Editing Railroad switch (section)

== Components ==

=== Switch rails (points or point blades) ===
[[File:Point blades.jpg|thumb|left|A pair of tapered moveable rails known as ''switch rails'' (''points'' or ''point blades'').]] ''Switch rails'' (''points'' or ''point blades'') are the movable rails that guide the wheels towards either the straight or the diverging track. They are tapered, except on ''stub switches'' occasionally found in industrial sidings, which have square ends.

In popular parlance in the UK and most other Commonwealth countries, the term ''points'' refers to the entire mechanism. In professional parlance, the term refers only to the movable rails and the entire mechanism is named ''turnout'' or ''points and crossings''. Turnout and switch are terms used in North America in all contexts.

In some cases, the switch blades can be heat treated for improvement of their service life. There are different kinds of heat treatment processes such as edge hardening or complete hardening.

The cross-section of the switch blades also influences performance. New tangential blades perform better than old-style blades.

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=== Crossing (frog) <span class="anchor" id="Frog"></span>===
<!--"Switch frog" redirects here.-->
[[File:Cast frog.jpg|thumb|upright|left|A one-piece cast ''crossing''. The shiny line crosses the rusty line. This North American "self-guarding cast manganese" component without guard rails has raised flanges on the crossing, which may bear on the face of the wheel as it passes through.]]
[[File:Eisenbahnweiche detail.jpg|thumb|Left, the ''crossing'' or ''frog'' with its adjacent ''wing rails''; right, the ''guard rail'' or ''check rail'']]

The '''crossing''' or '''frog''' is the component that enables passage of wheels on either route through the turnout. It can be assembled out of several appropriately cut and bent pieces of rail or can be a single [[Casting (metalworking)|casting]] of manganese steel. On lines with heavy use, the casting may be treated with [[Shock hardening|explosive shock hardening]] to increase service life.<ref>{{cite book |last=Meyers |first=Marc A. |date=1994 |title=Dynamic Behavior of Materials |publisher=John Wiley |location=New York |isbn=978-0-471-58262-5 |pages=5; 570 }}</ref>

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=== Guard rail (check rail) ===
{{Main|Guard rail (rail transport)}}

A ''guard rail'' is a short piece of rail placed alongside the main (stock) rail opposite the crossing. These ensure that the wheels follow the appropriate flangeway through the frog and that the train does not derail.<ref>{{Cite journal |last=Donahoe |first=M. |date=October 1914 |title=Proper Type of Track Accessories |url=https://books.google.com/books?id=v3kfAQAAMAAJ&q=railroad+guard+rail |journal=Railway Engineering and Maintenance of Way |volume=10 |issue=10 |page=[https://www.google.com/books/edition/Railway_Engineering_and_Maintenance_of_W/v3kfAQAAMAAJ?hl=en&gbpv=1&pg=PA415 415] |access-date=10 April 2025 }}</ref>{{Failed verification|date=April 2025||reason=Doesn't cover the claimed content.}}

''Check rails'' are often used on very sharp curves, even where there are no switches.<ref>{{cite news |url=http://nla.gov.au/nla.news-article10038956 |title=Scene of the Accident |newspaper=[[The Argus (Melbourne)|The Argus]] |location=Melbourne |date=29 January 1906 |access-date=20 July 2011 |page=7 |publisher=National Library of Australia }}</ref>

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=== Switch motor ===
[[File:FAW-points1.jpg|thumb|The ''switch motor'' (in this case an electric motor) and associated mechanism used to operate this switch can be seen to the right in the picture.]]

A ''switch motor'' or ''switch machine'' (point motor or point machine) is an electric, [[hydraulic]] or [[pneumatic]] mechanism that aligns the points with one of the possible routes. The motor is usually controlled remotely by the dispatcher (signaller in the UK). The switch motor also includes electrical contacts to detect that the switch has completely set and locked. If the switch fails to do this, the governing signal is kept at red (stop). There is also usually some kind of manual handle for operating the switch in emergencies, such as power failures, or for maintenance purposes.

A patent by [[1897 in rail transport|W. B. Purvis]] dates from 1897.

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=== Switch stand (points lever) ===
[[File:Railroad switch, Grain elevator district, Minneapolis.jpg|thumb|An example of a mechanism used at a switch. The two points are linked together with a throw bar (also known as a stretcher bar). The throw bar extends to the lever on the near side of the track, which is used to ''throw the switch''. This is an example of a low switch stand, used at locations where there is not sufficient clearance for a tall switch stand. This particular stand is designed to be trailed through by rolling stock, which will cause the points to become lined for the route that the wheels have passed through. It has a reflectorized target.]]

A ''switch stand'' (''points lever'' or ''ground throw'')  is a lever and accompanying linkages to align the points of a switch by hand. The lever and its accompanying hardware is usually mounted to a pair of long [[Railroad tie|ties]] (sleepers) that extend from the switch at the points. They are often used in a place of a switch motor on less frequently used switches. In some places, the lever may be some distance from the points, as part of a [[lever frame]] or ground frame. To prevent the tampering of switches by outside means, these switches are locked when not in use.

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=== Facing point lock ===
[[File:Facing points Broomhill.jpg|thumb|left|A set of points on the Strathspey Railway in Scotland. The facing point lock in the middle will need to be withdrawn using the blue lever (behind) on the left before the points themselves can be moved using the black lever (front). Once the points have been moved the lock will be pushed in again with the blue lever to lock the points in position.]]

A ''facing point lock'' (''FPL''), or ''point lock'', is a device which, as the name implies, locks a set of points in position, as well as mechanically proving that they are in the correct position. The ''facing point'' part of the name refers to the fact that they prevent movement of the points during facing moves, where a train could potentially ''split'' the points (end up going down both tracks) if the points were to move underneath the train. During trailing moves, the wheels of a train will force the points into the correct position if they attempt to move, although this may cause considerable damage. This act is known as a "run through".

In the United Kingdom, FPLs were common from an early date, due to laws being passed which forced the provision of FPLs for any routes traveled by passenger trains – it was, and still is, illegal for a passenger train to make a facing move over points without them being locked, either by a point lock, or temporarily clamped in one position or another.<ref>{{cite web |url=http://www.railwaysarchive.co.uk/documents/BoT_Requirements1902.pdf |title=Requirements in Regard to the Opening of Railways |website=RailwaysArchive.co.uk |date=1892 |publisher=British Board of Trade }}</ref>

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=== Joints ===
''Joints'' are used where the moving points meet the fixed rails of the switch. They allow the points to hinge easily between their positions. Originally the movable switch blades were connected to the fixed closure rails with loose joints, but since steel is somewhat flexible it is possible to obviate this looseness by thinning a short section of the rail's bottom itself.

=== Straight and curved switches ===
Turnouts were originally built with straight switch blades, which ended at the pointed end with a sharp angle. These switches cause a bump when the train traverses in the turnout direction. The switch blades could be made with a curved point which meets the stockrail at a tangent, causing less of a bump, but the disadvantage is that the metal at the point is thin and necessarily weak. A solution to these conflicting requirements was found in the 1920s on the German Reichsbahn. The first step was to have different [[Tangential turnout|rail profile]] for the stock rails and switch rails, with the switch rails being about {{convert|25|mm|2|abbr=on}} less high, and stockier in the middle.