OldSchoolScratchbuilder One step at a time. First I complete the demonstrator with straight only to see what is involved. I just got back from one industrial line (Hantsport gypsum) and one CN line (Windsor Junction) and have hundreds of close-up track photos along straights, curves, and turnouts. I also took plenty of measurements. Both lines are in my real layout area.
One step at a time. First I complete the demonstrator with straight only to see what is involved. I just got back from one industrial line (Hantsport gypsum) and one CN line (Windsor Junction) and have hundreds of close-up track photos along straights, curves, and turnouts. I also took plenty of measurements. Both lines are in my real layout area.
Rich
Alton Junction
I see that CN requires a maximum curvature of 9 degrees on industrial trackage. That would be 88" for an HO model. I look forward to how you handle that.
Ed
7j43k I do wonder at the need and wisdom of modeling a drainage slope, evidence of which cannot be detected in the final product. Ed
I do wonder at the need and wisdom of modeling a drainage slope, evidence of which cannot be detected in the final product.
I will know the slope is there and that's all that really matters. I will be able to say that my railbed meets CN Industrial track standards. This is not what CN does on their own lines as I can plainly see in today's photographs, but this is what their industrial customers must do. As for the Hantsport industrial lines I saw today, you cannot tell that there is a drainage slope either so I will be right on prototype.
As for the wisdom part, I will know how to do it for a model or for the real thing!
On the other hand, modeling the visual effect of the various "subs" is rarely done. People think that ballast "just sits on the ground". Drainage, in particular is rarely modeled.
I do hope that the track, once installed, is properly superelevated, as noted above. And also, that the curve radii are prototypical. THAT is very visually evident.
richhotrain...are you intending to apply these dimensions and maintain these slopes across the entire track portions of the layout? If so, this could be quite an undertaking.
I agree with Rich. Also, do the calculations take into account superelevation on curves or is that accomplished in a different part of the overall roadbed profile?
Wayne
I cannot recall the size of your intended layout or the number of linear feet of mainline track, but are you intending to apply these dimensions and maintain these slopes across the entire track portions of the layout? If so, this could be quite an undertaking.
The sub-ballast must be 24' wide and 12" deep. Since I only need a 1/2 cross-section drawing because of symmetry, the sub-ballast extends 12' from it's center. This, and the specified outside slope of the sub-ballast (2:1), are all I need to calculate the width of the top surface of the subgrade (foam) and the depth at the outer edges. Then I can modify the foam for the railbed before dealing with the sub-ballast.
The top surface of the subgrade is not horizontal on the ground. CN specifies that this surface must slope down from the center of the railbed by at least 40:1 (I am assuming for drainage). Because this is a mathematical inequality, the company's engineers must choose a slope then calculate how wide it needs to be. These calculations (simple algebra) require the CN specifications for the sub-ballast dimensions sitting on top of the subgrade as shown in my 1/2 cross-section.
Section 1: Subgrade
My demonstrator workstation is shown in this photo. It is a custom-made plywood platform with an area to rest tools (red), border wood (black) to contain everything, and two pieces of 3/4" EPS foam (white) stacked one on top of the other. The top one you can see is the subgrade.
I have placed an HO-scale Walthers GP9M Rail Link Locomotive on the subgrade so you have a better feel for the size of the work area.
This topic concerns the modelling of the railbed for my Cheverie Mountain Railroad layout. The prototype can be broken down into 4 parts: subgrade, sub-ballast, ballast, and interceptor ditch. The rails and ties are not part of this discussion.