44 DISCUSSION ON MAY MEETING PAPERS. 



serve as inlet and outlet valves in case of the four-cycle engine or as top-scavenging 

 valves in case of the engine working on the two-cycle principle, we would be able, assum- 

 ably and conservatively speaking, to develop 65 per cent more horse-power using the 

 same bore, stroke and revolutions. Account is taken of the power required to drive a 

 direct-driven scavenging pump and a somewhat larger air compressor, which means addi- 

 tional length for the engine in question. The weight thereof can be made less than the 

 weight involved to increase the four-cycle engine in size to aid the additional horse- 

 power, as it also should be tmderstood that no increase in the proportion of stress carrying 

 members or increase of wall thicknesses becomes thus necessary, because the peak loads 

 do not vary enough to make it a serious point of consideration — in particular if we real- 

 ize that the factor of safety assumed for materials used is very much on the safe side, es- 

 pecially in engines of the commercial type. 



Rather than go to double-acting four-cycle engines building higher than single- 

 acting engines, also having a complicated lower cylinder head and gear in addition to a 

 stuffing box, it is suggested that the two-cycle single-acting engine be given serious con- 

 sideration as well. The latter engine, for that matter, can also be converted to a double- 

 acting engine with equal chances for success if properly designed, although for all prac- 

 tical purposes the balance of a two-cycle six-cylinder single-acting engine is effective and 

 sufficient for good operation. In fact we cannot help keeping an eye on the development 

 now going on in England and Germany with opposed piston type engines, all of which 

 work on a two-cycle principle. 



Another factor which should not be overlooked is that general arrangements as now 

 commonly adopted are more or less duplicates of practices followed by the pioneer 

 concerns, and the desirability and merits of independent driven auxiliaries such as air com- 

 pressors and scavenging air pumps were simply sidetracked for good reasons prevailing 

 at the time. Further development along the lines of the last points mentioned is bound 

 to show considerable advancement in motor-ship construction and, rather than criticize 

 such advancement from the start, we should keep a watchful eye on the future in full ap- 

 preciation of the performances of the past in behalf of our American fleet. 



High-speed engines for electric drive are being developed and eventually may demon- 

 strate their usefulness in the unavoidable reconstruction of part of our emergency war 

 fleet. There is, furthermore, no reason why high-speed units should be limited to the 

 trunk-type engines, as the problem of height involved is in most cases negligible, par- 

 ticularly with reference to cargo ships so that high-speed crosshead engines could be con- 

 sidered. 



Mr. Ernest H. B. Anderson^ Member: — The paper by Messrs. Metten and Shaw is 

 a valuable contribution to the Transactions of the Society, and Messrs. Wm. Cramp & 

 Sons Ship and Engine Building Company are to be congratulated in commencing to manu- 

 facture this class of engine. 



I do not quite agree with some of the statements made in the opening paragraphs of 

 the paper, and it does not seem to me that the progress in the construction of large motor- 

 ship machinery in this country warranted shipowners, or the U. S. Shipping Board, 

 awarding contracts to engine builders on any large scale, and after perusing the paper it 

 will be seen that the authors to a large extent review the progress made by foreign builders. 



The engine builders in Great Britain are experimenting to some considerable extent 



