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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