Of-round wheels, polygons, flats, noise complaints from residents, use restrictions
- An issue in your company?


Might occur during use out-of-roundness (polygons) on individual wheels. Polygons can be heard as a booming rolling noise relatively uniform volume and stimulate vehicle components (eg inner lining, floor) to vibrations at. Polygons impair travel comfort and create an additional vibration stress of certain components. This should be eliminated by turning or rotating milling on an underfloor wheel processing machinery. Polygon formation is not only a geometric runout, but causes an inhomogeneous distribution of hardness in the wheels. If these embrittleed are not removed during processing, the wheel will be out-of-round (memory effect) once again after a short period of operation. Thus, a material removal of about 5 mm for the permanent removal of the relatively small eccentricities is required, which means a considerable economic loss in wear stock of the wheel of 40 mm.

A flat section is formed when the wheel of the moving vehicle does not longer roll, but slides over the rail ("slide"). By flats and polygons result very high dynamic forces with a plethora of serious consequences for rails, superstructure and vehicles:

  • Risk of rail breakage when driving through occurring "blows" (mainly in frost periods).
  • Damage to the track geometry - The influence of the applied force spectra into the track on the track quality decay rate can not be overestimated. Therefore, the planned route for an operation and the rolling stock used has a great influence on the frequency of maintenance work to be performed and the associated costs. A wheel load fluctuation of 30% is already attracting a 1.6-fold faster track geometry deterioration after themselves. This means that vehicles with out-of-round wheel units or ride instability damage the track disproportionately. There are also reductions because of the "liquid becoming" (elastic-liquid behavior) of the ballast at frequencies above 40Hz.
  • False brinelling refers to the emergence of wavy indentations in the driving mirror of railroad tracks. The causes are varied, more often they come about by abrasive wear during braking and cornering of trains and irregularities of the wheels.
  • During the trip can be heard a periodically occurring noise in the frequency of the wheel rotation.
  • Development of common annealed flat spots on the wheel tread.
  • Creation of plots, that is to say of the rail surface abraded and usually right in front of the flat section on the wheel, or elsewhere on the wheel material applied may result in the worst case to wheel lock (canting of brake blocks).
  • Blows caused by flat spots, also influence the components of the axle box -> Bearing damage and hot runner.


Permanent wayside train monitoring in highly repetitive tram, metro and subway traffic as the basis for condition-based maintenance by means of the monitoring system LASCA®:

  • Condition-based maintenance of the entire fleet - smooth running characteristics.
  • Timely delivery of the vehicle and wheel exact measurements - 2 minutes after the crossing - to the maintenance planning and operations scheduling of the workshop
  • Monitoring as a substitute for manual runout measurements - Cost reduction for the same security.
  • Increase the mileage of the wheels through the timely reprofiling at a lower depth of cut - reducing costs by exploiting the scheduled mileage.
  • The quality of the wheels in the operation is recorded reproducing and documented in order to perform a condition-based maintenance.
  • Depth of the reprofiling can be characterized roughly predetermined.
  • Reduction of dynamic forces in operational use to protect the infrastructure and vehicle fleet - Avoidance of wheel and rail breaks.
  • Timely detection of flat spots and out of roundness (polygons) to prevent the hardening to the tread - hardening means increased depth of cut at the reprofiling.
  • Detection of wear-causing variations in the running behavior of the vehicles - load shifts of the axles and bogies, incipient wheel flanges, defective shock absorbers.
  • 100% monitoring of the fleet under operating conditions in the dynamic running behavior - Cost reduction through planned proactive vehicle management and utilization of re-profiling and workshop capacity while reducing downtime.
  • The under operating generated results of the monitoring system LASCA® coincide 100% with the final measurements in the workshop.
  • Reducing sound and vibration emissions - particularly noise and residents' complaints - filtered data release to increase acceptance.
  • "The most monitored fleet" - by the German TÜV certified monitoring system.


  • Reducing of the noise levels of the residents
  • Protection of sensitive railway facilities
  • Significant resource savings and cost reductions in maintenance
  • Increase the mileage of the axes
  • Cause Investigation of tread damage



Using a calculation model based on Excel one can calculate the profitability of LASCA® -mobile dynamic high speed laser measurement system for the measurement of flat spots and out of roundness of railway wheels-. The data allow the creation of a business case and what-if analysis on the basis of its own fleet composition and the rail network. The findings allow statements about the future profitability, reduce costs and improve efficiency of maintenance through the use of the monitoring system LASCA®.