My first job in construction was QC on the Frankford El relocation to between the NB and SB lanes of I-95, in the mid 70s. This was before the common use of ΒΌ mile long rail. We used 33' long rail and thermite welded every joint. A small company out of NYC was contracted. Supervision knew their stuff, but they had to train local labor. A third-party contractor was used to Ultrasound every weld, for inclusions and porosity. The most difficult part was the rail set up. The rail ends had to be perfectly aligned in 3 dimensions while working on ballast. Ties were not yet installed near the weld location. A lot of hand jacks were used, along with muscle and long Johnson rods. The molds and exact procedures were a little different. After alignment, the weld area was thoroughly cleaned and the two piece mold was enveloped around the joint. Sand was packed underneath to support the mold. A specified number of metal discs were placed in the bottom of the mold, but above the rail. These were designed to melt at a specific temperature and let the liquid metal pour into the joint. Then the metal powder was measured and poured into the mold. Some magnesium powder was placed on top. A welder's sparker was used on the magnesium, which started the whole process, as everyone stood well away. As it cooled, we liked to spit into the mold to watch the spittle bounce around into a ball as it slowly fried. Once in awhile, the discs didn't melt evenly or quickly. The weld was a mess. Then the rail ends had to be recut and we did it all over again. After thoroughly cooling all the excess material was hand ground away, in preparation for the Ultrasound test. That tech came by near the end of the day. Failure rate was about 2%. Spent a whole Philadelphia summer on this phase. Working on ballast, with zero shade, made for hellish conditions. The only treat was the breeze while riding on the rail jitney, back to the office.
