Here, in words and pictures, we attempt to describe the method. Just as blacksmiths of old would use a lot of heat and a bl***y big hammer to forge two pieces of metal into one so the modern day rail welders employ the same principle, but with much more finess.

This is the team at work with Tim as observer. Click to enlarge

The 2 rail ends, having been dressed off with an angle grinder are brought together with the equipment shown in this picture. The equipment is clamped firmly to the rail and hydraulic rams apply pressure to the contact faces, lightly at first.

Around the contact point a ring of oxy-acetalene burners apply heat to the rail ends.

As the temperature of the rail builds up the 'craftsman' (not Mike) in this picture works the burner ring back and forth axially to produce the correct temperature gradient accross the interface.

When the rail is raised to red heat uniformally the burners are withdrawn and the hydraulic rams force the ends together, fusing the steel and causing the surplace material and slag to be forced out in a bulge.

With the rams released, the bulge is sliced away with a special shaped slicing tool to leave the finished weld. The truth of the alignment is checked in vertical and horizontal alignment with a 4-contact-point checking bar and minor alignment adjustment pressure applied with the steel is still very hot.

The final weld is revealed and just awaits final surface dressing when cool.

The final two pictures show the compound tool described above and the rail/road vehicle equiped with gas bottles, generator and hydraulic pumps.
Estimated time 15-20 minutes to complete. Impressed? Yes.