“MORE COAL!“, roars the deranged engineer, as the over-exuberant fireman frantically dumps seven tons of coal through the firedoor all at once, in an effort to get the “Cannonball” in on-time.
…Or so the stereotype goes. In reality, firing a steam locomotive in the ways movies, or popular culture suggests, would simply result in a smothered fire, a stabbed schedule, and a fireman out of a job. Coal-firing a steam locomotive involves the same principle critical to nearly every aspect of life: moderation. As anyone who has built a wood fire can understand, having good air flow is just as important as having enough fuel on the grate, and quickly dumping tons of fuel on at once is a good way to give a locomotive “black firebox disease”.
In a nutshell, the guiding idea behind firing a steam locomotive is “little, and often”. This allows the fuel to be burned at a rate that doesn’t let it pile high across the bed, and block the air flowing through from below. Additionally, just as important as the rate the fuel is fed, is how evenly it is spread across the grate. In general, the bed of fuel should cover all areas, with no holes where the grates themselves are visible. When adding fuel, the fireman will usually spread coal with a scoop for each area of the firebox: the front (below the tube sheet), the center, each side, the corners, and the back, right below the firedoor.
Every locomotive is different when it comes to which areas of the grate burn more rapidly, or how the firebed shifts as the locomotive runs. The draft pulled through the grate from the locomotive working will draw the firebed to different areas (usually from either the sides, to the center, or the rear, to the front), and a fireman has to know his locomotive to fire it properly, and avoid wasting fuel by dumping it in the wrong areas. As such, firing a locomotive has always been an art form, rather than an exact science. When adding water to the boiler, the fireman must also account for the cooler temperature of the water being injected, and will “fire against the injector (the appliance used to add water)”, and add fuel to prevent a significant loss in pressure from the cold water.
And with that, you should be all steamed up, and on your way!