The following was prepared for MREmag by Stephen Siddle.

In recent years there has been ongoing discussion in MREmag, and on other Internet sites, about coupling compatibility in 00 - in particular about the implementation of NEM coupler pockets. At the moment the height at which they are fitted (when they are fitted) varies on different items of ready-to-run stock, which means they fail to meet their objective of allowing an alternative type of coupling to be substituted by a simple swap. There have been calls for a standard to be set, to ensure consistency and compatibility.

At our AGM a few weeks ago, The Double O Gauge Association formally adopted standards for coupler pockets and sockets. These are taken directly from the standards for H0, established by the Continental 'federation of federations', MOROP, in its Normes Europeennes de Modelisme (NEM) - under data sheets NEM362 (coupler pockets) and NEM363 (swallow tail socket).

The figures are:

NEM362 ('NEM pocket')

A (width of pocket) 3.2mm

B (height of pocket) 1.75mm

E (depth behind buffer face) 7.5mm

F (depth of pocket) 7.1mm

n (height from rail to top of pocket void) 8.5mm

It is, of course, value 'n', the height at which the pocket is set, which has been the big issue with 00 ready-to-run.

NEM363 ('Fishtail socket')

Values of data sheet NEM363 adopted.

Given that some 00 ready-to-run vehicles now carry this type of coupling mount (e.g. Bachmann 16T minerals and inner ends of Bachmann Turbostars) it seems sensible to adopt a standard to cover this in 4mm before any problems arise.

At the same time, it was agreed to adopt a standard for axle length of 26mm over pin points. The difference in axle lengths, between Lima and Heljan stock and everything else available in Britain, has been a source of inconvenience for some years.

These standards were adopted by unanimous vote at the meeting following consultation with members.

There has been previous debate on MREmag as to whether it would be appropriate to adopt the H0 values or whether some other figure should be chosen for the height of the pocket. A number of factors have led DOGA to adopt the H0 mounting height of 8.5mm.

Firstly, a large majority of the British outline 00 models fitted with NEM pockets have them set to a height of 8.5mm above the rail. To adopt this value means the fewest possible existing models are incompatible with the standard. To have chosen any other value would have made most models currently fitted with NEM pockets incompatible.

Secondly, probably the most popular alternative coupling likely to be used in an NEM socket is a Kadee. The great majority of those using Kadees on 4mm stock set them to the same height as for H0 - if only because the best and easiest way to get a consistent height is to use the readily available Kadee height gauge for H0

Thirdly, NEM362 lays down the same height of 8.5mm for pockets in both H0 and S scales. Since 4mm scale lies between the two, the same height of 8.5mm should logically be chosen

DOGA is in the process of generating data sheets, covering these standards, which will be placed on our website in due course. These will set out the full details including tolerances.

Thanks are due to one of our members resident in Germany, particularly Stuart May (an occasional correspondent of MREmag) for establishing contact with MOROP via the main German Federation (the BDEF). This was in order to gain permission to clone the standards and borrow the artwork from the data sheets for use in our own data sheets. I understand NEM362 was originally a project of the German Federation.

We hope these new standards will help resolve this issue.

Stephen Siddle, Treasurer DOGA