Realistic radius curves for a roundy-roundy?

[Sturminster_Newton]

Baseboard width is the limiting factor not the radius of the track.

 

The radius of the track is that which fits within the width of the baseboard.

 

R3 will fit on a 4' wide baseboard with about 50mm to spare.

 

Countless 8' x 4' beginner layouts started as a double loop of Hornby R3 and R2 nailed to an 8x4 sheet of something wooden.

 

Define the available space and that will set the baseboard dimension which in most cases will set out the maximum radius.

Edited April 11, 2020 by Sturminster_Newton

[DCB]

I have a chain as 22 yards, around 11" in OO scale.  The GWR Loco dimensions I have give 8 chains normal 7 chains slow for the large 4-6-0s and 47XX, down to 4.5 chains normal 4 chains slow for the only 0-6-0 I can find which is the 22XX and also the 45XX.    The 2-6-0s and large 2-6-2Ts are 6 chains normal 5 chains slow . so you are looking at 7ft plus radius in OO for a sharp curve in a loco depot etc.    Think I'll go back to bending 1st radius curves down to 12" radius

[B McG]

On the layout I'm planning currently I aimed for no less than 36" radius on mainlines and no less than 30" radius in shunting areas, hidden areas and fiddle yards.  I may rethink the latter based on Junctionmads experience.