The profile measurement instrument has been developed for high accuracy measurement of wheels and tracks; it is used by personnel dealing with high-speed trains, sensible to wheel-track contact geometry, and consequently to running dynamics. It has also a great use in high level maintenance of wheelsets of locomotives, EMUs, DMUs, passenger cars, freight wagons, trams.

The measurement method (a probe in contact with the measured object) has been selected after a careful analysis of the available technologies.

We point out that an optical method would have the following drawbacks:

• It’s difficult, if not impossible, to design an instrument able to measure both sides at the same time, accommodating a range of gauges big enough (at least 1425 to 1455), and also light enough to be portable

• it would not possible to design a single instrument able to measure both the wheels and the rails, including the grooved rails.

  

The big advantage of this solution is that a single instrument measures train wheels and rails and light rail (tram) wheels and rails, everything with high accuracy, giving as the end result both sides in a unique coordinate system.

The instrument is therefore a manual device with mechanical probe capable of measuring both the wheels or the rails profiles. The two wheels or tracks are measured at the same time and in a single reference frame; this is very important because the measurement precision achievable on the profile shape is the same also in the relative distance between left and right profiles. Furthermore, relative angles between left and right profiles are determined in a unique and precise way, contrarily to other measurement systems that consider each profile isolated.

Data acquired with this instrument are thus not only usable for verifying wear parameters typical of wheels and track, but most of all for calculations relative to single wheel-rail contact, such as deltaR function and equivalent conicity.

A high moment of inertia mechanical structure is essential for granting the required accuracy level. A careful design has reduced the weights for easier handling.