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Aviation History
1921
1921 - 0372.PDF
JUNE 2, 1921 efficiency of operation at altitudes never before obtained with such an engine. This was accordingly done, raising the cylinder displacement to 1,237 cubic ins. It had originally been decided not to attempt to test this engine on full throttle at sea level since the increased stresses might be more than the engine could be expected to stand. It had been the intention, of course, to supply the engine with a safety stop on the throttle until an altitude of at least 5,000 ft. should be reached ; then the throttle could be opened wide. However, the engine behaved so well in its trial run on the dynamometer that it was decided to attempt a wide- open throttle run. The results were extremely gratifying, and the engine showed itself capable of being run under these conditions at speeds in excess of 2,400 r.p.m. A maxi- mum of 400 h.p. was developed although the engine was originally designed for only 300 h.p. This run was made on ordinary aviation petrol, and the engine did not suffer from either pre-ignition or detonation. This is in marked contrast to somewhat similar oversize engines constructed in Germany which cannot be run wide-open near the ground except with doped fuels. While it is not intended that the " 1237 " engine is to be run wide-open near the ground for any long period, it is extremely gratifying to know that this excess of power is available for taking off with a heavily loaded machine In. its general design the " 1237 " follows the lines of other Packard aero engines developed since the War, and it is of the twin-six type with the cylinder bank set at an angle of 6o°, with overhead valves and an arrangement of acces- sories giving the greatest possible accessibility. The crank- shaft is of the now generally accepted type where a main bearing is provided on each side of each connecting rod, and all bearings carefully proportioned to give uniform life. The crank cheeks are of oval section, giving the best combination of rigidity with minimum weight. The diameter of the main bearings is 2f ins., and their length as follows : No. 1, if ins. ; Nos. 2, 3, 5 and 6, 1 ins. ; No. 4, 3 ins. ; No. 7, 4^ ins. The connecting rods are of the straddle type, suitably proportioned. The pistons are of aluminium alloy, die-cast and equipped with floating rings ; three compression rings are fitted above the piston pin, and one scraper ring below it. The latter and its groove have been found in actual service to be extremely efficient in preventing excessive oil pumping. The standard compression ratio is 6J to 1, but pistons giving a 5J to 1 ratio can be fitted for low altitude work. The propeller hub is of the detachable type, carefully designed to prevent the propeller from either freezing on the shaft or becoming loose. The crankcase is of box section design. camshaft and rocker arm assemblies are of the enclosed type developed by Packard and used so successfully in the Liberty engine. A tachometer drive is provided on the end of each camshaft, permitting the installation of a tachometer in each of the two cockpits if desired. 400 350 360 340 320 3di:S 2.SQ 260 210 £10 2OQ I BRAKE ft£.P. 130. izo no f ru, — -ft: -(0- i 7* BNQINE RPn. (f/WDREDS) CARBURETTOR SETTINGS- CHOKBS 36iw tZOS m is 16 17 IS 19 20 21 ZZ 27 THE PACKARD "ALTITUDE" AERO ENGINE: Performance curves. The lubricating system is full pressure feed, operatingwith a dry pump, and it contains many improvements indicated by long experience. The oil pump and oil screens are readily THE PACKARD " ALTITUDE " AERO ENGINE : Side and end elevations, showing principal - -,- '....;.-.:;._rrv.:— ...-.....-.-^.i-...• ..sii.^... dimensions. __..- , parted on the centre line of the crankshaft with the main bearings carried between. Great rigidity is obtained by means of long through bolts which unite the two halves. The cylinders are of the individual steel type, and the valves are 2 ins. diameter in the clear with 30° seats, the intake valve lift being -fa in. and the exhaust f in. The accessible for examination and adjustment. A tapped boss is provided in the crankcase to serve for the oil tank vent. The engine is designed especially for the use of a nose radiator, but is equally adaptable to any other type of radiator. The water pump is located under the rear end of the engine, and the water outlet connections can be carried to four different .37*
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