Own your very own "live steam" locomotive built by Roundhouse Engineering in Doncaster England
A "live steam" engine is one which is actually driven by steam which has been produced by heating water until it boils, just like the real thing.
Water is heated inside a sealed container (the boiler) until it boils and produces steam. It is kept boiling while ever steam is required. Because this process is contained within the boiler, the pressure of the steam increases to a pre-determined limit and it is this pressurised steam that is drawn off as required to power the cylinders.
A safety valve is fitted to the boiler to prevent the steam pressure rising above its normal operating level. On Roundhouse models, this is 40 psi (pounds per square inch) which is about 2.7 bar. When the steam pressure reaches this level. the safety valve opens and allows excess steam to 'blow off' to atmosphere.
All their standard locomotives are all gas-fired using mixed propane-butane gas which is the simplest method of heating the water. The gas is stored in a special tank mounted on the locomotive and fed, via a gas regulator valve, to a burner mounted either outside the boiler (externally fired) or inside a flue which passes right through the boiler from one end to the other (internally fired). Whichever the method, whenever the burner is lit it is heating the water to produce the steam. The rate at which steam is produced is controlled by the gas regulator. Turning it up increases the heat at the burner and thus the amount of steam produced whilst turning it down has the opposite effect.
Steam drives the loco as it passes from the boiler through a regulator valve and down to the cylinders. In the cylinder it pushes a piston from one end to the other; first one way then the other. The piston is mounted on a rod (piston rod) which is attached by a special swivelling joint (the crosshead) to a second rod, (the connecting rod) which in turn is connected to the wheel or crank. As the piston is pushed backwards and forwards, it causes the wheel to rotate. The steam has to be sent to each end of the cylinder in turn and the used steam must exhaust up the chimney. This is taken care of by a valve in the valve chest mounted either on top or at the side of the cylinder. It must also do it at the right time on every stroke of the piston and this is accomplished by means of the valve gear. The amount of steam passing to the cylinders is controlled by the steam regulator.
See their website at http://www.roundhouse-eng.com or watch a short video from https://youtu.be/YR15XznsLZI?t=1h18m58s