The Accumulatorenfabrik AG, also known as AFA or VARTA, produced a battery operated arc welding device for making continuous rails for electric street railways. When electric trams replaced the horse drawn trams, it became necessary to have a good electrical connection between the rail ends, as these were part of the electric circuit from the power plant to the electric rail car.
The process was apparently similar to TIG welding, but using a carbon electrode instead of a tungsten electrode. A 60 Volt battery was charged by a generator, which was driven by an electric motor temporarily connected to the overhead power supply with a rod. The plus pole of the battery was connected to the electrode and the minus pole to the rails to be welded.
A mould, similar to the molds used for cast welding was put around the joint area. The carbon electrode was used to melt the faces of the rail ends and some filler metal. The filler metall dropped into the gap between the rail ends and connected them, when it solidified. Distortion was a major drawback due to the large amount of heat necessary to fill the gap. An American publication of 1906 describes the process, wich was successfully used on several German tramways:
A New System of Electrically Welding Rail-Joints
Street Railway Journal, Vol. 27, No 11, 17 March 1906, p. 419-421.
Since the introduction about twelve years ago of continuous rails with welded joints for street railway track, three kinds of welded joints have come into more or less general use in this country and abroad, viz., the Falk, or cast-welded joint; the Lorain, or the joint which is electrically welded by means of current from a transformer, and the Goldschmidt or thermit-welded joint.
Applying the flaming arc to the joint
A view of the joint after welding
A fourth method is now being employed in Germany, and has been adopted on several railways. It is being exploited by the Accumulatorenfabrik Aktiengesellschaft, of Hagen and Berlin, and it is a modification of the electrically-welded joints. It does not depend, however, upon the production of a welding heat by the resistance and transformer method, as in the system. Instead, a high temperature is secured by the use of a large electric arc, which melts a quantity of steel at the point of application, viz., at the joint. The negative pole of this arc is formed by the rails themselves, and the positive pole is a carbon supplied with direct current from a special generator and other apparatus provided for the purpose. The carbon or positive pole is attached to a holder so that it can be moved back and forth by hand over the pieces of steel, which are to be reduced to a liquefied condition at the joint to form the welding portion.
During this process the joint itself is held in a form or mold, so that as the metal melts it flows underneath and around the base and under the head of the rail. A small quantity of steel is first melted, and additional steel is fed into the arc until enough has been melted to form the weld. The steel employed is of the same composition as that used in the rail itself, and is obtained from old rails. The system has been employed to a considerable extent for joint welding by a number of the electric railway companies in Germany during the last few years, and has also been applied to welding steam engine cylinders, power shears, broken gears, and for other industrial purposes.
For rail welding, the two vehicles illustrated below are employed. The left hand vehicle contains a motor generator whose motor is connected with the railway circuit, and whose generator supplies direct current at 60 volts, the potential required for the arc. Owing to the great variations in the current which occur during the process, it has been found best to place a storage battery in parallel with the generator or low-voltage (not ‘low-tension’ as wrongly translated in the original journal) side of the motor-generator set. This battery is carried in the second vehicle, or the one at the right hand in the illustration, and is connected with the motor generator by cables. Both vehicles are mounted on wheels so that they can stand in the roadway and not interfere with traffic on the tracks, and the flexible connection with the trolley wire for operating the generator can also be removed to allow a car to pass.
The rail-welding outfit, consisting of motor-generator and battery wagons
About 30 kW-hours are required to weld one joint on track weighing 50 kg per running meter (100 lbs. per yard). The first practical application of this method was made by the Hagener Strassenbahn, where about 500 joints were welded during 1903, and during the first three months of 1904. This work was done on old track weighing only 32 kg per running meter (64 lbs. per yard), and which was laid in a moist soil. A number of defects developed in this pioneer installation, as was also the case with certain work which was done a little later in Aachen. The early difficulties, however, were soon overcome, and in the fall of 1904 about 500 additional joints were made in Hagen with much better results than the first time, as only 2 per cent of the joints were broken and a smooth-riding rail was obtained.
In September, 1904, the Grosse Berliner Strassenbahn welded 100 joints on its heavy traffic lines, Strassburg installed 100 in November, 1904, Gladbach 250 in the summer of 1905, and Dusseldorf about 250 in December, 1905. It is reported that on none of these lines have any breakages of these welds developed. The longest continuous sections of rails welded did not exceed 500 m. (1640 ft.), but the Accumulatoren Gesellschaft recommends a maximum of 50 m. (164 ft.).
An interesting application of this welding method was made by the Berliner Elektrische Strassenbahn, which uses mitred joints. At ten joints, which had become worn, a piece of rail was cut out
and a new piece welded. The resulting elevation of the joint was so great that it became necessary to cut out pieces one meter long before perfectly successful welds could be made.