Falcon. The bore and stroke were 6in x 6.6in, and the engine was supplied as standard with a medium supercharger capable of being used to its fullest extent on the ground, so as to give the maximum possible take-off power. The Series I, II and III engines had reduction gear ratios of 0.632, 0.553 and 0.477 respectively, and the normal power was 825 h.p. at 2,000 r.p.m. at sea level. At 2,300 r.p.m., 955 h.p. was available at sea level. The dry weight was 1,540 lb.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
