DISCUSSION ON MAY MEETING PAPERS. 43 



that the performance was splendid and in harmony with figures given. The reliabiHty of 

 such installations is illustrated by the course followed during the last years of manufac- 

 ture, by standardizing on a general construction, which speaks for itself. 



America has already entered the field of motor-ship construction to a limited extent. 

 Foreign-type engines are and have been duplicated and Americanized at the same time, 

 as far as production methods are concerned, but much is yet to be done and should be done 

 for the benefit of the American industry in general. In this respect, I wish to offer com- 

 ments on the remarks regarding four versus two-cycle engines, as commercializing splendid 

 performances of four-cycle engines as referred to is legitimate, but at the same time does 

 not picture the actual situation from a heavy oil-engine engineering standpoint. 



The limit set in this paper for the diameter for cylinder units of 500 indicated horse- 

 power and pronounced to be 31 yi inches seems justified, as it is known to the followers 

 of the constructional end of the game that the conventional shape and design of cylinder 

 heads does not render further increase of the bore practicable. It should be borne in 

 mind that all four-cycle engines are subject to unequal heat distribution throughout the 

 cylinder-head casting, in particular the lower disc, for the reason that the exhaust valve 

 or valves are located on one side of the head while the air-intake valve or valves are at the 

 other side, thus unavoidably disturbing the uniformity of the all-round heat problems — the 

 larger the engine, the greater they become. 



The next step advocated in the paper in order to increase the power of four-cycle cyl- 

 inder units to more than 500 indicated horse-power by resorting to double-acting units is 

 at least problematical. The belief expressed about heat problems of the double-acting 

 four-cycle engine holds good only in case the authors intended to point out that a four- 

 cycle cylinder head receives half the number of heat applications in a given time as com- 

 pared with a two-cycle engine. Assuming that the general construction of cylinder heads 

 had to be the same for both types, there is no question left as to the more favorable con- 

 dition under which the four-cycle engine works, but it should not be overlooked that the 

 two-cycle cylinder heads can be and are made much simpler in shape, tending to offset the 

 known disadvantage. Furthermore, improvements are possible above the conventional 

 practice followed for the effective cooling of parts subject to high heat. 



Built as double port-scavenging engines, the cylinder head contains only one boss, 

 thus allowing a very symmetrical casting, while, built as a top-scavenging engine, this 

 casting can also be made absolutely symmetrical, and care should be taken to provide 

 efficient means to allow for undisturbed expansion and contraction. Heat applications, al- 

 though twice as many in a given time, do effect the cylinder disc more uniformly, and in 

 case of a properly designed cooling agent system there is no reason why the two-cycle 

 principle should receive undue criticism. 



There is much misunderstanding on the subject indeed, and the truth is sometimes 

 sidetracked for commercial reasons, which in turn does not add to the possibility of more 

 rapid progress than thus far obtained. Controversies about weight and sizes of various 

 designs of engines such as are found in practical magazines are sometimes one-sided and 

 published to advertise a specific make. 



Assuming that the reduced weight for a given horse-power in a ship means a direct 

 gain in carrying capacity, I may illustrate a way to impartially look upon the question. 



If we had a conventional type of engine of a given horse-power working on the four- 

 cycle principle and the valve gear coud be so arranged that the valves proper could either 



