This example shows a tyre width of 3.5 mm for Gauge 0 Fine.
For Scale7 remove more metal from the back of the wheel to give a tyre thickness of 3.2 mm instead of 3.5 mm.
3′ 6″ diam., 10 rect spokes, rectangular inner rim, 3″ apparent tread.
Hub 12″ face dia., ½″ out from the tyre.
Casting: 24.5 mm tread dia., 21.0 mm i/d., hub 0.3 mm out from the tyre.
Scan of the castings in sets for a Stockton & Darlington 4-4-0 Saltburn.
4 Feb 2015