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Aviation History
1918
1918 - 0128.PDF
THE 260 H.P. MERCEDES AERO ENGINE. ::::]> WEB 1 1JFl Ibi Carbon .. Silicon Manganese Sulphur .. Carbon .. Silicon Manganese (Concluded from page 92.) Tests on 260 h.p. Mercedes Engines at R.A.F. 14.7.17. POWER readings were taken at full throttle from 950 r.p.m. to 1,600 r.p.m., simultaneous fuel consump- tion readings being taken. During this test the water outlet tempera- ,--"-• ture varied from 750 to 8i° C. The water brake was then set to absorb full power at 1,400 r.p.m. and the engine gradually throttled down to 900 r.p.m., power and consumption readings being taken. The results of these tests are shown graphically on the appended chart (C, 335). At the conclusion of the \i • above tests, a run of one hour's \, duration at 1,400 r.p.m., full throttle, was made with the following results :— 252 '52.50.605 Connecting Rod. 0.13 Phosphorus .. 0.014 0.19 Nickel .. .. 2.83 0.52 Chromium ., 0.29 CarbonGraphitic carbon Combined carbon Silicon Manganese Sulphur Phosphorus Camshaft. . 0.16 Sulphur .. ... 0.052 0.27 Phosphorus i.. ; 0.014 0.60 :,'..• ., , Camshaft Case. Body. Cover. 0.24 per cent. .. — — . . 2.97 percent. — .. o.62 1.81 o-S3 0.118 0.085 Average b.h.p. Petrol—pints per hour .. pints per h.p. hour Oil—pints per hour pints per h.p. hour .. Oil temperature at end of run Water outlet temperature 8.125 0.032 54-5° 8o°C. POWER CURVES, 260-H.P. MERCEDES. 270 250 200 Q. X <°150 JOOh?" rip vF ? Per. Cori Power 10 00 0.02 percent. 0.46 ,, O.O41 „ O.OI2 „ Valves. Exhaust. Inlet. 1.75 percent. .. 1.82 percent. 0.58 ,, .. 0.52 , ,, 0.10 ,, 0.10 ,, 0.048 ,. .. 0.048 ,, 0.013 ,, .. 0.010 „ Nil. .. Nil. 10.85 ,, • • IO-47 Nil. .. Nil. Crankcase. ' * r~ per cent. " per cent. . 0.96 Zinc .. .. 3.65 . 0.35 Iron .. .. 0.81 . 4.22 Valve Spring. 0.52 Sulphur .. .. 0.060 0.07 Phosphorus .. 0.031 0.59 Nickel and Chromium, Nil. Crankshaft. 0.41 Manganese .. 0.64 0.29 Nickel .. .. 2.36 0.052 Chronium .. 0.86 0.042 MECHANICAL TESTS. Mechanical tests on the valve spring gave the following results :— Outside diameter of spring Diameter of wire Carbon Silicon Manganese Sulphur Phosphorus Nickel Chromium Vanadium and Tungsten Total silicon Graphitic silicon Copper Carbon .. Silicon Manganese Carbon .. Silicon Sulphur .. Phosphorus 3 900 1000 11001200 1300 R.P.M. 1400 1500 1600 It was noticed that at speeds below 1,150 r.p.m. the vibration was rather excessive. No adjustments were made to the engine these tests. MATERIAL SPECIFICATION OF PARTS OF 260 H.P. MERCEDES ENGINE, NO. 30111. Analysis shows the chemical composition of the parts to be as follows :— Gear Wheel. per cent, Carbon .. Silicon Manganese Sulphur .. 0.30 0.27 0.74 0.025 Phosphorus Nickel . . Chromium Vanadium per cent. 0.030 4.17 1-39Nil. Number of free coils Length of spring .. Compression in inches, o .1 .2 -3 •4 • S JZ> - , • • " .7 • . •9 1.0 •;.•'•.• •.,:" 1.1 • '•• :-• ''^ I .2 Closed 1.5 Permanent Set, Nil. Tensile Test— Yield point.. Maximum stress . Elongation .. Reduction of area. Specific gravity Tensile Test— Yield point. , Maximum stress Elongation .. Reduction of area Load in lbs. o 6 12 18 24 • 30 # 42 #« 54f 6o| 66| 73* 81 88£ 97* Crankcase. 1.250 to 1.352 111. 1.56 in. 73 in. Unloading, o 4f rof i6i2 3 29* 35* 41 47 53* 59* 72*79i 88 Crankshaft. 8.7 tons per sq. in. 9-35 ,. 3.55 per cent, on 2 in. 3 .5 per cent. 2.867 55.7 tons per sq. m. 62.0 ,, ,, 13.5 per cent, on 2 in. 23.5 per cent. 124
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