THE MOTOR SHIP adaptation of the Diesel engine to marine purposes has made remarkable progress since the first motor ship was put into service. The economic advantages of this type of ship compared with the steam-driven vessel are numerous, and are more conspicuous than in a ship driven by direct oil-fired boilers, which, in its turn, is a considerable advance over the coal-fired ship.
It is true that the internal combustion engine for marine use is still in its early infancy, and the various engineering and chemical problems involved in its design have not yet been thoroughly mastered. At the same time, the advanced state of general knowledge in these two branches of science is an advantage which the early years of the steam engine did not possess, so that it may be expected that the weaknesses of the later type of power production will be quickly eliminated and the engine brought to such a state of perfection that it will be safely adaptable to vessels of much larger tonnage than it is at present associated with. There are many, indeed, who assert that the internal com bustion engine will rapidly displace the older form of fuel firing, which is a point worth a moment's consideration.
The conversion of a coal-fired vessel to an oil-fired vessel is simple, and requires but a short time to effect ; moreover, the steam engines, which are of a very costly character, are retained. In the case of an existing vessel, to substitute internal combustion engines for the whole of the steam engine equipment would entail an enormous capital expenditure, apart from the fact of the much higher cost of the former. The cost of a direct installation is considerably higher than that of a steam plant of similar horse-power. Generally speak ing, the former may be roughly taken at between 25 and 33 per cent higher than the latter, but it must be remembered that there are many counter-balancing advantages in the use of a Diesel driven ship over a coal-fired steamer. There is, for instance, a larger amount of space conserved for cargo, etc., by the elimination of the boilers, and, therefore, the earning capacity of the vessel would be proportionately increased.
The cost of fuel is also another important item in favour of the motor-driven ship. It is clear that the saving in oil as compared with its consumption when burnt under boilers is great ; in fact, it has been proved in practice that a motor ship can be operated on about half as much oil as that required for running an oil fired steamer, and that a ton of oil in a Diesel engine will do the work of between 4 and 5 tons of coal. It
stands to reason and chemical knowledge that when oil is consumed under a furnace in the manner it is at present the thermal efficiency obtainable from it cannot be secured in so high a proportion as when employed in an internal combustion engine.
Comparing oil with coal, it has been estimated that a ton of oil, when used in a Diesel driven ship, will do as much work as from 4 to 5 tons of coal. The advan tages of such a means of propulsion are obvious, while at the same time there is the further benefit of not being dependent on coal. Expressing this fact in a simple manner, the consumption of oil an hour i.h.p. on a Diesel vessel amounts to 1.02 lbs., compared with 1.5 to 1.6 lbs. of coal. This means a saving of fuel of approximately half a pound of fuel i.h.p. an hour, which, if calculated out for a long Voyage, %%111 show an enormous saving in the fuel bill alone, while at the same time a very great reduction of time occupied in transit effected on account of the higher speed at which the vessel will travel and the elimination of the lengthy business of coaling.
In the early days of motor ships 8 and 9 knots was the speed attained, but this was very soon increased by improvements in the design of engine, resulting in obtaining higher thermal efficiency.
The motor ship Vulcanus, one of the first vessels equipped with internal combustion engines, consumed 134 tons of petroleum in 65.7 steaming days, or an average of 2.03 tons a day. This boat was of 1,235 tons deadweight capacity, and was fitted with six cylinder four-cycle NVerkspoor-Diesel engines, and had a speed of 8 knots. Its cargo-carrying capacity was between 12 and 15 per cent greater than that of a steamer of equal dimensions. In the Juno, a vessel with a displacement of 2,345 gross tons, and a mean speed of 9 knots, the total consumption of fuel, for all purposes, worked out at 86.21 tons of 4.75 tons a day for a certain mileage. The Sdandia, a motor ship of 4,950 gross tons, over a mileage of 268, consumed an average of 8.6 tons of petroleum a clay.