Fishplate Bolt Hole Spacing and Rail Connection Strength
- What is the design basis for the bolt hole spacing of fishplates?
The design basis mainly includes rail type, design load, train running speed, etc. For 60kg/m rails, to ensure connection strength and uniform force transmission, the bolt hole spacing is generally designed to be 100 - 120mm; the bolt hole spacing for 50kg/m rails is usually 90 - 110mm. The greater the load and the higher the train speed, the stricter the design of bolt hole spacing. Mechanical calculations are required to ensure that the stress of bolts and fishplates does not exceed the allowable value of the material under the maximum load.
- What specific impact does bolt hole spacing have on rail connection strength?
When the spacing is too large, the contact area between the fishplate and the rail is relatively reduced, the bolts are stressed unevenly, the bolts near the rail gap bear greater tension, and bolt breakage is prone to occur. At the same time, the integrity of the rail joint is reduced, and large displacement is prone to occur under the action of train load. When the spacing is too small, the cross-sectional area of the fishplate material between the bolt holes is reduced, the strength is reduced, and cracks are prone to appear between the bolt holes, affecting the connection strength.
- What are the differences in bolt hole spacing between different types of fishplates?
The bolt hole spacing of ordinary joint fishplates (used for straight lines and small-radius curves) is relatively large, such as 110mm for ordinary fishplates used for 60kg/m rails; insulated fishplates, to ensure insulation performance, have the same bolt hole spacing as ordinary fishplates, but the size and distribution of holes need to match the insulating sleeves to ensure insulation effect; special fishplates for turnout areas have small bolt hole spacing, generally 90 - 100mm, due to complex stress, to enhance the stability of the connection.
- How to detect whether the bolt hole spacing of fishplates meets the standards?
Use a vernier caliper or a special measuring tool to measure the distance between the centers of two adjacent bolt holes, with a measurement accuracy of ±0.1mm. Measure at least 3 groups of adjacent bolt hole spacing for each fishplate, take the average value and compare it with the standard value, and the deviation shall not exceed ±0.5mm. For mass-produced fishplates, 5% are sampled for inspection. If one is unqualified, double the sampling is carried out. If there are still unqualified ones, the batch is judged as unqualified.
- What harm will be caused to the track when the bolt hole spacing does not meet the standards?
Excessive spacing deviation will make fishplate installation difficult, unable to accurately align with the bolt holes on the rail. Forced installation will cause additional stress on the fishplate and bolts, reducing their service life. Under the action of train load, the connection strength is insufficient, and problems such as step, rail gap expansion are prone to occur at the rail joint, aggravating wheel-rail impact, leading to premature damage of rails and fishplates, and even affecting train operation safety.