How do welded rails expand

However, a common issue was that the bolts would oftentimes crack the joint bar, especially under the strain of a heavy train. Furthermore, the joints oftentimes had to be insulated when signal circuits were present, where an epoxy type substance was installed between the rails, strengthening the joints. Jointed rail additionally provided for a bumpy ride for passengers, as each wheel would slam the joint as it passed over.

As rail technology progressed and high speed trains began to come to fruition, an alternative to the old practice was duly needed. Although a replacement for jointed rail was on the horizon, it did evoke various benefits.

Although jointed rail was rougher on both the train and track infrastructure, it proved advantageous when the rail reacted to intense temperatures. Installed correctly, there should be a tiny lubricated gap between the rails at the joint bar to handle thermal expansion. However, an instance where the joint does not move would have similar reactions to CWR.

Beginning in the fifties, welded rail was installed on various rail networks and began to prove its worth. It encompassed a much smoother ride for passengers, and was less of a maintenance headache. However, due to the lack of joint bars, when the rail expanded due to excessive heat, the rails had no leeway, therefore, they expand and buckle under the pressure.

However, various precautions are taken to lessen the chance of the rail being damaged due to thermal expansion.

According to Progressive Railroading, if the force of the expanding rail is not repaired in a timely manner, the rail will have no more room to expand, thus, the rail will begin to buckle, resulting in the rail being out of gauge.

If the rail was shifted far out of gauge, it will be troublesome for a train to navigate, thus, causing a derailment. This highlights the importance of preventive measures to detect faults before they become a dire issue.

There is obviously a limit to this though, as failure at cold temperature extremes is still physically possible. Sign up to join this community. The best answers are voted up and rise to the top.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How do gapless rails deal with thermal expansion? Ask Question. Asked 3 years, 2 months ago. Active 3 years, 2 months ago. Viewed 3k times. Improve this question. Ghanima 5 5 bronze badges.

It was my understanding that the gap in rail track sections was to accommodate expansion and contraction. This question specifically asks about gapless rails. When I Googled this, I searched "gapless rail" and variations but didn't think to add "thermal expansion" in the search term DUH!

This is visible at a bulge of the track grid. Track buckling occurs under the effect of an external force. In the case of track buckling, the track grid is lifted and thus the resistance to lateral displacement is reduced. It is possible to run over buckled track at low speed, but it not possible to run over track that is laterally distorted.

In summer, due to high rail temperatures the rails expand in all directions, generally to the side, so that a standard gauge of mm can no longer be maintained.

In winter, however, the rails contract and break like glass, easily, quickly and in most cases rail breaks are not directly visible and recognizable. The almost invisible broken rails are usually detected by the signalling system, since this sends current through the rails. This book is dedicated to the many people involved in the day to day planning and performance of track maintenance activities. Providing a practical approach to everyday challenges in mechanised track maintenance, it is not just intended as a theoretical approach to the track system.

Railways aim at transporting people and freight safely, rapidly, regularly, comfortably and on time from one place to another. Note the expansion gap left between the rails. CWR therefore requires less maintenance than jointed track, and will remain in accurate alignment for longer. But if it is continuous , with no expansion joints, how does it cope with thermal expansion in hot weather? Posted by Vince Chadwick at Unknown 28 August at Unknown 4 October at Unknown 5 November at Jovet 9 March at Vince Chadwick 9 March at