Track Arrangements for Prototype Operation
The previous module provided an overview of different layout designs but in order to operate your garden railway in accordance with the prototype you will most likely need to be familiar with the following track formations.
One of the most useful of these is the run-around loop which is typically to be found at a branch line terminus where it is referred to as a head-shunt. This allows a locomotive to attach itself to the other end of the train for the return journey. Without this simple facility the locomotive would effectively be blocked in by its own wagons or passenger cars.
In some termini the train would be decoupled from the engine and a second locomotive (‘relay’ locomotive) would be coupled up at the rear end to take it on its next outward journey. The original engine would then shunt to the relay siding to await the next train.
Where a ‘spare’ locomotive in steam was not available the addition of this short length of straight track allowed the ‘trapped’ locomotive to decouple and proceed forward, the point then being switched to allow it to reverse along the parallel track (or loop) past its own train to return to the main track and then either reverse back to re-connect with the passenger cars or turn round elsewhere and return facing the right direction of travel. With the demise of steam operations run-around loops are no longer necessary
This loop arrangement is also employed at through stations to allow wagons to be dropped-off in a siding without obstructing the mainline.
A similar “run-around” formation (a ‘passing loop’) is often to be found on a station as a convenient point for two trains to pass in opposite directions but also so that freight marshalling can be performed without interfering too much with the main line:
Station Passing Loop
Station Passing Loop with Siding
Lapped Siding
There is also an innovative “lapped” siding (above) attributed to Dave Husman in the 2007 issue of Model Railway Planning. I cannot find a prototype for this design but one is bound to exist somewhere.
I recognise that there are some undesirable “S” curves incorporated in this design but these are common practice in “terminus” situations and can be eliminated by careful modifications e.g. longer straight sections, if preferred.
Other Track Design Considerations
You may also have a need to incorporate alternative track arrangements for completing other prototypical operations. For example, in a restricted space the following arrangements are sometimes used:
Wye Junction
Instead of using "standard" points, it is possible to use special switches where space is at a premium. A wye switch, as its name implies, is shaped like the letter "Y." Whereas on a conventional point one leg continues straight and the other diverges off to left or right, on a wye point both legs diverge in opposite directions.
A Wye arrangement enables the direction of a locomotive (or indeed an entire train if the single-track spurs are long enough) to be reversed where no turntable exists (a good example is to be seen on the Durango & Silverton Railroad in Colorado). This involves the use of either 3 Wye points (turnouts, switches) or a combination of one Wye point and two conventional points to perform the railroad equivalent of a “three-point turn” by reversing and eventually end up facing the direction from which it originally came.
Wye Junction using two conventional points (switches) and one “Wye Point”.
Curved Wye Junction
You can also opt for a curved Wye as shown below:
Switchback (or Zig-Zag)
On some railways a Switchback (or zig-zag) line is sometimes used for crossing mountainous terrain and to gain or lose elevation on steep hills (many examples are to be found around the world).
It is similar to a road that ‘zig-zags’ up or down a mountain via a series of hairpin bends which is why this railway formation if often referred to as a ‘zig-zag’. However, the similarities end there as the train must negotiate the ‘hairpin’ in two distinct stages. The train (sometimes double - headed because of the steep inclines or grades encountered) traverses up and down the mountain-side by means of less steep gradients using a series of alternating “switched” dead-end tracks which take easier inclines.
Depending on the elevation to be reached or descended safely it is possible to have several switchbacks one after another.
Switchbacks were commonly used on logging railroads to allow the track to gain elevation in a relatively small space dictated by the rugged topography. They were rarely used on mainline railroads because of the need to stop and restart the train at each switchback thereby adding time to the journey.
Advantages:
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This method avoids the need for costly tunnels or major construction work
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Requires appreciably less space than curved loops to achieve the same object and are more likely to be achievable from a civil engineering point of view.
Disadvantages:
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The traverse can be slow due to need for frequent stops in each direction and the need to throw the point switch each time.
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It can only be readily implemented on a single track.
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The length of the train can be severely curtailed in order to accommodate the shortest section of ‘stub’ switch-track to be found on the line.
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The train direction is reversed each time which can be precarious.
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Care has to be taken in marshalling freight trains to avoid derailment.
The principle is more easily demonstrated in the illustration below. When climbing the train moves from Point A up a gradual incline to Point B. The switch (point) is thrown and the train then reverses to Point C. That appropriate switch (point) is then operated allowing the train to proceed to Point D) and so on up the mountain side. The length of track at each point should ideally be long enough to accommodate the complete train. Otherwise, were topography does not permit this, the train will need to be broken down into two sections which is much more time consuming and could take the best part of the day to surmount the climb.
I am not entirely sure why this arrangement is variously described as a "Zig-Zag" which tends to imply something that veers from left to right, a "Switch-back" which suggests an "up and down" motion or a "Reverse" which again which only covers 50% of the movements so if you can come up with something better please let us know.
There are a surprising number of implementations of a “Switchback” to be found around the world including a well-known example on the Cass Scenic Railroad, a standard gauge former logging line in West Virginia, USA which operates Shay, Climax and Heisler geared locomotives although it only has one reverse.
For more details regarding this popular attraction use this link:
You are unlikely to need to incorporate a device of this sort on your outdoor line but on the rare occasion that you might you do, it should create interest and provide considerable operational involvement either as a separate or integral feature.
This track arrangement also requires special electrical wiring so be sure to carry out proper research before attempting to install.
A helpful product that claims to automate the entire process is available at the link below is available from AZATRAX, Colorado:
Helix (Or Spiral Loop)
To achieve height in a minimal space some modellers employ a helix arrangement which is basically a single spiral of track which gradually loops around itself in a tight circle until the required height is obtained.
As a hidden device this can achieve spectacular effects of a train disappearing into a tunnel and re-appearing several feet in the air from its start position.
I am indebted to a forum member Mark Pruitt of Model Railroader Magazine for the following simple definitions:
A helix is a three-dimensional curve of less than infinite radius (infinite radius is a straight line) wherein the center of curvature, as you move along the curve, itself moves in space. A few simple drawing explains this far easier than the description.
A spiral is a curve of ever-decreasing (or increasing) radius - essentially in a horizontal plane. Just for fun here is yet another example of a spiral (in H0 Gauge) on YouTube with 8 engines and a grand total of 228 cars by James Risner:
Most helices are generally cylindrical, circular helices - curves of constant radius whose center of curvature moves along a straight (up) line (usually at a constant rate). There are exceptions, and some modellers have built conical spiral helices (curves of ever-decreasing radius whose center of curvature moves along a straight (up) line).
One can conclude that the term "helix" is used fairly loosely to describe any helix-like structure designed to get track from one level to the next.
Here are a few more examples of a 'spiral helix' or is it 'helical spiral?'
Essentially the train negotiates one or more looped curves which spiral over each other allowing it to gain vertical elevation gradually in a relatively small horizontal space. It can be employed as a practical alternative to a switchback and avoids the need for the trains to stop and reverse direction while ascending. If the train is of sufficient length, it is often possible to view the train looping above itself (or the entire installation can be concealed to preserve the “mystery”).
In theory it would be possible to achieve any elevation using this technique provided the incline is not too steep but construction in model form can often prove to be as much of a challenge as on a real railway.
Apparently, strictly speaking only a track that crosses over itself can strictly be described as a spiral – otherwise a loop that curves sharply and turns back on itself in a U-shape is more commonly called a horseshoe curve or bend.
The night-time shot of Horseshoe Curve is the copyright of Brian W. Schaller - Own work, FAL
Somewhat surprisingly there are actually a number of prototype examples for just such a formation even in tunnels! One of the most famous early examples of this concept is the Pennsylvania Railroad's (now Norfolk Southern) Horseshoe Curve just west of Altoona, Pennsylvania. Completed in 1854, this graceful arc crosses two valleys and utilizes three ridges to gain elevation while keeping the grade to about 1.8%. In addition to helping trains get uphill, all of these curves also add friction which helps control the speed of downhill trains.
Other examples of a spiral are Brusio, Switzerland and Tehachapi Loop, central California (see images below):
Switchback, Zig-Zag or Reverse
A
B
C
D
E
F
Summit
Describe your image
Describe your image
Describe your image
Prototype switchbacks are not nearly as common in Europe where rack and pinion lines were used for elevation but the Darjeeling Railway in India features this device for its ascent into the mountains and there is an equally impressive line in Australia at Lithgow, unfortunately not fully operational at the time of writing.
By Kabelleger / David Gubler (http://www.bahnbilder.ch) - Own work: http://www.bahnbilder.ch/picture/11543, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=22541262
“Mix & Match”
As previously mentioned, several separate ovals, crossovers and dog-bones can be mixed together on the same layout to create different levels with multiple trains disappearing into tunnels only to reappear at a different point on the line. This complex arrangement can also be easier to wire and operate if the circuits are kept totally separate from one another allowing more than one train to run simultaneously. Needless to say, with the more widespread introduction of DCC this is becoming less of a problem than with conventional DC installations.
Easements, Superelevation, and Other Related Design Issues
The following section covers three elements of track construction that are slightly similar, but not directly related: viz: easement curves, vertical easements, and superelevation.
All of these are common practice on prototype railways that can be replicated on your garden railway to improve both the look of a layout and theoretically improve operational performance.
The topics of “Easements and Superelevation” are routinely covered from time to time in the model railway press but sometimes explanations get obscured by jargon and mathematical explanations that render them hard for many modellers to fully comprehend. I include myself in that category.
I will try to explain these in simple terms and you will need to decide to what extent you wish to integrate these features into your garden layout.
Easements (or Transition Curves)
An example of railway terminology that you may have already come across in modelling is the term “Track Easement”.
From a purely mathematical standpoint an easement is essentially a railway track laid in the form of a parabolic curve. Note 3 Or to put it rather more simply an ‘easement’ or ‘transition curve’ is a portion of track that gradually eases or smooths the progress of a train from a straight section (tangent) into a curve and vice versa. It is also sometimes described as a spiral curve.
This technique is a common feature on full-size railways as it reduces the side force experienced whilst allowing faster speeds and improving passenger comfort without undue wear and tear. This is not quite as simple to implement in a model railway situation and many would argue that even in large scale modelling it is an unnecessary complication.
Note 3: A parabola is a curve where any point is at an equal distance from: a fixed point (the focus, and, a fixed straight line (the directrix)! No, it’s a complete mystery to me as well!
You will have observed that, for simplicity, basic model railway layout designs invariably use a series of identical radius curves to “turn corners”. Real railways routinely avoid this problem by installing track in a gently tightening curve (or series of “easements”). This is common practice on full-size railways as it reduces the side force experienced and allows faster speeds to be achieved.
Where turns are unavoidable track “easements” are introduced (not to be confused with property easements or wayleaves whereby non-possessory rights are granted by one party to another e.g. those granted to utilities, etc. to lay their wires and pipes adjacent to the railway track).
I have seen the term compared to driving a car where to avoid a sharp change of direction (no doubt causing any passengers much discomfort) you simply "ease" into and out of the curve (sometimes referred to as 'straightening' the curve.)
This short video from TrainMasters explains it much better than I can:
If you feel that your garden railway might also benefit from adopting this practice in order to achieve added realism and smoother operation, not to mention a more fluid and graceful appearance, by all means experiment. As I say, some would argue that it really makes little difference in practice – particularly if you stick to using large radius curves (say 4’ or larger radius or 8’ diameter) but ascetically it always seems to look better and more realistic if you do. There are also other benefits in that easements also help to reduce any lateral overhang which can prove a problem when tight curves are used.
The true geometric “easement” effect is best achieved on a layout by using flexible track which is far more suited to being manipulated into smooth flowing curves of infinite radius.
In fact, if you decide to use Anyrail Software as your planning tool you will find that it contains a facility to apply easements to a length of flexible track. You may also find Trax2 or 3D Planit useful software tools for track planning. I will append a list of such applications at the end of this module.
Unfortunately, the same cannot be said of pre-formed fixed radii curves, which are still favoured by a significant number of modellers, especially in situations where the space available is in any way restricted.
So how do we overcome the non-prototypical “lurch effect” which is often said to be one of the key factors which distinguishes a toy train from a realistic model - most likely because of the obvious overhang of any connected cars.
With individual track segments it is certainly more difficult to achieve a gradual decrease in radius to transition seamlessly from straight to curved track but you can still simulate an easement by laying a combination of curves of diminishing (or expanding) radii until the required transition is achieved.
Thus, if you want to lead from a 5’ radius curve into a section of straight track you would precede it with gradually reducing radii curved sections of say 4’ and 3’ and 2’ radius. The longer you can make the easement the better.
The schematic below better illustrates the concept using Piko G Scale Track Sections:
A similar arrangement can be achieved using LGB sectional track:
"SUPER" EASEMENTS
The possibility occurred to me, whilst editing this module, that in the absence of flexible track smoother transitions can be achieved my creating the easement with pre-formed curved sections sourced from different manufacturers. 'Super Easements' is just a made-up term for this solution.
For example by mixing Code 332 sectional track pieces from both LGB and Piko who use a different track geometry allows one to use the next ascending or descending size radius of curve irrespective of manufacturer. Using AnyRail software to create a comparison chart you will observe that by mixing different radius curves from both sources offers much smaller increments facilitating a much smoother easement.
Please note that in the Anyrail image above Piko Radius 1 (600mm) and LGB 16000 curves have been omitted for clarity.
The resulting easements using this technique are appreciably smoother although the sleeper patterns are not identical and may need to be disguised a little using ballast:
So a complete oval using say, conventional Radius 1 curves in comparison to this suggested approach would look something like this:
If you prefer a more technical explanation of "easements" I recommend this web article published by Sumida Crossing - just use the following hyperlink to travel there at lightning speed:
The following YouTube feature is the only one I could find which covers all three track laying suggestions featured in this module in a practical manner - unfortunately it is directed at small scale modellers using easily malleable flexible track but it does explain the concepts. These are just more difficult to realise in G Gauge.
Gradients, (Grades, Slopes, Inclines & Declines)
Few prototype railways are level as they have to follow the contours of the landscape and that can mean going over hills and mountains rather than tunnelling through them which might prove very expensive to accomplish, both in time, and overall cost.
In fact, given a choice, railway companies will always tend to follow as a straight and level route as possible since locomotives use less energy, speeds are frequently higher, and there's less wear on rolling stock and permanent way. But the terrain rarely offers this luxury and the landscape rises and falls, both natural and man-made obstructions must be negotiated, and all manner of contingencies allowed for.
This means that changes in elevation and the introduction of curves are often unavoidable in order to reorientate the direction of the tracks around these obstacles by means of slopes (gradients in UK/Europe) or grades (in the USA) and elevated sections. Even when grades are unavoidable real railroads have very smooth, gradual changes in elevation and suffice it to say your model railroad will look best if it does the same.
When engineering these physical features care has to be taken to ensure that the planned locomotive roster has sufficient power to successfully traverse these undulations.
For an explanation as to why trains are not actually very good at climbing hills (or descending them) I suggest you watch this excellent video by James May entitled “Why Can’t Trains Go Uphill?”
Builders of real railways usually aim to lay their tracks on as flat a plane as possible to minimise the tractive effort and save on energy costs. In contrast the model railway fraternity delights in having several levels on their layouts to add interest and a touch of excitement
Builders of real railways usually aim to lay their tracks on as flat a plane as possible to minimise the tractive effort and save on energy costs. In contrast the model railway fraternity delights in having several levels on their layouts to add interest and a touch of excitement.
If your layout incorporates more than one level you will probably need to incorporate some means by which your trains get from one level to another. If you model USA railroads it is not uncommon to have 3 or more levels all inter-twined with each other using tunnels, ravines and bridges. In order to simplify operation, you can keep these loops separate but most modellers connect the layers up in some way. The most common way is to introduce inclines (or grades) to enable the train to climb and descend between different layers – particularly where one track is required to cross over another.
Grade Measurement Terminilogy
Around the world, inclines are expressed in slightly different nomenclature but in essence they all arrive at the same answer portrayed in different ways.
In the UK, and places with heavy British influence, gradients are expressed in terms of the horizontal distance required to achieve a 1 foot rise. For example a gradient where track rises one foot over a distance of 100 feet would be expressed as ‘1 in a 100’. Similarly a much steeper rise might be referred to as a ratio of ‘1 in 40’.
The terminology in Europe is much the same but may use the metric “per mille” parts per thousand system expressed as ‰ (similar to a percentage sign but with an extra 0 in the divisor).
In North America, gradient is expressed in terms of the number of feet of rise per 100 feet of horizontal distance. Thus a track rises 1 foot over a distance of 100 feet, the gradient is said to be "1 percent;" whereas a rise of 2‘6” would be a grade of "2.5 percent” and so on. In many ways this method is probably the easiest to comprehend and I have used this nomenclature later in these pages.
Inclines on prototype railways tend to be much gentler than one might find on a large scale model railway. On modern main lines, grades are typically 1 percent or even less whilst grades steeper than about 2.0 percent are quite rare.
For the most part the factors described in the video tends to limit grades on most major railways to a maximum of 4% (4’ in 100’) for high speed express trains tracks and a much less daunting 1.5% (1’6” in 100’) for slow moving freight trains.
Notable Exceptions
Needless to say there are numerous exceptions of even steeper railways around the world using the conventional ‘adhesion system’ (as opposed to those based on rack, cog or cable) which demonstrate that there is a prototype for everything.
The most notable example in the UK is the Lickey Incline in the UK at 1 in 37.7 (2.65%) , and the Docklands Light Railway, London, UK at 1 in 17 (5.88%).
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In the USA the steepest grade on a major railroad's standard gauge mainline track (as opposed to industrial spurs, narrow gauge lines, etc.) is reputed to be on the Pennsylvania Railroad north of Madison, Indiana which is said to rise 416 feet over a distance of 7012 feet -equivalent to a 5.89% grade.
This video clip recreates a ride on the section as alas, the incline has not been in operational use since 1992.
The effect of grades or inclines on train operations is significant. It is estimated that for each percent of ascending grade, there is an additional resistance to constant-speed movement of 20 lbs. per ton of train. This compares with a resistance on level, straight track of about 5 lbs. per ton of train. In the real world a given locomotive can haul only half the tonnage up a 0.25% (1 in 400) grade than it can on the level. Descending grades carry their own penalties in the form of equipment wear and tear and increased fuel consumption.
Three popular tourist lines incorporating steep inclines are the Cumbres & Toltec Scenic Railroad in Colorado, USA with 4% grades ( 1in 25), the White Pass & Yukon Railroad with a severe maximum of 3.9% (1 in 26) and notably the Cass Scenic Railway, West Virginia, USA at an incredible 11.1% (1 in 9) but these are very much the exceptions.
Impact of Grades
Ruling Grade
The term "ruling grade" is used to describe the limiting grade between two terminals. It determines the maximum load that can be pulled over that portion of line by a given locomotive. The concept is analogous to that of the weakest link in a chain; no matter how many lesser grades a train can handle, if it can't make the ruling grade, it won't be able to complete the run.
A ruling grade is also not necessarily the absolute steepest grade between two endpoints; it is assumed that trains will surmount certain steeper grades with momentum from descending grades or with the aid of helper locomotives.
For grades that are short relative to the total length of a train's run, helper engines - extra locomotives added to the front, rear, or even middle of a train - are employed. While the superior power of diesel locomotives has eliminated many helper districts, dieselisation has brought helpers for use on trains going downhill, where dynamic braking is used to control speed on the descent.
If a train cannot make a grade, and no helpers are available, it may have to "double the hill," a practice in which the train is taken up the grade in two separate pieces. On some hills, "tripling" is necessary.
(Reference By “Grades & Curves” by Robert S. McGonigal | May 1, 2006)
This video also offers some sage advice on the subject:
These practical limits on full-size railways are also best observed when building a garden railway layout as there is usually less room to accommodate a realistic incline. According to the experts one should always aim for as level a track as possible to avoid putting too much strain on your model motive power.
Notwithstanding this sage advice as to the acknowledged benefits of maintaining a horizontal plane for optimum running performance many model railway enthusiasts will still entertain a yearning to incorporate some measure of variation in height on their layouts even if the space available is somewhat restrictive. This may be to simply to add interest or perhaps more accurately represent the railway prototype they are seeking to reproduce.
To be honest a flat railway can sometimes appear a little boring so if you are determined to integrate some ‘rise and fall’ there are ways in which this can be achieved without causing undue wear and tear on your cherished motive power.
First we need to learn a little bit more about grades or inclines.
Grade — in railway terms this is the extent to which track rises or descends from one level to another. This can be expressed in a number of ways according to which country you reside in but essentially the formula is usually expressed as:
Rise is the change in height from the beginning to end of the grade.
Run is the horizontal distance from the beginning to end of the grade.
The important thing here is not to have too steep a climb as despite their pulling power locomotive
performance will be severely impaired the sharper the incline and the heavier the load. Whatever the chosen scale the general consensus among seasoned model railway experts seems to be that the maximum rise and fall, certainly on mainline operations, should be around 1 in 50 (or 2%) and ideally average no more than 1 in 60 (1.67%).
However, in certain circumstances (such as branch lines or logging and mining layouts) this can be be increased to 1 in 40 (2.5%) but "under no circumstances" must an incline ever exceed 1 in 30 (3.33%). This guidance is frequently ignored but a good yardstick for newbies.
This latter recommendation is frequently disregarded, despite these fore-warnings, and many modellers have successfully operated railways with much steeper grades than 1 in 30 without recourse to rack and pinion or other technique, such as the use of double heading "banking" locomotives to get better traction but these are the exceptions that prove the rule.
The more gradual the incline the better, especially if negotiating curved tracks, so careful measurements are necessary. Use this link to find a handy calculator for grades:
Below is also a chart for quickly estimating the grades of your layout. This tells you the gradient for a rise in inches per foot (or part of a foot) of run. Find the Rise on the left, and the Run on the bottom. Where they intersect will tell you the Gradient, or read across from where the gradient and run intersect to find the Rise. Alternatively look at where the Rise and Gradient intersect and read down to the bottom for the Run needed. This will quickly alert you to what is feasible on your planned layout.
This advice is all very well but observing these limits can produce some surprising results when it comes to actually implementing them in a garden railway setting. For example. to achieve even a fairly modest elevation in height of say 4" with a 2% (1 in 50) grade requires a minimum length of 200", or in excess of 16 feet, even before any allowance is made for "vertical easement" see below.
To create the slope it is customary to use ‘risers’ of incremental height which should be permanently affixed to a solid base to avoid movement and fixed height supports to underpin the track bed once the chosen elevation is reached. I use concrete for strength and rigidity but you can elect to use any method you prefer. Conversely, the process is reversed when traversing down an incline or slope.
One should also try to incorporate ‘smoothing’ elements to ensure a gradual ride transition from a level track into the incline and also where the incline reaches the summit of the incline to eliminate any tendency for the locomotive and stock to jump off the track - especially on the descent. This procedure is described in the following Vertical Easements section below.
Vertical Easements (or Grade Transitions)
We have already established that a grade (or incline) is normally measured in percent based on a rise in elevation over a certain length (ie. 1 ft up over 100ft length is 1%) but can sometimes be expressed as a fraction or simply "1 in 100". Just as "lateral easements" are recommended when tracks progress from a tangent (straight) to a curve it is also essential to add similar "vertical easements" (or grade transitions) at both ends of a grade in order to achieve a smooth flow from level to grade and grade to level without any sudden jumps or drops.
Such "vertical transitions" (apparently termed "vertical curves" in the civil engineering fraternity) are critical to smooth, reliable operation as without them, couplers are likely to disengage and locomotive wheels can even lift off of the rails, either of which could cause a disrailment. These are just a few of the possible bad things that can happen when vertical curves are missing or not done used correctly.
Essentially, a vertical easement (or grade transition) observes the same principle as for an ‘easement curve’ but in a vertical, as opposed to a lateral, plane. In order to smooth the entry of a train approaching a rising grade from a level track the nominal grade percentage is ‘softened’ so that locomotives, coaches or wagons with a long wheel-base are “eased” into the next stretch of line without experiencing a sudden hump or hollow. The same easing process is also followed at the exit of the grade to its new level. This has the effect of extending the overall length of the actual incline compared to a raw calculation but achieves a much smoother passage.
This diagram illustrates the theory:
Vertical transitions using cut-out marine plywood, or similar weather-resistant roadbed, are actually pretty easy to accomplish, with not much math involved. If you have known upper and lower elevations and also know the length of the run between them, then you can easily determine your grade percentage. While the grade percentage with vertical easements won't be constant, for the purposes of establishing the easements, we'll assume that it is.
Fasten the roadbed in place at both the top and the bottom of the grade, then find the mid-point of that run and, using a riser, fasten the roadbed there at a height one half that of the total climb - you may need to raise or lower the roadbed at that point to accomplish this. Next, without raising or lowering the remaining unsupported roadbed, add sufficient risers for proper support, simply setting their tops at a height equal to that of the bottom of the unsupported roadbed.
For long grades, after adding the riser at the mid-point, subdivide the two halves of the grade again, and raise those new mid-points to 1/4 and 3/4 of the total rise, and you can further subdivide as necessary for especially long climbs. To avoid negating the natural vertical easements which will have formed at the top and bottom, though, don't overdo this procedure - you only need to remove any obvious snags.
Irrespective of what method you use,the key essential is to try and ensure that your inclines are as gentle as possible as any sudden change in gradient can place a considerable strain on your motive power. In simple terms the steeper the incline the greater the load on the locomotive, especially on the motor and gears which can prove costly to replace. It is one of those tasks where it is probably better to abandon any attempt at making detailed calculations and simply install your track on a solid base using shims and, supports and piers at regular intervals to spread the load and adjust these until it "looks about right". Test with a locomotive pulling a reasonable load and check for any "jumps". Make adjustments and test again until everything runs smooth.
One tip I came across is that if it proves difficult to measure the actual run simply measure the track length. It can sometimes be awkward to measure the run. Scenery and structures may interfere. Fortunately, your grade calculation will be accurate enough if you simply measure the actual track length from the beginning to the end of the grade. This results in a relatively small inaccuracy but in not enough to seriously matter in the context of model railways.
Remember, if the grades are still too steep you might also consider adjusting the rise and fall of the surrounding scenic terrain to create the illusion of an incline whilst keeping your track fairly level.
Articles dealing with application of these principles to large-scale rack are few and far between but the following links are recommended for further enlightenment:
Greg Elmassian "Building Your Garden Railroad"
MyLargeScale.Com Forum: "Proper Use of Easements"
MyLargeScale.Com Forum: "Banked Curves"
The exception that proves the rule. A 12% grade on the famous Cass Scenic Railroad in West Virginia. Don't try this at home.
For more information click the link below:
S-Bends (S Curves)
Before I finish this module I feel I must mention the dreaded "S-Bend". In railway terminology an S-bend or curve is created when two sections of curved track are connected facing opposite to each other viz.
What do all the above illustrations have in common? Yes - they are all reverse curve formations.
Since the dawn of time (well not quite that far back) railway modellers have been cautioned to avoid using "S-Bends" (or "S-Curves") at all costs. It is a “big no-no” punishable by frequent derailments,’ locking couplers, unrealistic ‘toy train’ appearance and even’ tear a hole in the fabric of time’ according to one humorous hobbyist.
As a general rule, it is widely recommended that you avoid introducing “S” bends as much as possible as not only can they often be the cause of derailments the locomotives and rolling stock are placed in somewhat unnatural positions thereby destroying any realism.
As a result, individual cars of a train are obliquely offset as they change direction when crossing an S curve. Depending on the length of the stock and the radii of the curves, this offset can prove severe enough to cause coaches or wagons to tilt, since the facing couplers are unable to swivel enough to accommodate the bend.
Despite this sage counsel a quick look at any track plans is liable to reveal numerous instances of where S-bends are incorporated in nearly every layout design. Even a simple cross over between two parallel tracks will form an S bend but if negotiated at low speed is unlikely to cause operation difficulties.
In mitigation, such crossovers, invariably comprising of two turnouts facing each other, are rarely curved throughout and end in a straight section at both ends. Even on single track railroads there is a certain beauty in watching a train snake through a pass at slow speed.
I urge you to read his article in the inaugural January 2009 issue of Model Railroad Hobbyist by columnist Tim Warris entitled “PARALLEL LINES: Examining S Curves” which covers the situation in expert depth. Click on this link for an abridged version:
Whether or not a particular S bend will work from an operational standpoint is verymucg dependent on
1. Radii of curves used
2. Size of equipment used
3. Speed at which it is negotiated
4. Type of coupling (body or truck mounted) Click here for
So, if you do are tempted to install one and risk the wrath of the railroad gods, use as large a radius of curved track as you can accommodate and if this is not possible (e.g. in a goods yard) try to make sure that there is a straight section between the two opposing curved sections at least of equal length to your longest car.
Keeping Everything Level
In general, when laying model railway track, it is vital to keep the railheads level as far as possible (in both longitudinal and transverse directions) especially where points are concerned. In truth there is no real overriding need to introduce cambers other than from an aesthetic viewpoint unless you prefer the appearance but be careful as if it is not done properly you may create a raft of unwelcome problems.
