Reply To: EMGS Crossing Jigs

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Nick Ridgway

    I have used this book to calculate the geometry of GWR junctions in EM gauge and my write-up has been awaiting publication in the EMGS Manual for a couple of years now. The delay is explained in that it has come out as an odd number of pages, and the current thinking is that an even number of pages is appropriate for the purposes of sharing the maximum amount of information for the minimum weight of posted paper.

    So the book can be used.

    For the moment it will mean revisiting the calculations from first principles using the contents, pending publication of the Manual sheets.

    Something that might be useful is second-person-check, a peer review as it were, on them beforehand. Might I invite you to contact the Manual Sheet Editor for a copy of my draft so that it can be red-penned and returned before its publication forces a review and an update?

    Incidentally, I have used the contents of the book to review the dimensions of some of the junctions at Hayes Knoll on the Swindon & Cricklade Railway in 12in scale. There is good correspondence between the contents of the book and what has been installed – as of 2012, that is.

    WRT South Brent, the junctions selected will depend upon modellers’ licence on compressing the layout to save space – always a consideration when building a model. Generally, a crossover between track at double track centres needs to be no wider than 1 in 8 otherwise buffers will start to lock and corridor connections start to tear off. The minimum radius of locomotives is a function of chassis design; I generally take 5&2/3 chains, the radius of an LNER B & 6&1/2, as the minimum practical radius for steam locomotives in 12in scale. And go from there.

    It is possible to determine the geometry of prototype junctions using photos and counting the chairs. In the LNER series, for example, one can determine the switch pattern by counting the number of P chairs each side: 5 for an A switch, 6 for a B, 7 for a C and so on. Each switch had only a limited number of crossing angles with which it is compatible and this information is tabulated in the Manual sheets published to date.

    I’ve done my best to simplify the information into the sheets so far. There is more work to do as more 12in scale information comes to light. Which will keep me busy, I suppose.

    • This reply was modified 3 months, 2 weeks ago by Nick Ridgway.
    • This reply was modified 3 months, 2 weeks ago by Nick Ridgway.