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Why don't track plans include radius info

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Why don't track plans include radius info
Posted by rodsaw on Thursday, May 28, 2020 6:54 PM

I recently gotten back into the hobby after many years away from it and I have been looking at track plans to use. I am wondering why the curve radius and turnout size is not marked on the plans. If there is a grade, the height is included, but that is about the only meansurement. There is generally a square grid (1" = 1 ft or similiar) that can be used to estimate it.  I am not looking for sectional track numbering since flex track is probably used more often than sectional, and sectional will vary by manufacturer.  But...why not include the radius and turnout size?

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Posted by cuyama on Friday, May 29, 2020 11:00 AM

Hello and welcome to the forum. Your first several posts are moderated, so it may take a while for them to appear, especially over the weekend. But stick with it and that passes soon.

Many plans published in Model Railroader magazine and elsewhere are rendered with drawing tools like Adobe Illustrator, not CAD programs. So their accuracy depends on the input from the author, which can vary. Still, they are usually close enough to scale up using the grid. On the occasions when I have needed to figure out a radius on a published plan, a plastic circle template can often help “eyeball” the dimension. And then it can be converted using the printed scale of the drawing.

Especially for plans with dense trackage, including all of the curve radii would clutter the drawing. For a lot of published plans, many (most?) of the curves are at the minimum published radius, so that’s a good place to start in estimating. And most folks will need to modify a published plan for their space and interests anyway.

It makes for a more-complicated drawing, but I use a color code for my layout design clients to provide this information as one view (along with "pretty" versions). In the example below from an HO 5X9 layout, one can see that this probably would be too cluttered for most readers, who are looking for inspiration, not blueprints. And not as pleasing to the eye as the beautifully drawn MR plans.

What published plans are you considering? Model Railroader’s project plans (that they actually build) include this information, but that’s a small number of the overall published plans.

Good luck with your layout.


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Posted by RR_Mel on Friday, May 29, 2020 11:33 AM

I also find the missing dimensions annoying.  If I want to get serious I import the picture (normally a JEPG or MPEG) to my CAD then set the scale.  From that point on it’s easy to find the measurements.


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Posted by Paul3 on Friday, May 29, 2020 11:50 AM

Radius & turnout size would be tough to show as there are so many curves& turnouts on layout plans.  They do give a minimum radius & turnout size in the table, but that's it.

Sometimes, layout owners don't have plans to begin with; sometimes the owner just guesses.  Sometimes the radius is actually variable along it's length.  Layout plans in the magazines are more like artistic interpretations rather than true scale plans.  I like to compare the photos in the article to the track plan, and I've found many errors over the years.  Nothing to get excited about, but errors of missing track, switches in wrong places, etc.  If you tried to reconstruct some of these layout plans into a layout design program like 3rdPlanIt, you probably couldn't get it to work without some serious compromises.

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Posted by rrinker on Friday, May 29, 2020 12:13 PM

 One with turnouts handlaid in place, good luck reproducing - but if commercial turnouts were used and they give a minimum - many plans, in the info box they will list minimum mainline turnout and minimum branch/yard turnout, along with the two minimum curve radii - then you have something to work from. Unless they drawing adds a bunch of extra track that doesn;t exist, you know it all fits in the space, because it physically exists. What compromises there are, that's what you find out when reproducing it with exact dimensions. Oh yeah, it says minimum mainline radius is 30" , except over in that corner where it had to go down to 28" to get around the water heater. Just one small spot, so it sounds better to say the minimum is 30". Or if it says all mainline turnouts are #8 - oh yeah, except for that one over there, to get the industry in, a #6 was used in that one spot.

 One seldom sees the completely impossible actually make it to publication these days. I have I think a 1957 issue of RMC, in the Layout Doctor column a plan is presented along the lines of something just doodled with no care for radius or turnout size. Supposedly, IIRC, a compilation of things seen on multiple plans, not one that was received like that. The article calls out like 12 places with really questionable track and explains what's wrong and how to avoid that, even when making quick sketches. I poured over that article many times over from the time I discovered that an another equally old issue buried on a bookshelf when I was a kid.



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Posted by carl425 on Friday, May 29, 2020 1:05 PM

Some of the previous posts touched on the answer but didn't quite spell it out.  The only reason that radius and turnout info would be documented is so the reader could take the plan and build it.  That's not what these plans are for.  These are "here's what I did" plans, not "here's what you should do" plans.  They are only there to support the article about the layout.  They are not meant to be plans for you to follow to build your own layout.  Those type plans cost way more than the price of a magazine.  Send an email to one of the planning services and get an estimate on what a comprehensive plan you can build from costs.  Then you'll understand.

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Posted by dknelson on Friday, May 29, 2020 1:06 PM

My hunch is that going from a CAD or CADRail based design to layout contruction is one thing but that going from a finished layout to the reverse is quite another.  Particularly if the layout is, in common with most layouts, to a certain extent improvised/freehand as you go along.  For example I created templates for my primary double track curves which are either 42" and 40" radius, or 40" and 38" radius.  I use those templates to draw the lines which I then follow with subroadbed and cork roadbed.  But where in the "air" near my benchwork is the pinpoint of the "R" so to speak - where is the radius to be measured from, as you would need in a drawing of the sort the OP seeks?  I have no idea where to say it is.  

I also have easement curves which I created using a mechanical (versus math) method -- the subroadbed has kerf cuts and I bend it to create the smooth and gentle start of each curve.  So again I have no idea how I would convey that -- where exactly does the fixed radius start --- in a drawing of the precision that is being asked for.

And having visited/operated on layouts that have been featured in Kalmbach publications including MR and Great Model Railroads, I can tell you that the artists (who I assume rarely if ever get to actually visit the layouts they draw) do their best but they are called artists for a reason - there is some "impressionism" here.  Sometimes you can even tell from the photos in an article that things don't seem to sync up with the drawing.  

And in the final analysis a track plan article is ideas and inspiration.  It isn't meant to be copied in full.  You're on your own for your layout.  Even the "paint by numbers" track plans in the Atlas track plan books that are meant to be copied  - amazing how off you can get even when you think you're doing it perfectly.

Dave Nelson

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Posted by rodsaw on Friday, May 29, 2020 8:45 PM

Thank you Byron for all of the tips and the explanation. I will have to break out my drafting supplies to get the circle template out and I think it will help out quite a bit in looking at plans.

I am planning for HO scale. I am still all over the place on the design as I read/learn more about layout design. I have been looking at several 4x8 layouts, but moving to a 5x9 allows opening up the radius that allows for some of the bigger locomotives. Rice Harbor is one that I like in this size range. The next day, I start down the waterwing style, and today I saw the waterwing on your web page that is very appealing.  So I keep looking and downloading plans in the mean time. 

Thanks again -


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Posted by JoeinPA on Saturday, May 30, 2020 8:23 AM

And in the final analysis a track plan article is ideas and inspiration.  It isn't meant to be copied in full.  You're on your own for your layout. 


You hit the spike on the head. Too often we get involved in trying to exactly duplicate something that was meant to stimulate ideas. The fun is using the plan to come up with our own design elements.


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Posted by SeeYou190 on Saturday, May 30, 2020 9:34 AM

I use the track plans to compare the scenes and photography to the way that track is actually laid out. I find the "A to B" of track plans fascinating, but knowing actual curve radius, tunrout size, grades, elevations, etc. is not necessary and would reduce my enjoyment of studying the track plans.


Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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