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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.