Changing Class/Marker Light Colors?

[Sean R Das]

Hello. I am curious to see how train crews changed the colors of classification and marker lights in the steam and early diesel eras, but I am a bit puzzled.

Photographs of steam locomotives suggest that the class/marker lights were removable, thus when it was necessary to change the color of the lights (such as from green, indicating the first or an intermediate section of a multi-section train, to white, indicating an extra train), the crew simply removed the old lamps from the hangers and placed the new lamps in their place (and in the case of electrically-operated lamps, plugged and unplugged the lamp cord into a receptacle in a junction box on the side of the smokebox).

However, most diesels (as well as a few streamlined steamers) had the class lamp housings permanently attached to the body of the locomotive. In this case, what did the crew have to do to change the colors of the lamps? Did they have to un-snap the old lens and pop in a new lens (of a different color)? I'd imagine there's that chance of damaging either the lens or the housing if one was not careful in doing what they were doing. IIRC, the Alco century series had 6 lenses mounted on the ends of the unit, so that the engineer could change class light colors by simply flipping a switch, but what was it like with other loco's?

 

[NM_RailNut]

Steam locomotive classification lamps usually had a fixed base and a rotating body (with a locking mechanism of some sort) that allowed the desired lens to be positioned in front of the light source and reflector without removing the lamp from the locomotive. Class lamps on most U.S. diesel locomotives had a fixed clear outer lens with colored lenses that could be placed behind the outer lens as required.

 

[Bob]

I've seen the same thing that Michael mentioned. The lantern style could be turned, and the electric ones had lense/filters of colored glass that could be used to switch the colors. They worked in about the same way that semaphore signals did.