40 THE DESIGN OF AN OIL ENGINE. 
seven days in the week, even if used but once a month. While it would take a 
long time to get this water body up to temperature it would take but little energy to 
keep it there. For the navy this means that the watch on duty should see that this 
steam pressure be kept up. The fuel expenditure will be small. 
The probable change in the submarine will be to enlarge it to fit it for duty 
as a commerce destroyer on the high seas. For men to work at their best they must 
be kept reasonably comfortable. This does not mean to live in cold, damp quarters. 
The vessel must be kept heated and the auxiliaries run from the waste heat energy 
of the present-day engine. It is strange that this has not been taken up before, but 
because it has not been is no reason for further delay. 
The steam generator consists of a furnace with an air-tight door. When the 
ship is going into commission, or the boiler is being cut in, this door will be open 
and the steam pressure is generated by the combustion of fuel in this furnace. 
After the engine has been started, the exhaust from the engine should enter the 
outer casing of the boiler at the top and go around this casing till it enters the fur- 
nace, where the gases would follow the natural course of gases in a boiler and 
leave to go up the stack. Like other features in this design, no doubt better de- 
signed boilers can be worked up. The design of boiler is given to show one practi- 
cal arrangement. The aim is to get a large water body so that a very great amount 
of energy can be given off for a very short time. This means that if we use this 
boiler under the combustion of fuel alone it might be able to generate, say 25 horse- 
power. For the time needed on the starting cycle it is easily possible to generate 
from 500 to 2,500 horse-power according to the design. 
There are two types of engines to be considered in taking up the oil engine 
broadly. They are the commercial engine and the naval engine. Either of these 
two types may be highly successful in the field for which it is designed and yet 
leave much to be asked for in the other field. The naval engine should have a great 
reserve of power, while the commercial engine should have endurance so that it 
may run at full power all the time and still have a small upkeep charge. The gen- 
eral qualifications for the two types would seem to be somewhat as follows :— 
Nawal Engine.—In the naval engine it is desirable to have a higher pressure of 
compression at full loads and a greater variation in pressures of compression. In 
this type the partial compression cycle would give higher efficiency at partial loads. 
At the same time this engine should not be designed for the present full-load pres- 
sure of compression. 
Commercial Engine.—This type would vary from the naval type in that the 
pressure of compression would be a minimum. The engine should be designed with 
as perfect a scavenging arrangement as possible and the normal operation of the 
engine would be full power. 
It may be seen that an engine designed under these conditions for one service 
would not be the ideal engine for the other service. The object of this paper is to 
give data so that an engine may be designed from these theories to fit the particu- 
lar needs of the vessel in which it is to be installed. In 1904, when the author be- 
gan this work, it was not intended to work along a stock design which would fit 
