The CAT is an extremely accurate instrument that can be used to measure rail for acoustics purposes and for Quality Assurance of rail grinding. It has the great attraction that it can be both used and carried by a single person: the equipment, when packed in its flight case, weighs less than 15kg. There are few, if any, instruments that can measure metres of rail with similar accuracy and none, to our knowledge, which can be used conveniently by a single person.

It is the most recent development of a piece of equipment made originally at Cambridge University, England, in the 1970s for measuring corrugation. A further development was made in the late 1980s to make portable corrugation-measuring equipment for Australian National railways. This equipment is still used routinely on Australian railways. The first prototype of the present CAT was produced in 1997. Since then, examples of the present equipment have been used routinely and reliably for corrugation surveys, Quality Assurance work following grinding on all types of railway line, and for acoustics work.

The CAT is an appropriate instrument for measurement of rails to assess roughness in accordance with the recommendations of the provisional International Standard ISO 3095. Indeed it far exceeds the requirements of this Standard insofar as hundreds of metres of rail can be measured continuously, accurately and quickly through a test site, rather than simply isolated lengths of about 1m. Such a continuous measurement permits kurtosis analysis to be used to determine whether individual 1m lengths of track are typical of a full test site.

With relatively minor modifications, the portable CAT could also be used to measure wheel profiles, and RailMeasurement are happy to supply a customised version of the CAT if required.

During 2009 RML introduced the Mark 3 CAT, which is designed specifically to measure both conventional flat-bottomed (Vignole) rail and also grooved rail which is severely worn and deformed, and possibly also deeply embedded in the street below the level of the adjacent tarmac. It is also now even easier to adjust the lateral position of the measuring head right up to within 10mm of the gauge and field faces of the rail. We have found that CATs are increasingly being bought to measure acoustic roughness rather than corrugation. It is probably the least expensive equipment of its type available, yet in many ways also (as a client told us):

"The CAT is unique"

The capabilities of the CAT for measurement of corrugation and acoustic roughness are illustrated in an article that appeared in April's edition of International Railway Journal.  This contains measurements from a variety of railway systems worldwide, which have been supplied to RML by users.  Interesting differences between different types of railway system are apparent that have not (to our knowledge) been noted before, largely because no instrument of sufficient accuracy has previously been available and used as widely for measurements of this type.  This article also shows the requirements for residual corrugation in the European reprofiling standard, EN13231-3:2006, as a one-third octave spectrum and compares this to the spectrum in the acoustics standards ISO3095 / EN15610.  Since the requirements are very similar, it follows that an instrument to demonstrate compliance with EN13231-3:2006 should be of similar accuracy to one that is used to demonstrate compliance with ISO 3095 / EN15610.  Fortunately we can supply you with such equipment, even to work at 10km/h or more on a reprofiling train or hy-rail.  This helps the supplier of reprofiling services to know that they are reprofiling track to a high standard, and the railway system to know that the contractor is doing what they require.

Output from the CAT is available in several formats appropriate to both grinding and acoustics work: amplitude vs. distance, one-third octave band spectra and exceedences are amongst many standard functions. Examples of spectra of successive measurements of the same, extremely smooth rail are shown here, demonstrating the CAT's excellent repeatability even at wavelengths of a few millimetres and amplitudes of less than a micron. These spectra are plotted relative to the reference curves given in the draft ISO 3095. The capabilities of the CAT far exceed the narrow requirements of this draft Standard.

Further information on the accuracy and repeatability of our corrugation measurement products is given here.

A comparison of our product specifications and use is available here.