An overview of my contribution in the running behaviour analysis of cross-bracing links for a standard freight bogie design.

Background

There is a need to develop more advanced freight wagons that maximise payload and speed, while reducing the overall system costs, including wheelset and track deterioration. In the Shift2Rail project FR8RAIL, a consortium of wagon manufacturers, wheelset manufacturers, and research centres worked to develop a new generation of the widely used Y25 freight running gear, by improving the curving performance and hunting stability. For the new design, I studied the dynamic behaviour with simulations-based EN14363 tests up to 30 tons/axle, and calculated the expected impact on wheel wear and fatigue.

.. studied the dynamic behaviour with simulations-based EN14363 tests up to 30 tons/axle, and calculated the expected impact on wheel wear and fatigue.

FR8RAIL bogie design

The design and construction of the Y25 bogie design and the new FR8RAIL variant are described in detail in citer. The designing principle of the FR8RAIL bogie revolves around the much needed balance between lateral stability at higher speeds and steering capability in tight curves. From a track-friendliness standpoint, better curving performance translates to lower track damage in curves while better lateral stability pushes the operating envelope of the freight wagons to higher speeds without causing excessive damage to the track. The key features in the suspension that distinguish the running gears from each other are:

Cross-bracing linkages

This helps with radial steering along curved track sections, decreasing the wheel-rail forces by reducing the angle of attack. The linkages weigh 35 kg each, slightly increasing the unsprung mass that also influence the dynamic loading on the track. Such linkages have been implemented before in three-piece bogie designs.

Softer primary suspension

Due to the presence of an extra Lenoir link per wheel, doubling the longitudinal clearance to 8 mm. This substantially increases the capability of the vehicle to yaw.

No sidebearer clearance

Unlike the previous features, this stiffens the secondary suspension allowing for lesser relative movement between the carbody and the bogie-frame. However, this is beneficial when it comes to lateral stability at high running speeds.

The bogie is also lighter when compared to the standard variant by about 100 kg due to variations in design and materials. It is also equipped with disc-brakes instead of conventional tread block braking.

The designing principle of the FR8RAIL bogie revolves around the much needed balance between lateral stability at higher speeds and steering capability in tight curves.

Running behaviour & Track-friendliness

The assessment quantities given in EN14363 standards for the corresponding running conditions were checked to evaluate the running behaviour.The vehicle performance was assessed based on safety against derailment on twisted track, running safety at high speeds, track loading and ride comfort. The track-friendliness based on different damage modes namely

• Wear,
• Rolling Contact Fatigue (RCF),
• Settlement,
• and component fatigue

was also evaluated as seen in the figure below.

The full evaluation is published in the project report and articles below.

References

1. Project report:FR8RAIL: Deliverable 4.3 Preliminary running gear and wagon design concepts.
2. Conference paper: FR8RAIL Y25 running gear for high tonnage and speed. International Heavy Haul Association.
3. Journal article: Assessment of running gear performance in relation to rolling contact fatigue of wheels and rails based on stochastic simulations..

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