When WA modellers first started out in Sn½ scale, around 1980, we decided to stick to Kadee couplers mounted mounted at the standard HO scale height, even though the coupler height was lower than it should be for WAGR models (and also conveniently ignoring chopper couplers).
For most people, the HO height works and they are happy with it. However, a few people, especially those modelling more modern locomotives and rollingstock, feel that the HO coupler height looks wrong and prefer to use the correct coupler height for S scale.
The difference in height is 2.3 mm, i.e. 12.2 mm vs. 9.9 mm measured, as always, from rail level to the centre of the coupler itself.
One way to accommodate the different coupler heights, for example on a particular loco, is to make use of Kadee offset couplers, specifically the range of "overset" couplers.
For a quick fix, substituting an overset coupler on a model designed for S scale coupler height should work reliably in most instances, provided trackwork is pretty good with no major ups and downs. This is illustrated in the third part of the diagram below.
For a virtually perfect match, an overset coupler combined with a 1 mm packing piece does the trick.
Based on Kadee specifications, the head on the overset coupler is 1.25 mm lower compared to a normal centreset coupler.
By coincidence, the Kadee #206 coupler height gauge (i.e. the insulated one as recommended for DCC) is spot on for S scale coupler height if you place a piece of 1 mm styrene between the gauge and the top of the rails.
Very informative, thank you.
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