The RM 76-SM in operation for the Rhaetian Railway in Thusis
With precision through high mountains: the RM 76-SM "Capricorn" ballast cleaning machine ensures a high-quality ballast bed across the entire Rhaetian Railway network, making a contribution to sustainable mobility and safe railway operations in the Swiss Alps.
Extremely steep climbs, tight radii, and terrain that is difficult to access – the Albula line places the highest demands on man and machine. This is where the RM 76-SM from Rhomberg Sersa Rail AG proves what innovative technology can achieve. Specially developed for the metre gauge, it cleans the ballast bed precisely, efficiently, and sustainably – for a stable, safe, and climate-friendly rail connection through the high mountains of Switzerland.
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Mobility even for the most challenging terrain
The railway connects more than just places: it connects people and transports their goods to their destination. It is the lifeline of sustainable mobility. However, in alpine areas, mobility also means overcoming extreme topographical challenges. To ensure that the railway infrastructure here functions reliably day after day, precise and regular maintenance work is required in places that are often difficult to access.
This is where the RM 76-SM ballast cleaning machine from Rhomberg Sersa Rail AG, affectionately known as "Capricorn", comes into play. It ensures that narrow-gauge railways are safe, even on the most challenging terrain.
The 61.67-kilometre line, which is one of the most spectacular narrow-gauge railways in the world with its 144 bridges spanning over two metres as well as 42 tunnels and galleries, is part of the Rhaetian Railway's main network. The Albula line begins in Thusis. This is also where Rhomberg Sersa's renewal work starts during this operation: directly behind the station, the line crosses the Hinterrhein river and the A13 motorway before reaching the Schinschlucht gorge, where numerous bridges and tunnels follow one another.
The metre gauge specialist
The RM 76-SM is truly unique: it is the only machine of its kind today that was specially developed for ballast cleaning on the alpine narrow track gauge of Rhaetian Railway. Other machines clearly reach their limits on tight radii and steep climbs.
The one-metre track gauge offers decisive advantages in the mountains: it requires less space, is easier to integrate into challenging terrain, and can handle tight curve radii – ideal for the topographical conditions of many regions in Switzerland. Here, the Capricorn is in operation mostly at night. Steadily, precisely, and practically unnoticed, it helps to ensure safety and comfort on the entire Rhaetian Railway network.
A team from Plasser & Theurer set off into the alpine terrain to accompany a machine operating at night on a section of the Albula line.
Our Capricorn is exceptional: all eight axles are driven and it weighs around 124 tonnes. The overview of the excavating chain from the cab is very good, and overall it is easy to operate. Of course, the terrain in which we work with it is also special – the high mountains like here on the Albula line, between Thusis and St. Moritz. The subsoil on the metre gauge is very rocky. The RM 76-SM also operates on the Bernina line, for example, which has an altitude of over 2,000 metres, tight radii of 45 metres, and gradients of up to 70 per mil.
Thomas Hardegger, head machine operator of the RM 76-SM, Rhomberg Sersa Rail AG
Tonight we’ll be renewing 120 m of rails, sleepers, and ballast at the worksite in Thusis. Back in the day, this was still done by hand. When we cleaned the ballast, we’d excavate it with pickaxes and shovels. The material was then screened and returned to the track. With the RM 76, of course, everything is much quicker and more convenient. Every night, it allows us to cover the necessary distance, like the one today, or even more without any problems, whereas our previous machine only managed 60 metres. The maintenance work is scheduled so that we clean the ballast every 25 years and completely renew the rails, sleepers and ballast every 40 to 50 years.
Ruedi Kienast, Rhaetian Railway officer
The ballast bed needs to be clean
A ballast bed in good condition is crucial for operational safety. The ballast fixes the track position and absorbs forces by transferring the train weight evenly to the subsoil. It also has an important drainage function. With ongoing train operations and the associated operational loads, any fines introduced by traffic and climatic influences lead to fouling of the ballast. The ballast bed increasingly loses its functional properties and must be cleaned. Cleaning systems from Plasser & Theurer provide technologies that are optimally tailored to the operational area. They offer high performance and quality as well as a safe working environment for the crew.
The Capricorn picks up the ballast bed material with its excavating chain, which passes under the sleepers, and conveys it to the ballast screening unit. There it is separated into fine stones, oversized stones, and reusable ballast. Slewing conveyors return the cleaned ballast to the ballast bed. The spoil is then deposited as required to the side of the track via a transfer conveyor, loaded onto rubble wagons or, as here in Thusis, transferred to ballast transport wagons specially constructed by the railway. In a continuous process, spoil is removed and usable ballast is excavated, cleaned, and reintroduced, enabling high working outputs. Like a small factory on tracks, the ballast cleaning machine digs its way through the ballast bed and effectively recovers the ballast, a valuable resource.
Ecological advantages of track-bound ballast cleaning
The RM 76-SM is making an important contribution to mobility in the region, as Oliver Rieber, site manager and foreman at Rhomberg Sersa, explains:
Our work with the Capricorn enables us to keep interruptions to public transport as short as possible. That way, we allow both local commuters and tourists to enjoy a pleasant, carefree, and, above all, ecologically sustainable journey.
In a world in which mobility and climate protection are particularly important, the railway is undoubtedly becoming the means of transport of the future.
With this in mind, the RM 76-SM is contributing to greener, more sustainable mobility. Oliver Rieber confirms this:
Overall, I see the railway as a way to travel where there are relatively low CO2 emissions, which is a clear advantage over other modes of transport. There’s no doubt that our team and the Capricorn are making an important contribution here.
Project data
| Project description | Ballast cleaning (as well as sleeper and rail replacement) |
| Country of operation | Switzerland |
| Line | Albula line |
| Length of the line | 61.67 km |
| Company | Rhomberg Sersa Rail AG |
| Infrastructure manager | Rhaetian Railway |
| Machine in operation | Plasser & Theurer RM 76-SM |
| Field of application | |
| Working mode |
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