The RPM-RS-900 track renewal machine handles formation renewal, reballasting and tamping in a single pass with the option of recycling used ballast

Dipl-Ing Ingo Wiermann
Technical Director, Spitzke AG

CATHERINE the Great is the name Spitzke AG of Germany has bestowed on its latest acquisition — an 800 tonne track machine nearly 200 m long that combines ballast cleaning and recycling with formation renewal; when Catherine the Great departs the worksite it leaves behind freshly ballasted and tamped track on a relaid formation ready for use by service trains.

Known more prosaically as the RPM-RS-900, the mega-machine was developed by Spitzke in close co-operation with manufacturer Plasser & Theurer. With a price tag of €35m, the machine was only purchased after careful consideration of the company's long-term strategy and the market for track renewals. Studies of market requirements concluded that formation rehabilitation was increasingly in demand – a stable, dynamic superstructure depends entirely on a sound load-bearing substructure, and operators are constantly in search of the 'perfect track' offering excellent ride quality and guaranteed availability.

Representing Spitzke's largest investment to date, the RPM-RS-900 was delivered in March this year. It was put to work in the following month, renewing 1 300 m of formation protection layer on the Itzehoe – Glückstadt line near Hamburg in Germany. By early July it had completed 12 km of formation rehabilitation and ballast renewal — and it had a full work programme for the rest of the year.

The RPM-RS-900 is designed for flexibility so that customers can use it for inserting or replacing a formation protection layer, for ballast cleaning or reballasting – with the option of complete trackbed renewal – or for a combination of all these. Its ability to recycle ballast which is reused in the formation is of critical importance given the regulations which now govern the disposal of used ballast (RG 1.05 p44).

Formation protection layer

A formation protection layer increases the load-bearing capacity of the track system, at the same time offering a number of other benefits. A 'perfect' formation protection layer will help reduce noise emissions and matches the elasticity characteristics between the ballast bed and track formation. Axleloads are distributed evenly across the formation, surface water is dissipated, and stability between the foundation and the ballast layer is guaranteed. An additional layer can be installed to provide further protection against frost.

There are different methods and different machines available for installing formation protection layers, and the choice is made on the basis of the application, type of route and the technology required. The latest machines such as the RPM-RS-900 can insert or replace a formation protection layer on an assembly line basis without disturbing adjacent tracks – with obvious benefits to the operator.

Machine layout

The RPM-RS-900 consists of six sections (Fig 1) with five control cabins located at strategic points to monitor and adjust individual processes. At the front is the power unit mounted on a pair of two-axle bogies. This is followed by the screening wagon, also on two bogies, and the ballast processing vehicle, which has a pair of two-axle bogies and a central three-axle bogie. Behind this comes the excavation machine with cutter chains for ballast and formation material; this has a four-axle bogie assembly at the front and a three-axle bogie in the centre, with the rear part of the machine resting on a second four-axle bogie assembly.

Bringing up the rear is the tamping machine, which is normally followed by a rake of MFS wagons holding sand or similar material to be used for the new formation, with further wagons containing new ballast. Running ahead of the RPM-RS-900 is a rake of hopper cars to hold spoil and other used material.

The three operating modes are:

  • ballast recycling with formation rehabilitation;
  • ballast cleaning with the option of complete trackbed renewal;
  • formation rehabilitation with complete re-use of the old ballast.

The whole work sequence takes place solely within the track section under repair, and the substructure is replaced without removing the track panel. Once the substructure formation is in place, no loads are placed on it and nothing drives over it, so no damage can occur. The formation protection layer can be up to 400 mm deep, with an additional frost blanket layer up to 500 mm deep laid in one process.

If necessary, the formation protection layer can be moistened to ensure optimum compaction, and at the same time further protection material such as geosynthetics – non-woven geotextiles, sheeting, hard foam panels, geogrid or compound substances – can be installed.

When operating in recycling mode, the RPM-RS-900 excavates the old ballast which is cleaned using two free-swinging vibrating screens with double pre-separation. Material that cannot be reused is removed by conveyor and dumped in wagons ahead of or to the side of the machine. The recycled material is then processed for use in the formation protection layer, where it is laid with a metered feed to a specified height and width – this is adjustable from 4·0 m to 6·5 m. Uniform compaction is used to finish off before new ballast is laid directly on the formation, again using a metered feed, followed by compaction and stabilisation.

Performance when operating as a ballast cleaner is up to 900 m³/h. The ballast is excavated and again passes through the two free-swinging vibrating screens with double pre-separation. It is then returned to the track using a pivoting conveyor belt with height control before compaction. New ballast from the trailing MFS hoppers can be laid in parallel if required.

The integrated continuous-action tamper with 16 tines, satellite control and front compaction completes the process. A sweeper unit behind one of the MFS wagons ensures that no loose ballast is left on the site.

When in use as a formation rehabilitation machine, the RPM-RS-900 can re-use all the old ballast. The spoil from the old formation and the old ballast are excavated simultaneously, and the spoil is moved by conveyor to the MFS wagons or other vehicles on an adjacent track. The old ballast is crushed and blended in a controlled process with new formation material before placement on the ground and subsequent compaction.

An interactive presentation of the RPM-RS-900 can be found at

Table I. Technical specification and performance parameters of RPM-RS-900 track machine

Overall length over buffers (without MFS wagons) m 198·24
Gauge mm 1 435
Vehicle profile G2
Maximum width mm 3 150
Maximum height mm 4 650
Power rating kW 2 800
Fuel capacity litres 27 000
Total length of conveyor belts m 2 200
Maximum operational speed hauling one MFS 40-D wagon km/h 20
Maximum speed in train formation km/h 100
Empty weight, including MFS 40-D wagon tonnes ca 800
Ballast recycling rate m/h up to 100
Capacity of formation excavation chain m³/h up to 900
Capacity of ballast excavation chain m³/h up to 350
Ballast cleaning capacity m³/h up to 900
Maximum depth of frost blanket layer mm 500
(Proctor density 95% to 100%)
Maximum depth of compacted formation protection layer mm 500
(Proctor density 95% to 100%)
Maximum excavation width of formation cutter chain mm 5 600
Extension of excavation width, both sides mm 650
Maximum depth of formation cutter chain below rail top mm 1 200
Maximum width of ballast cutter chain mm 4 000
Extension of cutter chain width, both sides mm 300
Maximum depth of ballast cutter chain below rail top mm 700
Minimum curve radius when working (at 160 mm cant) m 280
Minimum curve radius for tooling up and tool removal m 350
Minimum curve radius when operating under own power m 150

  • CAPTION: Fig 1. The RPM-RS-900 is 198 m long, excluding MFS wagons
  • CAPTION: The ballast cutter chain can operate simultaneously with the formation cutter chain
  • CAPTION: The formation cutter chain can excavate to a width of 5 600 mm
  • CAPTION: Installation of material to form the formation protection layer
  • CAPTION: The new formation protection layer