QUOTE (wolverton bloomer @ 22 Aug 2008, 09:01)
<{POST_SNAPBACK}>My minimum radius will be 370mm (= Hornby 1st radius) within the fiddle yards and 505mm (= Hornby 3rd radius) on the mainline.
Hornby state track centres of 67mm but this doesnt look right to my eye.
Steve,
Glad to hear you are at the design stage. First thought for you to consider: the large majority of the better models are now specified for 2nd radius minimum. With a little careful adjustment many can be got to run on 1st radius, but no guarantees.
Set track centres spacing is necessarily much overscale to permit clearance between the longest items of stock on drastically underscale concentric curves. The standard minimum distance between centres in UK double track is 11 feet, scale 44mm. Peco's Streamline points wil give roughly 50mm centres which looks a lot better, and will allow vehicles the length of BR mk1 coaches to just pass on truly concentric curves of 22" and 24" radius. Longer vehicles yet will demand a greater minimum curve radius.
The use of 24" radius points as minimum, and preferably live frog, will not take up much more space than using set track points; but the gain in running reliability is like day from night.
If it is physically possible in the space available to you, ease all curves to greater than set track radii. This and the use of larger radius points than set track may place some limitations on the track formation that can be accomodated when compared to using set track radii. But it is a compromise worth accepting for the gains in both appearance and running reliability.