Other formats

    TEI XML file   ePub eBook file  


    mail icontwitter iconBlogspot iconrss icon

The New Zealand Railways Magazine, Volume 9, Issue 7 (October 1, 1934)

Locomotive Developement. — in — New Zealand — The “Pacific” Type. its Genesis and Triumph.

Locomotive Developement.
New Zealand

The “Pacific” Type. its Genesis and Triumph.

By the year 1900, experience with the “U” and “B” class of locomotives had made manifest the fact that the New Zealand locomotive designer was per se quite as competent as his competitor overseas; that his better knowledge of local conditions enabled him to design machines better adapted for the needs of the railway service, and that, with this initial advantage, the local railway workshops could build locomotives which, in the final analysis were more economical than the imported machines.

At this time, too, the policy of the Government of the day was strongly in favour of having, where possible, all work done in New Zealand. The Railway Department naturally, therefore, adopted the policy that in future all new locomotives required should be designed and built in New Zealand. And by the irony of fate immediately followed the largest importation of English and American locomotives that the railways had yet known!

The reasons for this anomaly were obvious enough. The colony was at this time just recovering from the severest and (let us hope) the longest “depression” that it has ever known.

This depression quickly reached its apex in 1888, but it was a long ten years after before the cloud lifted finally. During these years the provision of new locomotives was out of the question. By 1900 prosperity and progress had quite suddenly returned, and greatly increased traffic came to the railways. The new traffic called for heavier, faster, and more frequent trains. The locomotive equipment, after ten years' stagnation, was of course quite unequal to the demands of the new conditions; and, while the Addington workshops had proved that good locomotives could be built in New Zealand, and that the shops were able to cope with the normal requirements, the Railway workshops were unable to supply the large number of engines then so urgently needed.

Cabled enquiries went out to the locomotive firms of Britain and America. The British firms, however, were just resuming normal operations after a prolonged strike; the English railways were calling for new locomotives just as loudly as New Zealand, and it was impossible for the British firms to supply locomotives in the limited time available. The very virtue of the British locomotive shops proved their undoing on this occasion. Their practice was to build locomotives to the design and drawings supplied by the customer, while the American firms had always insisted on the customer accepting locomotives built in conformity with the standards adopted by the firm. This custom explains the fact that, while British locomotive history is a record of successive designs of various railway companies, American locomotive history is contained in the records and catalogues of the firms building locomotives and, indeed, is virtually covered by the publications of
New Zealand designer's sketch for the world's first “Pacific” type locomotive.

New Zealand designer's sketch for the world's first “Pacific” type locomotive.

the Baldwin Locomotive Company. The American practice did not usually prove to be in the best interests of the railway systems, but it did make for quick delivery. Indeed, the Baldwin Company were able on this occasion to ship the first twenty locomotives from Philadelphia a few weeks after the receipt of the first cable. These were tank locomotives (“Wb” and “Wd” class), and it is said that they were really built to a Japanese order that did not reach fulfilment. Possibly Japan's gain was New Zealand's loss. Eighteen locomotives of the 4-6-0 tender type were supplied almost as quickly, but the New Zealand authorities were more particular over the design of the remaining thirteen locomotives and quite a month was taken up with a cable discussion concerning their design. These locomotives were intended for the new fast express service in the South Island, and they had to be designed to burn the “lignite” coals of Otago. The Baldwin Company's first suggestion stipulated a wide firebox engine, and this was rightly approved. Getting down to details, the company then suggested a curiosity in the shape of a Wooten type boiler, the engine to have six driving wheels, 49ins. in diameter, with a rigid wheelbase of 200 ins. The Wooten type of boiler comprised two cabs, one in the ordinary position for the fireman, and one perched about the centre for the driver. Unfortunately time was too pressing to allow the New Zealand engineers to fully satisfy their natural curiosity as to the exact shape the proposed machine was to take. One would like to see how the company proposed to fill up the extraordinarily long rigid wheelbase of 16ft. 8ins. However, trailing bogies had been used already with four driving page 7 wheels (the well-known “Atlantic” type) and the Chief Draftsman (Mr. G. A. Pearson again) made the suggestion, obvious enough though it appears to-day, it was a revolutionary one at that time, that a trailing bogie should be added behind the six coupled wheels to support the weight of the wide overhanging firebox. The Baldwin Company could hardly be expected to see at once how this could be done, so a little more time was taken and a letter explaining the proposal more fully was drafted and dispatched, and with the letter went a sketch depicting for the first time the new “Pacific” type of locomotive.

“Cortez silent on a peak in Darien” had nothing on the Baldwin Locomotive Company when it first viewed this sketch. Such a simple solution was seized avidly by the Company, and almost before the first locomotive of the new type could be shipped to New Zealand, Baldwin's were building similar engines for all the American roads. It represents, indeed, a veritable “milestone” in locomotive progress. Engines with six driving wheels and a trailing bogie are, from the mechanical point of view, the most economical form of locomotive. They admit, as one with fewer driving wheels will not admit, the use of a sufficiently large boiler to enable power to be generated with higher efficiency from relatively inferior coals, and their adhesive weight is sufficiently adequate to allow for the traction of trains heavy enough for all but the few most exacting services. They also give such balance between power and weight as to arrive at the lowest possible ratio between these factors, and escape the large increase in friction and wear that is inseparable from the use of more coupled wheels; and, altogether, again from the strictly mechanical point of view, they reach the acme of locomotive attainment, combining power, speed, lightness, symmetry, simplicity and beauty, in a degree not possible with any other type.

The title “Pacific” was given to this outstanding type in recognition of the fact that a New Zealand designer had first proposed it and was entitled to the credit for its introduction.

The great majority of the locomotives built in or for New Zealand during the last thirty-three years have naturally been of the “Pacific” type. The experiment, about 1905, with compound locomotives, lead to the “A” class and the adoption of superheat led, in 1914, to the building of the “Ab” class. This locomotive is a simple superheated engine of the “Pacific” type with a cylindrical tender. Designed under the instructions of Mr. H. H. Jackson (then Chief Mechanical Engineer) it embodied all the best features that New Zealand experience or design had evolved, and is probably the most efficient locomotive ever built for all-round service in the world.

Its design incorporated the following features:—(1) The piston valve, which a New Zealand designer was the first (1899) to adopt as standard locomotive practice and which is now almost universally used. (2) The Walschaert valve gear which a New Zealand designer was the first (1888) to adopt as standard practice, and which is now almost universally used. (3) Outside steam-pipes, which a New Zealand designer was the first (1914) to adopt as standard practice and which are now almost universally used. (4) Cross-balancing, which a New Zealand designer was the first (1914) to adopt as standard practice, and which was adopted in 1932 as standard practice in America, and will soon spread to the
New Zealand “Ab” “Pacific” type of locomotive.

New Zealand “Ab” “Pacific” type of locomotive.

Baldwin “Q” “Pacific” type of locomotive, the first of its class in the world. (After a New Zealand design.)

Baldwin “Q” “Pacific” type of locomotive, the first of its class in the world. (After a New Zealand design.)

rest of the world. (5) Superheating of steam, which had been developed in Germany about 1908, but which by 1914 had not yet become standard practice in other countries.

Although seventy-five of these engines had perforce to be built in England as a result of dislocation due to the War, they were all built entirely to New Zealand drawings and specifications. New Zealand track conditions demand that the maximum routine in train speed must not exceed 55 miles per hour, but the “Ab” locomotive can reach seventy miles per hour with safety on a level track; it has developed one horse power for each 100lb. of locomotive weight, which is certainly a record for a moderate sized engine; its fuel efficiency is extraordinarily high and, although this may have been exceeded by special service locomotives, is probably a record for all-round service; it can handle passenger, goods and work trains with equal facility; and the repair costs are markedly low.

page break