why is a small gap left between rail road tracks instead of welding them together?

Answer 1

well i would imagine it would be to allow the rails to expand and contract in the heat and the cold with out breaking the line

Answer 2

Simply to allow for expansion - all metal expands when it gets hot, i.e. on warm day. Without a gap there is a risk that rails would distort and cause a derailment. This was easy to arrange when rails were laid in traditional 60 foot lengths, but nowadays rails tend to be welded together continuously. These rails are laid with much firmer foundations to contain the expansion and prevent distortion, but even so every now and again you will find a join where two rails are not welded together but are joined with a tapered overlap to allow for expansion.

Answer 3

Metals expand when Hot and Contract when cold.The friction between the railroad car's wheel and the rail is high during running,braking,acceleration.The rails heat up and expand to avoid deformity of rails and the rails from breaking the clamp on,a maximum achieve able tolerance is built in for expansion of rails at the joints..Hence the gap between the rails joints.Without this we would derailments every time and everywhere.

Answer 4

Actually, most main line trackage in the US is CWR (continuous welded rail), aka "ribbon" rail.

Rails were first manufactured in 39' sections and later in 78' lengths. These had to be joined together with "angle bars" with bolts on each end. The problem, from a maintenance point of view, is that where these joints were, they were subjected to constant pounding under the heavy cars and engines. This meant that they were always needing to be ground and smoothed to help prolong their life.

These 39 and 78 foot sections have another characteristic that makes for problems from the operating viewpoint. The rail joints are staggered. When a piece of equipment rolls over the joint, it takes a little dip to that side. At the next joint, it takes a little dip on that side. The degrees of tilt increase with each joint, causing the equipment to rock from side to side violently, and wind up tipping over on its side. This phenomenon is called "harmonic roll", and is at its worst at fifteen miles per hour.

Todays CWR starts out as a 1320' length of rail, transported on special trains designed to move and distribute the rail at its destination. Then, after being joined the welders come along, remove the angle bars, and weld up the joint. In some instances a length of ribbon rail can be miles long.

What about expansion? The person above who mentioned the temperature of the rail when laid is right on the money. Sometimes you may see a line of fire along a railroad track. This is called "burning a rope", and that is exactly what it is. It is a length of rope, soaked in kerosene, laid along basr of the rail and burned to raise the temperature of the rail to the target temperature. But what about expansion?

CWR is designed to do some expansion locally, in a perpendicular plane. If standing between the tracks, either right or left. The biggest problem, however, is the longitudinal or horizontal axis expansion. This has been remedied with the addition of "creepers" to the tie/rail structure. Shaped not unlike a candy cane, these are hammered on to the base of the rail ahead and behind of the cross tie, firmly locking the rail into place. In other instances, the rail is bolted to concrete or steel cross ties.

But, there are still temperature related problems. In extremely hot weather, the rail track can be kicked out of the ballast and out of alignment in what is called a "sun kink". A bigger problem in hot weather is that, from time to time, the outside rail of a curve (referred to as the "high" side) will buckle upwards, pulling spikes and tie plates up with it. Even worse, after cooling the rail can lay right back into place, only just sitting on top of the ties unsecured. There was a derailment of an Amtrak train near Corning, Ca., some years back where this is exactly what happened. When these incidents take place, the rail is unbroken, therefore not turning any signals red, and the train will encounter the problem at whatever the maximum authorized speed is for that train. In summer, maintenance of way crews are out patrolling in hi-rail cars inspecting the tracks for these defects.

The flip side of course is extreme cold. In this stuation, as the rail contracts, it will literally pull itself apart. This is a relatively quick fix, by burning a rope and applying angle bars temporarily, until the welders go out and weld the joint. In this instance, the signal governing the length of track where the problem exists will turn red, and the train will reduce to "restricted speed".

In addition, during periods of extremely warm weather, trains are regularly issued a track bulletin restricting their speed, usually
during daylight hours.

And they said it couldn't be done...............................

Answer 5

In order to determine a rail's neutral temperature, the length of an unconstrained piece of steel (or "gage") is compared with a similar length of railroad track rail which is constrained and thereby deflected at most temperatures because of the track structure's tie-in to the earth's surface. The gage represents the length that the counterpart piece of rail would be if it were not constrained by the track's connection to the earth's surface. The difference in length is an analog of an associated rail characteristic, such as the number of degrees that the rail's instantaneous temperature (e.g., in degrees F) is above or below the rail's neutral temperature. Length comparisons are made with precision measuring devices configured to directly read out in conventional units the rail characteristic being considered, such as pounds of force or rail neutral temperature in degrees F.

Answer 6

The distance between rails MUST remain exact. If the rails were all welded together, on a hot day they would expand and warp, causing the train to derail, it seems to me.....

The gaps allow the rails to expand and remain straight.

Answer 7

The point is, they do weld them nowadays. the gaps were left to allow for expansion and contraction of the steel with temperature. Modern steels can have their coefficients of linear expansion, ( the amount they expand when heated), controlled by alloying different metals so gaps are not left anymore. That is way there is no dih-dah-dih-dah when trains are travelling anymore.The rails are joined together with fishplates when they are seperate pieces, with slotted holes to allow for the movement.

Answer 8

I hope I can assist you !
Railroad trains are very heavy, and carry great weight's. The opening's in the tracks allow for expansion and contraction. If you noticed the tracks are held together with (Iron Plates, with bolts and nuts. in such a manner they allow the tracks to react to this enormous weight. The more impotant factor is when the tracks do wear ouot and/or damaged by what ever the reasons they are much easier to replace with good ones by the section gangs. I hope this answers our question good luck.
Now and old joke. Railroad crossing look out for cars "Can you spell that without any "Rs"

Answer 9

the rails expand its size during summer and contracts during winter, so when it is weld together it may damage the road or the rail. that's why that gap was kept there.

Answer 10

Its for expansion and contraction,as in summer they expand in the heat and the winter they contract.If you remember when we had relay hot weather two three years ago the tracks buckled from the heat where they welded long sections together.

Answer 11

i dont know i expect all the other answers to say expansion and contraction but if that is the case why is the track of the french TGVcontinuouswelded track the ride is so smooth and they have more adverse temperatures than us they are allso mutch faster note the plates whitch join britishtype track together are called fish plates