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Question about "S" curves

1K views 3 replies 3 participants last post by  Mattsn 
#1 ·
Basically do they work? I'm thinking of using one that would be a 23 inch radius going straight into an 18 inch radius with a straight section of about 6 inches separating the two curves. Before committing to this I want to make sure that this isn't a potential derailing problem.
 
#3 ·
There are three principal factors that govern whether an S-curve of a certain geometry will work: the length of the curve as a whole (depends on radius of curves and any tangent between them), the length of the cars' wheelbase, and the mounting and type of couplers.

S curves look good, and needn't be avoided if they are designed for current rolling stock AND possible new longer additions, including locomotives. In a perfect world, you would have a tangent segment between the two curves, and in a perfect world that tangent would be at least as long as the length of the cars between couplers. In fact, you can get by with less, provided the couplers are NOT body-mounted. When they are part of the swiveling trucks, they do better. Unfortunately, such arrangements usually mean a lot more derailments when shoving strings of cars, such as when backing, and it's usually on tighter radius curves.

If you will ever run longer passenger cars, auto-racks, and such, and if you might run a longer steamer that is not articulated, and has a centipede-type tender, your curves had best be about four inches wider than the minimum listed for the engine, and you should have at least 6" of tangent between the curves. Or, simply ensure that the inboard ends of the curves are heavily eased if they can't be truly tangential. In any event, your proof of concept will always be determined by the rolling stock, itself, in a carefully constructed and faithful mock-up. When the rolling stock works, so does the geometry.
 
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