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The New Zealand Railways Magazine, Volume 9, Issue 6 (September 1, 1934)

Locomotive Development — New Zealand — Designs To Suit New Zealand Conditions

page 6

Locomotive Development
New Zealand
Designs To Suit New Zealand Conditions.

The vexed historic question as to whether English or American locomotives were the better, occupied the minds of New Zealand railway men for many years after the “Josephine” and the Yankee “K” starred as the first antagonists. As with all vexed historic questions the answer remained inconclusive till the march of time so altered circumstances as to make the solution valueless.

For twenty years the railway authorities debated the question as to whether the English or American locomotive firms could design and build the better locomotive for New Zealand conditions. The debate was protracted, acrimonious and expensive. Six passenger engines (“N” class) would be ordered from the Baldwin Works at Philadelphia and, in the same breath, ten (“V” class) would be ordered from an English firm. Six goods engines (“T” class) would be ordered from Baldwin's and ten (“P” class) from the English firm. Neither maker knew anything of New Zealand railway conditions, and the only facts that emerged from the welter were that the American engine would pull the greater load, the English engine would have the higher fuel efficiency at moderate loads, and both engines were unsuitable for the requirements.

In the meantime, however, the New Zealand designer had not been altogether idle. While these somewhat futile comparisons were being made between American and English engines the traffic had been steadily growing and the “F” engines had borne the “heat and burden of the day.” By 1880, some twenty “U” engines had been imported and had proved very useful machines. Then, in 1883 (or thereabouts), it was decided to order ten more. Mr. Conyers, Locomotive Engineer for the South Island, took the opportunity of having many alterations incorporated in the new design with the idea of making the engines more suitable for local conditions. The result was a decided success, and the ten “J” engines then imported were the most useful engines of their day.

In 1889, two tank engines, the “W” class, were designed in New Zealand and built in the Addington Workshops. There was only one distinctive feature about these locomotives, but they did represent the inauguration of the policy that has been so successful since—the policy of having new locomotives designed by New Zealand engineers conversant with the conditions and requirements of the local service. One of these engines was exhibited in the New Zealand and South Seas Exhibition at Dunedin, in 1890, and I presume it was viewed with considerable interest!

The one distinctive feature about these two engines was the fact that they were fitted with the Walschaert valve gear. The story of this gear is illuminative. It was invented in 1844 by Walschaert, an engineer on the Belgian railways. That modern blessing—the Suggestions and Inventions Committee—was unknown in those days; and Walschaert was not allowed to patent his invention in his own name, or to get the patent (obtained as dummy by his friend Fircher) adopted on Belgian engines. In 1848, a German, von Waldegg, appropriated the invention, and by making a few detail alterations which he claimed as improvements, was able to obtain a new patent in Germany and some success in having the new gear fitted. By 1888 poor Walschaert was dead, his life embittered by disappointment, and his gear nearly forgotten.

Mr. G. A. Pearson, Chief Draftsman of the New Zealand Railways had become interested in valve gears. In 1885 he had invented a valve gear of his own, and it was tried out on a “V” engine. Pearson, however, recognised the defects of his
Addington “B,” the first goods class locomotive designed and built in New Zealand.

Addington “B,” the first goods class locomotive designed and built in New Zealand.

page 7

gear and did not persevere with it. He had, however, the satisfaction, years after, of seeing this gear re-invented and patented, about 1913, in America, where for some years it had a considerable (and I hope profitable to the inventor) vogue under the name of the “Southern” gear.

Finding that his gear was not altogether satisfactory, Mr. Pearson turned his attention to the Walschaert gear, and by 1888 he had decided that this was the best form of valve gear for locomotives. He accordingly designed what is still, beyond doubt, the best arrangement of this gear. In 1889 he had it fitted to his “W” engines, and it has ever since been the standard gear for New Zealand and has been applied to all engines built in or imported to New Zealand since that time—generally and preferably in the exact form designed by Mr. Pearson.

It was many years before the merits of this gear became recognised abroad, and certainly twenty years before it became adopted as the standard gear in England and America. Even in 1901, an American locomotive engineer who visited this Dominion expressed satisfaction at the general design of our locomotives, but considered they were spoilt by the (unprintable adjectives here) silly valve gear. To-day, this, the Walschaert gear, is fitted to virtually all new engines throughout the world, but the arrangement adopted is seldom as good as that designed by Mr. Pearson.

Some ten years later the same designer became interested in the valve itself. The old flat slide valve had obvious merits, but it is now known that these were overbalanced by less obvious demerits. Mr. Pearson turned to a new idea, the piston valve, which had been lately tried out by several independent designers in England and on the Continent. He recognised intuitively the advantages of the valve, saw the defects which had made their designs ineffective, designed a simple and effective form of piston valve, which he boldly fitted to a new class of locomotives which he was then (1899) designing, and once more had the satisfaction of seeing his ideas prove satisfactory in service and of having this valve adopted as standard practice for New Zealand. Again he was criticised by locomotive engineers abroad, and again had the satisfaction of living to see his ideas become slowly favoured elsewhere, and to-day the piston valve is a standard detail of locomotive design.

In 1897 the next great step in locomotive development in New Zealand was made. A modern, powerful (for those days) design of new locomotive was under consideration, and this time it was decided that the engines should be designed in New Zealand by engineers conversant with local requirements, and built in New Zealand in the Railway Workshops. It was still, however, thought necessary to build one type of locomotive for passenger and another for goods traffic, and the “U” and “B” classes were accordingly built.

The “U” class engines were (and are) very handsome engines, with simple graceful lines and, although a trifle under-boilered, they have given very successful service. The driving wheels are 54in; diameter and (since the highest routine service speed of a locomotive is determined by, and is roughly equal to, in miles per hour, the diameter of the drivers in inches) they were the first engines in New Zealand capable of running fifty miles per hour with a reasonable train of carriages behind them. These engines were fitted with the Walschaert valve gear, and were very economical engines in every way, except that we know now what was not known in 1899, namely, that the adhesive weight is sufficient to admit of larger cylinders, and this would call for larger boilers. A trailing bogie would have been required to carry this extra weight, but the consequent type of engine had not yet been built anywhere in the world. It can therefore be quite truthfully said that these engines represented at that time the best possible design; in many ways they were definitely in advance of locomotive practice anywhere else, but, we will see later, it was only a few years afterwards that Mr. Pearson himself was the first locomotive designer in the world to take the bold decisive step that was necessary if the “U” class were to be improved.

Virtually, at the same time the “B” class of engine was designed to handle goods traffic. This class of engine was a 4—8—0 type, that is eight driving wheels were coupled together to give increased adhesive weight. Looking back from the heights of the better knowledge of to-day we know that the whole design was a mistake; but this could not have been apparent at the time. The increase in train speeds that was found necessary early in this century, and with which the small wheels of the “B” class were unable to cope, could hardly have been foreseen; and, for the rest, the faults of this class were those already mentioned for the “U” class, and, as has been stated, were due to the erroneous ideas held by all designers of the time. The design appeared so successful in service that it was repeated in two very similar classes of engine in New Zealand, ten and fifteen years later; and similar types are still being built for many railway systems. The “B” class of engine was noteworthy in that it was the first design to incorporate both the Walschaert valve gear and the piston valve, now standard practice throughout the locomotive world. It was, however, nearly twenty years afterwards before the locomotive designers elsewhere arrived at this stage.

The man in the street is inclined always to gauge the excellence of locomotive design by size alone. This is a very mistaken idea, since this feature is one which is determined, not by the locomotive engineer, but by considerations (mainly governed by density of traffic) quite outside his scope. Those who appreciate the true inwardness of locomotive design will realise that these two designs (the “U” and “B” classes) of engine were well ahead of locomotive practice elsewhere. They represented a quite definite step forward in the locomotive development of the world; and, while it would not perhaps be correct to say that locomotive designers elsewhere knowingly copied New Zealand work, it is undoubtedly true that the New Zealand designer was definitely in advance of progress elsewhere.

The vexed historic question as to whether English or American locomotives are the better for New Zealand conditions has, therefore never been solved. The truism that New Zealand engines were best for New Zealand conditions became doubly true when it was realised that the New Zealand design incorporated all that was better in either the American or English designs, and in many features surpassed either.

Lumen accipe et imperti!

Addington “U,” the first express passenger locomotive designed and built in New Zealand.

Addington “U,” the first express passenger locomotive designed and built in New Zealand.