Track Recording Trolley

KRAB 84.09 for Track Geometry

Approved by CD, RENFE, DB

The KRAB system has been designed to complete the larger and more sophisticated measuring cars, and it is ideally to be used on secondary routes, sidings, switch points and for new track acceptance.

  • The measurement speed is limited to approx. 15 kph.
  • The trolley has a triangular bogie which is made from steel or duralumin profiles. The trolley is provided by telescopic measuring axe.
  • The electrically insulated wheels have separated wheels and flanges in order to remove different circumferential velocity.
  • The wheel surface treatment is executed in hard chrome.
  • The trolley surface finish is yellow powder paint.
  • The trolley is available in wide range of nominal gauges (1067÷1668mm).


Trolley DesignTrolley-design

During the measuring running the following track parameters are scanned:

  • alignment (horizontal versines) of right rail
  • level (vertical versines) of right rail
  • gauge
  • cant
  • twist on base 1.15m
  • rail length

In real time the following derived geometric signals are computed:

  • twist for selectable length of chord
  • radius R
  • gauge variation over 1 or 2m

Geometric quantity to be measured

Transducers to be used

The trolley uses contact LVTD potential sensors combined with an electronic pendulum device. An IRC sensor is used for track length measuring. Especial attention is awarded to the selection of asymmetrical chord length.


On board computer

Screen of the PDA computer1

Screen of the PDA computer

The real time processing of signals from the sensors is performed by the on-board rugged PDA computer TDS Nomad (Windows Mobile 6.5), whereby the following items are warranted:
• reading and scanning of signals given above
• on-line processing of the signals:
– anti-aliasing
– smoothing of long wave part
– optical and acoustical signalling when the geometry data exceed the selectable thresholds
• display of numerical values of the geometry data
• entry of the geometry data into non-erasable storage of on-board computer at the distance 0.25m. The measuring distance is 30-120 km (depending on
memory amount 2?8MB).
• entry of the informational description of the track section to be measured
• entry so called events (mud spots in ballast, damaged sleepers etc.) with exact position along the distance


Assessment of the collected data by KRAB6.12/7.00/8.0 software


The example of track geometry graph printed by assessment software Krab6.12


After measuring, the collected raw geometry data are transferred from the on-board computer TDS Nomad into any PC computer. Sophisticated assessment software computes so called actual geometry (with unit transfer function) in the waveband λ=1÷25m via FFT (Fast Fourier Transformation) technique. Thus the following items are available:

  • actual alignment and level in waveband λ=1÷25m
  • separation of all geometric signal into long wave (λ>25m) and short wave (λ<25m) parts.
  • so called section assessment – statistic evaluation of the track geometry based on standard deviation and quality index
  • table of local defects, print out of geometrical lay and tables


Basic technical data:

  • Mass: 63kg basic form
    4kg auxiliary twist arm
  • 20 hours without battery charge
  • Working temperature: -5÷55°C.
  • Waterproof


Towing of the KRAB trolley behind road/rail car

Towing of the KRAB trolley

It is very popular using the track recording trolley KRAB84.09 as “pocked” measuring vehicle. The maximum measuring speed is 15kph and the capacity is more than 100km of the track per shift.

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