Of course curves let most of the expansion go, they move.
long straight track is still a wonder to me. Must be laid with enough gap to compensate, but how about 1/4 mile of welded rail?
The answer is at what temperature the rail is laid at (pretty high) and sometimes the rail does have to be cut, shortened and re-welded.
How do railroads deal with thermal expansion? Railroads deal with thermal expansion by heating the rail prior to installation. Therefore, the rail
worldwiderails.com
Greg
That attachment sums up what I've been thinking about how to explain things all day while at a GR meet.
First of all, understand the concept of SFT Stress Free Temperature. In NZ we use a SFT of 32°C. That means when the rail is at that temperature, the steel is in its natural state.
Either side of that, the rail trys to expand or contract. To contain this, movement of the rail is held by fastenings with the sleeper. This transfers the thermal forces to the sleeper. Spring clips, such as Pandrol etc. are very good at this, dog spikes are pretty poor, that is why rail anchors are used hard up against each side of the sleeper. All this energy going into the sleeper is dissipated by the ballast, which is why ballast profile has to be meticulously maintained. Allow any of the above to get out of whack, and you WILL get track buckles..... which in this country, I have to investigate.
The cutting and welding mentioned is usually associated with the laying or repair of CWR (or ribbon rail to our American friends). Depends on what temperature the rail is at this time relative to the SFT. To compensate for the difference sometimes a calculate length is cut out, then the rail remaining is 'stretched' back to the actual length, and welded. You never lay rail when it is too hot, because theoretically you may have to compress the rail, which you can't do, and if you fastened down the hot rail above the SFT it will actually tear apart when it cools down to very cools temperature.