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Turntables, Traversers Points and Slips
Turntable points and slips are devices that connect two tracks together so that stock could move from one line to another. In the very early days of the railways points were prefabricated in a factory and supplied in kit form to be assembled on-site, by hand. Making points was pushing the limits of the technology, they were expensive to make and maintain and a fault would result in a derailment. They did allow an entire train to be drawn from one line to another but this required a gentle curve to connect the tracks. To avoid the use of points and save a lot of space the early railways made great use of small hand operated turn-tables to transfer rolling stock and even locomotives from one track to another. On a standard gauge line these would be circular and perhaps twelve feet in diameter, usually with two sets of tracks across then in the form of an X.
One point to note is that the tracks leading from the wagon turn-table need not be at right angles, in some locations several tracks converged and actually overlapped slightly where they met the turn-table.
The early railways often took a single siding into a goods yard, where a turntable then fed a series of sidings radiating out from it. In the mid 1830's the Liverpool and Manchester railway had over sixty such wagon turn-tables at it's Manchester goods depot, which by this time extended over more than four acres. Goods yards were generally re-laid with points from the later 19th century, but this required more space and occasional surviving turntables were seen in goods yards into the 1960s. One notable example being the station at Llanfairpwllgwyngyllgogerychwrndrobwllantsiliogogogoh on Anglesey, opened in 1848 and known locally as Llanfair P G, where a cramped site meant the single wagon turntable feeding several sidings in the goods yard remained in use up to the end of goods traffic in the 1960s.
The typical small wagon turn-tables could handle wagons of up to about a maximum of twelve foot wheel base, anything longer represented a problem. By later nineteenth century the century several companies were using much longer wagons which were too big for the existing turn-tables. Large wagons mounted on bogies could however be handled on wagon turn-tables using the technique illustrated in the sketch below. First you position the wagon with the leading bogie on the turn-table (1), rotate this to line it up on the new track (2) and pull the wagon along, usually using ropes and either powered capstans or horses, until the rear bogie reached the turn-table (3), then turn this (4) so the wagon could be pulled off the turn-table (5).
Fig___ Wagon Turn-tables & Bogie Stock
Using turntables wagons could be transferred between tracks that crossed at right angles, which had several advantages in a factory or railway goods yard but by the 1850's it became apparent that the turn-tables were becoming a bottle-neck. With wear and tear they were not as reliable as had been hoped and they could only transfer a single wagon at a time, requiring a man or horse to move it. It was at about this time that the technology for bending rail using portable equipment such as hydraulic jacks became available, so that points could be readily made on-site and making them cheaper than turn tables. Thereafter points and other complex track formations started to appear in greater quantity, allowing locomotives to be used for shunting.
Turntables remained in use in many industrial locations into the 1950's and 1960's and the railways continued to use them in some large goods yards and in their own works. Probably the last turntables in regular use were on the dockside lines feeding coal tipping apparatus. They were required as wagons with an end-door at one end only had to be turned round to face the right way and they lasted until the end of the coal hoists in the mid 1980's.
In some locations the turn-table was located at the entry point to the factory (this arrangement appears to have been quite common at wagon works) however this did mean that locomotives could not be used to move the wagons as they were too big and heavy for the turntables. The British favoured fairly small four wheeled railway goods vehicles so individual wagons could be pushed about using man power but in busy locations such as town goods yards it was common to use horses or ropes run to 'capstans'. This saved running a locomotive and even after the turntables had been replaced the shunting horse and 'capstans' remained very common in British yards. A capstan is a revolving drum, generally with a `pinched' middle section, set on end and in railway yards they were usually powered by electricity. Some capstans were controlled by a lever operated clutch but others simply ran all the time, the rope was dropped over in a couple of turns and friction hauled the wagon into place. A skilled man could throw the rope over the drum and clear it very quickly, however accidents did occur. The last British railway installation equipped with capstans was completed in the 1950's.
One thing to note is that not all capstans were motorised, some were simply bollards placed so the rope from the shunting horse or from a powered capstan could be looped round them. These were provided where the track ran up against a wall or other obstruction to enable a horse (or a separate powered capstan) to pull the wagons right to the end of the siding.
A single siding at a warehouse or factory might have a track running along one wall with a row of wagon turn-tables, each feeding a different bay. In some cases the bay would be a small dead-end recess or there might be further turntables inside a building serving tracks inside. This can be used to advantage as it makes the building appear more important than might otherwise be possible, an example of such an arrangement is shown in Fig___ below.
Fig___ Wagon turn-tables & Capstans
On some narrow-gauge quarry lines the wagon turntables were often very simple, one consisted of a simple circular metal table with a raised circular centre the diameter of which was the same as the gauge of the track. As the wheel arrangement on the quarry wagons was virtually a square this design worked well. These simple one-piece turntables are often called 'turnplates'
Fig___ Suggestion for using wagon turn-tables.
I have not yet seen a working wagon turntable in N (there have been a few in OO and O) however Peco offer a dummy wagon turntable in their 009 range, this can be used with N Gauge wagons but only as a cosmetic item. Some ranges of set-track include a 90 degree crossing, this can be cut down and used as the basis for a wagon turntable and would allow smooth running along the line.
A variation on the turntable used for locomotives was the 'sector plate', this was a length of track sitting in a quadrant shaped pit and pivoted at one end (effectively a half-turntable). The free end was arranged to line up with (usually) two tracks and this was used on some passenger termini to allow a locomotive to be released and run-round its train. These sector plates were usually fairly small, only able to handle a large tank engine, although they a definite space saver they do require some skill to build.
The final alternative to the wagon turntable was the 'traverser', a platform on rails sitting in a shallow brick-lined trough running at right angles to a row of sidings. A wagon was placed on the traverser and could then be moved to any of the other sidings it served. These were fairly common in goods sheds, as wagons were emptied they were moved onto the traverser and thence to a release road, so they could be removed from the shed without moving all the other stock still being worked on in the shed. There were also used in some passenger stations, notably at the end of a 'carriage shoot' where private road vehicles were being handled, this allowed each wagon to be unloaded without things having to travel through or across several other wagons. Larger version were also used in large railway establishments where locomotives and coaches were being built. Again I have not yet seen a working traverser (other than in a fiddle yard) for N Gauge but they are an easier option than a wagon turntable.
It was necessary to indicate to staff where the various controls associated with the hydraulic or electrical machinery were located, the cast iron signs shown below are typical, these were photographed at the Manchester Museum of Science and Industry, part of which is the original 1830 goods warehouse for the Liverpool and Manchester Railway, later part of the LNWR.
Points and Slips
Most points, or turn-outs as they are often called today, simply allow one line to split from another, there are however variations; the 'double slip point' is a complicated arrangement which serves as both point and crossing and the 'single slip' is a variant which allows line changing in one direction but not the other. In N Gauge single and double slips as well as standard points are now available in the Peco range. The Fleishmann N Gauge ready-ballasted 'profi track' range has no single slip but it does offer a double slip and also a most useful three-way point with tracks diverging to both right and left.
In cases where one track has to cross another a 'diamond crossing' is used, named after the diamond shape formed where the tracks cross. In Britain crossings on the level were not common and tracks very seldom crossed each other at right angles, other than at junctions and in the approaches to stations one or other track would normally pass over or under the other via a bridge, however Jeremy Skelton commented that:
You say you don't know of a right-angled crossing on a running line in the UK - I may be missing something, but doesn't the flat junction just north on Newark on the East Coast Main Line count? The other line is the one from Lincoln to Nottingham. The two double-track lines crossing each other constitutes a serious bottle neck.
Further information can be found at Level junction From Wikipedia, the free encyclopedia I had completely forgotten about the Porthmadog crossing between the Cambrian Coast line and the Welsh Highland, which for added interest is mixed gauge, maybe because I've never been there!.
Points on running lines used by passenger stock were arranged wherever possible in a trailing direction, that simply means that the train would normally never encounter a diverging track on a running line. Trains were normally required to reverse over points on running lines to change from one line to the other. Where this could not be arranged the point was fitted with a locking device, this could be a lever operated device connected to the signal box (in which case the point would have a protective bridge in wood or (more commonly) metal over the mechanism). In some cases the point was manually locked for main line running using a padlock. The illustration below shows (left) such a mechanism exposed (photographed inside a passenger station), and (right) what it would look like when covered.
Fig___ Point locking mechanism
The use of points and slips and the rules on the trailing junction and the trap point, are well illustrated in the track plan shown below, which is based on Hale station, built by the Cheshire Midland Railway south of Manchester on the old Cheshire Lines route to Chester. This station is a particular favourite of mine as the basis for a model railway and it is more fully discussed in Appendix ___.
Point 'A' serves as the trap point, protecting the main lines from the goods yard. Points 'B' and the single-slip point 'C' form 'trailing cross-overs', that is trains have to reverse to change from one line to another, the two sets form a loop to enable goods trains to run round the rake whilst shunting. Note that 'C' is a single slip point, if it were a double slip it would present a 'facing point' to the lower track of the main line. Access to the coal yard 'D' would normally face the direction of travel (as shown by the arrows on the right), so instead it is fed from a trailing head-shunt 'E'.
Fig___ Typical double-track station track plan
At junctions the methods varied, with the development of
mechanical point and signal inter-locking systems things became
easier, but in general facing points remained rare. Even on branch
lines it was common practice to use a crossing (or 'diamond') to
carry the line across the facing line on double track lines.
Fig ___ (1) shows two double tracks forming a junction, note the trailing cross-over which allows emergency 'wrong line operation'. Where a single track joined a double track line it was common practice to split the single line into two, carrying one across the facing line of the double track via a diamond crossing as shown in Fig___(2). Note the sand-drag on the branch line feeding onto the double track line, sand drags were also put in where the diverging line ascended a gradient to catch run-away wagons. This track plan also shows how a single slip could be incorporated to provide a trailing crossing, again to allow 'wrong-line operation' on the double track line in an emergency. Crossings were even used where the line being joined became single track immediately after the junction as shown in Fig___(3). Note the track plans shown are only based on the quoted examples, they are not complete or to scale.
After an accident in the 1870's involving a passenger train, where some wagons rolled back out of a goods yard and fouled the points on the main line, a new regulation was introduced concerning 'trap points'. These resemble about half of a conventional set of points but they do not connect to another track, their job is to de-rail wagons rolling from a yard toward a main line. In practice this tended to damage the errant wagons, and they then needed to be manoeuvred back onto the rails to clear the line for other traffic, so quite a few companies used a full point leading onto a length of track which was banked up with sand to catch the wagons. The banked sand was called a 'drag'. On some yards where there was no gradient as such they simply had a short length of track with a set of buffers on the end as wagons travelling slowly would be stopped by these and did not require the 'drag'.
A variation on this idea is the 'catch' point, installed at the foot of an incline these resemble trap points but the blades are spring loaded. A train going up the hill will pass through with no problems but loose wagons rolling back on the wrong line will be de-railed. These catch points always had a large wooden sign close by, painted white with CATCH POINT written on it in black, typically the lettering was about a foot (30cm) high.
British terminology divides the point into two sections, a number, indicating the length of the switch rails and a letter indicating the crossing angle of the frog (the bit where one rail crosses the other). There is little point in having a table of these units however as on a model railway the rule of thumb is to use the longest point with the shallowest crossing angle you can fit in the space available. This is especially important where an 's' curve in involved, such as when a train has to cross from one line to the other on a section of double track.
The Americans use a slightly different system, their points are identified by a number which refers to the angle at which the track diverges. For example the two diverging tracks from a 'No.6 switch' will separate by one unit for every six units of length (i.e. six inches from the frog the tracks will be one inch apart).
In N the Peco set track point has a nine inch quoted radius and should only be used in docks or industrial establishments, the Peco medium radius point has an eighteen inch quoted radius and is suitable for most purposes and the Peco large radius point has a quoted radius of thirty six inches. The most common point on British lines has a radius equivalent to about thirty inches in N and hence the Peco large radius point is suitable for high speed cross-overs on main lines.