Apologies in advance as this subject has probably been done to death in the past before I joined. What is the recommended safe minimum radius for Code 75 to enable ANY current Bachmann/Hornby/Heljan/etc stock to run? I am planning on 24 inch (hidden) curves but is this enough? Hornby seem to recommend their Radius 2 which is about 17.25 in. Many thanks in advance, Tom.
In my experience, all my modern Hornby, Bachmann and kitbuilt stock is able to negotiate 2nd radius curves. The problem with 2nd radius (about 17 inches) is that when trains negotiate it they tend to look odd. The bogies swing out and in some cases foul footsteps, drain pipes etc. It can also cause problems with close coupled coaches. I have managed to solve the fouling problems, but the trains still look odd. It doesn't really matter as all my 2nd radius curves are hidden. I have found that 3rd radius (about
19 inches) looks a lot better. Your 24 inch curves will look even better still.
Of course, the point is moot as your curves are hidden. However, using 2nd or 3rd radius curves could mean your hidden curves will take up less room on the baseboard, leaving you with more room for scenery.
24" radius is the minimum on my layout and it does cause one or two problems. There is a tendency for the front bogie or pony truck to catch the front footsteps (when fitted) on the Hornby Black 5 and Bachmann Crab.