Steam engines in all forms are dependent on boilers to supply the steam at pressure to their cylinders to produce work, sooner or later the boiler water level will drop, which needs replenishing when a certain level is reached. Various types of mechanical pumps, connected to the steam engine crank shaft, have been used in the early days. Since the invention of the steam injector by a French engineer around 1860, mechanical pumps have fallen into disfavour.
In the model world very reliable injectors in model size's can be made by some skilled model engineers, but not all model builders achieve success in this direction. A steam driven mechanical pump can be made and is very reliable in model form.
Although I produce my own injectors a mechanical pump was seen as a interesting exercise in building, besides being fascinating to watch in operation, it never fails to attract people, from all walks of life when put to work.
Piston Rod Assembly
Slide Valves & Steam Chest
Valve Chest Assembly