Funicular
A funicular, or funicular railway, is a type of cable railway system that connects points along a railway track laid on a steep slope. The system is characterized by two counterbalanced carriages permanently attached to opposite ends of a haulage cable, which is looped over a pulley at the upper end of the track. The result of such a configuration is that the two carriages move synchronously: as one ascends, the other descends at an equal speed. This feature distinguishes funiculars from inclined elevators, which have a single car that is hauled uphill.
The term funicular derives from the Latin word, the diminutive of, meaning 'rope'.
Operation
In a funicular, both cars are permanently connected to the opposite ends of the same cable, known as a haul rope; this haul rope runs through a system of pulleys at the upper end of the line. If the railway track is not perfectly straight, the cable is guided along the track using sheaves – unpowered pulleys that simply allow the cable to change direction. While one car is pulled upwards by one end of the haul rope, the other car descends the slope at the other end. Since the weight of the two cars is counterbalanced, the engine only has to provide energy to pull the excess passengers in the uphill car and the cable itself, plus the energy lost to friction by the cars' wheels and the pulleys.For passenger comfort, funicular carriages are often, although not always, constructed so that the floor of the passenger deck is horizontal rather than parallel to the sloped track.
In some installations, the cars may also be attached to a second cable – bottom towrope – which runs through a pulley at the bottom of the incline. In these designs, one of the pulleys must be designed as a tensioning wheel to avoid slack in the ropes. One advantage of such an installation is that the weight of the rope is balanced between the carriages; therefore, the engine no longer needs to use any power to lift the cable itself. This practice is used on funiculars with slopes below 6%, funiculars using sledges instead of carriages, or any other case where it is not ensured that the descending car is always able to pull out the cable from the pulley in the station on the top of the incline. It is also used in systems where the engine room is located at the lower end of the track – in such systems, the cable that runs through the top of the incline is still necessary to prevent the carriages from coasting down the incline.
Types of power systems
Cable drive
In most modern funiculars, neither of the two carriages is equipped with an engine of its own; propulsion is provided by an electric motor in the engine room, linked via a speed-reducing gearbox to a large pulley – a drive bullwheel – which then controls the movement of the haul rope using friction. Some early funiculars were powered in the same way, but using steam engines or other types of motors. The bullwheel has two grooves: after the first half turn around it the cable returns via an auxiliary pulley. This arrangement has the advantage of having twice the amount of contact area between the cable and the groove, and returning the downward-moving cable in the same plane as the upward-moving one. Modern installations use high-friction liners to increase the friction between the bullwheel grooves and the cable.There are two sets of brakes in the engine room: an emergency brake which directly grips the bullwheel, and a service brake mounted at the high speed shaft of the gear. The cars are also equipped with spring-applied, hydraulically opened rail brakes for emergency use.
The first funicular caliper brakes which clamp each side of the crown of the rail were invented by the Swiss entrepreneurs Franz Josef Bucher and Josef Durrer and implemented at the, opened in 1893. The Abt rack and pinion system was also used on some funiculars for speed control or emergency braking.
Water counterbalancing
Many early funiculars were built using water tanks under the floor of each car, which were filled or emptied until just sufficient imbalance was achieved to allow movement, and a few funiculars still operate that way. The car at the top of the hill is loaded with water until it is heavier than the car at the bottom, causing it to descend the hill and pull up the other car. The water is drained at the bottom, and the process repeats with the cars exchanging roles. The movement is controlled by a brakeman using the brake handle of the rack and pinion system engaged with the rack mounted between the rails.The Bom Jesus funicular built in 1882 near Braga, Portugal, is an extant system of this type. Another example, the Fribourg funicular in Fribourg, Switzerland, built in 1899, is of particular interest as it utilizes waste water, coming from a sewage plant at the upper part of the city.
Some funiculars of this type were later converted to electrical power. For example, the Giessbachbahn in the Swiss canton of Bern, opened in 1879, was originally powered by water ballast. In 1912 its energy provision was replaced by a hydraulic engine powered by a Pelton turbine, which in 1948 was replaced by an electric motor.
Track layout
Three main rail layouts are used on funiculars; depending on the system, the track bed can consist of four, three, or two rails.- Early funiculars were built to the four-rail layout, with two separate parallel tracks and separate station platforms at both ends for each vehicle. The two tracks are laid with sufficient space between them for the two carriages to pass at the midpoint. While this layout requires the most land area, it is also the only layout that allows both tracks to be perfectly straight, requiring no sheaves on the tracks to keep the cable in place. Examples of four-rail funiculars are the Duquesne Incline in Pittsburgh, Pennsylvania, and most cliff railways in the United Kingdom.
- In three-rail layouts, the middle rail is shared by both carriages, while each car runs on a different outer rail. To allow the two cars to pass at the halfway point, the middle rail must briefly split into two, forming a passing loop. Such systems are narrower and require less rail to construct than four-rail systems; however, they still require separate station platforms for each vehicle.
- In a two-rail layout, both cars share the entire track except at the passing loop in the middle. This layout is the narrowest of all and needs only a single platform at each station. However, the required passing loop is more complex and costly to build, since special turnout systems must be in place to ensure that each car always enters the correct track at the loop. Furthermore, if a rack for braking is used, that rack can be mounted higher in three-rail and four-rail layouts, making it less sensitive to choking than the two-rail layout in snowy conditions.
Some four-rail funiculars have their tracks interlaced above and below the passing loop; this allows the system to be nearly as narrow as a two-rail system, with a single platform at each station, while also eliminating the need for the costly junctions either side of the passing loop. The Hill Train at the Legoland Windsor Resort is an example of this configuration.
Turnout systems for two-rail funiculars
In the case of two-rail funiculars, various solutions exist for ensuring that a carriage always enters the same track at the passing loop.One such solution involves installing switches at each end of the passing loop. These switches are moved into their desired position by the carriage's wheels during trailing movements ; this procedure also sets the route for the next trip in the opposite direction. The Great Orme Tramway is an example of a funicular that utilizes this system.
Another turnout system, known as the Abt switch, involves no moving parts on the track at all. Instead, the carriages are built with an unconventional wheelset design: the outboard wheels have flanges on both sides, whereas the inboard wheels are unflanged. The double-flanged wheels keep the carriages bound to one specific rail at all times. One car has the flanged wheels on the left-hand side, so it follows the leftmost rail, forcing it to run via the left branch of the passing loop; similarly, the other car has them on the right-hand side, meaning it follows the rightmost rail and runs on the right branch of the loop. This system was invented by Carl Roman Abt and first implemented on the Lugano Città–Stazione funicular in Switzerland in 1886; since then, the Abt turnout has gained popularity, becoming a standard for modern funiculars. The lack of moving parts on the track makes this system cost-effective and reliable compared to other systems.
Stations
The majority of funiculars have two stations, one at the top and one at the bottom of the track. However, some systems have been built with additional intermediate stations. Because of the nature of a funicular system, intermediate stations are usually built symmetrically about the mid-point; this allows both cars to call simultaneously at a station. Examples of funiculars with more than two stations include the Wellington Cable Car in New Zealand with five stations, including one at the passing loop, and the Carmelit in Haifa, Israel with six stations, three on each side of the passing loop.There are a few funiculars with asymmetrically placed stations. For example, the Petřín funicular in Prague has three stations: one at each end, and a third a short way up from the passing loop. Because of this arrangement, when a car on one side stops at Nebozízek the car on the other side stops without a station access.