ELECTRIC PROPULSION OF A BATTLESHIP. 79 



In regard to the steam consumption of a prime mover the only fair way to handle this 

 matter is to measure all steam used in connection with propulsion. The Jupiter was run for 

 three days on trial. For two days her auxiliaries consumed 22,212 pounds of steam per hour. 

 For one day, the third day, they consumed 15,246 pounds per hour. This difference is 6,966 

 pounds of steam per hour. The horse-power was reduced by 4,480 in terms of shaft horse- 

 power (Cyclops data). This presumably was the only difference in the three days' run. By 

 reduction in power 1.55 pounds of steam were saved for each shaft horse-power cut out. 

 This should be charged to the propelling plant, even if it be not used in the engine-room. 



The contract for the California calls for a certain steam consumption for turbine and 

 all engine-room auxiliaries in terms of the shaft horse-power. From the data given out by 

 Mr. Emmet and Mr. Robinson it is very hard to see how the guarantee can be attained. 



This argument is of more importance in showing up a very grave fault in engineering 

 practice than it is in connection with the performance of the turbo-generator plant. Last year 

 I spoke on this subject to draw attention to the great advantage of the oil engine over the 

 steam engine. The fact that a reputable engineer should have disputed my figures of 1 1 per 

 cent for the efficiency of the Jupiter without any more proof or reason than because "I know 

 it is more than 11 per cent, or we would not be using it" shows a great need for an analysis 

 of our figures concerning the operation of power plants. Personally I never accept the 

 results of a test by itself. Errors are more apt to creep into test than into theoretical con- 

 siderations of plants. 



Coming back to the turbo-generator plant, it is not denied that there is a loss of around 

 8 per cent in the motor-generator set. The turbo-generator plant is a motor-generator set 

 with a turbine thrown in. There is every reason to expect that there is a loss of 8 per 

 cent in addition to the losses in the turbine. The figures presented by Mr. Robinson, 

 and indirectly used by Mr. Emmet to uphold his contention for the superiority of this type 

 of plant, show the great danger in using figures given in actual operation to prove a con- 

 tention. Such figures should always be checked by a comparison with other data, and when 

 the results are favorable to an unreasonable degree the figures should be generally rejected 

 till explained by some reason. If wonderful results be obtained for which sound reason can- 

 not be given, it is well to consider the data very carefully before accepting it. It was the 

 discrepancy between the Cyclops' figures and the figures of the Jupiter that made me write 

 to the Navy Department for an explanation. 



It is my opinion that this series oi papers and discussions has clearly demonstrated that 

 the torsion meter should not be depended upon as a measure of power. If this be impos- 

 sible, the torsion meter should be calibrated with the utmost of care. 



It is an unfortunate condition where the boilers are furnished by one contractor and the 

 propelling machinery by another. In a case of this sort there is a great chance for trouble 

 in regard to the responsibility for the final economy of the vessel. In the case of the Jupiter 

 it is apparent that 1.55 pounds of steam per shaft horse-power were used to get the extra 

 results needed by the increase in speed, but this steam is not charged to the propelling plant. 

 This most clearly shows the need for basing all results upon fuel consumption, as I stated 

 last year. If this be done, the engineering fraternity will be brought face to face with the 

 low efficiency of the steam plant, and experimentation will result to rectify this. This 

 condition will be objected to by the boiler manufacturers, but as engineers it should be our 

 aim to investigate conditions regardless of whom is hit by the investigation. 



Finally, it is no more than just to say that I have been converted to a belief in the 



