PLANNING & BUILDING
 A SHUNTING PUZZLE LAYOUT
 
 

Deciding which shunting puzzle to build - Layout size and prototype modelled -
Trackplan - Baseboard - Track - Points (Switches)
 
 
Planning and building a model railway layout is a tricky thing - there's no definitive way to get it right, but many ways to get it wrong.
 
  A fair number of clever and talented railway modellers with tons of experience have compiled some very helpful websites or written some rather smart and enjoyable books on the subject. However, even with a wide selection of different approaches and even modelling philosophies, a few basic rules remain the same: good quality track should be laid in a manner providing trouble-free running on a sound baseboard.
 
Whatever the building strategy, it is always a good thing to stop, look and check before getting on with the next step.
 
Planning and building a shunting puzzle layout is slightly different because special attention needs to be given to certain aspects of layout planning and building, such as defining and then also adhering to certain lengths of trackage.

Slipping up on such points could mean that the completed layout will work fine in a technical sense but won't allow a specific shunting puzzle to be operated properly.

  
 
 
Deciding which shunting puzzle to build
 
Obviously, the first thing to do is to decide which type of shunting puzzle to build. Opting for one of the classics, an Inglenook Sidings layout is the most straightforward shunting puzzle layout that can be built due to its simplicity (which also makes it a rather cheap layout to build).
 
Building a Timesaver layout is, however, not much different apart from a slightly higher degree of trackwork complexity (and cost due to the higher number of turnouts (points) needed).

Or maybe you'd like to build one of the less often modelled shunting puzzles such as Linn Westcott's Switchman's Nightmare (actually a very early example, dating from 1956 and published in Westcott's classic 101 Track Plans).

  
 
Whatever your choice - before actually going about any construction work, try to check that the complexity of your choice matches what you'd like to see in terms of an operational challenge. If you're not entirely sure about this, an Inglenook layout is most likely the best choice, not the least because you will be up and shunting in next to no time. On the other end of the scale, puzzles such as the Switchman's Nightmare are fairly complex not only to build but also to operate, and usually more suited for advanced modellers and puzzlers.

Designing your own "new" shunting puzzle is another option, although you will find that usually elements of the two classics will creep in, and if you have a truly new concept you need to make sure it really works before fully assembling it in layout form. As a general rule, however, it is better to turn your own creativity to the setting and scenery for a classic shunting puzzle, rather than come up with your very own.

But at the end of the day the only rule here is to set the points so you can travel on your own track of railway modelling fun.
 
 
Layout size and prototype modelled
 
Having chosen the shunting puzzle type, the next question which needs to be answered is the size of the layout. Because the rules of a shunting puzzle are firmly linked to the length of the sidings in terms of their capacity (i.e. how many items of rolling stock a given siding must be able to hold), it is quite clear that you need to know the length of the rolling stock you will be using on the layout before making any further steps.

This in turn means that you have to settle on a prototype in order to be able to measure the items of rolling stock to be used on your future shunting puzzle layout.
 
  The length of an Inglenook Sidings type layout is easy to establish - it's a total of 8 times the length of the rolling stock to be used (5 in the uppermost siding plus 3 in the headshunt) plus the length of the locomotive to be used plus the length of the first point.
 
The width of the layout will depend on the make of points used (different makes have different radii) and whether or not the third siding is kept running straight on (as in the trackplan above) or whether it is curved inwards to run in parallel with the other two sidings - generally the width turns out to be around a quarter of the length of the layout. Figuring out the length and width of a Timesaver layout is, of course, much the same affair.
 
The longest track and as such the defining element for the minimal total length of the layout is the line running through from C to D. Its length is a total of 6 times the length of the longest rolling stock (including locomotive) used plus the length of two points (the third, turning off to E, forms part of the middle track section holding 2 pieces of rolling stock).

When working out the dimensions of a planned layout and determining track lengths, it is really important to do this as a "dry run" 1:1 and diligently, in order to make sure that the lengths of the tracks conform to the capacities needed to properly set up and play the shunting puzzle.

  
 
Temporarily laying out the track and using rolling stock to determine the true lengths avoids nasty surprises at a later stage. An important part of getting the lengths of the tracks right is checking for clearances. This includes taking into account that certain lengths of track around points are "collision areas" - an aspect obviously just as important in the real world, as an industry advertisment illustrates. After all, the shunting puzzle will only work if all the cars intended to go on a section of track will actually fit there completely and with enough clearance for other cars to run through the points.
 
   
 
If the layout is intended to be operated as a shunting puzzle using only a specific set of rolling stock, then measuring track lengths and clearances with that set is sufficient. However, if the plan is to use different sets, then clearances need to be checked for more than one set of rolling stock.

Shown here are the capacities of the three sidings on Little Bazeley (Mk2). Primarily intended for British rolling stock, the lengths of the three sidings have been determined accordingly and allow for both the 5-3-3 and the 3-2-2 Inglenook formula.
 
 
However, from time to time US prototype rolling stock is used, and for that purpose the track lengths also needed checking. Using 40ft boxcars, the longest siding could actually hold four rather than just three cars - in order to keep the Inglenook shunting puzzle a challenge, a rule is simply introduced that prevents four 40ft boxcars to be pushed onto the warehouse track. The track lengths also allow for 50ft boxcars, in which case clearances are tight but workable, and the warehouse track will only hold three cars anyway.
 
 
One other point which often gets overlooked is the position of the uncoupling devices - if you plan to use magnets, make sure that there is enough track length to allow uncoupled items to be left clear of the magnets, otherwise it will be impossible to couple back on as the magnet will have the coupler locked permanently in the "uncouple" position.
 
If you're really starved for space, or if the shunting puzzle layout will be a second layout which will need to live side by side with a larger layout which takes priority in terms of space, you might also consider a less common track configuration not necessarily known as a switching puzzle but which can be operated as one - the "tuning fork". The scene below on my HO Pecan Street layout fits into a width of no more than six inches (15 cm).
 
 
But just how small can a traditional shunting puzzle a la Inglenook (actually, Timesavers aren't that much longer) get?
 
In theory, working in a smaller scale (e.g. looking to N scale when you're mainly modelling in H0/00) and going for sharp point angles and tight radii will shrink your shunting puzzle layout substantially.

However - it's not a route you should consider taking without caution, as "sharp and tight" often spells out as "derailments" and "stalling of locos" - something you don't really want to have to deal with on a shunting layout.

Naturally, you can have an N scale Inglenook layout that's only 2 feet long and 7.5 inches wide. But the real advantage N scale offers is to have a more flowing Inglenook Sidings layout in about the same space the original 00 scale version took up.

  
 
This also explains why Z scale (the smallest commercial railway modelling scale) won't produce the smallest shunting puzzle layout possible. This is due to the fact that Marklin Z scale points are fairly generous affairs with a 490mm (1'1-1/4") radius.
 
  As a result, you can't get away with less than approx. 80-85cm (32-34") in length for a Z scale Inglenook Sidings layout (Rokuhan of Japan now make Z scale track with roadbed and offer some very tight angled points in their large choice of track geometry, but these are clearly to be avoided for any layout that expects to see reliable and trouble-free shunting).
 
The bottom line then perhaps is to be careful not to be too greedy in terms of space - it's pretty much a law of nature that larger radius points are less likely to cause problems when used for repeated shunting and slow-running. No doubt medium and small radius points can work fine, but be sure to thoroughly check them before going much further in layout construction, because a shunting puzzle with frequent derailments and/or locos which stall on points and refuse to get moving again under their own power will not provide you with much fun.
 
 
Trackplan
 
Having determined the shunting puzzle type and layout size, the trackplan should now be a more or less logical affair. You can either follow the chosen shunting puzzle type's track plan very closely, or introduce some amount of variation, making sure that this injection of personal creativity doesn't interfer with the requirements needed to make the rules of the shunting puzzle work - although there's no reason, for example, why you couldn't cut down the number of cars of the Inglenook Sidings formula if you're building an indoor G scale version - the important thing is to make sure the layout is still "in balance". The late Carl Arendt, micro layouts expert par excellence, for example considered an Inglenook formula of 3-2-2 (instead of the original 5-3-3) to still be complex enough to provide interesting shunting orders. In the end, as with almost everything in railway modelling, it eventually boils down to a matter of taste.
 
One point to bear in mind which experience has shown to be good railway modelling sense is to make sure the trackplan and layout built from it allows for a self-contained shunting puzzle without the need for any add-ons to operate it - if at all possible.

The trackplan shown here allows the shunting puzzle to fit on the 1'x4' baseboard completely, and even though it is designed to be extended at a later stage, it does not rely on these pipe dreams to become reality - it is a completely self-contained shunting puzzle layout by its own.

 
 
 
The price for this - within the dimensions of 1'x4' - is that modern image is, by all practical means, ruled out as this layout size will only accomodate fairly short freight stock. If modelling standard gauge railways, this usually means turning back the clock to the steam/diesel transition era.
 
 
Baseboard
 
Now that the dimensions of the future layout have been worked out, it's time to turn to the question of baseboard construction. Although a shunting puzzle layout will usually be small enough to be portable in any case, it's good to bear in mind that the traditional method of building a frame from 4'x1' (10cm x 2,5cm) timbers usually results in massive and very heavy baseboards.
 
However, sturdy and rigid (very important) doesn't necessarily equate to heavy baseboards.

One excellent option is to use 10mm birch plywood for a framework structure which serves as the main structural support for the layout. It provides extra strength and rigidity whilst at the same time keeping the overall weight down considerably. The actual baseboard top can then be set onto the frame, which thanks to the spacers is rock solid and the best insurance against warping.

There are many websites (and specialist publications) dealing with the topic of baseboard construction for layouts, and you will even find instructional videos on youtube.

  
 
Note that regardless of whether you build your own baseboards or buy some ready-made furniture to serve as base for your layout, "good quality" is the key word: only a durable baseboard which is level and won't warp will allow you to lay track which in turn is level and true - and stay that way.
 
 
Track
 
No model railway layout can really do with bad track, but when building a shunting puzzle layout, it's one of the most important things to consider. After all, you will want to be able to run locomotives and rolling stock at low speed back and forth and back and forth and so on. If the track on your layout won't allow you to do that more or less flawlessly more or less all the time, then your shunting puzzle layout will be just as much fun as missing the last train of the day at a lonesome country station in the middle of nowhere.
 
 
For the major modelling gauges, there are many different makes of track available, and very often, the choice is a matter of personal taste and past experience. If you have neither, you will find hat the topic has been widely discussed in internet modelling fora. One aspect to take into consideration is that both on the real railways as well as in modelling terms track doesn't equal track.
 
In the UK the current standard steel rail used on standard gauge (non high-speed) mainlines is the so-called UIC 54 rail which weighs 113 lbs per yard (54 kg/m) and has approximately 2,400 sleepers (ties in US terminology) per mile of track. In places where the tracks are used less frequently and/or by less heavy trains, such as in yards, lighter rail is used for economical reasons. In the US rail weight can vary from 80-90 lbs (small yards) to 100-110 lbs (light duty track) to 130-141 lbs (heavy duty track, where 141 lbs is the new mainline standard). 
 
Originally rails were laid down in standard lengths which were then bolted together, at 60 foot intervals in the UK and 39 foot in the US, with the joints allowing sufficient space for expansion. Whereas the UK placed the joints side by side, they were always staggered in the US - which accounts for the curious dipping and swaying of freight cars running on poorly maintained track. Today, track is welded into lengths of up to several hundred metres, and expansion is minimised by installing and securing the rails in tension. Sleepers are traditionally wooden (mostly oak in the US) and impregnated with preservative (soaked in creosote in the US), which will make them last up to 25 years. Other materials used are steel (seen here at a Swiss industrial siding and also illustrating the "transition spot" from heavier to lighter rail) and concrete.  
 
All of this means that simply by looking at the rails it is often quite clear whether the track in question is a modern heavy duty main line or a lightly used siding in a yard laid decades ago. In modelling terms, this translates into a wide selection of track.

The choice between track with either wood or concrete ties (which obviously you do not want on a shunting puzzle) is now available even in Z Scale, and steel sleepered track is available in 00/HO, but far more important for a shunting puzzle are the various "codes" of rail offered, which refers to its height in thousandths of an inch. In the most popular modelling scale 00/H0 the different codes on offer are 100, 83 and 75, therefore indicating a rail height of .100", .083", and .075".

 
  The long established standard also used for set track is code 100. It has the disadvantage of being noticeably out of scale, although careful ballasting and weathering can go a long way in hiding this. On the up side, most old stock will run on it without problems and the track is sturdy and reliable.

Code 75 track on the other hand is often refered to as "finescale" and has a much lighter and slimmer (and therefore more realistic) appearance. Its main disadvantage is its more fragile nature and the fact that most older stock will not be able to run on it due to deep wheel flanges.

A specialty is code 83 track which not only has a finer rail profile but is also modelled on US track characteristics. These differ markedly from UK and European standards - one element immediately visible is the higher number of ties (sleepers) used. In the case of point trackwork, differing construction methods are apparent also.

 
The choice of code is therefore not only dependent on aspects of reliability, appearance and compatibility, but also of prototype modelled. And don't forget that the track also has to deliver power to your locomotives. Even with DCC it's certainly a good idea to have a couple of power feeds even on a short layout.
 
 
Points (Switches)
 
Perhaps the most important aspect of track on a shunting puzzle layout are the points (switches in American railroad terminology), primarily because, for obvious reasons, they will have to work flawlessly. Applying extra care in laying, weathering and ballasting points therefore simply is compulsory. But before actually installing the points, you will have to decide what kind of points you are going to use.
  As with plain track, there's a wide selection of different brands to choose from, but more importantly there are differences in terms of frog angle and radius (the frog is the part of a point where the curved rail for the diverging line crosses the straight rail).

In the UK and on the European continent, the angle is usually indicated directly in terms of degrees (e.g. "12 degrees"); in the US, a numerical system for the frog is used (e.g. #4, where the diverging rails are one unit apart when measured four units past the point of the frog, i.e. a #4 frog takes 4 inches to diverge 1 inch). Therefore, a higher frog angle in degrees (or a smaller frog number) means a sharper set of points.

It is obvious straight away that sharp points have an advantage if you're thinking of building a small layout: they are a lot shorter than points with higher frog numbers. That's why so many trackplans for small layouts feature sharp points, often from a range of sectional track.

However, there's a big catch to such "shorty" points: some of them are simply derailing devices for all but a few pieces of rolling stock when you need to push cars onto the diverging track - and some won't even let you pull anything but the shortest goods vans out of the diverging siding without wheels jumping the rails.
 
The reason for this is, of course, that there is a horizontal force acting on the wheels moving in a curve. We all know from practical experience that objects which are in motion want to move on in as straight a line as possible once they're moving. In other words: rolling stock which is moving and sent on to the diverging track of a point is actually set to carry straight on. This conflicting situation also produces additional friction force of the wheels on the outer rail, which has to prevent the wheels from going straight on - and derailing.

Sharply angled points therefore put a lot of strain on the wheels of moving rolling stock, and unless you can move them really s-l-o-w-l-y, you will end up with far too many derailments to make operating the layout fun. The only way to reduce the horizontal as well as the friction forces is to choose points which flow more easily. If at all possible, try to avoid anything sharper than a #4 or 14 degrees frog angle (Peco "Streamline" points, both small and medium radius, have a 12 degrees frog angle but work fine from my own experience; on the other hand, Kato N scale Unitrack #4 switches are known to frequently cause derailments unless "tuned").

It should be remembered that shunting puzzle layouts don't by definition fall into the category of "micro layouts" - sharp points really should only be used if lack of space leaves no other option. The extra length this adds to the layout is well worth it.
 
 
Another aspect of points which used to be of some importance and which continues to be a topic of heated discussions is the difference between (to use the Peco terminology) "electrofrog" points (which have a "live" frog and require a certain amount of wiring in order to change the polarity of the frog according to how the points are set) and "insulfrog" points (which have an electrically insulated frog and require no extra wiring to operate) - and which ones to use.

Many modellers won't touch "insulfrog" points. However, the only reason why "Electrofrog" points were made in the first place was the bad electrical pickup in older models and subsequent stalling on electrically "dead" frogs. But since this is no real problem with more recent locomotives and older ones can easily be improved, the extra wiring required to switch the polarity of the frog in snyc with how the point is set seems rather a lot of trouble for no real gain - which is probably also why Peco introduced the "Unifrog" point in 2017; out of the package it will behave like an "insulfrog" point but the frog can be made to act like an "electrofrog".
 
Some makes of points / switches, on the other hand, come with current carrying frogs and ready installed power routing, such as Kato's N gauge UNITRACK - the #4 switches come with factory installed power routing, but by simply changing a screw the switches can be set to be non-power routing, whereas the #6 switch is permanently power-routing. Other options exist for other brands and scales (such as Rokuhan's power routing points for Z scale), and it is worth checking before deciding on a specific product line.
 
 


Page created: 24/JUN/2002
Last revised: 28/MAY/2023