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Planning Super Elevated Curves
Ross M sent in this question for readers:
“I am planning an HO layout with super elevated curves of 28 inches to 30 inches in radius I think. My question is how much higher would the outer rail be than the inner rail?”
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8 Responses to Planning Super Elevated Curves
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Super elevation is used in railroad construction and motor vehicle road construction. It assists in negotiating a curve and maintaining speed through the curve. Have a look at the article by Michael Highsmith ” Super elevation made easy” http://www.rgwrail.com/SuperElev.pdf
It’s funny you should ask this as only today I stumbled on a video about this very topic and the guy said it was .040 inches. He was using virtually the same set up.
I would say to you about elevated curves is that most proto typical layouts are really much the same. I like to practice my curves with different rail cars, my layout is unique because my main line curves are more elevated than other areas, this is because at faster speeds this method is more realistic. Here in Houston Tx. There are areas that I have seen this to be true, there is one spot that amazes me is over at Hwy 90 @ southmain where the rail cars lean at least a 45 degree angle when traveling at low speeds. I love to see the auto racks travel through their, it is an awesome site when they are moving at 50 miles per hour or slitely less. Try a different idea as I did, it will be cool to watch your rolling stock glide through the leaning curve without derailing off the main line of course.
Do you mean 4.5°? 45° cant would require a superelevation of 28.25″. As far as I am aware, superelevation is never more than a few inches.
This is for Ross M,
In my openion, 4 percent gradient should be sufficient for elevated track. Nessecary support should be given under the elevation in order to keep the balance and smooth performance.Happy rail modelling, Cheers
Gopal Daga, India
Forget trying to scale down real railroads super-elevation figures to HO scale unless you have a lot of model real estate. A 30 inch radius curve is what the real roads would call about a 25 degree curve. The tables for super-elevation stop at 15 degrees, which translates to about a 53 inch radius curve in HO scale. The amount of super-elevation on the real roads depends on the design speed of traffic for the curve. The sharpest curve designed for 70mph would be a 3 degree curve (264 inches radius in HO scale) would have a super-elevation of 10.125 inches (.11638 inches in HO); but a 3 degree curve designed for 40mph would have a super-elevation of only 3.25 inches (.03736 inches in HO). A 15 degree curve would have a top design speed of 30mph and a super-elevation of 9.25 inches. For routes with mixed speed traffic, the super-elevation was reduced by 3 inches from the table figures. In the super-elevation table in my book (Data Book for Civil Engineers – Design, 1945) the highest super-elevation on the chart is 10.125 inches. (3 degree curve designed for 70 mph – a 1 degree curve designed for 70 mph would have a super-elevation of 3.375 inches.)
So where does that leave the modeler? All you can do is experiment and discover what works best for your rolling stock and average speeds. You probably want enough super-elevation to see that it’s there, but not so much that you help the cars near the head of the train fall over to the inside of the curve.
It is interesting to note that in real-life railroading, super elevating a curve begins at the point of curve where the curve elevation spirals up to the maximum curve elevation (2, 3, 4, 5″, etc.) based on the degree of curve and the desired speed the train is designed to travel around the curve. The elevation spirals down before the end of curve where both rails become level again. The length of the spiral is based on the maximum elevation the curve is engineered for so the length of the spiral varies. The mathematics for determining the spiral, curve, maximum elevation is quite involved. On a model railroad, simply ramp-up to the desired elevation, but don’t forget to ramp back down before the end of the curve. One last thought, elevation is always added the the outside rail, not the inside and I wouldn’t over-due the amount of super-elevation provided- your train will end up on the ground, which is something that can happen in real-life.
I was under the impression that the superelevation started before the transition curve (I don’t know how far before) and reached its maximum where the minimum radius occurs. That is certainly what I have seen recommended in at least 1 book about railway modelling.