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Superelevations Techniques
Here’s a question from Online Train Club Member Tyrone:
“I am just beginning to lay track on my latest HO layout. I am using flextrack because I find it easy. My question is whether or not it is necessary for me to super-elevate my curves? If the answer is yes, then how should I do it? Also, would I use easements into my curves? This is my second layout and I never did any of the above with my previous layout, and didn’t have any major problems.”
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10 Responses to Superelevations Techniques
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I have never elevated curves and have had absolutely no problems navigating them. If it’s a prototype thing, that one thing, but prototype and I don’t get along real well together.
Superelevation usually looks better, but is not essential unless you’re running your trains at Shin Kansen speeds. If, by “easements”, you mean “transition curves”, again, your track will look better, but it’s not essential for normal model operating speeds. If you do decide to go in for superelevation, with or without transition curves, I read somewhere that you need to start it on the straight – perhaps surprisingly – so that the appropriate height has already been reached by the time the curve begins. There are at least a couple of ways to determine transition curves which I cannot explain here, partly because I would need to draw a series of diagrams and partly because they are so complicated I don’t understand them.
Transition curves allow the train to start ‘leaning’ into the curve BEFORE entering the curve. I agree that if you are not running “scale” speed bullet trains, transition curves are not needed and an unnecessary construction headache.
I would agree with Sheldon. Superelevation is only appropriate for fast passenger trains.
If you are keen on running a very high speed train (or just like super-realism), superelevate by a small amount, perhaps just enough to be visible.
If you have a good grasp of physics, you could calculate the centrifugal force at the scale speed for the curve radius, and be very precise in determining the track angle !
(Maybe someone on a Scalextric user forum could supply the formulas !-)
I used flex track to solve a few problems with finding fixed track that wouldn’t work. It’s great, just like a welded rail in real life but you can bank the turns slightly (very very slightly) if you like to race the small engines around. I made my radius curves too tight ,as it’s easy to do with flex track, and then the larger passenger cars won’t make it nor will the longer steam locomotives, so once you buck the radius and set it up for smaller trains that can run fast, you find out your new race track can’t run your longer trains so you go build another layout with slow nice curves because the race track isn’t cutting it. So it takes more “discipline of design” to use the flex track but it was eliminating some derailments (for amateurs) and I was at that level of HO railroader.
I use transition curves and to elevate the track I use white garden line and glue this in position before laying the tracks the string raises the outside of the curve about 1 to 2 mm. Even though I do not run fast trains and I always think they look more realistic and the cars seem to track better
Super elevation, which gives that “leaning into the curve” effect looks great and is not all that hard to do, but is not necessary at normal model railway speeds.
To super elevate H0 flex track I would use match sticks under the outside track for the whole of the curve, and half height for 1/4 of each end of the curve. After ballasting the track should look the part. There was an article a couple of years ago which give formulae for working out exact prototype to model elevations.
That article also explained transition curves and how to firstly work them out mathematically, and then to build them. See if you can find it because it is a bit complicated to work out properly. I think one of the British mags also had a method which entails drawing the “tangent” track line line in the base board, then finding the centre of the curve with the compasses set at the required “normal” radius. The circumference should fall short of the “tangent” by about 1/4″ or 5mm. One then freehand a line from the radius line to the tangent to create a “transition curve”.
Some chaps have used the natural tendency of a wood lath to form transition curves. To do this, draw your inner rail of your “tangent” (that’s the straight line approach to your curve). Place a supple piece of wooden lath along the tangent and bang in a line of nails to within 30mm of the intended curve. Bend the lath to a degree such that the main part of your curve is your minimum required radius. If you have a curve template (Card or hardboard circle cut to size), use it to “prove” you are not going under your minimum curve and your “transition” curve will be perfect..
Superelevation on a model pike isn’t necessary, and unless you’re planning to run trains through the curve always at the same speed, not even prototypical. Superelevation is matched to the anticipated speed through a curve, and varies with the sharpness of the curve.
Transition curves are nice. They take modeling to the next step, but again, they’re not absolutely necessary. There are some complicated calculations to plotting a transition curve, but it’s probably easier just to add some width and length to the layout and use a stiff but flexible guide. For example, in HO scale (1/87) a half circle curve will need about an extra inch in radius at each end of the curve (where it would straighten out without a transition) and about an extra foot in length before the track actually straightens out. To plot the curve, use a 4 foot or longer piece of wood, plastic, or metal that will bend to the curve’s tightest radius without cracking or breaking. Align one end of the guide with the straight track (at an inch wider than the curve and a foot beyond the curve). Secure the guide on the straight side so that it does not pivot at all on the point closest to the curve. Then gradually bend the guide until it meets the plotted curve about a foot to the other side of the start of the curve, and make it match the curve beyond that point. Do not push or pull the guide along its length; just move it from side to side and let it find its own length. The guide will define a smooth transition curve about two feet long. If using wood, it should be clear of knots so that it will bend evenly. If using metal it needs to be able to spring back to straight on its own after holding it to the curve, yet thick enough so that it doesn’t flex from the pencil tracing its edge.
If you want make super elevations use very thin strips of plastic under the outer edge of sleepers on a curve. For prototypical modeling the following is based on FRA regs:
Main lines: 3.6″ to 4″ with 6″ max height difference between tops of inner and outer rail;
@ 4”: HO scale = 0.045″ or 1.143 mm N = 0.025″ or 0.635 mm
Branch lines: 2″ to 3″. HO = 0.0225″ to 0.03375″ or 0.5715 mm to 0.85725 mm N : too small to be
noticeable.
I agree that super elevations are mostly a visual effect. On the other hand, easements give the effect making any curve act like a larger radius curve. On a model RR this is a very useful tool. This is especially true for bigger engines and longer cars. This is also useful for higher speeds. Now there are instructions for (easily) creating a template to make easements by just tracing the template on the layout. Do a search on the Internet for easements or creating easements.