On the real railways, have you noticed that curved trackwork sections appear to be banked at an angle? Take a look at the photo below. A4 Sir Nigel Gresley is seen navigating a curve in Newton Dale, on the N.Y.M.R. Notice how the locomotive is leaning slightly to the right? This is due to the banked trackwork on the curve. The banked track is known as a canted track or superelevated track.
The outer rail on the curve is gradually raised above the inner rail to provide a cant/superelevated track. The inner rail on the curved superelevated/canted track is known as the Gradient Rail. The inner rail serves as the reference rail when determining superelevation, it's typically kept at its original level where it enters the curve.
Photo: Iain Leach
What is the purpose of the canted track?
Canted trackwork on railways helps to assist, guide, and steer trains around curves. It also helps with the following:
- Helps keep the flanges on the train wheels from touching the rails.
- Reduces friction, wear, and rail squeal.
- Improves the load distribution across both rails.
- Reduces wear on rails and wheels.
- Reduces the effects of lateral forces while traveling around the curve.
- Improves passenger ride comfort when traveling through curved sections.
- Allows trains to run at higher speeds through curved sections
Canted trackwork on curves should have the sleepers set at closer spacings, while the ballast is generally of a higher depth to cope with the increased forces exerted by trains running around the curved section. Near or on canted curved sections, you may also see a lubrication device connected to the rails. The passing train activates the lubrication device and applies lubrication to the rail, which helps reduce wear and flange squeals.
Easing into the cant
The height of the cant rises gradually and gently via what is known as a transition curve. A transition curve eases the track from straight into the tightest radius of the curve and then back to a straight track again. The speed limit for the curve dictates the length and cant of the transition curve required.
What is the height of the cant?
The maximum height of the cant, which is the difference in elevation between the outer rail and the inner rail, is approximately 6 inches / 150 mm on standard track. On high-speed lines in Europe, the maximum cant reaches around 7 inches / 180 mm. However, on certain high-speed lines, slower-running freight trains may not be allowed.
Canted track on the ECML at Moat Hills - Photo: Iain Leach
How do I model the canted track?
Modelling canted curved trackwork is best done at the track laying and test running stage before installing scenery and ballasting, etc. Doing the canted track works best on a flexible track. Like the real thing, use gentle transition curves that ease from straight into the tightest radius of the curve, then back to straight again.
The height of the cant starts at a height of zero on the straight track. Then, as the curve tightens, gradually the height of the cant will rise to its maximum height at the curve center point. In model form, the height of the cant isn't very high. So, for a 6-inch (150mm) cant in real life, in model form, it is around 1.9mm high. For a 7-inch (180mm) cant in real life, in model form, the cant is around 2.3mm high.
To raise and pack the track up for superelevation/cant, use various thicknesses of cards, Plasticard. Ready-made shims can also be found by searching online. Cut the card, Plasticard into various lengths. This will give you more packing pieces to play around with when packing & setting up superelevation/cant.
In the image below, you can see some plastic card (Plasticard) strips cut to various lengths.
Image care of Wagons Mike from Community.railwaymodellers.com
Starting on the straight track section just before the curve. Slide the thinnest strip of card/Plasticard under the sleeper. Position it so that it is positioned under the outside rail. As you work around the curve, the next strip to be inserted under the outside rail is slightly thicker. Inserted this under the track at the end of the previous packing strip. Continue working your way around the curve, inserting thicker card/Plasticard strips until you reach the max height cant height. After passing the curve center point, where the thickest packing should be used, they start to reduce the height of the packing again. Remember, the maximum thickness should be between 1.9mm to 2.3mm.
As the curve starts to gradually ease out again to a more gentle radius, as mentioned above, the height of the packers used is reduced. Upon reaching the straight track, it will be the thinnest packing as the track transitions from superelevated to the flat section again.
Testing time
Next, conduct test running sessions with all of your trains. Check for any running issues such as derailments and clearances. If any issues arise or are found, adjust the position and height of the packers as necessary. It is recommended to take your time over several weeks to thoroughly test run, check, and make any necessary adjustments. This investment of time will result in trouble-free running. Once you are satisfied that everything is running smoothly & without any problems, the packers can be permanently fixed in position using glue. Afterward, the track can be ballasted and weathered as usual.
The photo below shows superelevated/canted trackwork on one of our modelling community member's layouts, by community member Wagons Mike. Notice that Mike has allowed enough clearance between the two running lines. This is so the rolling stock and locomotives do not collide & pass each other freely.
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Image care of Wagons Mike from Community.railwaymodellers.com
In conclusion...
Adding superelevation/cant to your curved trackwork will add that extra bit of realism to your layout. Your trains will certainly look impressive as they lean into curves at speed around the superelevation/canted bends. Take your time and don't rush. Yes, it will take time to set up and make the fine adjustments. But don't skimp on the testing phase; spending time on testing will save hours of frustration.
Happy modelling