The double slip switch is a central element of modern track infrastructure – compact, technically sophisticated and indispensable for smooth train traffic. In this article, we show how they are constructed and what function their frogs, switch points and point locks fulfill.
What is a double slip switch?
The double slip switch is a complex combination of two turnouts and a crossing. It makes it possible to run trains from four directions and switch to both branches – space-saving and versatile. While a simple turnout only allows one branch, the double slip switch offers the option of connecting several directions of travel in a confined space. This makes it particularly important in stations, track changes and branch lines.
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Construction of a double slip switch
The double slip switch combines two turnouts and a crossing in one compact design. Their design is one of the most complex constructions in track construction – every component must be precisely manufactured and perfectly coordinated to ensure track accuracy and operational safety.
At the center of the double slip is the so-called crossing quadrangle, which consists of four frogs and the connecting intermediate rails. These frogs form the intersections of the tracks and ensure clean track guidance when passing over the crossing. High-quality, forged frogs – as offered by manufacturers such as Bharat Forge Railsystems – are crucial for durability and smooth running.
There are two switch devices at each end of the crossing quadrangle. These movable rail sections guide the train into the desired route. Each switch device is fitted with a
Intermediate rails connect the switches to the frogs and compensate for changes in length or curvatures in the track. In addition, wheel guide rails guide the wheels safely over the gaps in the track in the area of the frogs, while wing rails support the transition between the rail sections.
Underneath the turnout is the sleeper grid, which supports the entire structure and keeps the track gauge stable. Modern systems use concrete or plastic sleepers with precise geometry to reduce vibrations and distribute the load evenly.
Operational safety also includes adjusting rods that mechanically connect the tongues and drives, as well as monitoring devices that check whether all tongues are in the correct position. In heavily used track areas, heating elements are also used to prevent the mechanics from freezing up in winter.
Together, these components form a high-precision system that guides trains reliably and smoothly through the crossing – a technical centerpiece of modern rail infrastructure.
Difference between single slip switch and double slip switch
The single switch combines a turnout and a crossing, but only allows switching from the main track to a branch track in one direction.
The double slip switch goes one step further: it allows switching in both directions and combines two turnouts with a crossing. As a result, it contains four switch devices, four frogs and several intermediate rails that are precisely connected to each other. This design saves space, but places high demands on the control system, point machine and maintenance.
Functionality of the double slip switch
The double slip switch make it possible to run trains from four directions and flexibly change the direction of travel – without additional track junctions. It therefore combines the function of two points and a crossing in one compact element of the track network.
During operation, two coupled point machines control four switch devices, which set the route according to the desired direction. The point locks secure the position of the switches, while the frogs and wheel guides ensure that the wheelsets run smoothly through the crossing areas. All movements must be precisely synchronized – even small deviations can lead to increased wear or, in extreme cases, derailments.
The double slip switch can be operated in four basic positions:
- Straight ahead on the main track.
- Turn left.
- Branch off to the right.
- Diagonal crossing from track to track (crossing travel).
They are usually controlled via a central interlocking or digitally via a point operating system. In modern systems, sensors are used to monitor the switch position and automatically report incorrect positions.
Thanks to this mode of operation, the double slip switch enables a high operating throughput in confined spaces and is therefore primarily used in railroad stations, shunting areas and track changes.
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Special technical features and areas of application
The double slip switch is considered one of the most demanding constructions in track construction – both in terms of manufacture and operation. Their technical design is heavily dependent on the geometric conditions and the intended load.
Geometry and load
The geometry of a double slip switch is based on the standard crossing with an inclination of 1:9. Depending on the design, the switch devices are either inside (radius approx. 190 m) or outside (radius approx. 500 m) the crossing quadrangle. These radii determine the travel speed and ride comfort – the smaller the radius, the lower the permissible speed and the higher the wear.
In addition, the entire system must be precisely aligned so that the frog points, wheel links and intermediate rails interlock exactly. The position of the crossing center defines the entire geometry of the double slip switch and is measured to the millimeter during construction and maintenance.
Materials and production
High-strength, low-wear steels are used for frogs, tongues and closures. Manufacturers such as Bharat Forge Railsystems supply forged frogs and robust switch fasteners that guarantee dimensional stability and durability even under heavy loads.
Locations
The double slip switch is used:
- in stations with a high track density,
- for track changes on main lines,
- in marshalling yards where rapid changes of direction are required,
- in model railroad construction to represent realistic track connections in a compact form.
Due to its complexity and high maintenance requirements, it is often replaced by simpler combinations of two points and a crossing in new buildings. Nevertheless, it remains an indispensable component of many existing systems and a fascinating example of engineering precision in track construction.
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Advantages and disadvantages of the double slip switch
The double slip switch is a central component of modern track systems and combines the functions of two turnouts with a crossing in a very small space. It is therefore a technically sophisticated product that is used both in station areas and in track changes. Despite its complexity, it is regarded by professionals and newcomers alike as a fascinating element in track construction and model railroading – for example with Märklin, Roco or Tillig.
Advantages
- Compact design: A double slip switch combines four switch devices and four frogs to create a space-saving solution. This allows trains to change direction in a confined space or transition from a main track to a branch track.
- Flexible use: Thanks to different radii, inclinations and angles, the double slip switch can be adapted to a wide variety of track systems. Whether in the main track or in a curve – it offers versatile options for every journey.
- High robustness: Forged frogs, stable point machines and durable switch blades ensure a long service life and precise track guidance.
- Quick assembly: Thanks to modern plug-in connections, the double slip switch can be assembled in the model range in almost no time at all – items are often available directly in the shopping cart, including item number and delivery time.
Disadvantages
- Complex construction: A double slip switch requires high manufacturing tolerances. Even small deviations in the position or at the intersection of the rails impair the function and lead to increased wear on wheelsets and wheel guides.
- High costs: Due to the complex structure with many components (tongues, intermediate rails, locks, drives), production is expensive. The manufacturer has to adapt each piece individually to the existing track.
- Maintenance-intensive: The precise control of the four tongues and the synchronization of the drives require regular inspections – especially in older new buildings or heavily used stations.
- Restrictions in new construction: Due to changes in length, temperature dependency and the difficult design, double slip switches are usually only used in existing track systems today.
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Connection to curved turnouts, frogs and track gauges
The double slip switch has similarities with the curved turnout: In both cases, the radius, angle and inclination of the rails determine the direction of travel and the smooth running of the wheelsets. Small radii in particular require precise track guidance and increase wear on the wheel links and switch blades.
The heart of the system is the functional center. It guides the wheels over the intersection of the rail tracks and ensures that the train remains stable on the track even when changing direction. Depending on the track gauge and track system, different designs are used – for standard gauge, narrow gauge or model railroads, for example.
Technical terms and control technology
A switch blade (or switch tongue) is the movable rail section that changes the track and thus determines the desired direction of travel. It is moved by the point machine and securely locked by the
This precise coordination of all components is crucial for the function of the entire double crossover. Even minimal deviations in position can impair ride comfort or reduce the robustness of the system.
Application and meaning
In practice, the single slip switch is usually used where one-sided connections are sufficient. The double slip switch, on the other hand, is the space-saving solution for complex track changes, especially in stations or on busy routes. Both variants are key track construction components that ensure precision, safety and efficiency in rail traffic.
Conclusion
The double slip switch shows how the art of engineering and functionality work together in track construction. It combines two points and a crossing into a precise, space-saving system that enables flexible directions of travel and efficient track changes. Its complex control system, the precise position of the points and the robust design of the frogs and point machines make it a sophisticated but indispensable component of modern railroad systems.