196 THE APPLICABILITY OF ELECTRICAL PROPULSION TO 



Water consumption data : — 



Total pounds per hour 105,764 40,066 



Pounds per hour auxiliaries 22,212 15,246 



Turbine 83,552 24,820 



S. H. P. (turbine) 11.68 12.316 



Guaranteed water-rate, pounds 13 15 



Fuel consumption data: — 



Pounds of coal per hour 1 1,900 5)05o 



Pounds per hour per S. H. P 1.662 2.5056 



Pounds per sq. foot heating surface .613 .261 



Tons per day 127-39 54-o82 



Kind of coal New River & George's Creek. 



Quality of coal Run of mine. Run of mine. 



Slip of propellers, per cent 9.9 8.74 



S. H. P. per square foot of grate surface 15.9 4.48 



Knots per ton of coal 2.82 4.43 



The Jupiter has been in commission over a year and a half. During that time 

 she has conducted two official trials and has carried on the usual routine work of a 

 navy collier. She has steamed about 14,000 miles and has been handled a great 

 deal around docks, in narrow channels, and other places where a great deal of 

 engine handling was required. About one-half of the steaming has been done in the 

 tropics with circulating water over 80° F. and with correspondingly poor vacuum, 

 so that the economy of the ship is known under all conditions. The fuel economy 

 has proved to be excellent, being, on the average, about 25 per cent better than the 

 best of her sister colliers. 



During the whole period of commission, two repairs have been made to the 

 main engine. The first was to reblade the first stage of the turbine. This work 

 was done entirely by the ship's mechanics. The first stage blading was injured by 

 a bolthead from the segment carrying the fixed blading. This bolt was broken off, 

 probably through having been set up too lard while assembling. These bolts were 

 all tap bolts and have been replaced by fillister head screws with countersunk heads 

 and a repetition of the accident would not be possible. The accident, however, was 

 in no way peculiar to the electric drive as it might very well have happened to any 

 other engine. The other repair was to replace one of the porcelain cylinders which 

 carry the resistances; this cylinder was cracked when the ship went into dry-dockj 

 but it was never discovered whether the cracking was due to the oiler putting 

 undue pressure on the cylinder or due to some strain brought on it when the ship 

 settled on the keel blocks. At any rate the damage was repaired by two ma- 

 chinists in about two hours. 



The amount of work expended in keeping the equipment in condition has 

 been very small. After coming in from a rvm, the turbine clearances are taken 

 to see if they have changed; and the motor clearances are also checked; there 



