Does anyone have a ‘rule of thumb’ for super elvating track?
Should be XX degrees of SE on a main line…
Should be XX degrees of SE @ 60 mph…
Should be XX degrees of SE on a YY degree turn…
Thanks for you help!!!
[#welcome] to the forum. My goodness, what a good but techinical question. Is this for modeling purposes or general railroading?
Superelevation really only applies to curves. Straight track is never superelevated, except perhaps a short transition leading into a curve. It doesn’t take much to get the job done. In modeling the placement of a series of ties along the outside of the curve, should get the job done. It should be noticable, but not severe. Remember railroads are not rollercoasters.[swg]
I’ve got a humongous book at home that has your answer. On a model railroad, I’d go for appearance and operational smoothness. And, while you’re at it, don’t forget easements into curves! Just as important.
You never hear about this but roads also are superelevated. How many of these do you see on a model RR?
Also, straightaways are superelevated. Let me explain. The rails are slightly facing inboard (boards each other), tilted via the tie-plates. Of course this is a different kind of superelevation than the one on curves.
In NS line from Manassas to Front Royal (the B-line), I’ve seen track in the mountains that resembles a roller coaster to a certain degree.
The superelevation is the square of the velocity divided by the acceleration of gravity and by the radius. If we ran toy trains at realistic speeds with realistic radii, they would need only 1/48 the superelevation of the prototype.
The inward tilt of the rails is called “cant”. As the wheels wear from their new conical profile to the cylindrical profile at which they are condemned, the cant distributes the wear between the inside and outside edges of the rail.
You likely wouldn’t need superelevation on industrial spurs but it sure looks good on the mainline and at the hi rate of speed some operate there trains, it must do some good. I don’t know if it increases the likelihood of stringlining, however.
Just for fun, I calculated the superelevation for a train at 79 miles per hour on a prototype curve as sharp as O27 (50-foot radius). The track would be tilted 83 degrees from the horizontal.
This question is not new, but there are some interesting things that happen when one is using a model of the prototype. First our models are not directly proportional in all aspects. Even the finest models that I have seen are not at a perfect scale weight. Some are close, but most are not.
Therefore when one super elevates a track, the cars due to their lightweight will tend to stringline and derail. This is especially true if a up hill grade is also involved with the curve. The super elevation promotes the problem.
In fact I once met a modeler in HO that used reverse super elevation on his layout where he had built a spiral to the next level. His theory was the reverse super made the models less prone to derailment by stringlining.
So go ahead and superelevate the track, but it should be for appearences and not operational performance. It looks real cool seeing the big steamers tilt around those curves at high speeds. [:)]
My understanding of superelevation is that it is very much dependent upon the speed of the trains using that track. A fast train using superelevated track can do OK; if there is a slow train on the same track I understand there is the risk of “rolling” the rails. I have read that on the Horseshoe Curve west of Altoona that the amount of superelevation has been decreased as the proportion of (faster) passenger trains to (slower) freight trains has decreased over the years.
Gee Bob, I wish I had known that when I was 8.
The back stretch of my layout had a long straight section that had a 110 trestle set under it. At the bottom of the hill, an 027 curve, and the edge of the table. The milk car got away, as the train was nearing the top. When it reached the bottom, it continued straight over the edge.
I stood there helplessly watching my favorite car plummet to the concrete below, landing with a loud crash. To this day, the doors on the back side are broken as a result of that accident. Minor damage all things considered.
If only I had known about superelevation.[swg]
On the prototype, the superelevation has to be approached gradually which is one reason for easements. If you applied the proper cant to toy train curves, there would be a sudden jump of a quarter inch between the straight and curved sections.
I was watching the Toronto subway last week, and noticed that the cars coming out of a curve seemed to straighten up in about one car length.
Nothing like answering your own question!!!
For the 1:1 railroads, a 6 inch difference in the individual rail height will allow for 95 mph operation on a 1 degree curve and 45 mph on a 5 degree curve according to John H. Armstrong in his book ‘The Railroad, What It Is, What It Does’
How that relates to my S scale, I haven’t done the math butttt
Thanks everyone for your inputs!!!
Gill, here is a complete method for computing the difference in rail heights in inches from the curvature in degrees and the speed in miles per hour:
Take the sine of half the curvature.
Multiply by the square of the velocity in miles per hour.
Divide 559315 by the square of the product.
Add 1.
Divide 56.5 by the square-root of the sum.
For your example of 1 degree and 95 miles per hour, this gives 5.917 inches. For 5 degrees and 45 miles per hour, 6.627 inches.
Nope, don’t do it. My JEP postwar 054 curves are factory superelevated and everything derails like a mad. The elevation is only a few degrees, but it is an absolute no-go area with the 0 3rail stuff. Every part had to be filled out 'till level.
The wheels are tilted and on the beginning of the elevation everything under power (driven wheels of the locomotive) jumps out of the track.
The elevation is about 1 to 1.5 degrees, made to keep the prewar lifesteamers on the track when running.
I would strongly advise not to do, or test it thoroughly first before you build it in the layout.