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July, 1916 used is in the neighborhood of 100 horsepower. As compared with gasoline engines, the first cost of a diesel engine of small power is such that if below this limit, the saving in cost of fuel is only sufficient to offset the interest and depreciation. As the size in- creases, the economy in fuel becomes of greater importance,especially on a vessel engaged in long voyages or running almost continually. The upper limit of size is, at pres- ent, fixed by the designs and ma- ‘terials now in use. Up to the present, the upper limit is approximately 400 horsepower per cylinder in single- acting units; that is to say, this rep- resents about the upper limit of en- gines which have been built and are in successful operation. From the point of view of the designer, it would seem possible to build successful en- ii gines of double C= this power in sin- gle-acting units, and of four times this . Vf power in double- acting units. In fact, call eR : H ty experiments have a7 \ been made on dou- ble-acting two-cycle engines developing 2,000 horsepower per cylinder. This l | . SA VANS SANSA a y) a 3H IS Yk \ j ae Kae YA ay \a => smMINA, Nikon a BIH] SY 4 all A | Aly | WA y Lu latter figure repre- ANN sents about the WA Nc theoretical limit to the designer unless some radical de- parture is made. Such _ departures are, however, pos- sible so that the upper limit may broadly be stated as depending upon the’ amount of money and energy available for development work along these lines, and is entirely a matter of the future. Marine diesel engines of the present day may be roughly divided into two general classes according to weight per horsepower. The light-weight class is represented’ by the engines used in submarines. Such engines run at a very high speed. The piston speed varies from 1,000 to 1,200 feet per minute. <A. 1,000-horsepower, six- cylinder engine will, in some cases, run as high as 450 revolutions per minute, and will weigh approximately ss 40 pounds per horsepower. A _ heavy- duty slow-speed engine developing 1,000 horsepower at 100 revolutions per minute, will weigh as much as 300 pounds per horsepower. Inter- mediate types are, of course, also Diameter Cylinder 9” Sone lee" dection on Working Cylinder built. For instance, the 1,000 horse- power Nuremberg engine on the U. S. S. Furton, running at 260 revolu- tions per minute, weighs 100 pounds per horsepower. Diesel Engines for Naval Use For naval purposes, the following successful applications of diesel en- gines have already been made. For submarines, about 300 engines had been built previous to the European war. Since the war began, a large number have been built or are being built. From such information as can be obtained, it seems likely that from 200 to 300 engines for this purpose alone are under construction. These engines range in size from 300 horse- 1,000 horsepower. power to Much Alt Ct OPT ESSOL- Frequiaiiig Va/ve SSNS AS ASS SECTION OF FOUR-CYCLE ENGINE larger powers have been talked of, but; so far as-is: known, have not been actually built. Destroyers require such enormous power (from 10,000 to 15,000 horse- power) that it is not practicable, at present, to install diesel engines to give this output. Certain foreign countries have, however, installed both steam turbines and oil engines in destroyers. For ordinary cruising pur- poses, the diesel engine is used, there- by effecting economy in fuel and also increasing the cruising radius about 400 per cent above what would be obtained with turbines. For battleships, the German govern- ment intended to adopt the same scheme. By having a ship with triple screws, a diesel engine could be used for cruising on the middle propeller, THE MARINE REVIEW Ay Le DSSS Jectior? on Air Compressor Cylinder 290 while steam turbines could be used for high-speed on wing propellers. At least two engines of approximately 12,000 horsepower have been built in Germany for this-purpose. A num- ber of battleships are also fitted with diesel-engine, electric-generator sets. These have proved very successful. The United States navy has not yet made any attempt to benefit by the use of diesel engines as auxiliaries, either for cruising or for lighting sets. In Russia, certain gunboats pro- pelled by diesel engines have been in successful operation for a number of years. » Austria has° a cruiser equipped with a pair of 1,000-horse- power Nuremberg diesel engines. Craft of this type, requiring from 500 up to 5,000 horsepower, offer a large field for die- sel engines. While gunboats and cruis- ers can no longer be considered regu- lar fighting units, they are still very necessary parts of any large navy. Such minor naval craft, if fitted with diesel engines could be made more com- fortable, more ef- ficient, and have three or four times the cruising radius they now have using steam. Fleet auxiliaries, such as fuel SEO DIS charge ya/ve SS — EES ships, repair _ ships, and ammuni- tion ships, could also be driven by diesel engines to advantage. Some of the European countries have al- ready made a start in this direction. The United States navy is now building the fuel ship MaumeEsr, to be equipped with two Nuremberg two-cycle engines, developing about 2,500 horsepower each. These will be about the largest slow-speed heavy-duty engines thus far attempted, and represent a bold step, as the government has had no previ- ous experience in building engines of this type, even in smaller sizes. The one reason for going ahead with diesel engines for marine purposes is fuel economy. For naval purposes it is not a question of money so much as a question of increased radius, and other military advantages. For this reason, we may look forward to a steady development in this form of motive power in all navies. For commercial work, the resolves itself simply into question one of