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Aviation History
1934
1934 - 1219.PDF
NOVEMBER 15, 1934. FLIGHT. I22T The Napier-Junkers " Culverin " 6-cyl. compression-ignition engine of 720 h.p., and (right) the supercharged " Rapier " II, which delivers 305 h.p. at 10,000 ft. of the engine without airscrew hub it. approximately 1,785 lb., and the air- screw hub weighs 35 lb. On rated power (720 b.h.p. at 1,700 r.p.m.) the engine weighs 2.48 lb. per b.h.p. Overall length is 6 ft. n| in., the width 1 ft. nin., and the height 5 ft. 7 in. Fuel consumption is given as 0.375 lb./b.h.p./hr. at rated power and lubricating oil consumption as 0.023 lb./b.h.p./hr. The British Air Ministry has interested itself in the Culverin," particularly with regard to its possibilities of installation in long- range aircraft such as bombers and flying boats. A smaller compression-ignition type known as the "Cutlass" has also been produced by the company, but particulars are not available. POBJOY AIRMOTORS, LTD. SMOOTH and quiet running qualitiescombined with cleanliness and eco- nomy of operation and lightness are characteristic qualities of Pobjoy engines. Three types are now in production, all developments of the Pobjoy "E" engine which was produced three or four years ago. These types are all 7-cylinder radials, and are known as the '' Nia- gara," " Cataract," and "Cascade." The former two are geared, and the " Cas- cade " is a direct drive type. Normal powers are 84 h.p. at 3,200 r.p.m., 75 h.p. at 2,900 r.p.m., and 65 h.p. at 2,600 r.p.m. respectively. All three engines have the same bore and stroke. The crankcase of the "Niagara " engine is in four parts, and carries a single throw, two- " piece crankshaft on four sub- stantial bearings. The single crankpin is hardened, and on it runs a floating bronze bush run- ning inside the hardened eye integral with the nickel chrome steel master rod, to which are linked the six articulated con- necting rods. The die-cast alu- minium cylinder heads are screwed to the steel barrels and locked by a patented method. Oil-tight cast aluminium casings completely enclose the valve gear. Each cylinder head car- ries one inlet and one exhaust valve, the clearance of which need not be readjusted more frequently than every 125 hours. Double helical reduction gear- ing is employed, and includes a shock absorber to eliminate "chattering" at low speed. The two independent ignition systems each consist of a B.T.H. magneto, firing its respective sparking plug in each cylinder via a separate H.T. distributor. Shielded ignition can be provided for use with radio. The hand starting mechan- ism, of the ratchet type, is completely- disengaged when in the normal running position. The Claudel Hobson carburet- ter is oil-jacketed to prevent freezing, and a controllable hot and cold air intake is fitted. Cowling is supplied as an inte- gral part of the engine. All the air entering the cowling ring is forced to cir- culate over the cylinder heads or around the barrels by deflectors and helmets. Eh li ^d inside the The neat cowling and exhaust system of Pobjoy "Niagara " 84 h.p. radial. outer bonnet. Complete accessibility to such items as plugs, valve gear, magnetos and petrol pump can be had by raising this bonnet. To remove any possibility of fire risk, a sheet-aluminium guard is provided which surrounds completely the rear of the engine and shields it from the exhaust pipes. In a serious crash the exhaust pipes would be trapped be- tween two layers of cold aluminium, thereby eliminating one of the main causes of fire after a crash. The exhaust collectors are specially designed to avoid expansion troubles. They are reinforced at all corners with internal fillets and are protected against corrosion by a pro- cess known as " aluminization." An adaptor is fitted as standard in the induction manifold for use, if required, with a priming pump. This is of assistance for cold-weather starting from the cabins of multi-engined machines or flying boats. On the starboard side of the rear cover a sealed type of " Veeder" indicator is fitted, which records the number of hours run up to 1,000. The new valve rocker gear is so made that inspection is desir- able only every 125 hours. It has been found that, owing to the cool running of the engine, valve rockers require no atten- tion. Top overhaul is neces- sary only every 250 hours. It is claimed that the noise per horse-power is less than half that of any other engine due to the slow speed airscrew, smooth exhaust flow and ab- sence of vibration.the
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