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BigBoy Butterfly Firebox Doors

BigBoy Butterfly Firebox Doors
June 2001

The following images are of the BigBoy Butterfly Firebox Doors' construction...

click on any smaller picture to view a larger picture

A scratch built, working replica of the Union Pacific's Class 4000 BigBoy's Firebox Doors. The doors were machined from bronze and stainless steel and are fully functional. A small piston and slide valve are housed within the upper cylinder. When steam is admitted into this cylinder, the doors automatically open. If no steam is available, the doors can be operated with the use of the lever.

Here you can see the doors in the half open position.

The doors fully open.

A bad photo detailing the lettering on the doors.

A closeup of the piston and handle mechanism.


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