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Aviation History
1945
1945 - 2283.PDF
55° FLIGHT Napier Sabre VII Over 3,000 b.h.p. for Take-off tLowest Specific Weight of Any Pro- duction Piston Engine REGULAR readers of Flight may remember that adetailed description of the Sabre engine was givenin the March 23rd, 1944, issue, together with a good many illustrations, including a special cut-away drawing; but the subject of that description was the Mk. II, whereas the latest Sabre is the Mk. VII. Series II engines were developed in three guises, the II, IIA and IIB, in which the boost pressures were progressively increased and the power outputs stepped-up from 2,090 . to 2,220 and then to 2,420 b.h.p. Weight had also in- creased, but not proportionally, so that specific weight went down respectively from 1.12 to 1.06 until, with the IIB, it dropped below unity with the value of 0.981b. /b.h.p. With increased output and increased rate of development the equipment for research and production testing natur- ally had to be extended, and in their choice of additional testing equipment those responsible displayed the estab- lished tendency of Napiers to explore and utilise the latest developments. By building a complete test establishment with fully regenerative dynamometers for .engine and unit development the firm created an extremely valuable pre- cedent. (It is interesting to point out that this idea was proposed many years ago by Mr. G. Geoffrey Smith, Managing Editor of Flight.) Thousands of gallons of high- octane fuel are no longer burned to produce only hot water, which is immediately cooled again; by using regenerative dynamometers the power output is used to produce elec- tricity for the factory and outside supply, and an example of the output is that if a Sabre is running on a Sunday (when the factory is not working) the electricity generated by a single engine is sufficient to supply the entire demand from the whole Willesden area and still leave sufficient over for feeding into the national grid system. Teetliing Troubles Cured As with all engines developed at high pressure during the war, teething troubles were experienced with the Sabre. One such trouble was sleeve wear due to the ingress of sand and dust from new airfields and landing-strips. The resultant wear was in the nature of a groove, and piston- ring failure followed if this was allowed to become exces- sive. The consequent investigations were carried to great lengths in order to find a solution, which eventually lay in having the sleeves nitrided and lapped before assembly; >but some 18 difierent materials and manufacturing processes were investigated before the final choice. Trouble was also experienced with supercharger clutch linings, which was found to be due to the speed-up of pro- Maximum Power 3,055 h.p. Dry Weight 2,540 Ib. Sabre from above, show-ing magnetos, distribu- tors, hydraulic pumpand combustion starter.
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