I’m sure this has been asked before, but I didn’t find it while searching.
The plan calls for twin main lines running parallel. Minimum curve radius is 24" to allow for passenger cars. I’m thinking the minimum distance (center to center) between the 2 tracks should be 2" with 2 1/4" on the curves to prevent the cars from sideswiping each other. Will this give me a safe distance between the tracks??
Thanks,
Kent
Assuming HO Scale – Atlas Code 83 sectional track shows curve radius at: 15" then 18" then 22" then 24". This is a decent starting point to experiment for your specific requirements.
Assuming HO scale, those spacings should work. Parallel tangent tracks could be as close as 1-3/4". Check the NMRA standards online for their recommendations.
Dante
The OP wants to run ‘passenger’ cars - The NMRA spec is a minimum of 2.5" for full length passenger cars. Check out NMRA Standard S-8:
http://www.nmra.org/standards/sandrp/s-8.html
Even this may need a physical test run to verify. I have 2.5" for my 30"/32.5" curves.
Jim
As Jim said, the usual recommendation for full-length passenger cars and 89 foot humonguboxes is 2.5 inches on an inner 24 inch radius curve - the outer curve is 26.5 inch radius. This obviously blows the use of fixed radius sectional track, which come in two standard sizes, too tight (26 inch radius) and too loose (28? I don’t know. Never use the stuff.) Either the inner curve or the outer curve will have to be laid with flex track.
Another sticking point is the method used to spread the track radius on curves. I do it by using a longer spiral easement with an extra 1/2 inch offset for the inner curve - nice for prototype appearance but a real space hog on a typical layout. Another alternative is to simply leave the tracks 2.5 inches apart on tangents. Modern Class I construction has been that wide or wider (up to 21 feet) but the more usual standard for the transition era and before was between 14 and 15 feet - close to two full-size inches in HO.
Prototype track design can easily become a study unto itself.
Chuck (Modeling Central Japan in September, 1964)
Thanks to all who have responded. It sounds like I need 2.5 inches between tracks instead of 2.25, which is an easy adjustment.
It’s just a personal caution, but I always trial the set-up with the actual equipment and in place. I recently built a spiral tunnel (helix) that was to run inside a mountain. Understandably, I wanted the tracks to be as close to perfect as I could possibly make them. So, I laid out the parallel tracks on their respective 33" and 36" curves on the curved roadbed and then placed my most imposing steamer which I know has the worst overhang, and a representative heavyweight passenger car along side at a couple of the places where it looked tightest. When they were well clear of each other at those spots, I knew I could cover the helix with my mountain scenery and expect to only have to access the underside rarely.
Crandell
Perhaps not absolutely necessarily. If you think of making the entire curve with the same radius sectional track… no you can’t easily build good clearance double track curves at a more generous track spacing on nthe curve than on the straightaway.
But by the stratagem of the mathematically and mechanically impaired modeler, you might be able to make transitions from tangent to double track curve using a different wider radius section as the transition into the curve-- a kind of low-tech and imperfect substitute for a spiral easement. I am too lazy to work it out in detail, but this N scale track plan hints at how the idea works.
