Tracks Do Not Match/Connect As Shown in a Given Layout Plan

Sometimes, when you are trying to represent a layout, seen in a model trains related book or magazine, it just won’t fit in SCARM as described in the book’s picture or magazine’s article. Why is this happening? Is it possible the track plan to be wrong? Or SCARM does not drawing the tracks accurately? Probably none of these, but let’s see what to do if this is the case.

As an example, take a look at the following real layout and its track plan below:

This layout is called “Rhenshagen” (TT scale 1:120; 1600mm x 800mm) and is originating from an old “BTTB Gleisplane” book. After rebuilding in SCARM, using BTTB tracks lib, it looks like this:

As you can see, even with the BTTB tracks, which geometry is precise and straight­forward, there are two places where SCARM is unable to join the tracks.
The #1 is a small gap. However, there are 4 more straight tracks and a turnout on the left side of the opening, so in the real world, this gap can be compensated by little stretching of the tracks, because their joiners are about 5mm (0.2″) long each and will insensibly allow this without impair the quality of the railroad line.
The #2 is displacement between the curved track and turnout. Again, it is not a problem, because both tracks are close together, with correct directions and there are a lot of curved tracks above, which have enough natural flexibility to allow correct join to be obtained in the real world.

But what to do when the gaps and/or displacements are bigger than showed in the example? Well, you can rely on the following rules:

1. If there are enough track sections, which are able to compensate the gap or dis­place­ment with little stretching or natural flexibility, you will be able to make the join.

Regular straight and curved track pieces (even those with built-in roadbed) have some little flexibility, mostly at joining places. To check this, connect several long straights together and then try to bend them a little, holding both ends of the joined section – you will see that they are really bending, but not as much as real flex-track. However, this is not always valid for turnouts, because they are joined at least on 3 places and are more stable by design.

2. If the gap on a straight route is bigger than the length of a half joiner or if the directions of displaced tracks are visually not the same, you will probably not able to make the join without “forcing” the tracks.

You can experiment by disconnecting of the problematic part of the route in SCARM at some place and connect it to the point of the gap/displacement and see how it will look on the other side. You can also try to use different track pieces or flex-tracks instead to cope with a potential problem in the real world.

In general, most of the track plans that are published in books or magazines (especially old ones) are initially assembled with real tracks and then are transferred to paper drawings. Because of this, it is common that some of these plans will not able to be exactly reproduced in SCARM or any other CAD software, but this is not a problem and should not be a cause for concern. If you like the original plan, but want to change it, start with the parts, which you want to keep and continue with the changes. Try to avoid sectional tracks and use flex-tracks instead (if present in the given track system). Try to keep minimal recommended center-to-center track distance and always take into account placement of track side accessories and hidden parts (such as point motors, wiring, etc.).

A new setting for user-defined joining tolerances is available in SCARM starting from version 0.9.19. Update your installation if you have not done so and set the necessary tolerances in order to resolve potential joining issues in the track plan.

See also
How to disconnect and connect the tracks
How to work with flex-tracks

24 thoughts on “Tracks Do Not Match/Connect As Shown in a Given Layout Plan

  1. OK, so, um, how do I force the gap to close? Especially when using flex track I am never able to close the circle – even on a shape as simple as a circle! Seems like a programmers oversight not to have a force-connect option…

  2. Also – I notice that on occasion the arrows for the connectors are yellow – but nowhere in the directions does it tell me what yellow colored arrows at a joint mean…

  3. Hello Eric,

    Working with flex tracks can be little tricky sometimes and requires practice in order to obtain quick and accurate joins. However, creating a circle with flex-tracks should not be a problem. To make the final connection easier, try to zoom in with mouse wheel to the area with the connection arrows, which will give you more precise control while moving the flex-track end. The arrow will become green when the gap or overlap distance is about 1mm and direction angle is less than 1,5 degree. These dimensions are really small and not very convenient for work, but I will add a feature for the user to define bigger tolerances for connections in some of the next versions of SCARM. Also, I am planning a function for automatic connection between two track ends with flex-track, which should make things more easy. I will write dedicated article about working with flex tracks in the following days.

    Please, tell me, when do you see yellow arrows? Is this happening when you are working with flex-tracks or when you are moving and connecting other parts from the route?

  4. Milen, still love the track software. I have experienced what you described in this blog entry. The minor issues are workable as long as your track is on a flat surface. Probelms begin to happen if the track gap in on a planned incline. A force connection option is a good idea because then I can raise the incline smoothly from start to finish.

  5. Hello Bruce,
    You are right about gaps in sloped sections – I never thought about them. I will consider adding “force connect” or similar option in some of the next versions of SCARM :)

  6. Yellow connection arrows appear when there’s a secondary connection that also is within margins.
    Secondary = you already have the red/green arrows “highlighted” but there’s another connection too that is indicated by yellow arrows.
    For example, if you remove a piece in a completed track section and then put it back again, this can happen.
    So there’s nothing wrong, just an extra aid to show that more than one connection will be completed.
    The confusing part is, that often the yellow arrows does _not_ show up even if the piece fits in both ends…

  7. By the way, you said “The arrow will become green when the gap or overlap distance is about 1mm and direction angle is less than 1,5 degree.”

    Here’s a feature suggestion: Press a key (for example ‘S’) to “stretch” the higlighted piece/pieces within these margins. Hold down S and click’n'hold on the end of the highlighted section, and pull sideways as desired. This way you can make minor adjustments just like you would in real life, and possibly avoid a lot of little 8mm and 16mm pieces… (Märklin H0 M-track in my case.)

    By the way, after using the program for 3 days, I already have a rather large list of feature suggestions (and also one or two bug reports) in my head… could this be of interest, then just let me know and I’ll write them down… :)

  8. just a couple questions.
    Is there any easy way to do curves with an easement?
    Is it possable to select more than one flexitrack and flex them togeather

  9. Hi,
    Is there a possibility that the LeftTurnout (LT) and Right Turnout (RT) for the Bachmann Ez-Track Nickel Silver has one leg(the curved one) that is too long? I am trying to entera layout that is pretty well specified at in dualoval design. I am seeing a rather large mis-alignment when I try to finish off the run between points B and C. I think the curved leg is supposed to be the same length as the curved leg for just the 18/30 curved track and its definitely longer when I measure it with the tape measure.

    Thanks for your consideration in this.


  10. Just a follow-up on my last post. I used AnyRail to cross-check the issue I reported. It too suffers from the same misallignment issue as seen with SCARM. So I am guessing that the issue is with the published layout and not with SCARM, Just kinda frustrating to enter a design and find it has significant major problems. I don’t see the track flexing this much to account for this discrepancy

    BTW, I really prefer SCARM over AnyRail… much better mechanism to add track pieces to the layout..

  11. Hello John,

    Yes, there is always a possibility that some track piece or turnout to be entered with wrong dimensions and/or geometry in the library. This is because most of the libraries are created only by data from the manufacturer’s catalogs and cannot be verified by me with a real tracks. However, sometimes in the catalogs there are mistakes or missing information. I checked these turnouts and they looks really weird, as the curved branch is much longer than straight. But they are exactly copied from the Bachmann’s online catalog data. I also tried to search if there is a detachable curved part (sometimes this is not listed in the data), but all pictures that I found are like in the catalog. If possible, please post a link to the track plan – I will also try to reproduce it. Also, if you have these turnouts or if there is a shop near you when they can be seen, please let me know if there is a detachable curved track piece – there were already such case with other track system. Of course, the layout may be wrong too and it will not be the first – here is another example of non-reproduceable track plan: But most of the layouts that are published, especially in the railway modelling magazines, should be checked with real tracks and real locos and rolling stock and they should work in the reality.

  12. When I work with flex track then even with green and red arrows at the same time the connection is not made proper for some reason. After connecting you are left with gray arrows which says no connection. Normally not a real problem until you have the problem in a slope, track heights are now calculated wrongly. So a force option or an option to set it manually would be very welcome.

    I like the program, thank you for making it available.

  13. Hello Joop,

    This is happening when the two tracks have different heights. After making the connection in 2D editor, SCARM does not know which track to which height do you want to align, so you will need to alter one of the heights manually. When the two heights are equalized, the connection will be done automatically. Note that you will need to mark all the tracks in the slope in order to correct the heights and make smooth grade to the whole selection. After selecting, you need to alter the one height in one end at one step up and then one step back – this will recalculate and fix the heights in entire selection.

  14. Hello Milen,

    Thanks for your quick response. It happens also with all on same heights, ie absolute zero.

  15. Hi all, I am here after having discussed this topic in the TT Forum, SCARM section. As Milen has properly written, I can confirm that the chief cause of this bug are the incorrect i.e. rounded dimensions supplied by track manufacturers, and trusting in whichever software that uses those data to build track libraries can lead to wrong solutions when laying the actual track plan. I have been using for a long time Winrail 3 to 5 and now 3rdPlanIt, both with the possibility to change/create one’s own track libraries, and in both cases I had to dust my trigonometry know-how off to analyse the tracks I had to use for planning and set the real dimensions, all with at least eight decimals in order to minimize the above mentioned bug. I stress the concept: it’s NOT an issue that comes out when laying track, but it’s crucial for the proper sofware functioning; fixing such bugs with additional pieces of track, whatever tiny, in the software project very often leads to have kinky rail joints, because the actual track dimensions diverge from the official ones LESS than the correction so drawn in the software project.
    Milen, if you like I can send you some data about several HO libraries (Peco, Piko, Rocoline, Roco GEOline, NMRA among the others) in order to minimize the bug; in some case the need to add some “virtual” piece of track arises, but a couple lines of explanations in the library itself can easily lead the user to properly place these items in their projects (an example is the Rocoline R10 curved track: when used to compensate a turnout I use another piece of track composed by that curved track plus a tiny piece of straight one, grouped together and so labeled as the official one for inventory purposes, because Roco R10 has a vertical projection value LESS than the official track clearance used in that system).

  16. Hello Gian Paolo,

    Yes, you can send me the data at SCARM e-mail. It is always good to check and verify the params of the track systems from more sources :)

    My overall experience with the program is that some track systems are just more precise in geometry than others and this is clearly visible in a CAD software like SCARM. But even non-precise systems will do their job in the real world, because the tracks are designed and produced to be used on a real layouts with all the consequences of the real world.

    However, if somebody see a big mismatch where there shouldn’t be such, let me know – it is possible some dimension in the library to be wrong – and I will correct it for the next update.

  17. I’t sure seems there is an error with the Bachmann turnout as discussed above. But it’s not the curve, it’s the straight portion I think.

    I’ve overlaid the image from Scarm with the official Bachmann photo, and the Scarm is just a bit longer on the right hand side. You can see the vertical alignment marks on the right hand side extend past the roadbed. Image can be found here:

    I just ordered a set, so I don’t have any track in hand yet, it would be nice if someone could confirm.

  18. Hello Steve,

    This Bachmann turnout is exactly 9″ long and straight leg cannot be wrong in SCARM for sure – it is also 9″. May be the photo is taken at some angle and the overlapping is not 100% accurate. If you ordered these parts, let me know when you receive the order and I will guide you how to do accurate measurements to verify the data in SCARM, as there is a small possibility that curved leg may be really wrong.

  19. I guess it is optical then. Rats, I thought that was it.

    I don’t have any turnouts ordered yet, as I’m trying to decide what to order by using your program. This issue is throwing a wrench in things, as now I’m unsure if things are fitting in the program will they be off in real life, since there are these discrepancies in published layouts.

    Fantastic program, by the way. Really well done.

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