Electric Drive in Garage and Workshop.
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III. Electric Welding and Motor Transport.
There are many industries which are more or less dependent on others for their effective progress. A ease in point is that of electric welding as specialized for rapid repair work, implying the usage of movable electric-welding plant, and consequently the means whereby it may be transported from place to place. On land the most convenient method of transporting the electric-welding generating plant and its necessary gear is by means of the motor lorry • on water, around harbours and docks, the method Of transport adopted is usually the self-propelled barge. Both these methods are extremely convenient, as by their means welding plant can be taken into practically any locality, the two means of transport being exceedingly free in movement., the first-named—the motor lorry—having the additional advantage of being speedy in transit.
Electric Welding and the Motor Lorry.
As already stated, many industries—one can say most industries—are interdependent upon one another to a greater or lesser degree. This being so, it behoves the business men of the industry to possess knowledge of those other industries which are concerned with his own. For example, the manufacturer of electric motors is bound to concern himself with, and studiously apply himself to, the thousand and one• industries into which he proposes to introduce his motors as the means of power application. He must of necessity do this in order that he can both design suitable motors and enter into full discussion in regard to their merits as a driving power in comparison with whatever means they are intended to replace. In like fashion, it is to the advantage of the men in the motor-transport field to know something of those industries for which they provide transport vehicles. In the present article we are concerned with electric welding, and therefore it is proposed to deal somewhat briefly both with the methods of welding as in practice at the present time, and With the generating equipment which may conveniently be installed upon a motor lorry.
In normal use there are two method.; cif eleatric-are welding—the carbon process and the metallic- electrode process. The first-named process is largely used for general welding work and for heavy cutting. As its name implies, a carbon electrode is utilized as one terminal ot the electric circuit, the article to be welded forming the opposite terminal. The arc by which the welding is accomplished is drawn between these two electrodes.
The metallic-electrode process is often adopted for light service and general repair work, and in cases where the strength of the weld is important. This method consists of the use of a metal electrode— usually an iron rod of small diameter—instead of the carbon electrode.
Actual welding is very skilled work, and careful training of the budding craftsman is very necessary. Although linked to the old and honoured craft of blacksmithing, it is quite different in practice. By means of the modern methods of welding, it is possible to accomplish innumerable tasks which could not possibly be done by blacksmith work. Building up and repair work of all kinds can be effectively performed, and it is possible to weld electrically iron and steel of various kinds, cast-iron, copper; copper alloys, and aluminium. In trades where these metals are in use there is a wide field for the electric welder. The cost of electric-welding repair work compares very favourably with that of other methods of effecting the same class of repairs. Further, the operation can be performed on any convenient plane—either horizontal, vertical, or at any other angle, and from above or overhead.
The equipment for a complete self-contained arcwelding plant, suitable for use on a motor-transport wagon, consists briefly of :— (1) A low-voltage direct-current, electric generator with exciter ; (2) A petrol engine for driving the generator ; (3) Switchboard ; (4) Electrode holders for carbon and metallic electrodes, protective coverings for operators, electrodes, flux, and filling material. Generators constructed specially for electric welding a:re now made for circuits of from 60 to 70 volts, higher circuits than this being wasteful. Fig. 1 depicts a typical specially-designed, portable arc-welding plant, consisting of a generating set of 26 k.w. output, driven by a. petrol engine. This, as shown, is mounted on a motor-transport wagon, and in consequence is extremely pliable as regards its range of duty. This equipment permits the manipulation of multiple arcs in parallel and intermittently when using either a carbon or metallic electrode.
Generator, Exciter, and Engine.
The generator, which is of special and protected design, is of a type permitting of heavy overloads being carried for long periods without undue heating. The direct coupled exciter also provides current for lighting and portable machine-tools, such as drillingmachines and grinders. The petrol engine which drives the generator develops 55 h.p. at a speed of 1150 revolutions per minute. This engine is closely governed to deal with frequent and sudden throwing on and off of heavy loads. arc method. The set here shown is of the stationary type. A gear wheel and a broken shaft are to be seen lying beneath the generating set, awaiting repair by the same method. Electrode holders are of two distinct types : the carbon holder, consisting usually of an aluminium rod, one end of which, is provided with a suitable connection to the cable supplying the current. A tube is welded on the other end, serving as a receptacle for the jaws or clamps to hold the electrode. The carbon electrode is a hard, solid carbon rod, of special manufacture for electric welding, measuring from six to eight inches long and an inch in diameter. As the brilliance of the -electric arc would seriously affect the worker's eyes if unprotected, it is necessary to wear a hood when operating. It is also essential that gauntlets be worn as well, as there is some danger incurred from exposure of the body to the ultraviolet rays of the arc. The hoods are usually arranged with a window of specially-made glass.