SPEED FACTOR.

Auckland Star, Volume LXV, Issue 129, 2 June 1934, Page 7

SPEED FACTOR.

NEW ZEALAND TRAINS CAN THEY RUN FASTER? GAUGE WOT THE HINDRANCE Railway speeds are not limited so much by a narrow gauge as by the curves and grades of the line. The rolling-stock and loads are proportioned to the gauge, and high speeds are possible in straight, level stretches even on the New Zealand gauge of 3ft Gin. Suggestions that there is scope for the improvement of speeds on New Zealand railways have been made, but the Department, answering a correspondent of the "Railway Circle" (South Africa), shows that in view o£ the grades and curves of the New Zealand system, the results obtained are very creditable, states the "Post." Sixty Miles Per Hour.

Drawing attention to a striking.speed experience of his on one of the 3ft 6in gauge main lines of the South Island, the correspondent states that the Christchurch express, made up of thirteen coaches .of a total weight of 335 tons, covered the 35.5 miles from Rakaia to Christchurch in 48min lOsec from stop to stop, but as a 20-mile-per-hour speed limit over the Rakaia viaduct, which is over a mile long, caused the first 1.9 miles to occupy lOmin 42sec, the next 25 miles were covered in 20min 31Jsec. This gives an average speed of 56.5 miles per hour, mostly on slightly falling grades, but the maximum speed was 60.9 miles per hour, and was the more noteworthy, as the driving wheels of the locomotive were no more than 4ft Gin,, in diameter,, and the cylinders 17in in diameter by 26in stroke. "At present," he concludes, "the scheduled running speeds .of the best long-distance expresses in New Zealand average only 32 miles per hour, excluding stops, and other than the mountainous sections there seems, on this showing, scope for improvement." . .. — *

It is not only the "mountainous sections" which pull down the speed, but the numerous curves. Commenting on the percentages of straight and . curved lino and gradients on the New Zealand tracks, the assistant editor of the "Railway Gazette" (London), says: "There are, I should think, few railways in the world that have a higher percentage of steep gradients and sharp ourvations, when the whole service is considered." Bridges Slow Speeds. Taking the North Island Main Trunk as a sample, it is pointed out by the Railway Department that a rather remarkable speed performance is achieved for the total distance travelled, 426 milea in just over 14 hours. Tunnels. range from 250 ft .to over 3515 ft in length. There are 22 viaducts and bridges, five of which are over 100 ft above their river beds, two over 200 ft, and one, Makatoto viaduct, 200 ft above its stream level, with a span of 860 ft. The length of the span of these bridges varies from 200 ft to 1185 ft. It is the grades "and curves which prove the greatest obstacle to speeds. Compared with most other railways in the world, they are striking. There is a climb from Auckland to Poro-o-tarao of 1148 ft, the line drops to 560 ft at Taumarunui, and then, in the 32 miles to National Park, rises to 2636 ft. At Ohakune it drops to 2018 ft, but again rises to reach its highest point at Waiouru, 241 miles from Auckland, of 2660 ft, or more than half a mile above sea-level. Thence the descent is fairly rapid tp Palm'erston North, which is only 103 ft above sealevel. From there there are two climbs over the Pukerua and Johnsonville rises. The quality of the construction work is shown in the maintenance of a start-to-stop average speed, from Auckland to Wellington, of 30 miles per hour, which means that on parts of the route very high speeds have to b'e maintained.

About half the total mileage of the New Zealand railways is constructed on grades steeper than 1 in 200, while one mile in every eleven is on a grade steeper than 1 in 50. r ,

Of the total mileage nearly 6 per cent has curves of 10-chain radius and under, 12 per cent has curves of 15-chain radius and under, and 26 per cent, or more than a quarter of the total, consists of curved track and there are 54£ miles of bridges,