Can someone explain how and by what technology curves are formed on rail tracks?

Question

Rail tracks look straight. But when we see laid out tracks, there are many curves. By which machinery , these curves are formed? Are they formed on site or are formed in advance?

Answer 1

Rail is spaghetti.  It bends with hand tools, at least as much as it needs to bend for gentle railroad curves.  (Streetcar track is another thing entirely...)

To give you an idea just how flexible rail is... take a look.

http://southern.railfan.net/cwr.html

You're seeing two trains of flatcars equipped with special racks for carrying welded rails.  Here is a better view:

http://www.wsorrailroad.com/projects/pro...

That train travels over the railroad normally, and all 50 rails bend around every curve.  

So rail is pretty flexible stuff.  Even after being used in a curve for 30 years, it can be picked up, ride in a welded rail train, and reused anywhere.

On streetcar track, take a look...

http://www.railwaypreservation.com/vinta...

Two problems here - first that's a very tight curve, and second streetcar rail is stiffer than normal rail because it has a lip which wraps around the flangeway.   This rail must be bent with a hydraulic press.  They can't use extreme heat, because that weakens the rail.

Answer 2

All rails are manufactured straight. Once they are on the ground, they can be lifted on to the ties, often with a side-boom dozer. The rails conform to a curve with no real difficulty. The longer the rail, the more flexible it is. Think of it this way. You can pick up a 1x4 board of pine. Say that board is 20 feet long. The ends bow down somewhat. Imagine you could pick up a 40 foot rail. The ends would also bow down. Once the end of the rail is spiked in place, the rest of it can be manipulated. Take a close look at my avatar. There is a heat-kink in the track. (the bridge burned) But it indicates how flexible steel can be.

Answer 3

These tracks are preformed and then laid down with machinery.  Usually they are preformed at huge Steel & ironworking factories that have contracts with the railroads and the machines that prefab them are very precise in their measurements. The machines that maintain the ridges and shape are called "RailGrinders". Hope this helps.

Answer 4

The rail is flexible and can easily be bent to shape a curve.  No special machine is needed.

Answer 5

newton's law of curvature wher it tells towards the centre n away from the centre,centripetal and centrifocal forces

Answer 6

There is enough natural "flex" in rail that, for the most part, it can easily be laid down on top of the ties as is, and wrestled into position and spiked down by brute force.  The rail is spiked down to the tie at the end, just after the fishplate joint connecting it to the end of the previous rail, and for several ties after.  After it's secure to the end by spiking it to a few ties, the far end of the rail can be tugged a bit in the direction of the curve, and spiking continues.  This can be done manually, or with tracklaying equipment designed for the job.

For very tight curves, such as found in industrial spur tracks, rail is sometimes bent into shape on site by heating it first, making it more pliable, and fastening the rail to the ties as before.  When it cools, it will have the proper curvature.  This is rarely necessary, however.