Tilting train
|
|
A tilting train is a train with a tilting mechanism that enables increased speed on regular railroad tracks.
| Contents |
Introduction
As any vehicle rounds a curve at speed, independent objects inside it experience so-called centrifugal force since their inherent momentum forward no longer lies along the line of the vehicle's course. This can cause packages to slide about on the floor, people seated in chairs to feel squashed against their outboard armrest, and standing passengers to lose their balance.
Aeroplanes and bicycles simply tilt in place; but automobiles and railway trains cannot do this on their own. To make their turns easier, the roadway of a high-speed highway or railway is canted inward around the curve. To a passenger in such a vehicle, the outward centrifugal force is countered by an inward gravitational one, thus removing the discomfort. (It should be noted that vehicles with high centers of gravity rounding very sharp curves at very high speeds may in fact topple over altogether; banking would also be the answer to counteract this threat. However, since passenger comfort becomes an issue at much lower speeds and gentler curves, railway designers, having kept their passengers comfortable, do not need to worry about trains overturning.)
The particular angle of tilt ("superelevation") is determined by the speed at which it is intended that vehicles will pass — faster speeds require more banking. But with a growing desire in the 1960s and 1970s to build high-speed rail networks, a problem arose: the amount of tilt appropriate for the new high-speed trains would be unacceptably over-tilted for slower-speed local passenger or freight trains which must share the lines. France, building its TGV, avoided the problem by building a special new rail network for the high-speed trains which minimized curves, likewise Japan's bullet train and many other high speed lines have necessitated new infrastructure.
Other countries, with less elbow room, weaker governmental planning powers, and more hilly terrain, were unable to follow. Specifically, Spain's national railway RENFE took a domestic invention, the TALGO, and developed it into a reliable high speed train for a low traffic density railway; British Railways (the UK state railway) invested heavily in tilting train technology to overcome the limitations of a rail network constructed through built-up areas early on in railway history when running speeds were very slow; and Italian State railways has invested heavily in tilting technology to speed trains through Italy's mountainous terrain.
Tilting trains
Tilting trains are trains the upper part of which, where the passengers are seated, can be tilted sideways. In a curve to the left, it tilts to the left to compensate for the centrifugal push to the right, and conversely.
The train may be constructed such that inertial forces themselves cause the tilting, commonly referred to as passive tilt, or it may be actively induced by a computer-controlled mechanism, referred to as active tilt.
The first tilting trains were the TALGO trains of Spain, developed in the 1930s as a lightweight, fast train using passive tilt. The TALGO is still in production in their 21st generation. TALGO trains are in service in various parts of Europe, and built under licence in Latin America and Asia. In North America, Amtrak uses TALGO trainsets in its Cascades service in the US Northwest, having earlier experimented with them in the Northeast Corridor.
The first tilting train to enter into regular service in North America was the United Aircraft Turbo train, used by Canadian National Railways, in 1969. Plagued with frequent breakdowns of its turbine powerplants, it nevertheless assured daily service between Montréal and Toronto until it was retired in 1984, having been replaced by Bombardier LRC trains. United Aircraft Turbos were also used by Amtrak between Boston and New York in the early 1970s. The UAC Turbo was inspired by the TALGO, and had a passive tilt mechanism; its ride quality was rather mediocre due to the use of single axle trucks (bogies) between the cars.
Another tilting train to enter into regular service was the Pendolino. The original ETR 401 train was built by FIAT in 1975 for the Italian State Railways following a prototype in 1970 and ran successfully for many years. The Pendolino project ticked over on a low budget developing a hypothetical successor until the early 80s when the go ahead was given to build a new fleet, which was the ETR450. Later developments of this train have been very successful and are used throughout Europe.
In the 1970s and 80s, following the success of its InterCity 125, British Rail built a tilting train called the Advanced Passenger Train. British Rail was never able to make the train reliable enough to go into service and so the project was scrapped, although the project was purchased by the Pendolino group to enlarge their technology portfolio.
During tests passengers reported that the tilting motion made them nauseous. Subsequently it was learned that this could be prevented by reducing the tilt slightly, so that there was still some sensation of cornering.
Canada's contribution is the LRC (Light, Rapid, Comfortable) train, built by Bombardier. This train is rather conventional, having separable carriages instead articulated trailers, and whose it can be intermingled with conventional non-tilt cars. In the United States, Amtrak experimented with the LRC in 1980, but retired it a few years later. In Canada, it entered service in 1981, and the carriages remain in use today. The LRC tilt-mechanism is power-assisted, driven by accelerometers. The ride quality is very smooth, even on relatively low-end tracks. Bombardier have since used updated versions of the LRC carriages are for Amtrak's Acela Express and the experimental JetTrain.
Another early train with tilting technology was Deutsche Bahn's class 403, used for airport transfers between Düsseldorf and Frankfurt which entered into service in 1978 (see also: AiRail Service). An attempt was made to use tilting technology to improve speeds on the extremely twisting Rhine Valley route. Shortly after the train went into service, the tilting technology was disabled as many passengers experienced motion sickness due to sudden and heavy tilting.
Switzerland got its first tilting train ever in its territory (discounting the Cisalpino, which entered Switzerland in 1996) on May 28, 2000. The ICN (InterCity Neigezug, or InterCity Tilting Train) entered service, running first from Geneva via Biel/Bienne and Zürich to St. Gallen. It was a major carrier in the national exhibition Expo.02.
Many of the problems with motion sickness are related to the fact that a traditional servo system cannot respond instantaneously to the change in trajectory forces, and even slight discrepancies whilst not being noticeably perceivable cause nausea due to their unnatural nature. The original ETR 401 used individual gyroscopes in each carriage so there was inevitably a lag, even though nausea had not been a major problem with this train. The APT was supposed to supersede this problem by using gyroscopes at the ends of the train and a master slave control system which defined a "tilting curve" for the whole train. It would appear that the technology of the era was not able to implement this technique as well as required.
Modern tilting trains have the blessing of the latest signal processing technology which reads the line ahead and is able to anticipate a very precise control signal to the individual carriages and complaints about nausea have become a thing of the past.
Some tilting trains run on narrow-gauge lines. In Japan there are many narrow-gauge lines in mountainous regions, and tilting trains have been designed to run on these. In Australia the link between Brisbane and Cairns, which uses tilting trains, now claims to be the fastest narrow-gauge link in the world.
Tilting trains around the world
Trains with tilting by inertial forces:
- Talgo XXI (Spain)
- UAC Turbo (United States, Canada)
Trains with tilting controlled by accelerometers:
- LRC (United States, USA)
Trains with tilting controlled by a computer:
- ICE-T, also called ICT (Germany), tilting version of ICE
- X2 with tilting mechanism of ABB (Sweden)
- Pendolino (Italy, Finland and Britain), built by Alstom (formerly Fiat); see also British Rail Class 390
- InterCitySlovenija - high-speed tilting train in Slovenia operating between Ljubljana, Maribor and Koper.
- Acela Express - American high-speed tilting train operating between Boston and Washington, built by Bombardier.
- ICN (Switzerland)
- Queensland Rail's Diesel and Electric Tilt Train - the world's fastest Narrow gauge train operating between Brisbane and Cairns in Queensland, Australia.
External links
- Queensland High Speed Line (http://www.railway-technology.com/projects/queensland/)
- Passive vs active tilting (http://www.hitachi-rail.com/products/rv/tilting/tilting_features.html)
- Tilting Trains (http://www.o-keating.com/hsr/tilt.htm)
- Pendolino (http://www.railway-technology.com/projects/italy/)
- Photos of Japanese trains - some tilting (http://www.jrtr.net/jrtr08/pdf/photo.pdf)
- Tilting trains - analysis and discussion (http://www.sncf.com/wcrr/SESSIONS/003.PDF)
- Amtrak accelerates at last (http://www.travelandleisure.com/invoke.cfm?objectID=CA07F993-C17D-43E4-A432EBF2120ED267)
- JR Hokkaido Tilting DMU (http://www.railjournal.com/2001-02/japan.html)de:Neigetechnik