This may have been asked before, but I couldn’t find it in any search. Is it a good idea to start / end a grade on a curve? The grade will be 2% and will start the incline on a 13 ¾” radius and end on a 12 ½” radius (this is N scale btw) If it makes a difference I will be running 6 axel locos and coal hoppers only on this part of the layout (usually). If I used a 3% grade I could start and end on a straight section, would this be the better way to go? I don’t want any trouble at all since the grade will end in a tunnel that I won’t have very easy access to. Thanks in advance for any help.
I have two on my layout that start/end on a curve, one in a tunnel. I made the top of the mountain with a lift off section. Also since it backed up against the facia, I made an access panel for emergencies. The one thing I did have problems with was that I didn’t ensure the track was level side-to-side (double track curve). I had derailements and found that the outside rail was slightly lower than the inside rail. Once I fixed this, things were fine. The funny part was that it only impacted 6 axel diesels. 4 axel locomotives were fine. So while it may not be the most desirable solution, it is doable.
I think the 2% grade starting on a curve is going to be more trouble-free than a steeper grade starting on a straightaway. Anything you can do to reduce the grade will be better.
Do provide access to the tunnel, though. Even if the grade never causes a problem, something else will. I’ve got 5 liftoffs on my small (5x12 foot) layout, because I run a complete loop of subways. A couple of them have never been off for emergencies, but there’s one where I’m always fixing derailments caused by not throwing the turnouts.
There are 2 considerations to keep in mind:
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the effect of a curve on a grade is to add to the grade. John Allen once had a formula for HO that basically arrived that you were adding about 1.3% or so in extra friction to the actual grade using a 24" radius curve. Nobody I know of had done any research to verify or correct his formula. I would guess that your radii in N would have a similar impact. However, it sounds like the entire train will not be on the curve at the same time, which would reduce its impact.
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your track has to be carefully laid in all 3 dimensions. As was pointed out, the track must be kept level from side to side while curving and changing grade.
The best info I have suggests that a vertical transition (same as a curve easement in the vertical dimension) of the length of your longest car times the final grade percentage is appropriate. In other words, the rate of change of grade should be limited to about 1% per longest car length. If you bend a plywood or spline subroadbed, you automatically get a reasonable vertical transition.
my thoughts, your choices
Fred W
It will be fine. Go for it.
Yes, it will be fine. Just note the above caution about the outer rail being lower than the inner (in fact a reverse superelevation)… this a sure thing for derailments…trust me, I learned the hard way…
Brian
Thanks everyone,
I will be using WS risers and incline sets for the grades. I’ll make sure the track is perfectly level all the way through the turn. The transition between level and inclined track shouldn’t be too much of a problem because my longest car length on this part of the layout will be about 3.8". I’ll just have a transition length of 1’ now that I have more of a choice of where the grade will go. Thanks again for the help.
As others have noted, if your trackwork is good, there should be no problem. Most of my grades are on curves, and most, both the grades and the curves, exceed normal train length. There are also several with multiple curves, either “S” bends or opposing horseshoe curves. The main effect of these combinations is that either train length needs to be limited or locomotive performance needs to be enhanced. My choice was the latter, although 2.5% grades on curves will tend to limit train length regardless of what’s doing the pulling.[:D]
This grade’s probably only about 1%, and it’s laid out on about 10’ of a fairly broad curve, so that 2-8-0 isn’t having any trouble with her 12 car train. However, after the next water stop, lies the subdivision’s 2.5% ruling grade, laid out on about 15’ of “S” bend. Even one more car would require a doubleheader.
Wayne
Doctorwayne, great pic… may I ask what you used for ground cover on the hillside…it looks MARVELOUS…
Brian
Thanks for the kind words, Brian. All of the ground cover is various colours of Woodland Scenics ground foam, mostly coarse, with a little fine stuff here and there. The ground cover on the nearside of the road is a bit of a/c filter, stretched out, then covered with ground foam. The trees on the opposite side of the road are made with twig armatures, covered in polyfibre, and then sprinkled with ground foam. The tree line along the horizon is made from a rough-cut strip of foam (cushion material, I think), painted dark grey/green, then covered with more ground foam. Immediately in front of that is a row of fairly coarse bits of lichen, again, covered with ground foam.
Here’s a view from the opposite direction, although there’s not too much background in the scene.[:)]
Wayne
All of my grades are on curves, ranging from 1.5 to 3.5%. I haven’t had a problem with them yet & my daughter loves to have trains at full throttle unless I say otherwise.
Gordon
Hey Doc,
Another gorgeous pic… I hate to get off topic here (so maybe you can just email me or put in a different thread…)… I love that bridge pier in the second pic. Very nice, and I expect, custom crafting… what did you make it out of? A homemade mold? Just wondering. Very very nice…
Brian
I agree, and apologize for straying from the original topic. I’ve posted a brief description, including pictures, in response to your question. Here’s a link:
Hope this helps.
Wayne