Hello, Robert. Thanks for your thoughts and the most useful link to the Templot site. Now in my autumnal years, and with a couple of ‘hair shirt’ layouts in other scales (one still under construction), I’m looking to have a bit more enjoyment without tears from the hobby. I have been tempted by the Grainge and Hodder baseboards , the curved ones usefully forming a two metre diameter circle, so allowing something like 3’2″ radius curves at the outer edge; getting tight in P4 but acceptable in EM. I have a ‘push-along’ Hornby T9 converted to P4 and it will take a 3′ curve at 19.1mm gauge on a small test piece I’ve thrown together, and I’ve also tried a P4 0-6-0 with 15′ 6″ wheelbase which seemed fine. However, we are at the cutting edge with these combinations.
I have a bizarre interest in eight-coupled machines and large Edwardian/WW1 four-coupled (denied me in my other scales), and fancy watching them go round a circuit. I don’t feel it would be easy to get satisfactory running at those radii in P4, though doubtless someone has done it and I’m not denying it is possible. However, I don’t want to be shooting for the moon any more. The Martin Wynne standards of 18mm for straights and turnouts, easing to 18.2mm on curves with 16.7mm B-to-B and .8mm crossing gap therefore seem a great compromise, as long as RTR wheels are not used. My experience with the T9 and other large-wheeled locos has lead me to believe that metal-centred wheels are a safer bet to minimise wobble and thus retain clearances in splashers on low footplates; fortunately, whilst completely un-trained formally I can use my small lathes for trueing or re-profiling.
Would be grateful to hear any other thoughts on this, and also whether true 18mm track gauges are available anywhere.