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The New Zealand Railways Magazine, Volume 7, Issue 4 (August 1, 1932)

Railways and Ships

Railways and Ships.

Seeing how closely allied is the railway and the marine engineer in their services to the prosperity of the Dominion, perhaps a few brief sidelights on the little known work of the latter will be of interest to readers of our Magazine. Both have one thing in common—they render an indispensable service to New Zealand. John Bright's famous saying, “Railways have rendered more service and received less gratitude than any other institution in the country,” applies with equal force to the engineering branch of the mercantile marine.

The following impressions were gained on a recent brief visit to the engine room of a typical motor ship, the “Hauraki.” page 50 Motor ships and steamers represent on water the competition between the internal combustion and the steam engine which has become one of the greatest problems of land transport of to-day.

There are several kinds of Diesel engines employed for marine work. The “Aorangi,” for example, has double acting two-stroke engines, while the “Hauraki” has four-stroke single acting engines. There are also other types of Diesel
“And let our barks across the pathless flood Hold different courses.”—Scott. (Photo, W.W.Stewart.) A section of Wellington's busy waterfront.

“And let our barks across the pathless flood Hold different courses.”—Scott.
(Photo, W.W.Stewart.)
A section of Wellington's busy waterfront.

engines employed on other ships—some of more modern design than those employed on the “Hauraki.”

The chief difference of the Diesel engine from other oil engines is that the oil is fed (from an atomizer without previous vaporizing) direct into the cylinders in the form of a spray, and without any form of ignition device as used in ordinary internal combustion engines. The system of cams and tappets in design is not unlike those used on an ordinary motor car engine. In the “Hauraki,” air enters the cylinder only on the charging stroke, being highly compressed on the return stroke. At this stage oil is introduced into the cylinder, and owing to the high temperature of the compressed air, immediately ignites. The explosion then propels the piston downwards as in an ordinary motor car engine. The “Hauraki,” having twin screws, has twin engines. Each has eight cylinders, these being all of 24 inches diameter, and having three valves (instead of two as on a motor car engine); one to admit air, one to admit the charge, and the other is the exhaust aperture. The writer was exceptionally fortunate on the occasion of his visit, as the vessel received orders to shift her original berth to another further down the harbour. This necessitated the vessel doing considerable manoeuvring under her own power out in the stream; and allowed one to get a fine inspection of the whole sequence of operations in the starting, stopping, and reversing of these wonderful engines.