David Hanson

Field Trials of Gauge Face Lubrication and Top-of-Rail Friction Modification for Curve Noise Mitigation

This paper presents the results of a comprehensive trial of friction management techniques carried out over a 7 month period at a curve in Sydney. The trial tested various top-of-rail friction modification and gauge face lubrication products, both in isolation and in combination, applied at different volumes and locations around the curve. Noise and vibration transducers were situated at three locations around the curve, one upstream of the treatment and the other two downstream. At the upstream location, rolling stock data was also available from a permanent wayside geometry monitoring system.

An Investigation of the Influence of Track Dynamics on Curve Noise

Experience has shown that curve noise issues can become more severe when curved track is upgraded from timber to concrete sleepers. This suggests that changing the dynamics of the track structure, for instance using a softer rail fastening system and/or sleeper, could provide ways to reduce curve squeal. The problem, however, is that the changes in dynamic characteristics between timber and concrete sleepers that explain the difference in curve noise behavior are not currently understood. Observations and anecdotes have hinted at the effect of different rail pads, fasteners, rail dampers and gauge relief on curve noise, but have failed to definitively identify either a successful mitigation strategy or a quantitative relationship with curve noise generation. This paper presents the results of field trials on curved track, conducted before and after an upgrade from timber sleepers to concrete sleepers, aimed at improving this understanding.

Wheel Squeal: Insights from Wayside Condition Monitoring

This paper summarises the insights gained by analysing wayside condition monitoring data from a curve of 300 m radius in Sydney over a three year period. The aim of analysing a large dataset is to derive statistically significant results on how angle of attack, speed, rail lubrication and rail grinding influence wheel squeal. The key finding is that the generation of severe wheel squeal is strongly determined by the angle of attack, which is consistent with the theory: severe squeal was almost entirely absent when the angle of attack was less than 10 mrad, and rose with increasing angle of attack. Squeal was therefore associated only with basic three piece bogies as these were the only bogies to return high angles of attack. Other freight bogie types, such as the one-piece freight bogies, three-piece freight bogies fitted with cross-bracing or steering arms, all steered well around the curve and did not squeal. Other factors, such as speed, rail lubrication and rail grinding, would influence wheel squeal generation when combined with high angles of attack. These factors were found to influence squeal behaviour, but are secondary for controlling wheel squeal compared with solving the poor steering performance of the three-piece freight bogies.

Low Cost Noise Barriers for Mitigation of Rail Noise

Noise barriers are a widely used mitigation measure for rail noise, particularly for new rail line developments. Precast concrete barriers are typically used for rail noise mitigation as their high mass allows them to effectively mitigate low frequency noise from sources such as freight locomotives. However, there are considerable capital costs associated with the design and the construction of concrete barriers due to the large scale earthworks required for barrier footings and vegetation clearing. As such, there exists an opportunity to reduce the cost of noise barriers by optimising their design to suit the particular noise characteristics at each site.This paper presents an approach for the design of low cost noise barriers for the mitigation of rail noise. This approach involves: Categorising the type of rail noise at the target location. Categories include locomotive noise, squeal noise, rolling noise, bunching and stretching etc. which reflect the frequency content of the noise at the site. Designing the barrier to treat the specific noise type at the site (i.e. specifying barrier material, height and length). Examining the cost components of each barrier design using a life cycle methodology that considers all costs associated with design, construction and maintenance of the barrier. As an illustration of how this design approach can be applied, this paper presents two case studies showing the low cost noise barrier design at two locations on the Sydney Trains Network which experience squeal noise and locomotive noise, respectively. Each design considers the predicted performance and costs of the designed barriers and compares them with industry benchmarks.

A Survey of Freight Locomotive Passby Noise Emissions

A survey of freight locomotive passby noise emissions has been undertaken across five locations on the RailCorp network, including identification of “subjective outlier” events. This paper describes the objectives of the survey, the measurement locations and methodology. Results are presented in the form of statistical parameters for each measurement location, as well as parameters categorised by operating condition (up steep grades, down steep grades and on straight and level track).