Once inspections were complete, we had our roadmap: No. 12 needed major repairs, starting with her firebox, the furnace where coal burns to create the steam that drives the engine.
Engineering the Repairs
First challenge? The original Baldwin boiler drawings could not be found. A research trip to the Pennsylvania State Archives confirmed it. It took four months to create custom engineering drawings of the firebox from scratch.
And here’s something cool:
When No. 12 was built, fireboxes were riveted.
Today, we use improved welding technology—no rivets, just precision welds for strength and durability.
Running Gear Repairs
While boiler plans were underway, the running gear got attention. The work that is required:
Driving wheels must be removed and turned on a massive lathe.
Material removal is precise; all wheels must be within thirty-thousandths of an inch (0.030") of each other.
The same person handles measurements using a custom-made gauge for consistency.
New suspension springs will be fabricated (the old ones dated to the 1940s).
Broken wedges will be replaced, rods repaired, and the pilot truck wheels inspected.
Did You Know?
Precision matters. Even a tiny difference in wheel diameter can cause uneven wear or derailments at speed.
Next Blog: Inside the firebox—why it’s the heart of the engine and what it takes to rebuild it.