By Nigel Town
This one was built by John Brittain and is coal fired. It took me a while to get the knack of raising steam. At the time I ordered the engine I went for the safety option and ordered it with both coal and gas firing configurations. The engine came with a coal firing tuition session – it turned out to be quite a pivotal day as I am now a committed fan of coal firing.
NGG16 and NG15 lurking in the lower sidings at Butterley
The coal firing ritual starts with charcoal soaked in meths – my party piece is to raise pressure quicker than the gas fired locomotives in the steam up bay! With the suction fan sitting on top of the chimney to draw a draft through the charcoal fire both the temperature and pressure start to rise. Unlike a gas fired “one shot” engine the boiler of a coal fired locomotive is usually half to two thirds full of water during the initial phase of raising steam. Once the pressure is up to around 30 PSI, the electric suction fan is switched off and the steam blower is used to draught the fire. By now the engine which was initially deposited on the track clean is starting to look rather dirty. As the charcoal is burnt up small particles are drawn through the fire and land on the boiler. As the steam blower is used to draught the fire drops of condensation now start to land back on the boiler adding to the mess! This is not a clean process.
Initial steam raising on charcoal
As the pressure continues to rise the fire needs to be fed with coal rather than charcoal. These small pieces of coal vary in size from peas to broad beans in size. Dropping them in the firebox left – right – centre ensures that an even firebed is built up on the grate. With the safety valves lifting at 65 PSI it’s either time to make a lap or two or alternatively pump more water to the boiler.
Firebox door wide open – for photographic purposes only as it draws cool air into the fire!
These engines have two pumps – an axle pump which adds water to the boiler as the wheels rotate, and a hand pump in the front tank. As the temperature of the fire comes up and the safety valves lift the water level needs to be maintained. Holding a conversation whilst firing a coal fired engine is an art. It is essential that as an operator you don’t loose sight of the water level on any lap. It’s very easy to engage in conversation with interested onlookers when running this engine – keeping the levels in check at the same time is the hard part! I try and run the NGG16 with about 1/4″ of water sitting in the bottom of the gauge glass. Too much risks overfilling the boiler, too little and I risk loosing water temperature when adding more water. At one exhibition I was asked what sort of LED’s lights I had used to generate the glow in the ashpan.
That telling glow in the ashpan
With a constant pace and steady load the fire, water, and pressure levels can all be nicely balanced and held for a 90 minute running slot. After this period the engines are both ready for a lubricator top-up, this is apparent as the pick up from stationary starts to become less smooth.
On the freshly ballasted lower loop at Butterley with a rake of B Wagons
Since it was new I’ve added a number of additional cosmetic details to the engine, dummy valves flanges and pipe unions. The engine was built to represent a specific prototype, number 125. The NGG16’s were a varied class and there are both batch differences, and manufacturer differences. The most obvious difference is the headlight, this engine has the twin beam version, earlier times saw the engines fitted with a larger diameter single beam unit, and if I’d remembered I’d have switched them on for these photographs!