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24 also that it is not satisfactory for engine use. The answers to these may be very brief and ~ cate- gorical. There is more down-draft producer capacity working on bitum- inous coal than of all other types combined, and of the total engine power in the United States derived from "artificial gas (that is, other than natural or' blast furnace gas), in units of over 300 brake horsepower, 65 per cent are working on gas from bituminous producers. The paper also, somewhat arbitrar- ily, assumes that, for reasons not ap- parent, the size of gas engine cylin- ders cannot exceed 20 in. x 24 in., and 'that larger powers must be obtained by using multiples of this size, and conjures up a vision of a 5,000-horse- power installation consisting of 50 cylinders 20 in. x 24 in. single acting, 'making a. line of 150. ft. in length. The only indication of why this size and type is assumed to rep- resent the limit of advance the experimental engine of the Rat- tler is so designed. Two years ago the same author said "there will be no future for the single acting motor for large powers in marine work." On the erecting floor in almost any of our large engine-building estab- lishments can be seen gas engines designed for producer gas with double acting cylinders up to 36 in. x 42 in. and even larger, while the trade and technical publications are full of descriptions and *illustrations of working plants which refute the statements referred to. Two exam- ples of this, lying immediately at hand as this is written, are found in Power tor Dec 8. and 22, 1908; descriptions of actually existing plants, and the most cursory review of the literature on the subject will bring to light mumbers of others. Certainly Capt. Willits will not wish to. go on' record to the effect that a cylinder which will work satisfactorily in a horizontal position will not do ' at least equally well in a vertical. The stationary gas engine labors under conditions that do not exist im marine work, Practically. in. all cases. they run under governor con- trol, and, except possibly in the case of blowing ,engines, must uniform speeds under widely varying loads. treme variation in angular strains, require not only an abnormally heavy fly-wheel, but that the crankshaft, frames, etc., shall also be extremely heavy, while automatic control en- tails all the additional complication of governors and adjustable valve is that maintain © These conditions with the ex-. Tae Marine REVIEW gear with the multiplication of parts attendant thereon. These conditions do not exist afloat. The marine en- gine, in good weather, has the ideal load; governor control and great in- ertia are not required, and the same conditions that necessitate multiple cranks (handling and maneuvering), contribute to uniform turning effort. For equal powers and revolutions, with a four-cylinder, four-crank, dou- ble-acting gas engine, the crankshaft strains are almost identical with those of a three-crank triple expansion steam engine. Neither is there any such disproportion in number of cylin- ders or space occupied as compared with steam as the paper would have us believe. For instance, the diagram herewith exhibits the crankshaft strains of a triple engine and a gas engine of equal powers, and also the cylinder sizes. Both engines occupy about the same fore-and-aft space; the difference is. in favor of the gas engine. Possibly in much higher powers the number of cylinders neces- sary might become an objection, but on the other hand, where. propeller speed does not fix the revolutions, as in most merchant ships, the revolu- tions and piston speed may be in- creased beyond those possible with steam, where the difficulty lies not in the piston speed per se, but in getting the steam to and from tne cylinders, the very same difficulty that gives the turbine its opportunity. Coming now to. the question of space and weight for producers: This article is not written to advertise any particular design' nor to criticize those mentioned by Capt. Willits, but "we must exipress surprise at the exclu- sion or oversight of widely known and successfully operated types de- livering gas for engine work from bituminous coal. First as to space: 1,000-brake horsepower capacity in . two units, based on 80 per cent ef- fereney with 13,500 B: TT. U. coal, with all necessary apparatus, finds ample stowage in a floor space of 15 -- o0 Tr, or O45 sa. ff; per brake horsepower; a 2,000 B.HP. in three nite; i a space 18 x 35 ft., or 0.31 sq. ft. per brake horsepower, com- pared with the 1.8 sq. ft. as quoted. This takes no account of the reduc- tion in bunker space which the pro- ducer makes possible. The weight of both plants, complete with all pipes: and connections, scrubbers, etc., up to the manifold on engine, is about 85 pounds per brake horsepower. These are not estimates of imaginery or experimental plants; they are based on actual every-day performance of producers making gas from bitum. inous coal for engine work, and are a long way from the 285 pounds per brake horsepower quoted and com- pared with 110 pounds for boiler room weights of a battleship. Pos. sibly the figure quoted for the battle- ship is correct, but after all naval work is a relatively small and unim- portant part of the whole, and if the development of the producer and_ gas engine wait for the navy none of those now interested in the subject will live to learn much about it. The question will be threshed out in the merchant service where boiler room weights approximate 170 pounds per brake horsepower with water in the boilers. Altogether the gas power question is in vastly better shape than Capt. Willits seems. to be aware, but the fact that it is so 1s not due, to amp support the bureau of steam en- gineering has given it. The fact that the new magnetic survey ship for the Carnegie Institution is to be fitted with a producer and gas engine will go farther to offset the gloomy views of the pessimists than all the pages that could be written. It is to be hoped that the conclusion "in the light of present experience with turbine machinery we would be loth to turn again to reciprocating engines without more than a promising outlook and © this we are wholly unable to per- ceive; as yet, in the marine gas en- gine" is not the key to the disinclin- ation to look in the direction where accurate information is to be _ had. There would seem to be rather sud- den enthusiasm for the turbine, see- ing that the first turbine ships in the U. S. navy are hardly more than out of the builders' hands, and the "light of recent experience', after the first general overhaul at a navy yard, may be as widely dissimilar as Capt. Will- its' two papers on marine gas power. Tt is not to be expected that. per | fection will be reached at one bound and with the first installation; rather it will serve to point the way to satisfactory operation, but only there- by can satisfaction come. Even the turbine, for the rapid adoption and growth, of which mechanical history furnishes no parallel, did not escape its share of difficulties and fail- ures. The writer has seen within a few days the dismantling and scrap- ping of several very large power sta- tion turbines which have been run- ning successfully and steadily for five or six years simply because they are already out of date. Yet the ma= rine producer and gas engine are fur-