I’m new to the hobby and have a question about sloped curves. Is it ok to have a grade on a curve (either ascending or descending) or am I asking for trouble? I don’t know if gauge matters, but I’m considering O27, On30 or HO. Thanks.
You can have a curve on a grade. I do.
tom
As long as you don’t make the slope too steep it shouldn’t be a problem.
I believe a 2% grade in O- gauge & Ho is really Quite adequit or sufficient & that calculates out to a rise of one quarter inch per foot. Less is even better, but it will take a longer run. Easements help on curves & may want to check on them. I always seem to go too high & end up buying dbl. units to pull any amount of cars up the grade or at least 2 motor units. Just my[2c][:)] ! Thanks, John
If you mean “is it okay” from the standpoint of will it work, the answer is probably “yes,” assuming the grade is not too steep. Both grades and curves are something most prototype roads do their best to avoid whenever possible, and the combination of the two of them is something they really try to avoid.
However, this is the model train world, and most model railroads have curves, and more than a few of them have grades. In many cases, it’s nearly impossible to avoid one or the other, or borh.
Anything you want to do on your layout is fine, of course, but try to keep both the curves and the grades as gentle as possible (meaning as gentle as your space will permit). Other than that, go for it! If it doesn’t work for you, you’ll soon find out for yourself, and then you can share your experience here.
[(-D] Thanks for the vote of confidence. I’m sure to have a few mishaps while I experiment with layouts.
You can certainly have a grade on a curve. Real Railroads do. However, you are dealing with slope plus friction; not a good combo if the grade is too steep and the curve too curvey. If at all possible, try to locate you grade on straights. But if you choose not to do so, you can always cut, climb and retrieve like the real railroaders did in places like Rollings Pass.
The ultimate form of curve and grade, THE HELIX. Works just fine, but like Allan said, not too sharp on the curves, and not too steep on the grades.
This one is 10’ diameter at 2% grade. I must say that it is very cool watching a 35’ intermodal train go around it. At that length, the engine is directly above or below the last car.
I have a curve that is elevated, what I suggest to do is see how many cars your
locomotive will pull around the curve at differant speeds and watch for derailments and lifting of wheelsets from the track. Also from my experiance do
not start on a curved hill section due to derailing.
I am using a Pennsylvania S-2 steam locomotive from Willliams and my only problem is starting on the curve or pulling too many quad hoppers.
Lee.
[#ditto]
The lifting of the wheels from the track is often refered to as “stringlining”. The real railroads have the same problem.
I’ve experimented with superelevation in the past, where you just shim the outer rail about a sixteenth of an inch. Also I had a tape where this guy had a helix with opposite superelevation. I may still have it & it was really fun to watch, cause the trains just flew through this thing! Real RR’s have used superelevation, & I haven’t seen it mentioned lately. Thanks, John
I have a grade question for you guys.
I’ve seen and heard max inclines specified around 2-4% “grade”. Is the “grade” the tangent? ie a 4% grade= 4units rise in 100 units run (appx 2.29 degrees) or 4 “gradians” as used in the military (which would work out to 3.6 degrees)?
I’m building a double-decker layout around my 16 month old boys room. The inclines will be fixed along the wall and constructed of 1x6 cedar planks. I dont want to build the thing only to find out that my unit will only run down the thing.
Any wisdom is certainly welcome. The room is 11.5 feet by 11 feet. I figure to lose about 10 or so inches due to the train not actually running the room extremety. I plan to have the layout with inclines along the 11.5 foot wall edge, double decker on 1 wall, and two wide on the other side. Should be cool if it works. I’m just trying to do a little up-front engineering to avoid long term cursing after construction…
Thanks,
Shane
It is rise over run. There is still ambiguity however, since it is not clear whether the run is the slant distance measured along the track or just the horizontal component of that. These two alternatives correspond to the sine and the tangent respectively of the angle that the track makes with the horizontal.
The AREMA (American Railway Engineering and Maintenance-of-Way Association) Manual for Railway Engineering does little to resolve the question. It defines “grade” as “The elevation difference between two points of the Absolute Vertical Space Curve a preselected distance apart”. But there is no clarification of how the “preselected distance” is measured, which is the crux of the problem.
Fortunately for railroading, the grades are so small that it doesn’t matter which definition you use, which is probably why the writers of the AREMA manual felt free to be so vague.
By the way, the use of the word “tangent” in a railroad context is problematical, since it generally is used to refer to a straight track (which is geometrically tangent to the curves at either end of it).
May I recommend, Shane, you incorporate the smallest, lowest, most gradual grade you can possibly use as you go 'round the room. I am astonished at the effect of a very small inadvertent grade on my layout on even traction-tire engines. Of course, with Magna-traction, you can get something more out of a train…
I have some sort of delicious teacher-ish pun about ‘grading on a curve’ bouncing around my brain - just out of reach…
Let me assure you that the term “grade” when used on any type of route survey, be it highway, railway, bike path, or golf cart path is the vertical rise divided by the horizontal run expressed in percent. (A typical plan and profile sheet of any project is based upon this concept. Plan and profile sheets in pdf format were in the past available for download from several highway departments.)
Furthermore, the horizontal alignment for a highway is normally based upon the arc definition for the curves and on a railroad a chord definition is used. The chord definition is sometimes called the “railroad definition”.
The curves that are found on the vertical alignment are parabolic. We commonly have tried in the past to make the grade, in percent, divisible by 4 on highways. Can anyone guess why? Yes, you guessed it! We put the grade stakes in at every 25’ making it easier to calculate the grade in the field.
To confuse the public, surveyors use terms such as P.O.T, P.T, P.C., P.I., P.O.C., I, Delta, R, D, to reference specific points on a route survey. It is great job security.
One of the very best references used by all surveyors and engineers is a book titled: ROUTE SURVEYING AND DESIGN, by Carl Meyer. SURVEYING by Harry Bochard and Francis Moffitt is also a good reference about surveying, earthwork, stadia, astronomy, etc. Both books also explain the mathematics of super elevation.
Some evidence of an incomplete consensus:
http://en.wikipedia.org/wiki/Grade_(geography)
The tractive effort to move a train varies as the sine of the angle, increasing to 100 percent for the improbable angle of 90 degrees. So the sine definition is better adapted to calculating drawbar forces. On the other hand, the tractive effort available from a locomotive varies as the cosine, which leads to ratio of the masses of the locomotive and train varying as the tangent.
Strictly speaking, the sine and tangent should be converted one to the other as appropriate for the calculation being made; but this is never done in practice because the small value of railroad grades makes the difference negligible. In my work, I have given the user the option of selecting either definition. But I am certain no one will ever be able to notice the difference.
Well, all that boils down to, send all questions to Buckeye and let him draw out the answer and email it back to you. WOW!!! He is a “first class” engineer. Now he is getting too smart in Surveying School. [;)] [wish I knew all of that [:)]]