©FINCKEN MINIATURE RAILWAYS 1997
HINTS & TIPS ON LAYING MINIATURE RAILWAY TRACK
Having designed the proposed miniature railway, to fit in with the limitations of the site and other relevant design criteria, the next task is to start the construction process. These notes should not be taken as a definitive construction manual but have been produced to help unravel at least some of the mysteries of track laying. If at all possible it is to be greatly recommended that even if the railway cannot be built in its entirety at the first instance at least the majority of the surveying and groundwork should be done in one go. For a small line it is quite possible to create the track formation by digging cuttings and making embankments by spade and wheel barrow, however if it is at all possible mechanical excavation is to be highly recommended. Small diggers are available from many hire shops and one can spend many a happy hour learning to master them. They can also be hired with a professional driver and it may well be that taking this option makes greater economic sense as a highly skilled operator may be able to do in a few hours what will take the novice several days to accomplish. These small diggers have quite a limited capacity and if access to the site will allow it a larger machine is to be preferred.
CLEARANCES
One needs to bear in mind when considering the track formation the clearances that are likely to be necessary. There are now recommended guideline clearances for safety and although they may seem to be over generous, they are now well established precepts. Although these have been prepared with a view to commercial operations, they remain good principles on which to build private railways. Very few railways are truly private, most have open days from time to time or at least carry invited friends and neighbours. There is a serious duty of care in carrying passengers and safety must be considered of paramount importance. It has been suggested that there be 1 metre clearance between the sides of stock and the sides of cuttings, tunnels or other structures. On embankments there should be 1.2 metre clearance between the side of the stock and the top of the embankment, There should also be 1.2 metres between sides of stock on adjacent lines and there should be a minimum of 2 metres between rail level and the underside of bridges and tunnels. Signal posts should be sited a minimum of 610 mm away from the side of vehicles.
SURVEYING THE SITE
This can be done with very simple equipment or with more complex professional surveying instruments. It is essential to establish at an early stage the levels of the proposed route. A simple way of achieving this over a long distance is by using an ordinary garden hosepipe with a clear piece of plastic tube a foot or so long fixed in each end. Lay the hosepipe along the ground over the proposed route and with the aid of a helper holding the end above ground level top up with water. This will then provide an extremely long spirit level and by driving posts in to a datum level, it will quickly become clear what the real levels of the ground are. Appearances are often deceptive and a piece of land can seem flat until it has been measured. The Victorian principles of Cut & Fill, where the amount of soil to be dug out equals the amount needed to fill or make up embankments is a useful precept to copy when calculating the earthworks for a given railway.
PEGGING OUT
Having roughly surveyed the site, the course of the route should then be pegged out at six foot intervals and mark on these, both the datum level and a level relating to the elevation of the track. A conventional spirit level, taped to an unwarped piece of wood, six feet long will enable the level mark to be transferred from one post to the next. It is likely that a cumulative error may creep in using this method , so it is a good idea to check occasionally over several lengths using the hosepipe method. Whilst straight track is quite easy to peg out using the sighting technique (6' garden canes are good for this) curves can be rather more difficult. If the ground is open and unimpeded, then arcs can be planned using a long surveyors tape, but if they are obstructed by building or trees it may not be possible to do this. Under these circumstances one can either produce a set of templates which can be laid down and followed or the progress of the pegs can be plotted by a series of offsets.
PREPARING THE TRACK BED
Once the line is pegged out the earthworks can begin, and these should be undertaken if possible some time before it is intended to lay the track to give the earthworks time to settle. Embankments in particular are likely to suffer from settlement over a period and it is as well to try and allow for this at the time of construction by making them slightly higher than intended. It will be necessary to transfer the level posts to a series of offset posts perhaps 3 metres from the centre line of the track formation as the first part of the earthworks is to take off the top soil along the line of the pegged out route and stack this somewhere handy. Wherever it is stacked will almost certainly be discovered to be the wrong place later in the operation!! Top soil is a valuable commodity and it may be needed later for covering the sides of embankments or cuttings. Although it is tempting where embankments are to be constructed, to just leave the top soil in situ it is much better to remove the top soil, as the made up soil of the embankment will ‘bond’ much better to subsoil than if the top soil is left. It is also important to allow for drainage through embankments particularly on slopes where rainfall can create unintentional ponds against the sides of the emnbankment. It may seem unlikely but if cuttings are deep, particular attention needs to be paid to the danger of collapse and land slides as even on a miniature railway the problem can be very real. The angle of the batter (that is the slope on the sides of cuttings and embankments) needs to be less than the angle of repose of the soil or subsoil. Having reached the desired depth of cutting it is a good idea to lay a semi permeable membrane down before laying the stone, this has the effect of stopping particles of soil working up into the ballast and from preventing weeds from rooting so easily through the ballast. Black plastic, (Silage sheets from an Agricultural supplier) is a cheaper alternative that still does a good job, though holes need to be made with a garden fork at frequent intervals to stop it acting as a pond liner! It is particularly important in areas where the subsoil is claylike to pay attention to the drainage in the bottom of cuttings, it is all to easy to end up with a long thin garden pond every time it rains. Once the earthworks have been prepared there should be a broad path (see notes on clearances,) extending over the entire route of the railway.
BALLAST
Ballast serves at least two main purposes, it supports the sleepers providing them with a firm base and allows the water to drain away. The counsel of perfection is to used clean hard drain stone. On no account use what is sold in builders merchants as ballast, otherwise known as shingle whether crushed or otherwise. All these types of stone are like trying to lay track on ball bearings. Many miniature railways are laid with ballast that is really far too small, It is fine to use small stone as a top dressing if the look of the ballast is important, but larger stones say of about 1" provides a really good robust and free draining basis with good levelling qualities. The sub base can be of very coarse stone, even ‘crush to run’ or ‘quarry waste’; ‘Scalpings’ are also good, the amount of dust helping to set the base very solidly. Once the ballast has been laid then it should be raked out level and compacted as far as possible either by walking over it repeatedly or by mechanical methods such as a "wacker" plate which can be hired from tool hire shops. After the track has been laid a small amount of fill should be spread over the track taking care that it does not come above sleeper height. An exception to the recommendation for using large size ballast is where the sleepers and their spacing is near to scale , under these circumstances the ballast alone is unlikely to hold the track sufficiently in place and some form of additional restraint (e.g. screwing down to battens or a concrete sub base may be necessary).
RAIL
Rail comes in all sorts of sections and materials. There is considerable discussion on the merits and detractions of Aluminium Alloy versus Steel rail and much of this is based on poor information and personal bias. Each has its application in the miniature railway world, Aluminium doesn't rust whilst steel does, (This has the added advantage of keeping engines and stock cleaner) Aluminium is quieter, Steel makes a more railway like sound, Aluminium is easier to work, Steel is more robust. Advocates of both claim each to have superior adhesion over the other (All rails have impaired adhesion factors under adverse conditions, e.g. The Wrong Sort of Leaves on mainline steel rails!!). Aluminium also has a higher coefficient of expansion, consequently steel needs less allowances for expansion. Steel has the advantage of being harder wearing and arguably requires less routine maintenance. On heavily used tracks on public lines with sharp curves this a major consideration. When choosing a rail section and material try and find the one that is most appropriate for your requirements.
SLEEPERS
Need to be much larger than would be suggested by scaling down full size ones. It is difficult to give precise recommendations as so much depends on the material and rail section used, the size of ballast, and the type of stock to be used. In any event the length should not be less than twice the gauge. The larger the cross section of sleeper the greater its 'footprint' and its resistance to side ways movement. Wooden sleepers may be of either soft or hardwood, but it is a mistake to think that hardwood sleepers will necessarily outlive treated softwood ones. Larch suitably tanalised has good lasting qualities and being home grown does not contribute to the depletion of the rain forests. Sleepers have also been made of concrete, pressed steel and plastic.
CURVES & CORNERS
When it comes to laying curved track; try and keep the radii of curves as generous as possible. Some engines will go round ridiculously tight curves but they are not happy!! Transition curves are a useful device which can be used to ease the transition from straight track to curve, but these must be planned and allowed for at the pegging out stage. Basically transition curves are curves of intermediate radius which lead from straight track, to a curve. It is a good idea to try and avoid reverse curves unless a trasition curve or portion of straight track at least the length of the longest vehicle can be incorporated. Rail whether of Alloy or Steel should always be rolled to the desired curvature before laying. Rail that has simply been sprung into position will always try and straighten itself at the weakest point (almost invariably the fishplates) resulting in track that is shaped like a fifty pence piece. As curves are laid the inner rail will stick out and need to be trimmed off and drilled for fishplates if it is desired to have parallel joints, alternatively the position of the joint can be allowed to become staggered progressively as the curve progresses and it can than be trimmed off square before joining the next panel. There is an advantage in staggered joints in that it tends to reduce the kinking of rail at joints. However drop joints can still occur, causing an alarming and potentially hazardous "rolling" of the stock. It is also a real nuisance if the track has to be lifted at any future date, as it is much easier to undo a few fishplate bolts than start unscrewing sleepers. It is easy enough to make a simple rail bender, but most reputable suppliers of rail will either offer to roll the rail for you or let you borrow their machine.
GRADIENTS
One of the most frequently asked questions is "what gradient will my equipment go up?" The answer is that miniature railway equipment will go up surprisingly steep gradients, but the hauling power is significantly decreased the steeper the gradient. The combination of gradients and curves has a double effect as the increased rolling resistance against the curves also reduces hauling power. Although locomotives will go up comparatively steep gradients, there is also the problem of coming down them! - both in terms of braking power and perhaps more fundamentally the danger for steam locomotives of the firebox crown being uncovered by water as all the water in boiler moves to the smokebox end. A good rule of thumb is to aim for a gradient of 1 in 100 or 1 in 80 and accept short lengths of 1 in 50 or so. If a railway has some gradients it certainly makes for more interesting driving, but one needs to provide adequate braking systems and safety chains for rolling stock.
ASSEMBLING THE TRACK
It is often easier to make straight track up in panels and then transport them to the rail head. If your railway is going to involve a lot of track making it can be worthwhile to make up simple a jig for sleeper spacing. It is a good idea if using screws to fix down the rails either with or without rail clips to invest in a good power screwdriver and at least one spare battery pack. The sleepers will also need drilling for the track screws and it makes sense to make a metal jig to facilitate this. Remember that a second jig which incorporates gauge widening will be necessary if you have curves tighter than about 50' radius but no more than an additional 1/8" should be allowed on the gauge. For laying curved track one can make it up in panels using a jig, but it is much easier to screw down just one rail to the sleepers and then laying it down on site screw up the other rail in situ. Its a good idea to tighten up a few of the screws to start with, and then go back and do up the rest later when it is absolutely certain the track is in the correct position.
LAYING THE TRACK
Once the formation is down track laying can commence in earnest. Assuming at least the straight track has been preassembled in track panels, they can then be laid down on the prepared levelled and firmed track bed. An expansion gap needs to be left between each rail joint. "Fishplates" are used to join the rails together and are used in pairs, one each side of a piece of rail. They should be fitted with four nuts and bolts with the nuts on the outsides of the rail. The holes in the rail should be larger than the size of the bolts and they need to be adjusted so that they hold the rail firmly but can still allow the rail to move with expansion. The width of the expansion gap depends on the type of rail used and the temperature when it is laid. As steel expands and contracts less it needs a smaller gap than aluminium. If the rail is laid in cold weather a larger gap needs to be allowed than if the weather is warm. If the weather is very hot, only a small gap need be left.
TAMPING & FETTLING
After the track has been laid on the prepared surface of the trackbed it will need "topping up" with ballast around but not above the tops of the sleepers. Unless the track base was prepared with absolute precision it is likely that the track will need some packing to bring it to level. This should be undertaken by shovelling ballast under each end of the sleepers. The easiest way to do this is to turn your garden spade around and with the back of it towards the end of the sleeper, make a series of 'chopping' movements. This will force the ballast under the ends just where it is needed.
SUPERELEVATION
Superelevation is the cant or raising of the outer rail on curves. When properly used it enables trains to negotiate curves at greater speed it should however be kept to a small amount on miniature railways, 1/8" being the maximum for 7¼" gauge lines. For lines where curves are generous and the speed is low (5mph or less) no superelevation is needed. The worst possible scenario is to have reverse cant where the outer rail is actually lower than the inside one. Superelevation where it is used should have a transition phase from the level not exceeding 1 in 300.
AND FINALLY.........
The laying of Miniature Railway Track is an area where just a little extra time and care with the preparation will produce dividends over many years not only in terms of reduced maintenance but also in terms of improved safety and trouble free running.
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