NEW ZEALAND RAILWAY STEAM 6




New Zealand Railways employed about eleven hundred steam locomotives in all. Early ones were from British builders followed by an early mid period of American suppliers, mainly Baldwin, then a mixture of home and North British building. Haulage requirements were growing so fast that successive new acquisitions rapidly became inadequate in power and numbers. Growth of the railway system was sustained by the relatively under developed main trunk roads of the times that were unsuited to heavy motor truck traffic. The main trunk Auckland-Wellington railway was single line that started to become clogged with the growing frequency of relatively lightly loaded trains, thus it was thought that if the power of each engine was doubled, train weights could be doubled and traffic density halved accordingly. So with that thinking, the highly successful South African Garratts were examined and it was seen that without increasing the driving axle loadings all of the above could be achieved. South African traditions were not followed and a home spun design and order for three vaguely similar locomotives was placed with Beyer-Peacock and delivered in 1928. Three years later I viewed one of these machines abandoned in rotten row at Taumarunui locomotive depot. It had handsome lines but all that glitters is not gold.

In my time at Taihape I was to meet drivers who had driven and fired these locomotives on their stamping ground between there and Taumarunui. From the information gleaned the boilers were really good steamers as long as the mechanical stokers kept going. The coal feed worm frequently failed through the presence of stones and steel scraps in the coal causing drive breakages. The engines could travel quite fast providing the Gresley linked middle cylinder valve did not over-run and throw the engine into violent wheel-spin. The water tankage was insufficient and on 1/40 grades the water flowed from the higher to the lower tank. Time was consumed with frequent stops to refill. In their brief existence two firemen were often carried to take over from the sure to fail mechanical stokers. But that was not all, the crossing loops of the time were too short to accommodate the trains that could be hauled and the draw-gear of most of the existing wagons was too light to withstand the newly imposed forces.

These locomotives were of 4-6-2+2-6-4 wheel arrangement. The driving wheels were 57” diameter and the 6 cylinders (three to each power unit) were 16.5” bore x 24” stroke. The boiler pressure was 200 PSI, the fire grate area 58 square feet. The tractive effort was 51580 pounds and the engine weight was 146.8 tons. In the wake of this failed experiment there has been and still is ongoing speculation as to what if they had met expectations! The system might not have seen the “K” series of locomotives. Perhaps if the Garratt concept had made use of the chassis and running gear of the time tested “Ab” and “Wab” locomotives carrying a slightly smaller boiler with a 48 square feet grate aimed at a more conservative tractive effort of say 42000 pounds they may have become the dominant class.

In 1940 the so called civilized world went mad when the most technically advanced nations entered hate relationships and commenced hurling tons of iron and explosives at each-other and smashing up national infrastructures. This turn of events took me into a three year spell working steam and diesel locomotives on the military railway in the North African desert.

NEW ZEALAND RAILWAY STEAM 5




The ten “Aa” class Pacific type locomotives supplied by Baldwin in 1914 were classical American in every way. I never knew them in their original form but caught up with them towards the end of WW2 by which time they had been rebuilt with “Ab” boilers and cabs and redesigned tenders. They were also equipped with compressed air power reversing. They hauled freight mainly between Palmerston North and Taihape, were good steamers but not as freely as the “Abs”, and rough riders at speed over 35 MPH. An oddity was that the shafts of the fire shovels of both the originals and rebuilds were three inches longer than those belonging to all of the other NZR locomotive classes.

Palmerston North was home-base for a fleet of “Bb” class 4-8-0 tender engines that performed the yard shunting, ran the usually lightly loaded Foxton branch goods daily service and supplied exchange locomotives for Marton Junction and Danevirke. Originally built for main line freight work they were grossly under boilered or over cylindered with their small narrow fireboxes, but proved highly successful in the main shunting yards up to the end of steam.

There was nowhere on the NZR network that members of the 141 “Abs” did not run. They represented the definitive locomotive of the time. They handled all of the main passenger trains relatively efficiently and economically. Indeed, they were incredibly free steamers and of most uncomplicated configuration. Their weight distribution was a little short of ideal being light on the leading bogie and heavy on the rear end single axle truck. Through their lives two tons of cast iron weight was added to the front ends. They were prone to fracturing their main frames through the arches behind the cylinders. Indeed one that I was on with a provincial express clean broke on one side at speed a mile short of our crew change point. The thumping with each piston stroke was like that of a power hammer.

The “Wab” engines were the tank version of the ubiquitous “Abs”. They had the same boiler, cylinders, running gear and cab. The rear bogie was of the two axle trailing type to carry the added weight of the coal bunker. The side mounted water tanks provided useful weight over the driving wheels that enabled the boiler pressure to be raised to 200 PSI thus returning an additional 2366 pounds pull at the drawbar. Although there was higher demand on the boilers they steamed even more freely than the “Abs” from which they were derived. They rode well but forward vision was restricted by the height of the tanks and their projection of 3 inches outside the width of the cabs. In the latter days of steam several of them were converted to “Ab” class tender locomotives.

The new “Ka” engines coming on line were a quantum leap in quality of service with their massive roller bearing axle boxes and extremely free steaming boilers. They rode well and the running gear gave trouble free service between programmed overhauls. They bore a clumsy style of so called stream-line smoke-box and boiler-top casings that added nothing to the aesthetics and hampered the maintenance staff. They were also equipped with the French ACFI feed-water heating system with which I was familiar on the Taihape based “K” 919. About halfway through completion of the “Ka” order the fitting of the cowlings and ACFI system was discontinued and eventually removed from all engines of the class. Easily maintained exhaust steam injectors as on the original “Ks” were made standard equipment.

The 40 “J” class engines of my time followed by 51 closely related “Jas” and “Jbs” to make a total of 91 with their oil sealed Cannon roller bearing driving axle assemblies and Baker valve gear were probably the NZR’s finest steam locomotive package. The first 40 bore fairings along the tops of the boilers that hid the funnels and steam and sand domes. The smoke-boxes bore coned fronts with the headlamps in the centres. This paraphernalia was eventually removed and all members of the class were turned out in their naked glory.