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depth, the excavation

may
be filled

up with hard gravel, stone or concrete; or a layer of concrete may be placed at the bottom, then a course or two of stone laid in cement mortar, and finally hard gravel well rammed in. The timbers should be bolted together at the corners or securely spiked, but owing to constant shocks, bolts are to be preferred. The top corners of the timbers should be bolted together horizontally. The masonry piers and timber foundations must not in any way be connected, as the constant concussions would soon disintegrate the masonry. All spaces around the masonry and timber work should be tightly rammed with hard gravel. The size of the timbers may be from 6 x 6 inches and larger, according to the size of the structure; but they are usually 10 x 10 inches or 12 x 12 inches. Timbers used in places where decay is feared should be coated with hot gas tar as a preservative.

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On one occasion, in soft and very yielding ground, a machine of forty tons weight was supported by a foundation built by excavating nearly 30 feet deep, piles being driven at 2 feet centers over an area about three times the width and length of the base. Upon these was built a timber structure in the manner described, up to within six feet of the surface of the ground, and gradually drawn in to four feet larger all round than the base of the machine, which was quite high in proportion to its width of base. On this timber work stone laid in cement mortar was built up to the level of the ground and the machine erected upon it. The foundation proved successful.

CHAPTER XI

THE CONSTRUCTION OF FLOORS

Earth and concrete floors. Vertical section. Stone and concrete floors. Vertical section.

Paving. Simple steel supporting beams. All wood construction. How the grain of the wood should run, in planks. The wrong way to cut up the log. The right method. Quartering the log. The machine shop floor. Construction of the gallery floors. Wood joist construction. Steel construction. Floor planks. The floor that failed. Ventilation of wood floors. Another failure. The kind of wood to use. The foundry floor. Foundry pits. The forge shop floor. The boiler room floor. Kind of bricks for floor paving. Metallic floors. Engine room floor. Carpenter shop floor. The cupola platform, or charging floor. Wash room and water-closet floors. The office floors. Pattern storage floor. Kind of lumber to use. A floor of wood paving.

In the construction of modern manufacturing buildings there are many methods of constructing a floor, varying all the way from the almost primitive "dirt floor” of the forge shop to the close-jointed smoothly-finished hard wood floor of the modern watch factory.

Those which principally concern us in these articles, however, are such as are necessary in the modern machine shop, forge shop, iron foundry, etc., and these we may properly divide into six classes, viz.:

First, those composed exclusively of earth, as the floor of the forge shop.

Second, those composed of earth and concrete, like the floor of an iron foundry, as shown in vertical section in Fig. 40.

FIG. 40. — Vertical Section Earth and Concrete Floor.

Third, those of stone and concrete, as the main or ground floor of a machine shop designed for constructing and erecting heavy machinery, shown

in Fig. 41.

Fourth, those composed of stone or bricks, as required for engine and boiler rooms, etc., shown in plan in Figs. 42 and 43.

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Fifth, those composed of wood, supported by iron or steel beams, as illustrated in vertical section in Fig. 44 and Fig 45.

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Sixth, those composed entirely of wood, as shown in Fig. 46.

There are also certain conditions which will, in a great measure, determine the kind of floor to be adopted, as, for instance, the situation, the kind of work to be done and the weights which the floor will have to support.

As to materials, there are those of each kind which it might be perfectly

proper to use in other portions of the work of construction, but which would be objectionable in a floor.

Stone should be of such nature and quality as to remain firm and hard, with no disposition to crumble away. Hence granite is the best, although there are other kinds which are nearly as good for certain purposes, and much cheaper. Generally we use such as can be obtained near the work so as to avoid the cost of transportation.

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For paving, a hard, smooth-surfaced stone is needed. Sandstone wears away easily, and therefore the harder varieties are preferable. Slate makes a very smooth-wearing and satisfactory floor. Granite is not usually employed for this purpose owing to the expense of obtaining it and the cost of cutting.

Paving bricks should be hard-burned and of a quality to insure toughness, so that they may not be easily broken by accident. Many brick companies, in different parts of the country, now manufacture bricks for street paving which possess as good wearing qualities as most kinds of stone.

Gravel should be free from soil, although a moderate quantity of sharp sand is not objectionable. When earth is used in making a floor a certain amount of clay should be added, to give an adhesive quality to the mass.

Sand should in all cases be clean and sharp, free from soils and alluvial earth, and not too fine.

Lumber should be so cut at the mill that the grain of the wood shall run as nearly as possible at right angles to the face of the board or plank, as shown in Fig. 47, rather than with the grain running in a direction nearly parallel with the face, as in Fig. 48.

FIG. 47. — Plank properly cut

from the Log.

Fig. 48. – Plank improperly cut

from the Log.

The reason for this is that the surface of the planks shown in Fig. 48 will

wear smoothly even under very hard usage, while in the other case it will easily splinter up and present a very unsightly appearance, and will not last more than half as long as when properly cut from the log.

Then, too, while the plank shown in Fig. 47 will warp very little, if any, that in Fig. 48 has a great tendency to warp, owing to the direction of the grain, and to the fact that the sap or outer portion of a log, being the newer growth, is less dense and consequently will contract more in the process of seasoning

Therefore the tendency is to distort the plank to the form shown by dotted lines in Fig. 48.

Logs are usually cut up at the mill on the lines shown in Fig. 49. The boards taken off at the right and left, called "sidings,” are trimmed on their edges separately and sold at a reduced rate, while the remaining center portion of the log is cut into stock boards, or planks of regular width and thickness.

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To preserve the direction of the grain with relation to the faces of the boards or planks, the form of cutting shown in Fig. 50 would be advisable, but not as economical. This latter method is on the principle of quartering, as referred to in the furniture makers' term of “quartered oak,” for instance.

This form of cutting is shown in Fig. 51. It gives comparatively narrow boards, is expensive, and generally used for expensive woods, and for expensive work, as for fine furniture.

The main or ground floor of the machine shop being intended to sustain moderately heavy weights, both of machines and materials as well as the hard usage in moving them from place to place, and the shocks of heavy work — is now usually made of concrete, and laid as shown in Fig. 41.

In some cases those portions of floor included in the side wings are constructed of wood. This form is objectionable on account of the obstruction formed by the joining of the concrete floor and the planks; for at this point the former is apt to be cracked and broken, and the latter dented, split, and defaced.

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