Articulated minimum radius??

I can't answer your specific question regarding min rad for the big articulated engines your considering. However I have developed definite opinions on club size layout engines. All my curves and switches are 072 or slightly larger. I had one big articulated and will never have another. Over the years I have limited my loco purchases to locos that require 054 and smaller even though I have 072 and larger. Why? Because I just can't stand that large ugly overhang. Its simply a matter of preference. Whats more pleasing to your eye the engine or a smaller overhang. Look at several you tube videos and you will soon develop a preference and answer your questions.  I have and just ordered the exception to my rule. The Burlington Route Zephyr. It requires 072. Its one of my all time favorite trains and it does not show the overhang like articulated due to it overall shape and construction.. It does however absolutelly require 072 track. 

The 2-6-6-2 is small enough to run on O54 and not look *too* silly doing it. I have one, and I have run it on O54 without problems.

My Rail King Y6b operates on 031 curves. 

thanks everyone I am looking to trade my Lionel scale Mohawk maybe for a class a, but I only could do 054 curves and I want all scale engines, don't know what to do so it is in my thoughts for a articulated steam engine And don't want it to look off to my settings

thx

The scale Class A does run through 054 without a hitch but inevitably looks a little "off" in doing so.

One of many problems with a larger steam engine, especially an articulated one is also overhang of the engine & tender. the reason I say this is because I have an MTH T-1 4-8-4 that will knock stuff over if I don't give enough clearence on the side of the track. You may need more clearence then you think, run the new engine around real slow at first and see if it will hit anything, also passing another steam engine may present problems too. You may have to open your curves to five and a half inches between center rails or larger on two tracks that parallel each other.

I have an 8 X 11 foot layout.

Lee Fritz

One of many problems with a larger steam engine, especially an articulated one is also overhang of the engine & tender. the reason I say this is because I have an MTH T-1 4-8-4 that will knock stuff over if I don't give enough clearence on the side of the track. You may need more clearence then you think, run the new engine around real slow at first and see if it will hit anything, also passing another steam engine may present problems too. You may have to open your curves to five and a half inches between center rails or larger on two tracks that parallel each other.

I have an 8 X 11 foot layout.

Lee Fritz

I have a K-Line articulated Allegheny. It runs through my Real Trax 031 turns and switches no problem.

 As others have stated they do swing very wide so you may have problems in your tunnels and towns unless you built your layout with articulated in mind.  Most people using 031 did so because of space limitations so the articulateds hit scenery and pretty much everything in there path.  Also while backing up the cab really swings wide. 

Overhang has never bothered me but I'm thinking as time goes by it just may.  Seems to be part of the evolution the longer your in the hobby.