Well, having made a jig for curves, I had to try it out! So another 'play' day for me.Here is the first 4m outside radius curve.
Upside down in the jig and right way up...
It takes 8 for a circle!
And Laurie, I did bash the ends into some sort of curve...(The rollers miss about 100mm on the ends).
As I have made the curve jig with scope for only 0.5-1mm gauge widening, more than two axle wheel sets will struggle with the tightest radius. So I limit myself to dual axle bogies and loco to 4-4-4 wheel sets - and assuming side movement on the bogies too...
