A Tale of Two Garratts

We look at two unique locomotives,both built by Beyer Peacock.Both went to Australia – and one came back!

1.Tasmanian Pioneer David Payling

The current Ffestiniog Railway Traveller’s Guide includes an exploded diagram of a double Fairlie. It aims to begin to explain the workings of these articulated locomotives to visitors to the railway. The diagram, which has been available for many years and has found use in many publications, is believed to have been produced by the railway’s first archivist, the late Michael Seymour. With the NG/G16 Beyer Garratts now well established on the Welsh Highland Railway it might be timely to have a similar diagram to show the workings of these articulated locomotives. South African railway author and draughtsman Leith Paxton has been persuaded to produce an exploded diagram of pioneer Beyer

Garratt K1 of 1909. As nearly as possible it is in the same style as the well-known Fairlie diagram. A significant difference between the Fairlie and Garratt drawings is the well-lagged pipe connecting the front and rear power bogies. It carries the exhaust steam from the high pressure cylinders on the rear bogie to the low-pressure cylinders mounted on the front bogie. The Walschaert’s valve gear on the two bogies differs, as can also be seen in the drawing. On the front bogie the piston valve rod for the low-pressure cylinders is connected to the top of the combination lever which is thus above the point where the radius rod is attached. On the rear bogie the piston valve rod is connected to the combination lever below the radius rod pin joint. The

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(Top) Snowdon summit forms a backdrop to K1, pausing at Rhyd Ddu on 8 September 2006 after hauling a special train for supporters of its restoration. Supplied in 1909 to the Tasmanian Government Railways, this pioneer Garratt was repatriated by Beyer Peacock in 1947 and became an exhibit at its Gorton works. Its fate hung in the balance when the works closed in 1965, but happily the locomotive was purchased by the Ffestiniog Railway. (Roger Dimmick) (Lower) Numberplate of K1. (Michael Chapman) difference is that the high-pressure cylinders are fed by steam from the steam chests via inside admission valve ports. The piston valves of the low-pressure cylinders are arranged for outside admission of steam. The steam circuit of K1 is quite unusual. It starts at a steam collector pipe whose open end is well above the boiler water level in the dome. This pipe carries saturated high-pressure steam inside the boiler barrel steam space to a point in the top of the outer firebox. Here it is led out into the regulator housing mounted on top of the firebox. Unlike the superheated Beyer Peacock ex-SAR NG/G16 Garratts on the Welsh Highland, K1 runs on saturated steam. On K1 high-pressure steam is carried through a shaped pipe from the regulator valve to a universal joint close to the rear bogie pivot. The pipe runs outside the rear left-hand side of the firebox where it is concealed behind raised cladding. From here the pipe bends to pass into the cab. It then passes through the cab floor to reach the universal joint inside the bogie. Here it divides to feed the two high-pressure cylinders, exhaust steam from which passes into the lagged pipe visible between the bogies below the firebox and boiler cradle. Within the front bogie the steam enters the ‘change valve’ mounted between the low-pressure cylinders. From this valve it is fed via the valve chests and valves to the cylinders, from where exhaust steam reaches the chimney in the usual way through the blast pipe and smoke box. This is the ‘compound’ operating mode of the engine. In this way steam is used expansively twice,

first in the high-pressure cylinders and then again in the low-pressure cylinders. K1 and K2 were designed to be operated normally in the compound mode. However, a simple steam mode is also available to the driver, to help to start a heavy train, for example, or if the locomotive is stuck on dead centre. The simple steam mode is not visible in the diagram but essentially is operated when the driver holds over a ‘simpling’ valve in the cab against a return spring. This is linked, via an operating rod, along the upper right-hand side of the boiler to a high-pressure supply on the smoke box side. High-pressure steam is led from this valve to a piston and cylinder close to the change valve in the low-pressure bogie. The piston is linked via a lever to the change valve and forces it over against a return spring. The low-pressure steam is then diverted from its normal route into the low-pressure cylinders so that it passes directly to the blast pipe and chimney. The operating piston also uncovers a steam port which routes the high-pressure steam to

The historical significance of KI is now commemorated by this special plaque. Prior to being fixed to the locomotive it was shown at a special ceremony in Tasmania to Charles Smith, who as junior assistant engineer found the locomotive stored at Zeehan in 1945. He initiated the correspondence with Beyer Peacock that led to it being re-purchased at scrap value. (Michael Chapman)

Exploded diagram of K1. (Leith Paxton)

the low-pressure valve chests and cylinders. The locomotive now operates with highpressure steam in all four cylinders. This is the ‘simple’ steam-operating mode and is maintained as long as the cab control is held over against its return spring, whereupon the change valve returns the locomotive to its normal compound-operating mode. At first sight it may seem surprising that the Tasmanian Garratts were built as compound engines. In his book Garratt Locomotives of the World, Dusty Durrant commented that only one other of the many hundreds of Garratts constructed between 1909 and 1968 is believed to have been built for compound steam operation. However, viewed in the historical engineering context of 1909, perhaps the expectation for articulated engines was more in favour of compounding. By this time the Fairlie principle had fallen largely into disuse, despite the operating

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