Track Templates

[Xiong]

I'm getting nowhere without reasonably accurate track templates. A turnout is not just the intersection of a circle and a straight line. I know you all want me to get XtrkCad and I'm sure I will but for now, I don't have a box that can run that application. Little luck, either, finding track templates online.

So, I'm drawing my own, starting with a #8 Left turnout. I fear to put the large image inline, so:

http://xuefang.com/rr/junction/number8-L.gif

I've shaded the area between points and frog mostly to make the turnout stand out as a unit in a layout. Obviously, the trailing lines will foul for far longer than this, depending on what trackwork is laid out there. The thin red lines represent clearance; on straight they are 1" away from centerline. As the diverging route represents a curve, I've added 1/8" to the clearance there.

The other lines are merely a drawing grid, with gridlines 6" apart. I'm not handlaying and I don't demand exactness; these are just schematics. They're designed to be viewed at a much smaller size in a full plan. My main concern is getting the overall geometry correct.

I figure I can make reasonable track plans by copying templates like these and rotating them around, lining up the centerlines by eye, and checking for clearances. I'll do a #6 turnout, some straight and curved track, and perhaps a curved turnout. Then, I'll see if I can't work out spiral easements.

Comments?

 

[nachoman]

FYI-

The fasttracks website has free downloadable templates in pdf form...Your method is what I am doing to help lay things out.

Kevin

 

[ScratchyAngel]

http://www.prototrains.com/turnout/turnout.html

and

http://www.urbaneagle.com/data/ I know has N Scale, but might have HO too.

and

http://www.handlaidtrack.com/printable-track-templates-ho-c-11_83.php is the HO page for FastTracks mentioned by Kevin.

 

[Santa Fe Jack]

Do you have access to a photocopier? I photocopied turnouts, made several copies, and cut them to size. Then I could lay out a full scale layout and play with it. That worked pretty well. OF course, I had to HAVE the turnouts first...

 

[Doc Holliday]

I picked up a complete set of Atlas track templates at my (not so) LHS for $4.95. Made a bunch of copies (after adjusting copy machine to make actual same size copies) and played around with them and layed out my entire layout full size. Once I had what I wanted I simply sprayed a light coat of spray paint over the templates to transfer the pattern to the foam.
Doc

 

[Russ Bellinis]

Xiong, you mentioned spiral easements in the last line of your original post. If you are talking about spiral easements for the turnouts, that is why a switch is more than a circle meeting a straight. I think most commercial turnouts have a spiral easement built into the diverging route.

 

[Xiong]

Before the oldtimers laugh so hard something breaks and falls to the floor, I'll just admit I'm new to this. I'm a quick learner and I do have plenty of experience with fine detail assembly but after months of study, I'm still discovering new things daily.

There is no such thing as a generic easement. I'm not finding templates particularly useful. The best is the minutely researched at http://www.trains.com/mrr/default.aspx?c=a&id=290 and they're still quite primitive.

Issues:

* There are five templates shown at the site above. Each template covers a wide range of radii; the difference is the abruptness of the easement. They seem geared toward the fairly abrupt end; there is no provision for more gradual easements.

* Given a certain section of radius, in a certain location, and given a length of straight (or the gods forfend, another radius) also in a fixed location, is there one and only one correct easement? I don't think so. There is, however, a boundary.

* I have to guess that it is *always* possible to construct some spiral easement between any two circles (or circle and straight). However, I have the nagging suspicion that in some cases, the minimum proper easement would be greater than any portion of the desired constant radius curve.

* In these templates, only track centerline is shown. All along the extent of the easement, each rail must be gauged to the centerline ( 0.649" / 2 ). This is made just a bit tougher because gauge is specified from inner to inner rail surface, not center of rail. So, 1/2 rail width must be added to gauge to find the center of the rail.

* At least at the radii at which I'm working, curves are so gradual that the eyeball is nearly worthless. Fitting templates to the drawing by eye, I suspect, is more fantasy than art, certainly more art than science.

* I have a smoggy feeling that calculus is required to calculate easements correctly. If x = distance in inches from the point of tangency and y = deflection in degrees from tangent, then a constant radius curve is represented by some y = C. (I'm assuming that for any given x, the instantaneous deflection is measured relative to point x itself. It's a mistake to think that a constant radius curve accelerates away from tangency.) So, a good easement would be represented by some y' = K; constant acceleration. Working backwards, correct deflection from tangency at any given point would be the integral of K -- and this gets murky for me, because indefinite integration throws up a constant at each step. Translating the correct formula for y( x ) into Cartesian coordinates is just a bonus.

This appears to me to have all the complexity of landing an airplane, where the goal is to reach zero altitude and zero vertical speed at the same time, with airspeed within tight limits, and depending on circumstances, initial altitude, airspeed, and distance from the airstrip may vary widely.

* * *

One thing is coming clear to me and I don't like it. I'm a nitpicker, always have been; that's not news. But given my lack of experience I did think I'd be better off laying store-bought turnouts and flextrack. The more I learn about track -- such as gauge widening on curves and the intricacies of turnouts and easements -- the more I fear I will never be quite comfortable unless I handlay. Since it's idiotic to bull right in without needed skills, that means I really do need to build a throwaway layout or two, just for practice.

 

[Gary Pfeil]

* *

One thing is coming clear to me and I don't like it. I'm a nitpicker, always have been; that's not news. But given my lack of experience I did think I'd be better off laying store-bought turnouts and flextrack. The more I learn about track -- such as gauge widening on curves and the intricacies of turnouts and easements -- the more I fear I will never be quite comfortable unless I handlay. Since it's idiotic to bull right in without needed skills, that means I really do need to build a throwaway layout or two, just for practice.

Xiong,
Your comment about being a nitpicker is spot on in regard to your concern about easements. All the considerations you speak of are important for prototype railroads to consider when laying their rail. You certainly do not have to go to anywhere near that level of detail to get a good looking and performing model railroad. If that is the type of thing that you will enjoy, more power to you, I don't mean to denigrate it. It just doesn't have to be that difficult. The planning process can be as simple as I wrote on your other thread. The key is in being meticulous in the actual track laying.

At any rate, not a bad idea to try some handlaying, I find it pleasurable. Good luck!

 

[pgandw]

The original Model Railroader article from which the 5 templates was taken was published in Nov 1969, IIRC. The article contained the formula used for computing the 5 cubic spiral easements that were published. I wish the pdf had the formula (I lost my 1969 issues in the last move).

Choosing the appropriate easement template is a function of choosing a template that has a reasonable easement length for the curve radius you are using. You want an easement length that is 1.5 to 2 times as long as your longest car. Anything shorter than the longest car length is a waste of easement.

I used to obsess over vertical and horizontal easements, and wanted to make them as prototypical as possible. Then I realized that my construction isn't going to be nearly that accurate or precise. Setting elevations for vertical easements with more precision than the nearest 1/16" is a waste of time because I can't build to any better than that. Similarly, a bent stick easement takes literally seconds to lay out, but when the track is down, nobody can tell whether the easement was created through cubic sprial computations or using a bent stick.

Finally, although XtrkCad features easements, I don't want them everywhere, and I don't always want them to be the size XtrkCad computes. So, I turn easements off in XtrkCad, and plan by allowing an extra 1/4" on the radius for my 18-22" radius curves in HO. I determined this 1/4" dimension by looking at the offsets in the MR templates for the approximate size easement I wanted to use. The offset is probably larger for your Free-mo radii (48") and easement lengths (18"-24", based on 12" passenger cars)

When I lay out the easement on the layout, I simply use an architect's flexible batten. At the offset point (1/2 the length of the easement), I fix the batten at 1/2 the offset between the curve and tangent track. The batten is pinned straight beyond the easement and into the curve radius beyond the easement on the other end. The flex of the batten then gives me a very nice easement. A suitable large French curve would be even quicker for N scale ( I haven't seen them large enough for HO.)

Since I hand lay my turnouts with custom hand-made curved frogs, I lay turnouts out right in the middle of easements and/or curves. Curved frogs are not prototypical for most North American practice (curved frogs were most common in narrow and dual gauge, and 19th Century), but I'd rather save the space and the disjointedness of straight frogs in the middle of curves.

Track planning software - for me - is a sanity check rather than an attempt to plan everything to the nearest 1/16". The software simply prevents me from cramming too much into the space or drawing a configuration that will not work. For this reason, I use commercial turnouts in the software libraries when designing layouts. If I handlay on site, I know I can fit in less space than the commercial turnout, so I know the plan is buildable. I accept that my as-built layout may differ from the plan by as much as a couple of inches.

XtrkCad requires very modest hardware. The 3.14 version probably even runs on Windows 98! I believe the current version will run on Windows 2K, as well as Linux.

Gauge widening on curves only becomes a concern if you are going down the Proto87 route, or are using very sharp curves. Most flex track has some widening already, with Atlas having the most, and ME having the least. Again, it only matters if you are pushing the norms in either direction. Having track right at minimum gauge is preferable, but will drive up minimum radius requirements of rolling stock. Wallowing of steam locomotives is a result of too much slop from excessive gauge widening. Certainly, track gauge right at minimum in turnouts is very desirable unless you are trying to force a large 8 coupled steamer or 6 axle diesel through a #4 turnout.

I have to repeat my opinion - this stuff is sort of fun from an engineering and theoretical standpoint for some of us. But 99% of model railroaders lay their track without a thought about any of these considerations and have just as much fun and success! Bent plywood and curved battens are tried and true very simple methods to get working vertical and horizontal easements without any calculations to speak of.

my thoughts, your choices

 

[MasonJar]

* I have to guess that it is *always* possible to construct some spiral easement between any two circles (or circle and straight). However, I have the nagging suspicion that in some cases, the minimum proper easement would be greater than any portion of the desired constant radius curve.

You do not need calculus to figure out the exact path of your easement. Any flexible "straightedge" will do, as it will automatically form an easement when one end is held along the tangent (i.e. straight) track, and the other is conformed to the curve. If you want to buy a fancy device, www.leevalley.com has a couple of sizes.

EDIT - this is the "bent stick" as described by Fred, above. Seems we were typing at the same time...!

MR published some guidelines a while back about the offset of the curve from the tangent track leading to said curve. They also included the recommended length of the easement for a given radius. I don't have the numbers at my fingertips, but the MR website and/or NMRA standards & RP's may have some more info.

Andrew

 

[Xiong]

Getting back to my stupid turnout issues:

It seems, after careful inspection of the Fast Tracks #8 turnout template, that I was completely mistaken. The entire diverging route beyond the frog is straight! Indeed, both rails are straight some distance *inside* the frog. Then they start to curve toward the points.

The template notes a "diverging route radius" of 67". However, when a circle is drawn of that radius, tangent to the straight track centerline at the very end of the points, it does not coincide with the diverging route. To get this diverging route circle to coincide with the diverging route centerline, it's necessary to shift it pointsward by 5/8".

The template notes a "diverging route angle" of 7.13°. Indeed, the diverging route is at this angle to the straight. Also, when the diverging route circle is drawn as in the last paragraph, it coincides with the diverging route at a location 7.13° around the circle from the point of tangency. That location is within the lead, nearly an inch inside the frog, depending on how you choose to measure it.

All this seems a bit peculiar to me. The straight route, logically enough, is straight its entire length. The diverging route may be found by two lengths of straight, connected by a fraction of a circle. After all the concern about easements, there does not seem to be anything like this built into the design of the turnout itself.

Surely this is all old news to the old heads but it's a surprise to me. I had assumed that the entire diverging route could be found as a continuous radius and that the point of tangency would be the physical tip of points.

I read elsewhere discussion of curved frogs; evidently, the Fast Tracks turnout uses a straight frog. Maybe it's all starting to fall into place for me but it's much more complex than I thought.

For layout planning purposes -- not for tracklaying -- it would seem sufficient to represent the turnout with the appropriate set of straights and section of radius. Back to the drawing board.

 

[pgandw]

The Fast Tracks turnout geometry is based on the NMRA turnout patterns here: http://www.nmra.com/standards/sandrp/rp12_3.html. These are reasonable replicas of North American practice prototype, but not exact. For more accurately scaled turnout templates, see: http://www.proto87.com/handlaid_track_templates.html.

You are correct; most modelers use the turnout as an easement into a curved path because of the usually larger than normal radius curve in the closure rail and the straight segments before and after.

Handlaid turnouts can be whatever geometry you want if you don't limit yourself to Fast Tracks jigs. Personally, I use curved frogs and turnouts, usually laid out with an appropriate radius or easement throughout both paths. This is done to save space on my small layouts, while achieving reliable operations and a "continuous flow" appearance.

Other hand layers prefer accurately scaled turnouts with straight frogs and hinged points.

Of course, with commercial turnouts you have to accept whatever geometry you are given or modify the turnout. The various track planning software package do a very nice job of representing a commercial turnout accurately in their libraries. That's why the libraries that have the turnouts you intend to use are key to selecting the software. XtrkCad has NMRA templates in addition to various commercial track libraries. The NMRA turnouts would be useful if you intend to use the Fast Tracks jigs.

Hope this makes sense and helps

 

[Xiong]

Okay. Here's another attempt at a #8 turnout:

http://xuefang.com/rr/junction/demo-number8.png

The diverging route is now straight past the frog, as is the frog itself. The curved portion of the diverging route has a 67" radius, as specified in the Fast Track template. I've also modified the clearance lines (shown in red) so that they follow strictly NMRA S-8 Track Centers for Class Ia equipment. Railhead width is correct to scale for code 83. Track centerline is aligned to drawing grid.

The colored portion still terminates at the actual physical points, although it seems that the radius they follow goes past another 3/8". On the trailing side, the cutoff is arbitrary. Perhaps I should move it back to the theoretical frog point?

There is one significant point of difference between Fast Track's template and NMRA. Fast Track states that gauge through turnout is 0.66"; NMRA sets HO gauge at 0.649 min, 0.672 max *and* states (S-1/1/D): "For turnout construction, the track should be laid as close to the minimum gauge as possible between the point of the frog and the running rails." I've drawn this turnout with a gauge of 0.649". Does anybody want to speak to this?

This is intended merely as a layout planning tool, not a turnout building template. Still, there is no reason to get wrong the few details shown.

Comments?

 

[pgandw]

There is one significant point of difference between Fast Track's template and NMRA. Fast Track states that gauge through turnout is 0.66"; NMRA sets HO gauge at 0.649 min, 0.672 max *and* states (S-1/1/D): "For turnout construction, the track should be laid as close to the minimum gauge as possible between the point of the frog and the running rails." I've drawn this turnout with a gauge of 0.649". Does anybody want to speak to this?

Comments?

That 0.66" sounds very wrong. I'm a fan of Steve Hatch, and he documents why turnouts should be right at minimum gauge on his web site (http://www.railwayeng.com/rrhints.htm). He has finally persuaded some critical members of the NMRA that he is correct. The only reason for having slop between wheel and track gauge is to enable very sharp curves. With #8 turnouts, you are obviously not going there.

Another advantage of minimum track gauge is that the flangeways get narrowed automatically towards the NMRA minimum of 0.040" to support an adequate check gauge. The narrower flangeways at the frog prevent wheel drop, especially with narrower (code 88 wheels) wheels and/or long frogs (#7 and higher). Fast Tracks gets around this issue by using an extremely sharp frog point, which extends the frog point further into the throat, reducing the unsupported space.

Fast Tracks has a very nice video showing the relationships of the various parameters such as check gauge, track gauge, and flangeway width.

hope this helps

 

[Santa Fe Jack]

Xiong -
There are a couple of different approaches mentioned in this thread. You started off with the mathematics: geometry and into calculus. As an engineer (civil/environmental, not railroad), I fully appreciate the appeal of working it out this way, and if you were laying rack for a real railroad, you would use something similar (at least in the old days) and develop points for the surveyors to mark out for the track crew.

The other approach is the physical one. Instead of working out the math, use some physical objects (bent stick, for example) to work out the smooth curves. This also has appeal for me as an engineer, because it is much more practical. I used a pin-on-a-string to lay out the circular arcs in the track, and then just laid in what came naturally with a bent stick (I went straight for the bent piece of flex track) to lay in the approaches and spirals. They may not be mathematically correct, but they look natural and perform well.

Nevertheless, I can see you are one prone to getting it right (and mathematically so) or it will bug the heck out of you later. If that is you thing, then great. If you want to get the thing built, use the off-the-shelf turnouts, and piece them together with curves that look natural. Just my 2c.

 

[Xiong]

Well, I have an engineer's habit of drawing everything before building anything. Yes, I tinker -- and often tinker first and draw later. But before I commit to any serious effort, I spend a long, long time in planning. Even when tinkering, I tend to work the calculator before choosing a part. I find this reduces the quantity of smoke rising from the bench.

If you'll excuse me while I jump the tracks, I completed a hardware design project for a client who was, I'm sorry to say, not entirely satisfied. I delivered a prototype and it did what it was supposed to do but the client had unrealistic expectations. I also delivered a fat documentation package; even he had to commend it. I got paid.

The point of my story is not that I'm a documentation, drafting, and technical writing wizard. I'm good, yes. But the point is that I'm *obsessed* with creating clear, accurate, precise, highly detailed documentaton of all my work.

I was not always this way. In my youth, I scorned documentation. I once built a test bench controller from time-delay relays, a traffic signal clock, and some other stuff; when I needed more functions, I added more relays. The panel was about a foot and a half square, with about a dozen parts, and uncounted wires. I never drew or even labeled any part of it. By the time I was through with it, I had no idea how it worked.

More practically, it may well be years before I start building track modules. I can draw them today.

That 0.66" sounds very wrong.

Yes, it does. *Very* wrong. That gauge is noted in several places around Fast Tracks, though, both on HTML pages and in the PDF turnout templates.

Why?

I've been studying the issue of frog drop. It seems that a properly built, in-gauge frog *should* support the wheel tread continuously, either on the wing rail or the frog itself. I read (somewhere) about the "importance" of filling and filing frog flangeways so that, during the time the tread is unsupported by railhead, the *flange* rolls on the bottom of the flangeway. I don't have enough experience to judge but that strikes me offhand as Bad Engineering.

NMRA standards are pretty specific and the explanation is clear, too:

http://www.nmra.org/standards/sandrp/images/S1-1_2.gif

Everything on the Fast Track site looks professional and smart except this.

 

[pgandw]

Yes, it does. *Very* wrong. That gauge is noted in several places around Fast Tracks, though, both on HTML pages and in the PDF turnout templates.

Why?

I've been studying the issue of frog drop. It seems that a properly built, in-gauge frog *should* support the wheel tread continuously, either on the wing rail or the frog itself. I read (somewhere) about the "importance" of filling and filing frog flangeways so that, during the time the tread is unsupported by railhead, the *flange* rolls on the bottom of the flangeway. I don't have enough experience to judge but that strikes me offhand as Bad Engineering.

NMRA standards are pretty specific and the explanation is clear, too:

http://www.nmra.org/standards/sandrp/images/S1-1_2.gif

Everything on the Fast Track site looks professional and smart except this.

Like I said earlier, I'm a fan of minimizing slop (part of the engineer in me). That means keeping track gauge at minimum. I like the appearance of minimum flangeways, too. Finally, the minimum flangeways (.040") will work reasonably with my preferred code 88 wheels, whereas a Fast Tracks flangeway of .050" will have wheel drop with code 88 wheels. This is based on the NMRA recommendation that wheel width be twice the flangeway width. In HOn3, code 88 wheels are the norm. Code 110 wheels look awful at the small diameters used in narrow gauge.

FWIW, Fast Tracks uses an extra sharp frog point to extend further into the frog throat, thereby helping to prevent wheel drop with the wider flangeway and gauge.

By the way, you are right, filling the flangeway to support the flange is bad engineering. And it requires very consistent flange depth on all your rolling stock to be a viable solution. Anything with deep flanges will bump up, and anything with shallow flanges will still drop.

because track is a model, too.....

 

[Xiong]

Now I'm completely baffled. I attempted a #6 turnout, again working from the Fast Tracks template and data.

Fast Tracks data specifies a diverging route angle of 9.46° and this agrees well with the template. However, it also specifies a diverging route radius of 43". When I draw a 43" circle tangent to the straight exactly at the points, it clearly is all wrong -- it doesn't coincide with the diverging centerline anywhere.

Granted, the #8 turnout's diverging route radius circle did not coincide exactly as expected; I found it necessary to shift it pointsward (in the direction parallel to the straight route) by 3/8". That bothered me at first until I realized that the physical points would have to stop short of the theoretical end; there is no value in a paper-thin point. (Note that I reported this incorrectly as 5/8"; sorry.)

But for the #6 it appears that a circle of 30" radius most nearly joins the straight route and the straight portion of the diverging route, doing so at a reasonable location some inch below the frog point. That lets the remainder of the diverging route and the frog itself be straight. That 30" radius circle I have is also shifted pointsward, by 3/16".

I checked that by finding that the location where the 30" circle coincides with the diverging route centerline is about 9.16° around the circle.

Clearly, I'm just guessing here with the 30" circle; it fits reasonably but so might a 31". This is all done by eyeball. But the eyeball is more than enough to disqualify totally a 43" diverging route radius.

Note that this has nothing to do with the substitution radius, given in the Fast Tracks data as 69". I consider the substitution radius as a nearly worthless piece of information, relying as it does on the assumption that the entire diverging route is curved. Perhaps you could build it that way but that's not what the template shows. If one attempted to drop the drawn turnout into a 69" circle, there would be an abrupt kink in the rails. (Indeed, it doesn't even seem to be roughly the right radius, either.)

Will someone please help me out here? Either I'm misinterpreting the Fast Tracks data or the data is very wrong. Combined with the fact that they state again that their gauge is 0.66", I'm starting to wonder about these guys. For all I know, their kits make great turnouts -- but I just can't understand their numbers.

 

[Xiong]

w24

Okay, here we go. This is version w24 of my "scratchbuilt" track template set:

http://xuefang.com/rr/junction/track-library-w24.gif

Note that it is pretty much pointless to view this in your browser unless you have a 6 x 8 foot monitor; the image is actual size. It's only 588 Kb in storage but I suggest you download it and view it offline in some image viewer that allows you to pan and zoom.

You'll see I have right and left turnouts, #8 and #6. There doesn't seem to be much call for sharper turnouts in free-mo; they'd be forbidden from the main line anyway. There are radii ranging from 48" down to 24". I figure it's possible I might put a sharp curve on an industrial spur and anyway, radus track is easy to draw. 42" is the mimimum allowed on main line with 48" preferred. As others have noted, free-mo is pretty generous compared to some pikes; I figure it's fine to put the second track of any double main *inside* the preferred, so with the NMRA clearance between them, that works out to 45-3/4". The straight is, well, straight.

Turnouts and radii are shaded more for quick visual identification than anything else. The shaded portion of each turnout is the lead between points and frog. Right now they're all the same color but each radius and turnout number is its own style so I can make global changes at any time. The thin magenta lines are half-clearances; if they don't overlap, the clearance is good.

I will be creating cubic easements dynamically, rather than pasting in easement templates.

 

[pgandw]

You are expecting something that doesn't exist. Study prototype turnouts - either through photos or the real thing. Points are not part of a continuous curve. Often in North American practice, points are actually straight and hinged. Only a section of the closure rail has the stated radius curve. The same is true with most model turnouts (Peco code 75 and code 100 being the big commercial exception). Only a section of the closure rail has the stated radius.

In drafting, before computer models, turnouts were represented as straight lines with a diverging angle. Picking the lead distance was the tricky part (and still is) because each manufacturer of a #6 turnout will have different length points and lead distances (distance of the points from the frog). #6 only defines the frog angle, and even there rounding games are played. For example, an Atlas #4 is really a #4.5. Walters/Shinohara increases the lead length and the closure rail radius over a standard #4 so it won't be quite as sharp.

Only sharp model turnouts require curved points - straight points would make too much of a "kink".

Fast Tracks is not as concerned with prototype emulation as Proto87 stores turnout kits. The goal of Fast Tracks turnouts is to build traditional handlaid style track reliably, quickly, and efficiently. Fast Tracks uses hingeless points, and flexes the rail to switch the points. This has been common handlaid practice for years in the smaller scales where flexing the rail works well.

Prototype stub turnouts work by flexing the approach rails - but it became impractical to "bend the iron" when rail size got much above 75lbs.

hope this helps