DIESEL SHIPS The Caspian steamer "Wandal," which was built by Messrs. Nobels in 1903, was the first sizeable ship to be given an internal combustion engine, but in her case it was used to generate elec tricity for the main drive.
Engines in which the charge was exploded by a hot bulb or an electric spark were found suitable for small craft soon after they had become general in automobiles on land, but their size was strictly limited. In the year 1892 Dr. Rudolf Diesel took out his patent for an engine in which the charge was exploded by raising its temperature by compression while it was still inside the cylinder, and ships propelled by such units, which have been built up to very large sizes and which many consider to be pre ferable to steam plants, are invariably termed "diesel-engined." The "Wandal" was followed in 1906 by the "Venoge," a motor barge on Lake Geneva, and in 1910 the motor tanker "Vulcanus" of 1,179 tons marked a great improvement in size. Two years later the motor ship "Selandia" was commissioned by the Danish East Asiatic Company, which is still one of the principal advo cates of the diesel engine, and is running successfully to this day. Her dimensions were 37o feet by 53.2 by 27.1 depth of hold, her gross tonnage being 4,950. She was a twin screw ship, each shaft being driven by an 8-cylinder four-stroke cycle engine with cylin ders 20i inches in diameter by 284 inches stroke, totalling a brake horse power of 2,45o at 140 revolutions per minute and driving her at a speed of twelve knots. She was rigged as a three masted schooner and the absence of funnel attracted general attention. Its suppression is now quite usual with some owners, while others prefer to run the exhaust from the engines up through funnels and make their motor ships practically indistinguishable from steamers.
After the success of the "Selandia," for although all the early diesel-engined ships had a certain amount of difficulty with their machinery she was a distinct success and very economical, a series of ships was built steadily improving in size, efficiency and economy. War practically held up experimental work in that connection as far as merchant ships were concerned, but the diesel improved rapidly in submarines and the Germans brought it to a very high pitch of perfection. In Great Britain the result of Admiralty experiments were also placed at the disposal of the mercantile engineers at the end of the war. Several sub marine diesels were fitted into German cargo ships after the war, their speed being geared down to the efficient speed of the pro peller as in the case of the turbine, with satisfactory results.
To begin with the diesel engine was more or less confined to the cargo vessel, but after the war it was realised that its adop tion in large passenger vessels would mean a very considerable saving in space and running costs, although the first costs were considerably higher than in the case of the steamer. After several trials in comparatively small ships, in 1924 the "Aorangi" of 17,4Q1 tons was built at the Fairfield Yard on the Clyde for the Union Steamship Company of New Zealand and has proved most successful on the service between Vancouver and Australia. She was followed in 1925 by the "Gripsholm" of the Swedish American Line, a ship of 17,716 tons designed for service between Sweden and the United States. There was considerable doubt as to the wisdom of building this ship, for the diesel shows to its best advantage on long runs, but she has proved an unquali fied success. In the same year a great advance in tonnage was made with the 22,00o-ton "Asturias," built at Belfast for the Royal Mail Steam Packet Company, and the diesel-engined passenger liner is now firmly established. Messrs. Harland and Wolff, the builders of the "Asturias," have specialised in a big double-acting Diesel built on the lines of Messrs. Burmeister and Wain of Copenhagen, one of the earliest diesel builders, and have developed high powers.
The "Augustus" of 32,65o tons, built for the Navigazione Generale Italiana in 1927, was the largest motor liner in the world in 1928. In deference to public opinion all these large passenger motor ships have been given funnels, the majority of them two, but the builders have evolved a typical Diesel funnel, short and very stout, which does much to obviate the echo which can prove exceedingly troublesome when the exhaust is carried through a funnel of ordinary design, particularly in fog.
The relative advantages of steamships and motor ships are still the subjects of infinite discussion and argument, each type possessing very real advantages for certain work.
The Still Engine.—In the Scott-Still engine, first fitted in the Blue Funnel Liner "Dolius" of 5994 tons in 1924, an effort is made to combine the steam and diesel systems, but although a remarkable economy has been obtained this is still in the experi mental stage.