Gauge 3 / 2.5"...getting in to some serious boilers there. I'm guessing you'd be looking at working pressures up to 80? To get an accurate answer we'd need sight of a drawing really, knowledge of the working pressure, if at all possible a view of an original casting.
You'd really need to run design calcs to properly satisfy boiler regulations
Got: 3½" Lilla, 5" Lion, 2½" Annie Body.
Building : 5" Edward Thomas/Peter Sam, 7¼" Jubilee1897
In planning : 4" Burrell Road loco, 5" Standard 4 tank
Would like to build : 5" Duchess, NGG16 Garrett
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