Less Wear and Lower Costs

A consortium consisting of Liebherr-Transportation Systems and NewRail (Newcastle University’s Centre for Railway Research) and led by the British railway company Grand Central Rail (member of the Arriva Group) is developing an active radial suspension system for rail vehicles called eCAS (electro hydraulically controlled axle steering).

In the UK, track-preserving running is particularly important, as track wear is a significant factor in the calculation of the Variable Track Access Charge (VTAC) –a fee for the use of the British routes, which each train operator must pay depending on the classification of their respective rail vehicle. The rolling stock is therefore evaluated and categorized according to its specific load on the rail system, with the following rule: the lower the wear caused, the lower the fee to be paid. Switzerland has implemented a similarly designed route pricing model, which also uses the individual contribution that a train makes in terms of wear on the infrastructure to calculate the charge.

The consortium believes that active radial suspension could significantly reduce rail wear and the project aims to demonstrate this, as well as the potential reduction in track access charges.

An eCAS prototype in a Grand Central Rail vehicle is to be put into operation on a test track from January 2020 to probably March 2020.

At the heart of “eCAS” is an innovative actuator that can be integrated into most of the bogies in operation today. The task of the actuator is to optimally adjust the wheel set to the curve radius.

The control system records the curve radius via the steering angle of the running gear, via corresponding position sensors between the bogie and the carriage body. Depending on the curve radius, the actuator moves the wheel set to the optimum position so that wear in the wheel/rail contact geometry is reduced to a minimum. The hydraulic unit, including electronics, is flanged directly to the cylinder, so that the actuator can be pressed into the axle guide as a complete part like a conventional axle guide bearing. In addition, there are electrical connections for the position sensors between the bogie and the carriage body, as well as the connection of the two identical actuators of both wheel sets. This means that the chassis system operates autonomously and requires only one power supply on the vehicle side. The unit also has a status indicator so that the status of the system can be identified at any time via visual checks.

Due to the decentralised pressure supply, the actuators operate independently from a hydraulic point of view. This has particular advantages for the installation and maintenance of the devices. There is absolutely no piping on the vehicle and/or chassis, and the associated work for proper cleaning of the oil circuit as well as for the correct filling and venting of the units remain the responsibility of the hydraulics specialist.

Experience and initial calculations of route prices show that the system can save about 50% of the wear-dependent route fee. This means that a ROI of approx. two to max. five years can be expected, depending on whether the system is installed in new vehicles or an existing vehicle is retrofitted. In addition, the wheel wear and rolling resistance are reduced, which leads to additional savings on the vehicle.

The system also offers great potential for track diagnostics. The sensors used to control the system can also be used conversely to diagnose the condition of the infrastructure or bogie.