5. Investigation of Front Rod Fracture Causes and Maintenance Methods to Prevent Fracture

Fractures of front rods can cause switching failure, leading to major transport disorders. Even today, transport disorders involving train delays, including those over 30 minutes, continue to occur almost every year. Efforts to deal with front rod issues, such as reviewing and improving the design and materials, and investigating causes, have been made, but they have been limited to addressing individual cases. As a result, the fundamental causes of fractures had not been fully clarified, nor had generalized countermeasures or key inspection points been established.

To address this, through field investigations, measurements, and a newly developed numerical analysis method, we demonstrated that fractures in front rods primarily occur at the L type connection device, a component of the front rod, and that the risk of damage is high at the stress concentration area of the L type connection device slotted hole due to torsion and bending deformation. We also showed that impacts during vehicle passage caused by equipment conditions, such as vertical steps at the heel of tongue rail, and improper lateral length adjustment of the front rod are causes of fractures.

Based on these causes, we proposed maintenance methods to prevent fractures, highlighting key points to check during visual inspections and adjustment guidelines that can be determined from appearance inspection (Figure 1). Furthermore, we also proposed example descriptions to assist railway operators in creating maintenance manuals.