THE DESIGN OF AN OIL ENGINE. 
By Joun F. WaeNmwoa Esg., MEMBER. 
[Read at the twenty-fourth general meeting of the Society of Naval Architects and Marine Engineers, held in 
New York, November 16 and 17, 1916.] 
The actual design presented here was made to fit the needs of the submarine 
—a light and reliable type of engine. If we were to consider a design suitable for 
a freighter, the matter of weight would not be so important, but the matter of relia- 
bility and low upkeep would be more important. The attempt has been made in 
presenting this design to give data and substantiating reasons for opinions where 
perhaps satisfactory data cannot be presented, so that this paper may be taken as 
a basis and, if desired, other designs may be worked up in any well-organized 
draughting office. 
In designing an engine there are several points to be settled upon as a matter 
of policy; from this point the design is not peculiar to the oil engine but rather is 
a straight matter of mechanical design. For instance, it has been suggested that 
the matter of bearing pressures is something to be settled by oil-engine experience. 
The opposite viewpoint is taken. It is felt that the bearing pressure in the oil en- 
gine should follow the same laws that are followed in other machines of somewhat 
similar action. For instance, we find the bearing pressure allowed in a locomotive 
is higher than that allowed in a triple-expansion steam engine. The reason is very 
easy to understand. In the locomotive the maximum pressure lasts for but a short 
part of the stroke, especially in single-expansion locomotives. On the other hand, 
in the compound marine engine the cut-offs are late and the maximum pressures ex- 
tend over a much longer part of the stroke. Since the limiting point is the heating 
of the bearings, and since a machine which has an intermittent action has a greater 
time to dispose of the heat generated by the pressure, the maximum pressure per 
square inch may run higher. Engineering science has many examples of how this 
works out in practice, and it would seem that such question need not be of great 
moment to an organization skilled in machine design. This point is mentioned so 
that it may be understood that, in some, if not in many instances, data from work 
quite dissimilar to the design of the oil engine have been used. In such cases the 
application of the force is similar, even though the resulting design may differ very 
much from the completed oil engine. 
The next point in a general consideration of the problem is the actual experi- 
mental data which already have been presented on this type of engine in the paper 
on “The Thermodynamics of the Marine Oil Engine” published in the Transac- 
tions of 1914. 
The third point consists in following certain deductions derived from experi- 
