Series E was intended to confirm the results of Series D and possibly show even greater improvements by completely avoiding the formation of cold laps. The concept was to increase the weld gap and thus increase the heat input to produce more melt-back, thereby avoiding cold lap formation: see FIGURE 19. This figure shows the results from a computer simulation of solidification in the center plane of thermite rail welds [10]. This simulation program was partly developed in this study and in a concurrent project with the TTCI. Predicted thermal profiles at the moment at which the head freezes (right) and predicted weld profile for a 25 mm and 38 mm weld gap (left) are shown in FIGURE 19