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HEAVY-OIL ENGINES FOR MARINE PROPULSION. 249 
Mr. Epwarp P. Rosinson, Member:—I regret the absence of the author of 
the paper, because I think that if he were here he could throw light oncertain parts of 
the paper which are not entirely clear. One of the things that occurs to me is the 
question of flexibility of the Diesel engine. Instationary practice this engine has 
proved itself very economical at full load, and it has also proved very economical at 
half load when running at full speed; but on a ship the conditions are different, 
because the power is reduced by reducing the speed of the engine. Now, if 
there is leakage of pistons or valves, the element of time affects this leakage, and 
it also affects the cooling of the compressed charge by the walls of the cylinder, 
and it appears to me that if you slow the engine down, as is at times necessary in 
marine practice, the compressed charge would not be hot enough to ignite the fuel. 
That is a point that I have not heard discussed anywhere, and it seems to me that 
it is of great importance. When the pistons and valves of the engine are tight, it 
may be possible to run the engine at very slow speed and still ignite the charge, but 
I should suppose that the leakage which is bound to come in service would seriously 
affect the ignition. If anyone can throw any light on that particular phase of the 
question, I should be glad to hear from him. 
Mr. C. LEE StRAuB, Member:—In the parlance of the street, Mr. Davison’s 
paper has only touched the “high spots” on this subject. 
I have had the good fortune of examining several of the types of engines he 
compares with the steam equipment on the Paul Jones, and having been affiliated 
with the construction of a number of stationary American Diesel engines, feel quali- 
fied to criticise a number of items in the comparison. 
The actual cost of repairs on Diesel engines exceeds the cost on good steam 
engines by fully 100 per cent. This is due to the exceedingly high pressures en- 
countered in the Diesel practice and the multitudinous details encountered in the 
engine, oil service, and auxiliaries, such as air storage, etc. The particular type of 
Diesel engine referred to by Mr. Davison is installed in two 6-cylinder, 300-horse- 
power engines in the Quivilly. The cam shaft, air valves, oil valves, and in fact the 
prime operating mechanism, are all located on top of the cylinders. In order to 
remove a piston, all of this mechanism must be removed, and the cylinder must be 
lifted from the frame. ‘This was of necessity required three times on the first two 
Trans-Atlantic trips of the Quivilly and as can be imagined, was on each occasion a 
big job at sea. I think that 300 to 350 revolutions per minute is too high for any 
commercial marine engine. Much of the gain of economy in the engine is lost in the 
necessarily inefficient propellers. : 
In the summary, the item of repairs, if properly kept, would exceed the Bor 000 
charged to the steam plant. 
The average cost of fuel per annum, based on Atlantic coast costs, which ap- 
proach more nearly the average cost of fuel oil, would be in the neighborhood of 
$9,000, based on the quantity stated as consumed. 
I think that 500 horse-power per single-acting cylinder is about the maximum 
practical limit due to the heat conduction capacity of the cylinder wall. 
