7. Live Steam Operation
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 full size steam locomotive. This is quite different to an engine that has the outward appearance of a steam loco but has an electric motor driving the wheels.
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 pressurized steam that is drawn off as required to power the engine. In the larger scales and full size locomotives, coal or oil is the most common fuel used. In models, you have the choice of Butane gas, coal or spirit (meths or alcohol).
Many G-scale locomotives are fired by 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 inside a tube (flue) which passes right through the boiler from one end to the other. As this flue is surrounded by water, when ever 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. G Scale models are also available for coal or spirit firing.

Advantages and dis-advantages in Live Steam Operation