andrew jukes wrote:Where it all gets interesting is when you start building curved crossings and want to keep to ones chosen rules for gauge widening. The attached photo shows a diamond with both roads at 1300mm radius. It is behind the scenes so not made to look good but has to perform reliably as it is where the main routing options for the layout take place. Digest 1.2 is very clear on the approach to use - "Gauge widening should not be applied to any sections of pointwork where CG, CF or BC dimensions are specified." - so in applying gauge widening you’re really on your own. What I’ve done is gauge at +0.2mm, set the check rails at 18.25mm and provide generous crossing
flangeways. Condition 4 of Digest 1.2 is definitely violated but this merely means a slightly bumpy ride. The crossing has worked really well with only one derailment in the early days because a check rail was not set quite far enough from the crossing nose. That said, I haven’t run decently long trains of 4-wheeled wagons over it, which would be a proper test.
Andrew further to my previous questions above, on the crossing nearest the camera in the photo you attached to this post I can see the crossing
flangeways are wider than the check flangeway
(though I can't tell if they are wider than P4 0.68) so how did you establish what width they should be? Re the Digest 1.2 surely all of your points with GW applied violate the condition you quote?
Looking at the diamond all the flangeways look
more equal so does the same apply there but to a different degree? On another post you talk about
more complex formations needing greater care. Does this diamond come into that category? At 17.82 BB does your S4 lite (as I put it) standard meet the criteria to solve the issue on K crossings which Ray Hammond showed and which I have never quite understood without a drawing although a recent S4/P4 thread came close. A train of coaches consists of several bogies that are similar to a 4 wheel wagon so why is a train of wagons a better test? - the instability I take it. Lastly your description of BB gauge use implies to
me your standard is 17.82 - 87 rather than bang on 17.82, is that right, so a practical widening of the prototype tolerance window in the narrower direction ?
Apologies to you and any reader for my tiresome questions, and Easter Greetings.