Skip to content

Steam Locomotive Controls: The Backhead

September 8, 2009

Running a steam locomotive requires much more than knowing what part does what, but it’s a necessary first step. Learn what each control does on the backhead of the steam locomotive and why it’s important.

Up for inspection is an OIL fired 2-6-2, the RVRy’s #7. The layout of the controls is for the most part identical to how a full sized locomotive operates, and ALL the controls present on the full sized locos are displayed here.

To see a larger version of this photograph, go here:

Steam Locomotive Backhead Controls

Okay, follow from “A to Z” to learn about each part:

A- Atomizer- atomizes fuel oil and sprays it into the firebox to ignite and keep the fire going

B- Blower- manages the draft of air flowing from the back of the boiler through the tubes and out the stack, helps complete combustion of the fuel by supplying oxygen.

C- Throttle Lever- Does the obvious.

D- Independant Brake Lever, which is used to apply brakes to the drivers and tender trucks to stop the locomotive

E- Train Brake Lever, if all the cars were equipped for airbrakes it would apply the brakes on all the cars behind the locomotive.

F- Firebox Door- used to access the firebox prior to steam up, a lever on the side manages the draft on the bottom of the firebox, inspection hole is used to manage the color of the fire, which tells you how complete your combustion is and how efficient you’re running your locomotive. Idealy it should be a bright golden orange.

G- – Gauge Glass Valve- Used to flush out gauge glass to measure how much water is in the boiler.

H- Water Check Valves- If the gauge glass is broken you can quickly check where your water level is by quickly turning the top or bottom valve for less than a second so you don’t scald your fingers.

I- Gauge Glass- Measures water level in the boiler to make sure you’re making steam, but also operating safely with enough water to prevent damage to the crown sheet. 1/4 or 1/2 the height of the glass is ideal.

J- Oil Firing Levers- Used to finely control the amount of oil being sent to the atomizer to be burnt as fuel.

K- Left side blowdown valve- used to blow crud out of the cylinders and the boiler to keep it from becoming a gunky mess.

L-Oil shutoff valve- the master on/off switch for the fuel.

M-Headlight toggle switches

N- Air Pump Lubricator- Keeps the Airpump lubricated and (hopefully) working smoothly.

O- Left Side Water Injector- Injects water from the tender into the boiler, performs same task as “S”

P- Steam Air Pump Lubricator Valve- For the most part it turns on a small supply of steam to turn the lubricator on and get the pump started.

Q- Shop Air Valve- To gain pressure more quickly, we hook the boiler up to an air compressor, turning on this valve and plugging in the air hose is all this is for.

R- Turret Valve & Main Steam Pressure Gauge- Measures the PSI (Poundsfor Square Inch) of steam pressure in the boiler and the turret valve controls the movement of all steam to te controls in the cab.

S- Right Side Water Injector- Injects water from the tender into the boiler, performs same task as “O”

T- Independant Brake Pressure Gauge- Tells you how many pounds of pressure you have in the airtanks that the steam air pump compressed for you to apply your airbrakes with.

U- Train Brake Pressure Gauge- Same as above, but for the entire train.

V- Right Side Blowdown Valve- Does the same thing as left side.

W- Cylinder Cock Lever- Drains sitting water out of cylinders, typically done before and as the locomotive begins to move, that’s why you always see jets of steam shoot out of the cylinders as a steamer pulls away from the station or a stop and not too long after it ceases as the engineer decides the water has been drained.

X- Reverser/Johnson Bar- Controls the valve gear which determines the direction in which the siderods, motion and drivers travel.

Y- Whistle Cord

Z- Fore and Aft sanding levers put sand on the rails in front or behind the drivers for traction.

I hope you learned something new, it’s a complex machine to operate but it’s quite a specticale.

3 Comments leave one →
  1. David Emery permalink
    September 8, 2009 11:37 am

    Nice! How about a version for a coal-fired loco, so we can see the differences?


  2. Jim Compton permalink
    January 18, 2016 12:40 am

    Thank you for your immense time and diligence. I miss steam which I am not the first among many to say it is the closest inanimate object to appear live and to have a soul.


  1. Picture of a Union Pacific Big Boy back head. « Railroad Jobs Forum

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: