In the field of railway track fasteners, WJ-7 and WJ-8 railway fastener systems are both important devices to ensure the stability of the track, but there are differences between the two in many aspects.
Structural design differences
WJ-7 is a split shoulder-free fastener, mainly used for shoulder-free ballastless track. It relies on T-bolts, nuts and flat washers to work together to apply buckling pressure to the spring bar, and transmits the vertical force to the lower ballastless track through the insulating buffer pad and height adjustment pad under the iron pad. The longitudinal and lateral forces are transmitted through the anchor bolts connected to the iron pad and tightened in the embedded sleeve.
WJ-8 belongs to the fastener system for ballastless track with shoulder. The shoulder is in direct contact with the bottom of the rail, and the lateral force is borne by the rail plate shoulder. Under this structure, the lateral restraint ability of the fastener system is strong, and with the assistance of the shoulder, the lateral displacement of the rail is more directly restricted.
Different component composition and details
Spring clip
WJ-7 spring clip has W1 type with a diameter of 14mm and X2 type with a diameter of 13mm. W1 type is used in general sections, and X2 type is used in sections with low resistance. WJ-8 spring bar also has W1 type and X2 type, but because it is equipped with a shoulder structure, its spring bar is different from WJ-7 spring bar in terms of the coordination relationship with surrounding components. For example, the specific bending angle, size ratio and other details of the spring bar need to match the overall layout of the shoulder fastener system.
Pad
WJ-7's rail pads are divided into two categories: A and B. Category A is 12mm thick and is used for high-speed railways that take into account freight, and category B is 14mm thick and is used for high-speed railways that only run passenger cars. Each category is further divided into ordinary rubber pads and composite pads with low resistance fasteners. The pads of the WJ-8 fastener system are designed in terms of size and material properties according to the stress characteristics of the shoulder structure and the track requirements. They are different from the WJ-7 pads in specific parameters and application scenarios.
Different applicable scenarios
The WJ-7 type is suitable for a variety of shoulder-free ballastless track scenarios, such as buried sleeper (double-block sleeper and long sleeper) ballastless tracks on bridges, tunnels and roadbeds. Due to the lack of shoulder structure, the track elasticity is better, and the design and performance requirements of the fastener system itself are higher. It is suitable for passenger dedicated lines and other lines that have certain requirements for track elasticity.
WJ-8 is mainly used for ballastless track of high-speed passenger railway with a speed of 350km/h. It is also suitable for high-speed railway with a speed of 250km/h (a small number of ordinary passenger cars and freight cars can be taken into account) with high-speed trains (maximum axle weight of 170kN) and intercity railway with a speed of 200km/h with high-speed trains (maximum axle weight of 170kN). The shoulder structure provides strong lateral stability and can better cope with various forces generated by high-speed trains during operation.
Differences in adjustment ability and force characteristics
In terms of adjustment ability, the height adjustment of the WJ-7 system is achieved by replacing different thickness height adjustment pads under the rail and under the iron pad, with a maximum of 30mm; the gauge adjustment relies on the oblong hole at the connection between the iron pad and the spiral spike, allowing the iron pad to move left and right, with an adjustment amount of ±10mm. The height and gauge adjustment method and range of the WJ-8 fastener system are different from those of the WJ-7 due to the influence of the shoulder structure. For example, its gauge adjustment may rely more on the different specifications of the gauge baffle and other components.
In terms of stress characteristics, the two spiral spikes in the WJ-7 have complex functions and stresses, and are in an unfavorable stress state of bidirectional bending and pulling. The iron pad must be fixed and part of the lateral and longitudinal forces must be transmitted. The WJ-8 is designed with a shoulder, and part of the force can be transmitted through the shoulder. The stress of the spiral spikes is simpler than that of the WJ-7, and there is no complex bidirectional bending and other conditions like the WJ-7 spiral spikes.