Friday, 16 January 2015

Loco-profile 7: 'Sapper' 0-6-0ST

'Sapper' takes an Up train out of Darley Dale. (Photo: Sheila Rayson)

Brief Locomotive History

'Sapper' was built by Hunslet in Leeds in 1944. The Works Number was 3163 and she was very similar to other six-coupled saddletanks built for military service during the Second World War. When 'de-mobbed' this locomotive, and some other members of the class, were acquired by Hunslet. Their aim was to sell-on the locomotives for industrial use. To make the locomotives more attractive to industry (which was, by then, more interested in diesel locomotives or rejecting rail altogether, in favour of road transport). Hunslet converted the locomotives to a Gas Producer Combustion System based on the work of the Argentinian engineer L. D. Porta. There's an excellent article by Martyn Bane on the 'Austerity' class as built and as modified here.

The Hunslet initiative wasn't an unqualified success and, whilst a number of 'Austerity' saddle tanks (both modified and un-modified) have ended up in preservation, I think all the ones actually in use have reverted to a more conventional firebox design and hand firing.

Steam Heating

Of course, as-built the 'Austerity' locomotives were not provided with steam-heating facilities but restored locomotives used for passenger trains on preserved railways have this feature added. In preservation, warming is typically carried out at a steam pressure of about 30 pounds per square inch.
This is only a fraction of boiler pressure so steam from the boiler is admitted to the heating system through a Reducing Valve. It takes a while for steam to work its way through the train so it's usual to open the steam heat cock on the back of the train until steam can be seen escaping, assuring that all the intermediate cocks between carriages are open and the steam heating hoses correctly coupled. This process should be started well in advance of departure to give the coaches a chance to start warming before the passengers board. Once steam heating is started, the fireman needs to account for the extra demand for steam - coal and water will need to be added more frequently.

Handbrake/Steam Brake

'Sapper' is provided with a handbrake and a steam brake. On each wheel, there is a cast-iron brake block which can be pulled against the steel tyre of the wheel through a substantial arrangement of brake rods and cross-members forming the brake rigging. The brakes are applied on all wheels simultaneously either by rotating the handbrake screw using an l-shaped handle in the cab or by the movement of a piston rod connected to the piston in the steam brake cylinder. The steam brake cylinder is mounted under the footplate on the driver's side of the footplate and the supply of steam to the brake cylinder is controlled by a valve in the cab.
Two brackets mounted on the boiler backhead support a transverse shaft which can be rotated by handles at either end. A steam brake valve is supported by the left hand bracket and operated by the rotation of the shaft from either side of the cab. A copper pipe runs from the brake valve to the piston in the steam brake cylinder. Pulling on either steam brake handle applies steam to the brake cylinder: pushing the handle cuts off the steam supply and vents the steam in the brake cylinder to atmosphere, allowing a substantial spring under the front of the locomotive to pull back the brake rigging and release the brakes.

Vacuum Brake

Following a series of dreadful accidents in the 19th century, it became a requirement that all passenger trains be provided with an 'Automatic' brake. There's a little more about brakes in a post called MIC - Brakes.

As-built the 'Austerity' locomotives were not provided with vacuum brakes but restored locomotives used for passenger trains on preserved railways have this feature added. In 'Sapper' a Davis and Metcalfe Type 'M' Ejector including the Driver's Brake Application Valve has been fitted.

Related posts in this blog

Preparation of Locomotive 'Sapper'.

My pictures

'Sapper' Austerity Tank Locomotive.