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December, 1924 MARINE REVIEW Table II 503 General Characteristics of Diesel Engines Offered Shipping Board ‘Class & Make Four Cycle Single Acting Pacific-ierkspoor n n N.Y.S.B.Co, " MoIntosh & Seymour Cramp-B & W Aver. Two Cycle Single Acting Nordberg-Carels Busch-Sulzer Bethlehem ie Aver. Two Cycle Opposed Piston Sun-Doxford n n Aver, Four Cycle Double Acting McIntosh & Seymour Two Cycle Double Acting * 3000 2900 3050 New London-MAN Worthington Hami lton-MAN Aver. 075 075 275 275 Bids as Submitted to Shipping Board Fleet Corporation 7 No. Cyl, 8 Bore & Stroke ins. 6 RPM 28 x 51 3/16 aif x 51 3/16 29 x 69 32 x 60 29 1/8 x 69 23.62 x 95 95 95 4000 3870 4166 85.7 86.9 87.0 86.5 27.55 x 43,3 28 x 40 A - These engines seem underated. Aver. Pist. Sp. could be increased to advantage. B = These engines seem overrated. C - These engines are in a.class by themselves, Piston Speed could be reduced, D - This engine slightly overrated, should show 85% better than 4c S.A. when properly rated, E - These engines slightly overrated, indicated pressure have been computed on the basis of the given indicated horse- power where available, and derived from assumed mechanical efficiencies where the indicated horsepower was not avail- able. These mechanical efficiencies have been taken from past records of en- gines of the same type and make, and covering several engines of the same class. Where, such efficiencies do not coincide with the manufacturers’ views, we shall be glad to make corrections as the case may warrant. It must be observed that the limit- ations imposed by the shipping board do not correspond with accepted practice but they can be considered safe and conserv- ative. For instance, the limit of 90 pounds per square inch mean indicated pressure for 4-cycle engine has _ been exceeded in practice by an appreciable amount. Numerous engines are operat- ing today under higher mean indicated pressure without objectionable results. Some go as high as 100 pounds but let us accept the shipping board limits as a starting point both for 2 and 4- cycle engines. On the other hand the limit of 900 feet per minute piston speed for both 2 and 4-cycle engines is not borne out by experience. Four-cycle en- gines can go higher than this limit with impunity, while 2-cycle engines should not even approach it, especially the port scavenging and port exhaust types where lubrication exigencies demand that a lesser number of rubbing alternations over the ports be adhered to; 900 feet per minute can be considered a safe 27.65 x 43.3 10 11 Total Cylinder Total Cylinder Volume cu. ins. Volume ou. ft. 9 Piston Speed ft./min. 153,82 184,64 180.41 166,98 181.96 266,808 319,072 311,752 288,542 314,440 123.84 127.56 88.48 118,27 214,002 220,518 162,898 206, 100 150,616 161,012 167,264 102,920 98,612 102,920 limit for 4-cycle engines while 750 feet per minute should be considered a better figure for 2-cycle engines. Based on the above considerations the Table III Comparative Characteristics of Diesel Engines Comparative Characteristics - Shipping Board Engines 2 BHP Cu. Ft. min, 3 Actual Ratio BHP Cu. ft. min. 4 Standard Ratio BHP Cu. ft. min. 2147 2147 2150 2148 2153 2149 2271 2261 2265 2269 Aver.3.75 2266 c 10 3,17 11 2.79 Aver,2,98 2516 2559 2537 D 12 3,40 2294 E 13° 1.88 14 1,86 15 1.95 Aver.1.89 2532 2538 527 2532 9 Standard $/cu. in. Ratio 8 Actual $/cu. in. Ratio wR eee . AOL w& Or nwxnn & NNOnNn war SS8Fk -The cost basis of two engines is used for this item, none other being available. -A proper mean rating for this group should be .157 BHP/cu. ft./min. Cost high. -A proper mean rating for this group should be abt. .275 BHP/cu.ft./min. Cost very high. D -Cost high. E -Cost is high,