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446<br />
<strong>Handbook</strong> <strong>of</strong> <strong>Railway</strong> <strong>Vehicle</strong> <strong>Dynamics</strong><br />
FIGURE 13.22 MiniPr<strong>of</strong> rail and MiniPr<strong>of</strong> wheel measuring instruments (courtesy <strong>of</strong> Greenwood<br />
Engineering). Source: Catalogue —Courtesy <strong>of</strong> Greenwood Engineering.<br />
appreciably alter the resultant contact conditions and the resulting equivalent conicity and must be<br />
avoided for realistic simulations. Several devices use the flangeback as the datum position for wheel<br />
pr<strong>of</strong>ilemeasurements.Thissimple approach may generate significant errors whenmeasuring pr<strong>of</strong>iles<br />
where the flangeback is worn, for example, by contact with check rails.Experienceshowsthat this<br />
simple approach therefore has limitations. For measurement <strong>of</strong> both wheel and rail pr<strong>of</strong>iles, the<br />
device should have an outrigger which bears on the opposite wheel or rail to ensure that the measuring<br />
head remainsinplane<strong>of</strong>the track/wheelset. Such equipment is not generally available for measuring<br />
wheels. In all cases, however, asystem usingtwo measurement heads capable <strong>of</strong> recording apair <strong>of</strong><br />
wheel or rail pr<strong>of</strong>iles and their relative orientation simultaneously will provide superior results.<br />
As the requirement is generally to gather pr<strong>of</strong>iles which are representative <strong>of</strong> agiven location or<br />
situation, the exact position at which pr<strong>of</strong>iles are measured shouldbechosenwith somecare to avoid<br />
localised pits or defects. Pr<strong>of</strong>iles should always be cleaned prior to taking the measurement as<br />
contamination on the wheel or rails (e.g., dirt, weardebris, or grease) may prevent accurate recording<br />
<strong>of</strong> the pr<strong>of</strong>ileshape. Similarly, it is particularly critical that the measuring head <strong>of</strong> contacting devices<br />
is also kept clean.<br />
© 2006 by Taylor & Francis Group, LLC