Planning New Layout–Grading Elevated-Crossover Feasibility?

[TheHighwayStar]

So I'm in the planning stages of my first layout. I'll have an approx. 3x6 ft. area to work with.
Here's my first draft. (Gridlines are in 6" intervals. All track heights are displayed, and the curved section of the outer oval is elevated at 2.5" above the straight section of the inner oval.)



What I'm mainly concerned with is the circled area; I thought it would be interesting to have a elevated crossover with the double oval, and given my loco and rolling stock–a small tank engine and shorty cars–I'd need about 2.5" of clearance. But I welcome any and all opinions as whether this might be feasible or not for my rolling stock to climb, and if so, how long would the maximum realistic grade on each side be?
The general shape given is what I'm no doubt proceeding with as the basis, and I have no problem with going with a simple "X" crossover instead of the up-and-over. My goal is primarily to maximize running length.

[Maletrain]

I am estimating about 48" for the track lengths from the points where you specify zero elevation to the points where you specify 2.5" of elevation.  That makes the grade 100 x (2.5" / 48") = 5.2%.  That is a very steep grade.  Half of that would be a practical, but still steep grade.  3.5% is about the max that most people try to use, and that cuts down on train length quite a bit.

Another thing to consider is that the transition from level to sloped needs to not be sharp, or it will cause cars to uncouple and maybe derail on the curve.  You need an easement in the vertical direction to avoid that.

You have plenty of room to make the sloped sections longer.  And/or, you could make the lower track dip as well as the upper track rise, so that each section contributes about one-half of the elevation difference.

[TheHighwayStar]

Thank you for your quick response, Maletrain.

I am estimating about 48" for the track lengths from the points where you specify zero elevation to the points where you specify 2.5" of elevation.  That makes the grade 100 x (2.5" / 48") = 5.2%.  That is a very steep grade.  Half of that would be a practical, but still steep grade.  3.5% is about the max that most people try to use, and that cuts down on train length quite a bit.

That's what I suspected. I tweaked the plan a bit (click) so the sloped sections were ~67" long and managed to knock it down to a 3.7 percent grade. Still not ideal, of course. They also end up "coming together" each other again, so to speak, at the kitty-corner of the layout when viewed horizontally. Maybe that's not a big deal for others, but to me there's just something about it that seems unnatural.

Another thing to consider is that the transition from level to sloped needs to not be sharp, or it will cause cars to uncouple and maybe derail on the curve.  You need an easement in the vertical direction to avoid that.

I am aware of this as well. Though I'm not too concerned with derailment (like I mentioned, very small loco and stock), uncoupling occasionally happens even on a flat surface right now. An issue for another time or thread, perhaps.

[DaveGard]

It looks to me like you could lengthen your grades... spread them out... a bit more. If you can spread your grades to 9' (108"), bringing you to <2.5%.

Also, the NMRA overhead clearance for N-scale is ~1-5/8" (one of the first things you should do is get yourself an NMRA standards gauge). That should clear any N-scale loco and rolling stock. If you make your overpass a bridge (trestle or girder), you could probably get your railhead to railhead vertical distance down to 2-1/8" to 2-1/4" (1-5/8" plus the bridge structure), rather than the 2-1/2" you have in your plans.

With some planning, I THINK you should be able to get your grades down to max 2%. My twice around layout is basically the same as yours... but a little larger 9-1/2 ft  x 3-1/2 ft, and I was able to get my grades down to max 1.8%. I run steam, and my small locos, Bachmann 4-6-0 and 2-8-0, can each pull 10-14 40' freight cars around my layout. My Challenger (4-6-6-4) can pull 20-22 40' freights, and my FEF-3 (4-8-4) can pull more than 25 freights (that's all I have).

[TheHighwayStar]

It looks to me like you could lengthen your grades... spread them out... a bit more. If you can spread your grades to 9' (108"), bringing you to <2.5%.

9' is about 85% of the length of the inner oval, and about 70% of the outer oval. That would frankly look ridiculous.

Also, the NMRA overhead clearance for N-scale is ~1-5/8" (one of the first things you should do is get yourself an NMRA standards gauge). That should clear any N-scale loco and rolling stock. If you make your overpass a bridge (trestle or girder), you could probably get your railhead to railhead vertical distance down to 2-1/8" to 2-1/4" (1-5/8" plus the bridge structure), rather than the 2-1/2" you have in your plans.

With some planning, I THINK you should be able to get your grades down to max 2%. My twice around layout is basically the same as yours... but a little larger 9-1/2 ft  x 3-1/2 ft, and I was able to get my grades down to max 1.8%. I run steam, and my small locos, Bachmann 4-6-0 and 2-8-0, can each pull 10-14 40' freight cars around my layout. My Challenger (4-6-6-4) can pull 20-22 40' freights, and my FEF-3 (4-8-4) can pull more than 25 freights (that's all I have).

Perhaps I should have specified that I'll be running HOn30 stock, which naturally require higher clearances than traditional N. I also won't have consists anywhere close to that length, so that's not a concern. (and 9.5x3.5 ft. is nearly twice the square footage I'm working with, so I'm not surprised you were able to ease your grades that much.)

[Maletrain]

It seems like you are going to have to decide or yourself what grades make sense to you.  Running "a small tank engine" means that you would not expect to run long trains.  But, it also may mean that you won't have much power to pull on steep grades.  You will have to decide where the "sweet point" is for you between train length and level sections of your layout.

I will suggest again that you should consider making the lower level of the crossover dip down, rather than leave it flat.  It doesn't need to be a 50%-50% split between one oval and the other.

You also have not specified whether you intend to put any turnouts on this layout, or if it will be as simple as you have drawn it for this thread.  If you want to put turnouts somewhere, especially if they are going to provide a crossover between ovals, that will create many more constraints on track elevations.