HEAVY-OIL ENGINES FOR MARINE PROPULSION. 239 
Attendance.—The economy in the cost of fuel is but one item in the total 
saving due to the use of oil engines. In general terms it may be stated that 
the cost of attendance of a heavy-oil engine is about half that of a steam 
plant of the same power. The expenses due to water tenders, firemen and 
coal passers is entirely eliminated. Due to the absence of these persons 
on board a ship there is an incidental saving of space in the living quarters, 
which would prove of considerable value in any vessel, and especially in a 
naval ship. 
Weight—As regards the item of weight of plant, exclusive of fuel, the 
advantages are all in favor of oil engines. Comparing light class installa- 
tions, the steam plant will weigh about 60 pounds per horse-power, while 
the oil engine will weigh less than 40 pounds per horse-power. ‘Taking 
heavier installations, as in a merchant vessel, the difference is still more 
striking, the oil engine weighing from one-half to one-fourth of the steam 
plant of the same power. 
Space.—As regards space occupied, the oil engine will require less than 
half that occupied by a steam plant. This applies to both heavy and light 
types of oil engines when compared with heavy and light types, respectively, 
of steam installations. 
Endurance.—To maintain full speed for considerable lengths of time on 
naval vessels propelled by steam involves such strenuous work on the part 
of the fireroom force that as a matter of fact very high powered vessels, 
such as destroyers, seldom if ever have been able to make a run at full speed 
corresponding in length with the total fuel supply. With oil engines, how- 
ever, there being no fireroom force, this drawback does not exist. The 
engines are designed with a view to continuous running, and aside from the 
extra vigilance which any engineer would naturally give his engine when 
running at full speed, no extra strain or hardship is inflicted upon the 
personnel. 
Repairs —The yearly average cost of repairs is much less for an oil 
engine plant than for a steam engine plant. ‘This follows from the fact that 
not only are the boilers and their auxiliaries eliminated, but also important 
auxiliaries such as condensers, and air pumps, disappear with the adoption 
of oil engines. The latter have only three small auxiliary pumps, usually 
driven by the engine. ‘These are the water circulating pump, the lubricating 
pump, and the fuel pump. On account of the consequent simplicity of the. 
oil engine plant, regarded as a whole, with the consequent reduction in the 
number of parts, it is easy to see why there should be such a great reduction 
in the cost of repairs. 
Reliability—In an oil engine, each cylinder is in many respects an 
