PLANNING & BUILDING
A SHUNTING PUZZLE LAYOUT
Deciding which shunting puzzle to build - Layout size and prototype modelled - Trackplan - Baseboard - Track - Points (Turnouts)
Planning and building a model railway layout is a tricky thing - there's no definitive way to get it right. A fair number of clever and talented railway modellers with tons of experience have 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).
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 taking 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 (5x in the uppermost siding + 3x in the headshunt) plus the length of the locomotive to be used plus the length of the straight track 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, although due to its greater track complexity, you will need to determine and add up more figures.
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 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.
Checking track lengths (in 4mm (00/H0) scale, left) and clearances (in N scale, right)
(click for larger images)
An important part of getting the lengths of the tracks right is checking for clearances, taking into account that certain lengths of track around points are "collision areas". After all, the shunting puzzle will only work if all the cars intended to go on one section of track will fit there while completely within the "green" zone.
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 wonder just how small a shunting puzzle ý la Inglenook (actually, Timesavers aren't that much longer) can get.
If you don't mind sharp point angles and radii (and the problems in the form of derailments and stalling of locos they can cause - something you don't really want to have to deal with on a shunting layout), then N scale will offer you the possibilities of building incredibly small Inglenook layouts - Jordan Foster's Oldbury Basin, for example, is a modern image British prototype N gauge Inglenook Sidings layout only 2 feet long and 7-1/2 inches wide.
Perhaps surprisingly, the smallest commercial railway modelling scale, Maerklin's 1:220 Z scale, won't produce the smallest shunting puzzle layout possible. This is due to the fact that - quite unlike some of the N and H0 track available - M”rklin 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 approximately 80-85cm (32-34") in length for a Z scale Inglenook Sidings layout.
Why go for Z scale when you can cram in an N scale layout in very much the same space? One point in favour could well be the fact that with such slim pointwork you can be almost sure of smooth and trouble-free operation, and as shunting puzzles involve lots of slow running and shoving about of stock, this must certainly rank as one of the highest priorities. Plus, thanks to the smaller scale, you can go beyond short locos and short freight equipment, and for example run heavy-duty Swiss mainline freight equipment (you'll find lots more information on modelling Swiss railways in Z scale here).
Turning back to larger scales, 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.
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". Carl Arendt, micro layouts expert par excellence, for example considers 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.
The track plan from my very first shunting puzzle layout (Battersea Sidings) illustrates a certain amount of individual variety injected into the classic Inglenook trackplan by placing the sidings on an "upper level" and therefore also having a scenic lower level, as well as adding a senic non-functional kickback point (a nice excuse to have some really worn and heavily overgrown track). It also, however, illustrates a major possible pitfall in building a shunting puzzle layout.
Due to the fact that this layout is a 4mm scale (00/H0 gauge) British modern image layout, the sidings need to be able to accomodate longer items of rolling stock than the original Inglenook Sidings layout. This means that in a given space of 1'x4' (30cm x 120cm), it is impossible to fit in an entirely workable "original Inglenook" - the layout requires some form of extension to act as headshunt. The common solution that small layout designers offer for this is to add a piece of subroadbed with track, hinged to the baseboard framing, so it can "swing into action" when needed and be folded back again when the layout is put away, thus saving space and making the shunting puzzle work after all. So where's the pitfall? Well, before introducing such an element into your track plan concept, make sure it will also be workable in the real world. Otherwise - as was the case with the track plan above - the hinged headshunt will never be built, and without this (or some other form of added layout segments) the loco might be able to trundle back and forth a bit, but the layout can't be operated as a shunting puzzle.
It is therefore much better - if at all possible within the given space available - to design a track plan which allows for a complete shunting puzzle track arrangement, without the need for any add-ons. Bearing this in mind, the track plan below was designed within exactly the same baseboard dimensions of 1'x4' (30cm x 120cm).
This shunting puzzle fits completely onto the baseboard, 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 a bit.
Alan Wright put his original Inglenook Sidings concept to work on a layout which also measured only 1'x 4'. This was achieved by using standard goods wagons of the British steam/diesel transition era which are comparatively short - the standard wheelbase measures 10'-0" (3m), which gives a total length over buffers of 20'-6" (6,15m). In 4mm scale (00/H0 gauge) this translates into goods wagons about 3,2" (8cm) long. Therefore, a siding with a length of 20" (50cm) will easily hold 5 pieces of rolling stock and provide enough clearance around the pointwork.
For the trackplan above, this means that time slides back from the late 1980's/90's to the mid-1960's, when shorter wheelbase stock was still the order of the day.
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 with chip- or plywood top usually results in very heavy layouts very quickly. In most cases, lightweight baseboards serve the purpose just as well - sturdy and rigid (very important) doesn't necessarily mean heavy.
As shunting puzzle layouts fall into the category of shelf layouts, there's also another possibility: find a ready-made baseboard in the form of a piece of shelf furniture. Obviously, this shouldn't be too expensive and lend itself to further "enhancement". I myself have found the IKEA "Moppe" chest with three drawers (measuring almost 4' x 1', namely 120cm x 28cm) to be ideal. However, the company has dropped the "Moppe" range from production as of early 2004, but it is fair to assume that pieces of furniture similarly adaptable to the needs of railway modellers can be found.
This picture shows a "Moppe" chest at an early stage with some 00/H0 scale track and rolling stock spread out for evaluation purposes. All in all, this is a complete ("ready-to-run", so to speak) "designer baseboard" for a small layout. The drawers are pretty handy too. The only possible setback is weight - at around 5 kilos, it's on the heavy side, but the positive aspect of this is that you really get a sturdy and good quality base for your layout if you want it to be portable but don't plan to move it about too often. Note that regardless of whether you build your own baseboards or buy something ready-made, "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.
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. Oh yes, and it's raining, too.
Set track on the prototype? Well, not quite... segments of track removed in the course of track renewal work on the Swiss narrow gauge Regionalverkehr Bern Solothurn (RBS) are stacked at Deisswil in May 2004 before being removed piece by piece from the working site. Also of note is the massive pile of fresh ballast in the background.
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. I myself have been using Peco track for many years, mainly because of the excellent pointwork available.
It is a good idea to first glue in place a sub-roadbed formed of cork (sheets of which are available at any DIY outlet). This provides a good base for laying track and also acts as sound deafening device. The track is then put down and fixed in place either with glue or track nails.
Don't forget that the track also has to deliver power to your locomotives. Unless you're running a digital command system it's certainly a good idea to have a couple of power feeds even on a short layout.
Perhaps the most important aspect of track on a shunting puzzle layout are the points (turnouts 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 0); 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 0 frog angle (Peco "Streamline" points, both small and medium radius, have a 12 0 frog angle and work fine from my own experience). It should also 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.
Sharp points often have another disadvantage: more often than not they are aimed at the "toy" segment of railway modelling, and in order to keep them cheap, their frogs are made of plastic, meaning that this part of the point is, electrically speaking, dead. A locomotive travelling over the frog therefore doesn't pick up any current on that piece of track. Usually, this is no problem with long wheelbase locomotives passing at speed, but it can mean that a short shunter will be left without power long enough for it to stall. It doesn't have to be that way, but if you don't want to take any chances, go for "electrofrog" points, i.e. where the current is fed to the frog according to the way the points are set.
Text and illustrations not labelled otherwise are © Adrian Wymann
Page created: 24/JUN/2002
Last revised: 06/MAR/2006