thanks for your advice, I have extended it to 50″

Thanks again
Brian

Brian

I an finishing up an N scale layout and found that 30 inches is absolutely unworkable from only one side. My next layout will adhere to the 24 inch rule.

I trust that with all the explanation above on radius, you are well versed. Another consideration is the S curve. That is a pair of curves connected together like the letter S. If there is not a full straight length equal to your longest coach between the two opposing curves, you will have problems with derailment. This becomes a real gotcha when a curve connects with a switch that redirects the curve in the opposite direction.

Radius is not 1/2 the circumference; it is 1/2 of the diameter of a circle. The radius is the length of a line drawn from the center of a circle to its edge (circumference). The diameter is the length of a line drawn through the center of the circle to opposite edges of the circle.

Brian may I suggest you consider the following:

I am also 77 and just started in this hobby last year. You mentioned a disability. Most modern scale train setup’s require a large amount of wiring to connect power/controllers to the various items that will be in your setup. Will you be able to crawl around under a table to do these activities? I am in pretty good shape (for the shape I’m in) and still find it difficult to get this old body to contort itself under a table.

I would suggest that you first consider what is the maximum size you have available for a table top. Then select a model scale that will work within those limits. Your scale size is 4mm to the foot or 1 to 76.2. In other words, a 76.2 foot car will be scaled down to 1 foot in OO scale. I am working in HO scale which is 1 : 87. My max radius is 22″ or 44″ in diameter. Add about 4 more inches for clearances on the edges of the table and that put me at 48″, if I were using a continuous table top.

The curve radius is normally taken from the center of the track so a 2nd radius track is about 18″ radius to the outer rail 36″ Diameter and can just squeeze round in 38″. That might be challenging if you need an upstand to stop stock hitting the floor. Most H0 stock will run on 2nd radius. Most will go round on 1st Radius as long as it is laid absolutely perfectly.

However it comes down to rolling stock. If you run sub 60 foot cars, you can squeeze the track spacing down from the traditional 1st radius /2nd Radius by simply easing the 1st radius out to 16″
However if you run 75ft 00 cars and 4-6-2 locos this wont work.
I cut the sleeper base and ease set track out to larger radius, it works well. I find Flexi track is hopeless for long curves below 24″ radius , it kinks on the joints and wont stay in place

You can still use transition curves with 36 dia on 38 ” by swinging the tracks in towards the middle of the board

Since you specify OO gauge I assume you are a British modeler. Track radii in Europe are slightly different than in the U.S. Click on the link that JBH provided. It shows the geometry of Hornby track.

On the baseboard you have, you can fit a loop using 2nd radius curves. These have a radius of 438mm (about 17.25 inches). This creates a semi-circle of 34.5 inches diameter (on track centers,) leaving space on each side of your layout of about 1.25 inches. While this is a little too close to the edge, it is workable. You can protect your trains from falling off the table by attaching a facia to the sides of the baseboard. Raise the facia 1 – 2 inches above the table to “catch” the trains if they should fall off the track.

This arrangement will create a very long oval with enough space in the center for additional track and scenery. You can add turn-outs from the straight sides of the oval and create several spurs and a switching yard. You could even add a turntable to turn trains around if you so desire.

It seems to me that you have enough space available to keep your railroad hobby hopping along for quite a while.

Reference: The book from which these statistics were taken is “Design – Data Book for Civil Engineers” by Elwyn E. Seelye, Copyright 1945 USA, John Wiley & Sons, Inc, New York and Chapman and Hall, Ltd, London, 417 pages. Box cars of that year did not include modern styles. This book also lists the maximum curve for 70 mph track at 3 degrees with 10.125 inches of super-elevation. The maximum curve for 35 mph is 10 degrees with 8.875 inches of super-elevation. For mixed speed trackage super-elevation is to be reduced by 3 inches.