Nearly every machine emerging from the Linz works of Plasser & Theurer is built to an individual specification. This makes it easy to incorporate improvements whenever they are developed

AS HEAD OF Research & Testing with specialist track maintenance machinery supplier Plasser & Theurer, Dipl-Ing Dr techn Bernhard Lichtberger believes that his company 'is not selling machines, but technology'. Today's machines are tailored to the conditions prevailing in individual countries, and 'we build only prototypes', he quips.

Lichtberger identifies three main trends in track maintenance technology. Firstly, 'we are building ever larger machines with more processes integrated into a single unit - they are complete processing plants.' He cites the RPM2002 formation rehabilitation machine, which recycles ballast for re-use as formation material, cutting the amount of new material needed and reducing transport costs.

A second trend is for the research department to respond to specific ideas from customers. Private or quasi-private infrastructure and maintenance companies have greater incentives to get ahead of their competitors - an example here is a catenary rewiring vehicle for Sweden able to complete the whole rewiring process in a single pass.

Lichtberger's third trend is 'higher and higher output'. The 09-3X Dynamic Tamping Express combining a three-sleeper tamper with a dynamic stabiliser (RG 1.02 p20) is economically advantageous. A single machine replacing two reduces staffing, and allows immediate resumption of service at line speed.

According to Plasser & Theurer's Dipl-Ing Helmut Misar, 'continuous-action three-sleeper tamping technology means that working speeds of 2200m/h are easily possible today'. Austrian Federal Railways has used three-sleeper 09-3X tampers since 1996, and confirms that 'an excellent track quality is achieved due to the simultaneous treatment of three sleepers'. ÖBB also says it has 'observed a general improvement of the track geometry', which is reflected not only in ride comfort but also in lower MDZ-ADA readings from the ADA on-board track quality evaluation system.

Heavier and stronger

The Dynamic Tamping Express has a total mass of 123 tonnes, with the tamping section alone weighing 83 tonnes. This is designed to cope with lifting today's heaviest tracks - a 10m section comprising two 60 kg/m rails on concrete sleepers weighs 11 tonnes. At the start of lifting the attached ballast must also be lifted, and this is estimated to weigh a further 5 tonnes, taking the total mass to over 15 tonnes.

With longer-wheelbase machines - the DTX has a distance between bogie pivots on the tamping section of 15·7m - the lifting forces can be reduced, ensuring gentler treatment of the track. A machine with a 6m wheelbase has to produce a lifting force of around 200 kN to lift around 600mm, while a machine with an 8m wheelbase needs only 100 kN for the same lift. For the 09-3X with a 12m wheelbase, the lifting force is slightly more than 50 kN.

Today's largest ballast cleaners are capable of an output reaching 900 to 1000m3/h, but a machine able to work at 1500m3/h is in prospect for the future. Lichtberger is also looking at the potential for higher output from track relaying machines.

Service Manager Uwe Peters supports Lichtberger's view that major strides in development are relatively few and far between. It is far more a question of 'many small improvements that are not obvious', he says. One example is the use of hardened tamping tools, with the tine cast as a single piece rather than with a tamping tip welded on. Peters says a conventional tool will last for 30 to 50 km of tamping, but hardened tools can be used for up to 500 km, and possibly more.

Peters makes the point that tailor-made machines can be built to suit quite different specifications, citing an 09-3X Tamping Express for Russian Railways' 1520mm gauge network. Russian track is typically laid in 25m lengths, and the rails may be changed without the sleepers being adjusted, so when building machines it must be borne in mind that the spacing can easily vary from the standard distance. Another example is the fitting of water sprays on tampers supplied for use in Italy and hot countries, where dust can be a serious problem.

Automated lubrication of the tamping units allows the machines to work for longer periods without stopping. Peters explains that a programmable lubricator will automatically resume in mid-cycle if the machine is stopped and restarted during a lubrication cycle.

Work in progress

Celebrating its 50th anniversary this year, Plasser & Theurer is now building around 150 to 180 machines a year. These range from 15 tonne tamping units to mega-machines weighing up to 500 tonnes. Current deliveries include large ballast cleaners married up with MFS spoil and ballast transport wagons fitted with their own conveyor belts. A unit for Kazakhstan uses six-axle MFS wagons powered by a generator car.

During 2002-03 Plasser & Theurer will deliver a RM900 ballast cleaner to Network Rail in the UK. This will work with 22 four-axle MFS wagons ahead of the unit to handle spoil, with a further 22 behind carrying new ballast. Where the conveyors feed or collect material from the main unit, a constant distance is maintained by an 'electronic coupling'. The RM900 will feature integrated monitoring and fault diagnosis able to identify problems on any of the 44 wagons. Temperatures and other measured indicators are transmitted along the train by a databus. Three monitoring units are fitted, one on the main machine and one on each of the generator cars supplying power to the MFS wagons.

Lichtberger also points to advances in automation that can be applied to many different machines. The latest switch and crossing tampers, he says, can 'memorise' the whole process for tamping a set of points. The same programming can be used for identical pointwork at other locations. Similarly, rail welding plant will be able to record the precise details of each weld, including the type of rail, location, and all the welding parameters. All of this will be potentially of great interest to quality control and safety engineers.

Global positioning technology is now becoming commonplace, and an Emsat track inspection vehicle being built for use in Germany will use GPS to locate the track in absolute rather than relative terms. Until now rail top height on main lines has often been measured in relation to specified bolts on catenary masts, but in future it will be possible to use GPS reference points located at 5 km intervals. A measurement train will then run through to record the location of the reference points, and the track can then be located to an accuracy of 5mm or less.

  • CAPTION: Plasser & Theurer is building 'ever larger machines with more processes integrated into a single unit'
  • CAPTION: The latest tamping heads feature automatic lubrication
  • CAPTION: These broad-gauge MFS spoil wagons are destined for Kazakhstan
  • CAPTION: Unimat 08-275/3S-16 tamper handles switch and crossing work
  • CAPTION: Experience has shown that a hardened one-piece cast tamping tool (left) will last up to 10 times as long as a conventional tool with a welded-on tamping tip (right)