Gradient vs track profile

[radionut44]

I have with much effort created a mostly round 2-1/2 turn 2 track helix on an HO route I am building. Each track has a spline point every 90 degrees. Classic surveyor shows all gradients to be less than 2.0, my goal was for 1.8. However, when I test drive it, the track profile shows gradient between 2.0 and 2.5%. The change of vertex height each 90 degrees is 2.21. Of course, the spline points are positioned with the mouse and the result is not exactly round and not precisely 90 degree spacing so I understand the gradients in surveyor vary, especially since the outside track is longer than the inside, but I have been driving the outside track and I assume that is what the track profile is showing. Please explain the difference on the profile vs gradients.

 

[TSwenson]

The gradient is the mathematic value of the slope, i.e. 2% (otherwise expressed as a 2m rise over a 100m run). The profile is what is actually "there" in virtual space, not the math value you entered. The program will automatically adjust the grade to ease/smooth any transitions (that's the first thing to check when you get wonky stuff like this). Additional points will refine the curves and allow better control of your geometry. I recommend a spline point about every 15 degrees or so, +/- 5 degrees as necessary.
The program doesn't use the exact gradient you set in surveyor, it gets close, and this can introduce errors. It says you want 2% between points A and D then it adds point B and C as the ends of the transitions, similar to the easements in curves, thus the grade from B to C will be more than 2%.
If you are working in HO scale then you have a fairly tight radius and that also makes possibilities for error. Triple check any plans you are working from and measure carefully, both on the plans and in surveyor. I have run into errors in published plans by well known designers.
Where it is double tracked I recommend laying out the interior track with fixed points (yellow circles in Surveyor 1.0) and use the "remove gradient" tool on the outside points (they should be white). The easy way is to then use the "smooth spline height" tool on the interior track and let the outside rest on the terrain that was generated. Otherwise you have to adjust each outside spline point to correspond with its adjacent interior one with the "get height" and Use Height" tools.
Hope this helps...

 

[radionut44]

Well, I looked at the data sheet for the helix kit used on the real HO layout. The 1.8% on their sheet is for entry/exit at the same point in rotation, whole turns. With a 31.5 curve radius, the 1.8 calculation is correct. But because the builder only used 2.5 turns, both the rise/fall height and the total circumference numbers would be different and the correct calculation would be the 2% that Trainz was showing on the track profile. The helix portion of the Trainz route just simulates the transition from one layout level to another, and I’m not going to fret over not having a perfectly round curve and perfectly aligned layers. It will be unadorned as a modeler treats a hidden staging area. The “track” spline is a steel bridge and because the layers are not neatly stacked ( at least for now) I don’t plan to add any support columns just for appearance. I appreciate your explanation that the vertex heights I enter get some manipulation and the profile tells it like it really is. Thank you very much for your help!

 

[TSwenson]

Thank you very much for your help!

No problem, that's part of why we look at stuff on the forums...

Unfortunately Trainz doesn't handle double level layouts very well. The best workaround I've seen is offsetting the upper level in some manner, usually by adjusting the helix, and usually it is only represented as a single partial turn. I suppose alternatively one could use a portal asset... but I imagine that would be at least a fair bit of work.
Normally a double deck layout is used for space reasons, of which we really aren't constrained with in Trainz, although I do believe there is a practical upper limit of a route in the ability of a creator to put track and scenery on baseboards (100 miles comes out to be just under 224 baseboards long).

 

[JCitron]

I suppose alternatively one could use a portal asset...

This wouldn't be as bad as you think. Using the iPortal, trains can be sent from one route to another either over the internet or within the local computer. The PC still has to be connected to the Trainz servers for this to work, though.

Using the iPortal, the trains enter the portal just as they do with regular portals. Once the trains have disappeared, the user opens up the second route in Driver. Any trains that have been sent to the iPortal will begin to spit out already assigned to drivers and still is carrying any commodities. The driver commands, however will need to be entered. This is where the Schedule Library and its related Copy Commands from... Driver command in handy.

I use iPortals all the time to send my trains from my old very large route to other routes such as Approach Medium's Pennsylvania and Berwind or his Dry Brook and Esopus.

 

[OddRails]

I've also used a pair of standard Portals to allow a train to change elevation where it wouldn't be convenient to place track. Often if I've merged routes without building a transition section of baseboards to handle the change in elevation.
(I'm usually not online, so I haven't paid much attention to iPortals.)