RAILWAYS ARE SPEEDING UP.

Star (Christchurch), Issue 17854, 24 May 1926, Page 4

RAILWAYS ARE SPEEDING UP.

N.Z. GAVE WORLD A FAVOURITE TYPE OF EXPRESS ENGINE. Steam superheating, or the passing of steam generated in a boiler through an ingenious heating apparatus before admitting it to the cylinders of the locomotive, is becoming a world-wide practice. Now it is finding greater favour on the New Zealand Railways. The object of superheating is. in the first place, to dry the steam before it is used, and secondly to give it a higher pressure efficiehcy. The great success of the heavy AB class of general service engines in the Dominion, which are superheated simple locomotives, has led to the addition of superheaters to several other classes. The AB’s which do all the heavy passenger work, are of the 4—6—2, or “Pacific” wheel arrangement type. The method of classifying railway engines by wheel arrangements is universal. A 4—6—2 type has a four-wheel bogie under the front end, six driving wheels in three pairs, .and two trailing wheels under the firebox, at the rear or cab end of the engine. The AB class are quite at home with 18 cars, loaded, or approximately 360 tons, between Christchurch and Oamaru at speeds ranging from 30 m.p.h. to 50 m.p.h. The predecessors of the AB’s, very similar in general dimensions, but lacking later improvements, were designed by the Locomotive Engineer of the N.Z. Railway Department a considerable time ago, and to the Dominion belongs the credit of having introduced to the world the Pacific, or 4—6—2. type of engine that has since attained universal appreciation for very heavy fast work. Owing to the sterling performances and low coal consumption of the AB class, the Q class engines are now being superheated. Though old, they were well made, and will yet put many years of service behind them. One Q is already superheated, and is at work on the West Coast, w'here in bringing up the passenger trains it is carrying out performances almost as good as the AB’s now running on the Coast.