OK, I am a novice so this is probably a dumb question, but...
Do temperature extremes have any significant impact on rails, i.e., is there enough expansion/contraction to cause problems? If so, how do railroads deal with it? Is the impact different on welded vs. jointed rail?
------------------ Rich
Posted by Cdr.Dick (Member # 408) on :
This is not a dumb question. This past December at the start of what was an extended cold period , we had numerous rail failures. These were not limited to any specific kind of rail. Both welded and stick rail are adverely affected by extreme cold. While the conductor on train OIPI,I also once saw the effect of sudden heat changes on welded rail. A contractor removed a temporary crossing without notifying the railroad. As we headed west on the Port Reading Secondary , we encountered a heat kink caused by the removal of the crossing and a 90+ day in early May. My engineer did an unbelieveable job of train handling as the bow in the rail was extreme. Understand that as we passed over the kink, I looked back and could see the long hood number boards from the engineers side as they rocked toward the fireman's side of the leader. We did suffer an empty tank rock off it's truck, but the fabulous trainhandling prevented a derailment. So to answer your question,YES, heat and cold do affect track conditions.
Posted by CSXBill (Member # 464) on :
I have replaced alot of broken rails this year. We also have a pull apart which is when it pulls the bolts or shears them off in a joint or a frog when the rail contracts. When we put a piece of rail in to fix the break we record how much was added. That way when it gets welded in the spring we can remove it so it will not buckel in the heat. We use things called rail ancors or "creepers" which we hammer on to the base of the rail on ither seid of the tie to help hold the rail from running to much.
Posted by georails (Member # 482) on :
Not a dumb question at all. In Australia we have many contrasts in temperature and in one location I can think of Lithgow, there are heated points for winter time and in summer the shade temperatures can hit 40 deg C or about 105 F, the rail temperature at the hot days is often 60C or 140F, the rail expands and if not in Pandrol clips on concrete track sleepers does buckle. we have speed restrictions in New South Wales using the code word WOLO wheich is a throw back to the telegraph days, when telegrams were sent for train running. a sign about 3 foot by 2 is placed on track side near platforms with Wolo in Black on a Yellow background. This tells train crews that the track speed of the train must not exceeed a certain amount, usually 80% of normal speed. It is summer here and so far a few days have hit about 47 c or 115F in Western area of Sydney and the Blue mountains. I placed no less than 10 Wolo boards out one day last week. Boy was it ever hot!
Posted by rresor (Member # 128) on :
Track buckles and rail pull-aparts are the two problems welded rail faces.
Track buckling is avoided by laying rail at a high "neutral temperature", so that it is in stress (trying to shrink) most of the time. This, and adequate ballast off the ends of the ties, will prevent buckles.
Pull-aparts on welded rail most often occur at points where the rail sticks have been welded together. If the rail is properly anchored, the ends won't separate much, and trains can probably get over the brake without problems (although at low speed). A clean vertical break in the rail also sets the signals to red. With buckles, on the other hand, you don't know they're there until you see them. So by and large, railroads prefer to put up with the pullaparts and avoid the sun kinks.
Posted by michiganrailfan (Member # 605) on :
I am a volunteer on a tourist line in Michigan. Often we will have to change a broken rail from our lousy seasons up here. Depending on what the temperature of the day will be, we cut the rail as much as 4 inches, in some cases, shorter than the gap, so an hour later when we put the replacement in. The rail will fit just right, a little snug, or a tad to short.
By all means your question is not a dumb one. Many people don't realize how much the rails contract and expand.
Posted by JDRumley (Member # 625) on :
One thing I did not see mentioned so far is that when the rail is rolled to shape, the molecules are magneticly alligned vertically to direct most of the expantion/contraction vertical. Expantion and contraction would be two to three times more without this.
It is summer here and so far a few days have hit about 47 c or 115F in Western area of Sydney and the Blue mountains. I placed no less than 10 Wolo boards out one day last week. Boy was it ever hot!