In the short term, it means millions of Swedish crowns in savings. In the longer term, it strengthens the competitiveness of train transport and enables the transfer of transport from road to rail. This means reduced carbon dioxide emissions for heavier transport.
The classification of railway vehicles affects the distances they can operate. The freight train operator Green Cargo needed to install locomotives with greater traction to get a reasonable economy in their freight transport. This meant that heavier locomotives with three-axis bogies would have to operate lanes that were normally operated by lighter, two-axis locomotives. However, the Swedish Transport Administration could not allow the heavier three-axis locomotives to traffic the lanes if the safety could not be guaranteed. The situation was so critical that it became a standing point at the meetings between the Swedish Transport Administration's Director General and Green Cargo's CEO.
The classification of Green Cargo's three-axis locomotive meant that the locomotive was in a higher class than many lanes have been classified for, which could mean low operating speeds. For bridges, calculation tools are available to analyze the impact of specific vehicles, but for geotechnics the situation was more complicated. An analysis may require expensive and cumbersome soil samples and the remaining geotechnical restrictions were numerous.
Anders Ekberg is the director of the competence center Chalmers Railway Mechanics (Charmec). He says that the main challenge for Charmec was to understand the problem. But with the help of the contacts and the understanding built up between Charmec's partners, a solution was soon to be found.
“In a few meetings with intermediate analyzes, we were able to gain insight through the experience and knowledge we have gained in previous projects. Once the solution method was identified, we could relatively easily reach a solution using our numerical tools” says Anders Ekberg.
In-house models from Chalmers provided a solution
The researchers from Chalmers proposed a comparative analysis between the stress resulting from a two-axis locomotive and that of a three-axis locomotive. Using in-house models their analysis showed that the marginally lower load per axis of the locomotive actually made the resulting stress in the ground lower for the three-axis locomotive despite this loco having an additional axle. To further analyze load, the Swedish Transport Administration conducted a dynamic analysis using software developed within Charmec.
“The analysis supported the conclusion that the locomotives provided a lower load on filling material and the underlying soil. The Swedish Transport Administration was now able to reduce the number of restrictions for Green Cargo's three-axis locomotives” says Ibrahim Coric head of Maintenance Railway system Permission Construction at the Swedish Transport Administration.
Markus Gardbring is head of Green Cargo's operations and believes that it is of great importance for their operations.
"Green Cargo can now use stronger locomotives and demolish a large number of circulations for a number of larger customers, which leads to more efficient freight transport and is a prerequisite for us to be able to have more goods on the railway" says Markus Gardbring.
Contributes to reduced carbon dioxide emissions
Another benefit is that heavier locomotives with more redundant traction slip less, which reduces maintenance costs. Markus Gardbring also sees gains in the longer term. The Swedish rail network is being rebuilt to allow longer trains. The Swedish government has decided to reduce 70 percent of all carbon dioxide emissions for heavier transport by 2030. The segment that can easily be transferred to rail is intermodal goods. Longer trains are more cost-effective and a prerequisite for enabling competition with trucks in an extremely competitive market. The traction force of the locomotive will be decisive as the weight rather than the length becomes limiting for the number of wagons per train.
Read more about Charmec