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1945 Theatre Catalog, 4th Edition, Page 167 (145)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 167
Page 167

1945 Theatre Catalog, 4th Edition, Page 167

addition to weight reduction. One of these is simplification of construction. In many cases, a single casting or wrought magnesium part can replace an assembly in another metal without incurring a weight penalty. Labor operationsesuch as assembling, riveting, or welding-ware thus greatly reduced. The fioor beam in the Douglas 0-47 is an excellent illustration of this principle. Here a single extruded'magnesium I-beam is now being used, which is 35 per cent stronger, 25 per cent cheaper, and 5 per cent lighter than the riveted aluminum assembly it replaced.


Another advantage which can be obtained in designing with magnesium is rigidity or stiffness. In sheets of equal weight, for example, magnesium is twiCe as stiff as aluminum and eighteen times as stiff as steel. Therefore, it is possible by increasing sections a certain amount to secure greater rigidity in magnesium structures and still maintain a weight saving compared to aluminum and steel.

Experimental magnesium airplane wings of pure monocoque construction illustrate the utilization of both rigidity and simplified construction. These wings are no heavier than conventional aluminum wings, yet they are easier to fabricate and have better aerodynamic efficiency. The thickness of sheet used for the skin gives suiiicient rigidity to eliminate the necessity for stringers and stiffeners ordinarily riveted to the skin, and at the same time reduces the tendency to fiiiutterfi

Reducing dead weight is an important function, but the lightness of magnesium often permits its use in products where it offers little or no weight reduction yet results in other improvements. This is particularly true when magnesium replaces wood. For example, experimental magesium skis made recently are about the same weight as wood skis. Preliminary tests show that they may be faster and more maneuverable. Many attempts had been made previously to produce skis in other metals but all had been unsuccessful. Sufficient stiffness could not be obtained without incurring too great a weight penalty.


Machinability is probably the second best known property of magnesium. It is so easily machined that very high speeds and deep cuts can be used, yet there is no difficulty in obtaining a smooth surface. In iron and steel, the cost of machining is r. high percentage of the total cost of the finished part. In many cases a finished magnesium casting may cost less than a similar casting in iron, even though rough cast, the magnesium may cost more than the iron. For example, some iron castings in a paper bottle machine were replaced by magnesium castings, which were about 75 per cent lighter and actually somewhat cheaper due to savings in machining. The lightness of these castings, which were reciprocating parts of the machine, resulted in lower power requirement, and smoother and quieter operation.


The mention of reciprocating parts brings up another interesting property of magnesiumeits high damping capacity, or ability to absorb dynamic energy. This means that a magnesium part which is subject to vibration will absorb these vibrations to a very great extent. In machinery where vibration is a problem this property added to the light weight of the metal contributes to reducing noise and wear. The experimental cast magnesium automobile wheels tested in road service have shown that the metal absorbs much of the energy resulting from roughness in the road surface, which in a steel wheel are normally transmitted to the axle and springs.

Other Properties

The thermal properties of magnesium are exceptionally good. The magnesium griddle, used over two burners, has such good heat distribution food will cook at the same rate on all portions of the griddle. Any difference in temperature between the part over the burners and that between the burners is not noticeable. It heats up to cooking temperatures quickly, and the lightness of the metal permits making the griddle thick enough to avoid warping in normal service.

The non-sparking characteristic of magnesium allowed it to replace wood shell loading trays in a small arms ammunition plant. Its use in compasses and gyroscopes is possible because it is nonmagnetic.


Just as light weight is magnesiumls best-known property, so aircraft is its

best-known field of application. Aircraft was the most obvious field in which to utilize the light weight of magnesium, and this industry was the first to adopt the metal. During the war, all the structural magnesium available went intp military planes. Two to four hundred pounds of magnesium castings were used in many aircraft engines, forged hydraulic parts and control links were used throughout the plane, formed and- die cast fittings saw service, and probably 95 per cent of all military planes haVe been equipped with shock-resistant cast magnesium landing wheels. Post-war civil aviation will take advantage of what has been learned during the war about the serviceability of magnesium. Few service failures have been reported, and of these the majority have been due to inv correct design rather than metallurgical deficiency.

Not so well known is the fact that magnesium has seen considerable service in civilian products other than aircraft. Sand and die-cast magnesium housings for portable electric and pneumatic tools were being used long before the war. Lightweight handling equipment, such as conveyors, dockboards, hand trucks, lift trucks, dollies, loading platforms, can forks, and wheelbarrows have been produced which reduce fatigue of workers and labor costs. For example, two men can handle a ZOO-pound magnesium dockboard, while a whole squad of men was needed to move the 625-pound steel one it replaced.

Textile machinery and equipment manufacturers have used magnesium for many reciprocating parts such as traverse bars, knitting bars and pickers, and for bobbins, pirns, and warp beams.

IDEALIZED MODEL indicates the basic process at the Dow Chemical Company for extracting magnesium from sea' Water as used at Freeport and Velasco, Texas. The same general idea is followed out in extracting magnesium from natural brines, such as those pumped up from underground brine lakes, with some modifications

depending upon the type of material locally available.

Dolomite or other limestones, for example, may be

Used in place of oyster shells as a source of lime. Varying concentrations of magnesium chloride in different brines and other chemical compounds present may also necessitate certain modifications in the basic process.

1945 Theatre Catalog, 4th Edition, Page 167