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1:22.6, Gauge 3
ECR 2-2-2T Gooch class A, driving wheel

6′ 6″ diam., 20 rectangular spokes, inner rim level with the face of the tyre, apparent tread 2″.
Hub 13″ face dia., 1½″ out from the tyre, pin between at 11″.

Source: works drawing.

Casting: 87.7 mm tread dia., 81.0 mm i/d., hub 1.7 mm out from the tyre, pin at 12.4 mm.

Gauge 3 loco set prices . Casting prices and stock

Scan of a casting in a sets for: ECR Gooch class A.

Suitable for the Gauge 3 Society 2010 minimum tyre width of 6.8 mm, or the earlier standard of 8.0 mm.

Scan of casting X267
Scan of casting X267 machined

Machined to the 2010 G3 standard.

Cross section diagram of casting X267

Cross section diagram of casting X267 machined
Turning diagram marked out to show the work-holding steps as used for the form tool method for a tyre 6.8 mm thick with a 2 mm deep flange.

1. mount the casting with its back out and cut the small step on the back.
2. with the front out,
  cut the larger step,
  face the hub so you leave the whole top face just planed over.
    (cut a little high, then another 1 or 2 cuts of 0.01 mm until it looks right).
  take several very small cuts over the pin boss to make a level surface.
  face the tyre 1.7 below the hub.
  bore the centre just under the size of the final reamed diameter.
3. with the back out, face the back to your chosen the tyre width.
4. mount the casting on a slightly loose (by diameter) mandrel between two discs, centre it, tighten up, and make the final cut with a form tool. For such a larger wheel use a slow speed, 30 to 40 rpm., and a slow feed rate.

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27 Mar 2013