What radius for super-elevation?

Discussion in 'Track Planning' started by Hammerli, Dec 15, 2005.

  1. Hammerli

    Hammerli Member

    I'm still working on track layouts, and some of them use rather sweeping curves, like in the 48" radius range. At what radius does superelevation look "right"? I assume at smaller radii, the CG shifts too far towards the center and could cause problems. Would super-elevation still look proportional on say a 30" to 36"R curve?

    Also if two tracks are parallel to one another, would both inner rails be at the same elevation, or would the smaller radius line be at a lower height?
  2. sumpter250

    sumpter250 multiscale modelbuilder

    Superelevation. As a visual, can be impressive, but used with modern excess height cars, double stacks, auto racks, and some passenger equipment can lead to trains collapsing into the curve. Models are a little more top heavy than prototype cars.
    Most of my experiences with superelevation have been less than positive, so I would have a tendancy to recommend not using superelevation, if you are running modern equipment. With steam era, and transition era, set up the desired "tilt", and test run before making the installation permanent.
    Typically, the larger the radius of curve, the less superelevation used, prototypically, the difference in rail heights would scale between .010" and less. It is usually exagerated to get the visual effect.
  3. pgandw

    pgandw Active Member

    Super elevation looks effective at all radii. Remember, for models it is there for looks only, so most folks who use it limit it to about 3-4 scale inches. The prototype goes up to about 6 inches on high speed curves. There can be problems with steam locomotives (or other long rigid wheel base rolling stock) on small radius (18-22 inches in HO) curves. Middle or blind drivers might not be contacting the rail in certain cases, depending on springing, equalization, or lack thereof.

    I have heard of negative super elevation in N scale on helixes to prevent string lining the cars in a long train.

    I have only seen double track super elevation on models. In those cases, the two tracks were not in the same conical plane. The inner track was raised to where the 2 inner rails were at the same height. Don't know what the prototype does.
  4. zedob

    zedob Member

  5. 60103

    60103 Pooh Bah

    Superelevation is a function of speed, curvature and how much discomfort your passengers can stand. Also, 48" radius scales out to about 350 feet, when prototype locos just squeaked around 1000' curves at a crawl, so there is really no prototype for this superelevation. Anything you do will look nice/be wrong/improve running/help derail your cars.
    The difference in superelevation between inner and outer curves would probably be unmeasurable on the prototype. Superelevation should be built up over a transition curve, with the outer rail rising as the curve gets sharper.
    Of course, superelevation is not always pleasant. Stopping on a banked curve gives a very queasy feeling, especially if you're on a bridge or embankment and you think you're about to fall off.

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