Getting all het up
Probably the most common question anyone in the 16mm fraternity is asked (apart from ‘why muck about in the garden when you have a perfectly good spare room to play in?’) is ‘what is it fired by?’ The answer, in increasing order of rarity is a) gas, b) meths or c) real black, messy coal.
Way back in the 1980s, when garden railways were in their infancy and there was little available commercially, most live steam models were hand-built meths-fired examples. The spirit is contained in a small tank (which was easy to overfill) from which it flows under the boiler into several small vertical tubes fitted with wicks (originally asbestos, more recently glass fibre or something similar). If you are lucky there is a draught shield to help concentrate the heat, but it can be a slow business starting from cold, particular in mid-winter. Lighting is also problematical, as it is tempting to lift the loco up to facilitate applying a naked flame to the wicks, at the risk of getting burning meths either in your eye or down your sleeve. Either event can promote much unfortunate language and dancing about. Melted trackwork can also occur (as our Gauge 1 colleagues can testify). The intensity of the flame is fixed by the length of wick exposed, and cannot be regulated. Curiously, putting the burners out at the end of a run can also be tricky, as there is no valve to turn off the flow. However one enterprising company has come up with novel solution - a pocket-sized fire extinguisher which can squirt a shot of CO2 down the chimney to asphyxiate the wicks.
As garden railways became more popular the need for a more efficient and controllable means of firing led to the development of gas burners, fitted in a tube inside the lower part of the boiler. They look, and work, rather like a gas poker, although at a higher pressure and somewhat noisier. The gas of choice is either butane (of camping gas fame) or a mixture of propane and butane. The latter gives you (literally) less bang for your buck but is easier to vaporise for cold weather running. The fuel tank is a small pressure vessel provided with a nipple to accept the gas container’s nozzle. The flow rate can be controlled by a valve fitted with the archetypal knurled knob. Ignition is by gas (or fag/cigar) lighter applied either to the chimney or into the open smokebox door, depending on manufacturer. Occasionally the burner can be temperamental and self-extinguish. An unwary operator may then find that undispersed gas causes the next lighting attempt to sacrifice whatever hairs may be growing on the back of the hand. Once lit, the loco’s internal firing reduces heat loss and makes windage less of a problem, so raising steam can be quite speedy. Pre-heated water helps, too.
To some of course this is all unreformed heresy, and only coal-firing will do. In truth this is still a minority sport amongst 16millers, although one that is gradually increasing. Your author has one on order to celebrate the arrival of his state pension, although he may well be 66 before it actually arrives. The main structural differences are a stronger boiler, and a firebox instead of a burner. Model engineers in the larger scales will recognise the skills needed, which include maintaining a decent fire, getting enough airflow and keeping the water topped up, all the time with a watchful eye on the pressure gauge. So if you look up from your loco labours to find a newly-minted pensioner peering over your shoulder at your work with shovel and fire-iron, you’ll know why.