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1:24 scale
H440, H441, H442
Driving wheels for the EAR (East African Railway) 4-8-2+2-8-4 class 59.

4′ 6″ diam., 14 oval spokes, humped inner rim.
Hub 14½″ face dia., 1.31″ out from the inner rim. Pin between at 14″. Tyre face 13/16″ below the inner rim.
If built as converted to run on Cape gauge the face of the tyre is 3/8″ above the inner rim.

Casting: 57.2 mm dia., 49.7 i/d., Pin at 14.8 mm. For Cape gauge, (tyre face 0.5 mm above the inner rim): hub 0.9 mm out from the inner rim.
Pin bosses: H440 1.2 mm out from hub, H441, H442 0.5 mm out from hub.
If built as converted to run on Cape gauge the face of the tyre is 0.4 mm above the inner rim.

Narrow gauge loco set prices . Casting prices and stock

Scan of a casting in a set for an EAR 4-8-2+2-8-4 class 59,

Castings H440 Castings H441 Castings H442

H440 outer coupled wheel; H441, mid coupled wheel with thicker weight; H442, driven wheel.

Cross section diagram of casting H440-2

The works drawings show that the wheels were also designed to suit Cape Gauge by changing the position of the tyres on the wheel centres. Metre gauge (39.37″) is narrower than the 3′ 6″ Cape Gauge (42″). As built for Metre Gauge the tyres were set back from the faces of wheel centres by 1 3/16″ to reduce the back to back by 2 3/8″ for the EAR Metre gauge. The wheels suit 3′ 6″ gauge with the tyres in the normal position which is how they are usually modelled. I have allowed enough material on the castings for either version to be machined.

1:24 is slightly underscale for metre gauge on 45 mm track, for a more exact scale of track use 41.7 mm track (or model at 1:22.2).

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27 Mar 2013