So my question is: was the standard track radius pretty much all 20”?
If you are talking about centerline radius the answer is about 19.125”. There has been much debate about this topic over the years and it never seems to get settled. A simple drawing or a bit of geometry will give you the answer. I hope to insert a .pdf file that should explain the answer.
The SHS centerline was 18.55” as stated in S-Trains #46632 January 11, 2008. You can see what happens with this radius in the first illustration, it results in a parallel track center to center measurement of 4.97”. Close to 5”, but that’s not what original AM Flyer used.
The American Models turnout is a #4 that has a diverging angle of about 14.30448°. It is cataloged as 27” radius, but one look at the picture and you can see it is not. -- http://www.americanmodels.com/misc/track.html -- The 27” radius is not a continuous curve like you are used to with toy train switches. You might what to Goggle NMRA Turnout Standards for more info.
Lionel S FasTrack is 20" radius. Turnouts are not available yet but will match the 20" radius curve.
I don’t know what it is cataloged as but a quick measure of a sample sent to me by Lionel yields a centerline radius of about 18.879”.
It is interesting to note the differences between what a manufacturer catalogs and what the field measurements show. One recent example is the old SHS #155 rail long rumored to be code 125. It actually measures out between .1375” to .138”, I call it .138".
Tom Stoltz
in Maine
