LEEDS CITY TRAMWAYS.

Conductivity test of "Thermit" welded rail joint on near rail, inward track, opposite St. Thomas Street, North Street, Leeds.

This track was put down in July, 1903, and has since been in continuous use.

I find that the welding has not made any difference in the hardness of the head of the rail. It is quite evident that the material forming the joint is much softer than the rail.

(Signed) Robert Hamilton.

Manchester Corporation Tramways.

Testing of Tram Rails. Bending Tests.

Chemical Tests.

Hardness Tests.

Metal tested from head of rail.

The relative hardness was determined by measuring the lengths of indentations made by a hardened steel die with a curved edge struck to a radius of 1 in., and having a cutting edge whose angle was 50°.

From these results it would appear that there is no appreciable difference in the hardness of the surfaces.

J. M. McElroy,

General Manager. 29th November, 1906.

A few instances of general repairs actually carried out will give an idea of the applications of the "Thermit" process.

Figs. 24 and 25 show a repair to an axle gear of a 200 h.p. traction motor. This was a new gear which had never been in service, but after it had been cut, blowholes were found in the casting which practically severed the ends of three teeth from the rim. These were not apparent in the blank, hence all the workshop expenses had been incurred. The defective halves of the three teeth were chipped out, and a solid block of "Thermit" steel cast in, as shown in Fig. 24. The cutter was then run through, leaving a perfect gear, as seen in Fig. 25. This gear is now in constant use on one of the London electric railways.

Fig. 24. - Repair before Machining.

Fig. 25. - Finished Repair.

Figs. 26 and 27 show the application of the "Thermit" process to large marine repairs.

The 8.8. Rockton, tonnage 1,971 tons, then owned by the Australasian Steam Navigation Company, of Sydney, entered Mort's Dock, Sydney, on "Wednesday, 5th January, 1905. On examination it was found that the keel of the cast-steel stern frame had three distinct fractures, each about 6 ins. apart, the first fracture being about 12 ins. from the stern post. These fractures were opened 1 in. wide by drill and chisel until solid metal was met with for allowing the "Thermit" steel to flow into.

The mould box, consisting of three parts, was manufactured of 1/8 in. plate, stiffened by angle irons, at Mort's Dock during Thursday, and the mould formed therein with clay and sand during that night and placed in the drying chamber. After the fractured part of the stern post had been heated to a dull red, the mould was carefully placed in position on Friday, well packed with moist sand, and the crucible erected above the inlet of the mould.

The crucible was then closed in the customary manner by an asbestos and iron washer with 1/2 in. magnesia sand on top of it, and charged with 1,200 lbs. of "'Thermit" mixed with 120 lbs.

Fig. 26. - Cracks in Stern Frame opened up for Welding.

of steel punchings, on top of which 1/2 oz. of ignition powder was placed. At 5.55 p.m. the match was put to the ignition powder. The reaction lasted for forty-five seconds, after which the crucible contained in the bottom part 720 lbs. liquid

"Thermit" steel of a temperature of 5,400° Fahr. and about 600 lbs. of liquid slag flowing on top of the liquid steel. After waiting for a further thirty seconds the lever underneath the crucible was pressed and the liquid steel allowed to flow into the mould.

Fig. 27. - Finished Weld.

From the time of placing the match to the ignition powder until the last drop of molten steel had left the crucible and flown into the mould 1 3/4 minutes had elapsed. The mould was opened five hours later, when it was found that the weld was a perfect one, the Thermit steel had entirely amalgamated with the metal of the stern-frame and formed one homogeneous mass therewith. The whole welding was then annealed for twelve hours, when the runner and two risers, which were formed by the shape given to the mould, were trimmed off. The toughness of the Thermit steel and the ideal amalgamation of the two metals, viz., the Thermit steel and the metal of the stern-frame, was much commented on by the leading marine engineers, marine surveyors, and managers of the various steamship companies, who witnessed the performance.

By this weld the opened up cracks were filled and welded with Thermit steel, and, at the same time, a steel collar 24 ins. long and 2 1/2 ins. thick at each side, 2 ins. thick at the top and 3/4 in. at the bottom was cast round the entire fractured part of the stern-frame, and pronounced by the N.S.W. Government and Lloyd's surveyors as a perfect repair. Anyone knowing the nature and magnitude of such repairs as the one performed on the s.s. Rockton, must reflect on the speed with which this repair has satisfactorily been accomplished by Thermit, namely, within three days from the time the steamer floated into the dock until ready for leaving again.

Blau Gas Welding.

The application of Blau gas for welding purposes is being introduced, but there are yet no data as to results obtained.