Major Projects & Infrastructure, Track & Civil Construction

Making light rail tough

STRAILastic track damping

Using vulcanised rubber, STRAILastic have a track damping solution that keeps trams moving.

Spend any amount of time in Melbourne and the refrain from the 1992 Crowded House hit, “Four seasons in one day” becomes very real. The city’s location between a hot continent and the cool Southern Ocean means that temperature variations of 10 degrees or more can occur in an hour.

But temperature changes aren’t unique to Melbourne. A southerly change in Sydney can turn a 40°C day into a 20°C evening, and south- east Queensland’s tropical storms can also cause the mercury to rapidly descend.

Besides wreaking havoc on any idea of what to wear for a day, these temperature variations also place stresses on infrastructure, particularly those in exposed environments. In many cases this includes tram and light rail tracks.

Whether embedded in asphalt, concrete, or earth as in a “green track”, rapid temperature change can place stresses on light rail tracks as the surrounding materials expand and contract. Unlike heavy rail structures, where the ballast foundations allow for some contraction and expansion, the nature of light rail, being embedded in a surface, means thresholds are much lower.

As Andreas Göschl, operations director at STRAILastic Australia explains, the company has developed a track damping chamber filling solution that grapples with this reality.

“Our systems are used in areas where you have a big temperature variation.”

Produced in a similar way to STRAILastic’s level crossing systems, the chamber filler avoids the use of bitumen joints by being level with the railhead. Being similar to the level crossing solution, the chamber fillers are designed to withstand the wear and tear of traffic crossing the rail line which acting as track damping.

While chamber filling elements are common to many light rail networks, not all are created equal. A common material not used by STRAILastic is polyurethane.

“The polyurethane products, they’re more like plastic, so they expand when it’s warm and they shrink when it’s cold,” said Göschl.

The systems that STRAILastic offers are instead made from vulcanised rubber.

“We don’t have this issue of expanding and contracting with our systems, as we have a temperature range between -40°C and plus 90°C,’ said Göschl.

“Because of our temperature stability, our system has a glass transition point – the point under deep temperature when a system brakes – of minus 55 degrees. Common systems have a glass transition point of minus 27 to minus 30. While this temperature is only reached in very cold countries, but that shows how the system can move and how stable it is.”

While these temperature ranges are extreme, the stability of the STRAILastic system at such a wide range of temperatures means that for normal operating conditions, the product offers a more reliable solution.

The benefits of the vulcanised rubber solution extend beyond its rigidity. While made from 95 per cent recycled rubber, the outer cover of virgin rubber ensures that the systems can withstand the elements.

“Vulcanisation has several benefits as it is more UV and Ozone resistant. As we use a virgin rubber cover sheet, we have a higher density than polyurethane bounded systems,” said Göschl.

The design of the system also means that the chamber filling element fits to the rail like a hand into a glove.

“We do not need any glue or adhesive – the system is self-clamping – due to the seat profile of our systems,” said Göschl.

Not only does this promote the longevity of the track structure due to less wear and tear, but the intrusion of foreign particles is reduced.

“Due to our very small tolerances allowed in moulding and very small movements in the track we avoid gaps between the rail and the chamber filler. A gap is the worst thing that you can get in a light rail track, allowing in water, sand, sediments, and dirt,” said Göschl.

“Over time the rail is then progressively lifted up, allowing the entry of moisture, which creates electrical problems, and these combine to corrodes and destroy the rail web, which is the weakest point of the rail.”

STRAILastic has introduced a unique naming system for each of its products in the track damping range.

“Our systems are called Type Berlin, Type Bremen, Bielefeld, Zurich, and so on. Cities or light rail authorities, all of them they have a special way of track building or track construction, so what we do is we create tailor made solutions for them.”

Once these solutions are developed they are standardised so that future networks that are similar can use them as a standard product. These products have now been installed in more than 30 cities around Europe, with the system bring put to the test over the past 20 years in comparison with polyurethane-bonded products. After only a year, the difference can be seen clearly, with gaps visible to the naked eye in the alternative products. In contrast, in cities where the STRAILastic product has been installed, the solution is continuing to measure up after 10 years.

To ensure that authorities gain the maximum value for the products, in each new city where the STRAILastic system is installed, a member of the team will oversee the installation.

“For all initial installations in all cities and areas we send at least one engineer to help and guide the installation,” said Göschl. “We have also done that also in Australia, for our noise-attenuation products. For this year on we will have people in Australia who are trained for the light rail systems and products.”

The design has also been optimised to reduce any variation during installation, while retaining the ability to be modified on site with regular tools. The lack of glue or adhesive means that removing or replacing the chamber filler is simple, reducing maintenance complexity.

Together, the product provides a reliable and sustainable solution to keeping trams running, no matter the weather.

The vulcanised rubber material ensures light rail tracks are not as affected by temperature changes.