A new take on tamping – electric, quieter, more effi­cient

A next-generation tamping-unit drive is being developed: electric and with adaptive amplitude control. The goal is less noise and even greater efficiency. How does the idea become a robust solution for operation?

Modern requirements for track construction and maintenance are driving development: lower noise levels and higher output. Electrically operated track construction and maintenance machines provide the basis for this. They work with zero local emissions and are significantly quieter. This means that instead of the diesel engine, the focus is now on the work units as the main source of noise, above all the tamping unit.

From needs to solutions

This is exactly the approach Plasser & Theurer is taking in terms of the vibration motor. Trading in hydraulic motors for electric ones opens up new possibilities. The control system reacts faster, the hydraulic system shrinks. Pressure losses are reduced, leakage risks are minimized, and servicing is simplified. At the same time, the proven non-synchronous constant pressure tamping principle with eccentric shaft remains unchanged – constant squeezing force, robust in use. This allows noise emissions to be reduced without compromising on compaction performance.

What's new?

The next step in the innovation process is to further develop the eccentric drive. A vibration shaft control precisely adjusts the vibration amplitude of the tamping tines to the ballast condition and process phase. During the squeezing process, the control system keeps the amplitude in the optimum range for grain rearrangement and compaction. In idle mode, it switches the vibration to zero. Timing is particularly important in the lifting phase: if the control system deactivates the vibration too early, voids are created in the ballast and the load-bearing capacity decreases. The adaptive amplitude control therefore keeps the vibration active in all phases with ballast contact and only reduces it where it makes sense from a technical point of view.

The new concept decreases noise, wear, and the dynamic load on adjacent components. The two complement each other: electric drive plus vibration shaft control increase quality, efficiency, and ergonomics.

The system must meet the highest requirements. In the tamping process, the oscillation amplitude must be adjusted within tenths of a second. At the same time, the mechanical system must be able to absorb high forces so that the amplitude remains stable even if the ballast is heavily fouled. This ensures reproducible compaction.

How does the idea become a solution ready for serial production?

The path from a requirements profile to a tamping unit ready for serial production is long and interdisciplinary. Mechanic construction, numerical simulation, and practical tests are closely interlinked. What does the development process look like in detail?

Customer and market requirements It all starts with listening. Plasser & Theurer combines structured feedback from operating staff, operating companies, and infrastructure managers and translates it into specific requirements. In addition, there are standards, specifications, and regulations, including those related to acoustic emissions. Major trends such as electrification, digitalization, and sustainability are also taken into consideration.

Requirements and concept development An overall technical concept is created from the specifications, in which the functional principle and target parameters are defined. A particular focus is on maintainability and standardized interfaces, as they reduce the variety in spare parts. Energy efficiency must at least match conventional solutions. Load profiles and service life targets provide the framework.

Construction and mechanical layout Now it gets to the specifics: components are mechanically dimensioned, raw materials and manufacturing processes are chosen, assembly concepts are defined. The development team takes existing machine platforms into account, which reduces the need for subsequent customization.

Simulation and virtual validation Numerical models provide the first endurance test. Two methods are combined: the finite element method (FEM) to investigate structural capability and the discrete element method (DEM) to analyse the interaction between tamping tines and ballast. This allows the mechanical loading capacity and compaction effect to be assessed virtually and geometries to be optimized before the prototype is created, which decreases development times and lowers costs.

Tests on the test rig Once the first prototype has been produced, it is put through its paces in the laboratory. The test rig offers reproducible conditions and enables quick parameter changes as well as complete service life tests. The results directly influence the construction design and validate the function, loading capacity, and reliability simulations.

Plasser & Theurer uses specialized test rigs with realistic load spectra for this purpose. A wide range of sensors makes mechanical, thermal, and vibration behaviour visible. This way, necessary improvements in the construction design can be identified at an early stage, component variants can be compared, and operating parameters can be optimized – an indispensable basis for subsequent field tests.

Field tests The next stop after the test rig is the machine itself. The unit will be tested under realistic conditions, focusing on tamping quality, robustness, and acoustic emissions. Our own test machines enable flexible applications and detailed analyses. The insights gained and the feedback from the operating staff form the basis for further adjustments to the construction design. Field tests not only validate, they also optimize the unit and bring it close to the serial-production stage.

Early-adopter phase At the pre-serial production stage, select customers test models in real-life railway operations and provide valuable feedback on servicing, operating comfort, and performance. Functional deviations and occasional failures are calculated learning moments. This is how the final touches are made before going into serial production.

Ready for serial production and market launch Once all test phases have been completed and the design is finalized, the unit goes into serial production: manufacturing processes are industrialized, documentation is created, and service and sales teams are trained to ensure a smooth rollout.

A look at the development process shows that quality is created step by step: specifying requirements, finding creative solutions, designing thoughtfully. Then test, test, test. Not a quick fix, but a process that ultimately brings reliable machines on track.