ENGINEERING PROGRESS IN THE U. S. NAVY. 59 



Delaware this maximum backing power amounts to 89.2 per cent of the ahead 

 power, while in the turbine vessel Salem it amounts to only 41.9 per cent. 

 That is, at these points, the backing power of the Delaware is 2.13 times as 

 great as that of the Salem (both being expressed as fractions of the ahead 

 power) . 



At the maximum powers developed by the engines of the two vessels, the 

 ratio of the percentage backing powers becomes: — Delaware = 2.27 Salem. 



These results are further corroborated by the backing tests of the Dela- 

 ware and the Utah upon their preliminary acceptance trials, where, with the 

 Delaware going ahead at 21 knots and the Utah at 20, the times taken to 

 bring the vessels dead in the water were, for the Delaware, i minute 52 

 seconds; Utah, 4 minutes 44 seconds. 



Delaware. Utah. 



Backing power divided by ahead power .. . 87.5% 35-7% 



These results are still further corroborated by the destroyers. These 

 vessels can easily steam ahead at 16 knots under one boiler, but when called 

 upon to maneuver they invariably, as a matter of safety, start a second boiler. 



Conditions (h) and (i) — Minimum Vibration ofHidl; Steadi?iess ofHidl as a 

 Gun Platform as Affected by Machinery. — In judging these points it seems only 

 fair to base the decision upon the results of target practice of the vessels in 

 service. If this is done, the decision could be given to the reciprocating type 

 of machinery, as the Delaware has just won the championship of the battle- 

 ship fleet, with the Colorado, another reciprocating-engine vessel, standing 

 second on the list.* From these results it appears reasonable to state that, 

 with well balanced reciprocating engines, no ill effects on gun fire should be 

 expected. 



CONCLUSIONS. 



Basing the choice between reciprocating engines and turbines for battle- 

 ship propulsion under existing conditions of speed and power upon the above 

 comparison of relative advantages of the two types, the advantage appears 

 to rest most decidedly with the reciprocating engines, and the Navy Depart- 

 ment has ruled accordingly (in the cases of the New York, Texas, and 

 Oklahoma). 



COMBINATION SYSTEMS. 



In the search for economy of propulsion through a wide range of speeds, 

 various combinations of reciprocating engines and turbines have been pro- 

 posed, both by the Bureau of Steam Engineering and by the shipbuilders, 



*The Delaware stood No. i in combined gunnery and engineering eflSciency, No. 2 in gunnery, the 

 Colorado, a reciprocating engine vessel, standing No. i. 



