Steam Overview

Motorized rail vehicles with steam powertrains are powered by steam, produced onboard by burning fuel to boil water .

To run a steam engine, coal or oil are burned in a firebox . This heats up water in the boiler , eventually turning it into steam. Since steam is compressible, so much of it can be generated in the limited volume of the boiler, that it becomes highly pressurized.

Through a series of components, such as the regulator , steam chest , cutoff , and cylinders , the steam can be admitted to push the engine pistons and propel the vehicle. With every cycle, after pushing the pistons in one direction, the steam gets released outside through the blast pipe. This creates a vacuum pull in the firebox, drawing fresh air into it , further feeding the fire.

Water and coal are sometimes carried in a secondary unit, called the tender . Coal is transferred to the firebox by manual shoveling , whereas water is transferred to the boiler using an injector . An adequate amount of water must be maintained in the boiler at all times, to avoid boiler explosion .

Steam engines have complicated mechanisms that need to be properly lubricated to function.

Firing up a steam engine from scratch is costly and can take a very long time. In Derail Valley, the startup process is sped up when the vehicle is stationary, simulating it being done in the most fuel efficient manner, until the boiler pressure reaches about 80% of its maximum capacity. The time scaling is there to drastically reduce waiting, but can be adjusted by a difficulty setting titled Steam Startup.