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Aviation History
1918
1918 - 0683.PDF
JUNE 20, 1918. THE 180 H.P. MERCEDES AERO ENGINE. [Issued by the Technical Department (Aircraft Production), Ministry of Munitions.] THE following report on the design of the new 180 h.p.Mercedes engine is based on an examination of the engine (No. 35254) taken from the captured German Albatrosbiplane D.5.A. (G.97), which was shot down by anti-aircraft fire in the 5th Brigade area on November 14th, 1917, andthe accompanying data on the design of the engine and the particulars of its general performance, have been compiledfrom results of tests carried out at the Royal Aircraft Factory. The 180 h.p. Mercedes engine is the first engine of a newtype to be used in service since the advent of the 260 h.p. Mercedes engines in the early part of last year. These 260 h.p.engines were apparently so successful that the 160 h.p. type have since been remodelled so as to introduce several of theleading features of the 260 h.p. practice. The result is seen in the 180 h.p. model, with which this report deals. It necessarily follows from the above that this report willpartake more or less of the character of a comparison between the 160 h.p. and 180 h.p. models. Frequent reference,therefore, is made in the text to the 160 h.p. engine, and in addition a table is given, showing the leading engine dataof the two engines. In many respects the design of this new engine is similarto the 160 h.p. Mercedes, which is now obsolescent. The cylinders are of the same construction and of the same boreand stroke as the 160 h.p., i.e., 140 mm. x 160 mm., as also are most of the reciprocating parts ; in fact, this engine mightwell be termed " The New 160 h.p. Mercedes." Briefly described, the 180 h.p. Mercedes is a combinationof the 160 h.p. and the new 260 h.p. Mercedes engines, and in view of this fact it will be unnecessary in this report todeal at length with the details of the design of those parts which are identical with the components of the above-men-tioned engines, of which fully detailed reports have already been issued, and the design of which is now well-known inthis country. In comparison with the standard type 160 h.p. Mercedes,the new engine shows a marked improvement, both in the design as a whole and in its general performance during powerand consumption tests, and as a comparison between the two engines the following comparative table of the leadingparticulars of the engines is herewith given :— BoreStroke Compression ratioAverage b.h.p. and speed B.M.E.P. (lbs. per sq. in.)"Total weight of engine (dry) Weight per b.h.p.Fuel consumption per hour 160 h.p.140 mm. 160 mm.4.50: 1 162.5 at 1400102.0 at 1400 618 lbs.3.80 lbs. 94.2 pints Fuel consumption per b.h.p. hr. .58 pintsOil consumption per hr< 5,0 pints Oil consumption per b.h.p. hr. .031 pintsInlet valve opens 20 L. Inlet valve closes 350 L.Exhaust valve opens 630 E. Exhaust valve closes 130 L.Ignition timing (fully advanced) 300 E. Delivery of water pump 180 h.p.140 mm. 160 mm. 4.64 :1174 at 1400 109.1 at 1400635 lbs. 3.65 lbs.94.83 pints. •545 pints.7.3 pintei .042 pints.T.D.C. 4o°L. 4o°E.io°L. 3o°E. 41.4 galls, per min. • This weight is weight of engine (dry), excluding propeller hub andexhaust manifold. Constructional Details.The six separate cylinders are exactly the same construction as those used in the standard 160 h.p. Mercedes engines,being built up entirely of steel, with the valve pockets screwed and welded into the cylinder heads, and the waterjackets of pressed sheet steel welded in position. The pistons also follow the Standard Mercedes practice and are similarto those used in the 160 h.p. engines, being constructed with concave heads machined from steel forgings, which are screwedinto the cast-iron skirts of the pistons and welded in position. Three rings are provided above the gudgeon pins and onering below, which is situated at the base of the skirt. The gudgeon pins are carried in lugs machined in the lower partof the steel piston crown. The compression ratio, it will be noticed, is slightly higher in the new 180 h.p. engines, being4.6 : 1 as compared with 4.5 : 1. Connecting Rods.The H section connecting rods with their floating cast iron gudgeon-pin bushes also follow the usual Mercedes practice,and are identically the same as those used on the 160 h.p. engines, and the whole of the camshaft vertical driving shaftand also the water and oil pumps driving gear is similar to the 260 h.p. engines. Albatros Scout D. 5 A. (G. 97), fitted with 180 h.p. Mercedes engine, showing radiator in centre of top plane. 681
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