Nearly every boy has had among his treasured possessions a small horseshoe magnet, painted red, with bright ends, and has spent many happy hours picking up needles, steel pins or other small objects, and finally tired of it because of its small lifting capacity and dreamed of one which would lift a hammer, or possibly even the family flatiron. Little did he know at that time of the long and interesting history of magnetism, the many stories and superstitions based on its strange power; or of its intimate relation to the wonderful growth of electricity within the last hundred years. His wildest dreams of lifting power would be realized if he could see a modern electric lifting magnet which has only come into use within the last ten years and is meeting with instant approval in nearly every industry where iron and steel is handled in any quantity.

Fig. 1.

There are three primary kinds of magnets: the lodestone or natural magnets, the artificial or permanent steel magnet, and the electric magnet. At present the lodestone is little used. The permanent steel magnet is used for compass needles, as the familiar horseshoe magnet, and in certain types of electric machinery. The electric magnet forms a part of nearly every kind of electrical machinery and is by far the most useful form of the magnet. The modern high-duty lifting magnet is a form of the electric magnet.

The properties of the lodestone and the permanent magnet have been known for thousands of years, while the electric magnet is a comparatively recent discovery.

A11 magnets, whether natural, permanent or electric, possess the same magnetic properties. Every magnet has two poles commonly called a north pole and a south pole. It has also been found that when a magnet is broken in two each piece becomes a magnet in itself with its own north and south poles.

For practical purposes it has been found convenient to assume that magnetism consists of a series of "lines of force" running through the magnet from one end to the other and back again through the air. Each one of these lines is assumed to have a certain strength, and the power of any magnet is determined by the number of lines of force flowing through it. These lines are clearly shown in Fig. 1, which was made by sprinkling iron filings on a sheet of paper over a bar magnet, and tapping the paper slightly so that the filings could arrange themselves along the magnetic lines of force.

* Illustrations by courtesy of Cutler-Hammer Mfg. Co.

Since Oersted's first electric magnet in 1820, electric magnets have been made in a variety of forms and for many different purposes. The simplest form of electric magnet is shown in Fig. 2. It consists of an iron bar with an insulated electric wire wound around it carrying an electric current,

Fig. 2.

Another form of the electric magnet is shown in cross-section in Fig. 3. This consists of a short steel cylinder with a groove in its face for the electric coil. The modern lifting magnet is a highly specialized form of this type of electric magnet.

Although the use of a magnet for lifting purposes seems to be a very simple idea and easily adopted, many difficulties had to be overcome and years of experimenting done before the lifting magnet was a commercial success. Nearly all electrical machinery may easily be protected from rough usage and moisture, but the lifting magnet must be so strongly designed that it will withstand the countless blows due to heavy pieces of iron flying against it, and the banging it must get against the sides of cars, ships, etc. All light parts must be placed inside of the magnet or in such a position that they can never be knocked off or broken. To moisture in some form or other nearly all lifting-magnet troubles can be traced. Hence the importance of an absolutely moisture-proof construction. The result of moisture in the interior of a magnet is to weaken the effectiveness of the installation, leading eventually to short circuits and burn-outs. It is necessary not only to guard against moisture in the form of rain, snow or dew, but precaution must also be taken against the entrance into the magnet of moisture-laden air, since moisture so introduced will presently be condensed in the form of drops of water. A very natural question is, how much such a magnet will lift. For a given size of magnet, the lifting capacity varies greatly with the nature of the load handled. With a magnet sixty-two inches in diameter, this may vary from in the neighborhood of 1,000 pounds for light scrap, to from 4,000 to 5,000 pounds for pig iron, and as high as 60,000 pounds for a solid mass of steel or iron such as, for instance, a skull-cracker ball or a casting affording surface for good magnetic contact.

Fig. 3.

A 43-Inch Magnet Handling Pig Iron.

The lifting magnet has been adopted for the handling of materials in all branches of the steel and iron industry. It is used for handling pig iron, scrap, castings, billets, tubes, rails, plates, for loading and unloading cars and vessels, and for handling skull-cracker balls and miscellaneous magnetic material.

Probably one of the best illustrations of the saving accomplished by means of a lifting magnet is its use in unloading pig iron from steamers. By the old hand method it required twenty-eight men, two days and two nights, to unload a cargo of 4,000,000 pounds. When the lifting magnet was introduced, the total time for unloading was reduced to eleven hours, and was done by two men whose labor consisted in manipulating the controllers in the cages of the cranes. Thus two men and two magnets did the work of twenty-eight men in less than one-fourth of the time. Furthermore, the vessels were enabled to double their number of productive trips. In railroad work, lifting magnets are at the present time used principally in scrap yards and around store-room platforms, where it is necessary to handle iron and steel rapidly and economically. For this class of work magnets are generally used in connection with a locomotive crane, making a self-contained, self-propelled unit which may be operated over the shop-yard tracks as required. The use of this combination has reduced very greatly the cost of handling both new and scrap material, both by reducing the actual expense of handling and by enabling the material to be handled much more rapidly than was before possible.

Probably the best possible endorsement of the waterproof construction of the

36-inch Lifting Magnet Picking up 3,500-Pound

Winding Drum modern lifting magnet is the fact that one of them was successfully operated seventy feet below the surface of the Mississippi River. At New Orleans a large load of kegged nails was raised from a depth of seventy feet. A load of steel cotton ties was raised near Natchez and a barge of iron wire near Pittsburgh. And these are only a few instances of such work.

The magnets used in this river work were three and one-half feet in diameter. They were dropped into the stream, the current turned on, and five or six kegs of nails or bundles of wire were raised each trip. The nails weighed 200 pounds to the keg, so there were lifted each time, from 1,000 to 1,200 pounds from the bed of the river.

The variety of uses to which these magnets may be put are shown by the accompanying illustrations and there are many industries handling iron and steel where the introduction of the modern, high-duty lifting magnet will effect a great saving in time and labor.

An amusing incident occurred recently in a factory where a large lifting magnet is used in connection with a crane to carry pig iron through the shop. Just as the operator was bringing it across the shop unloaded, he saw two laborers ahead of him in altercation. One held a short pinch bar and the other a heavy shovel. As he approached, they both raised their tools like weapons. In a flash the operator switched on. the current and the two men stood as if transfixed, hanging desperately to their weapons that were held aloft as by some giant's hand. The laughter of everyone who saw the tableau ended the quarrel.

36-inch Magnet Handling Heavy Castings Note that there is no hoisting tackle to be adjusted.