The newest form of shop roof. Appearance and symmetry sacrificed to utility. Perfect illumination. Broad buildings may be properly lighted. Preferable for large areas. Economy of heating buildings with this form of roof. Roof angles. Roof construction. Steel and wood. Example of this form of building. Side walls. A high central space. Materials used in the construction. General design. Traveling cranes. Auxiliary cranes. Distribution of power for traveling cranes. The electric system. Roof trusses of steel. Roof trusses of wood. Ventilating windows. Ribbed glass. Roof planking on steel trusses. Roof planking on wood trusses. Gutters and valleys. Conductor pipes. Economical construction.

One of the most important advances in the design of machine shops and manufacturing buildings of the past few years is what is generally known as the "saw-tooth" construction of roofs.

Appearance, uniformity, and symmetry, are sacrificed to the idea of practical usefulness; the principal object being to secure as perfect and equal illumination as possible over the entire floor, whether the buildings are large or small.

Heretofore this has been one of the difficulties not entirely overcome, and in consequence of this drawback it has not been possible to construct buildings beyond a certain width, owing, in this respect, to the dark zone along the center. With this new method of lighting we may practically make them as wide as we please and be assured that the central portion is, for all practical purposes, as well lighted as near the side walls. This is a great advantage in buildings in which large and heavy machinery is to be constructed, as this class of work may be much more economically built in shops having but one story; and as the earth furnishes the best foundation for a floor for heavy weights, this is desirable on that account. By this observation it is not meant, of course, that floors are to be laid directly upon the ground.

Again, for this class of work a large area is needed, and to construct comparatively narrow buildings in order that we may have the center of the room well lighted, is expensive as well as inconvenient in moving large machines, or in working around them.

By this method of construction the buildings may be very broad and low and consequently easy to heat, and, as has been said, with good illumination over the entire floor.

Longitudinal Section of Machine Shop with Saw tooth Roof of Steel Construction.

Fig. 16. Longitudinal Section of Machine Shop with Saw-tooth Roof of Steel Construction.

Transverse Section of Machine Shop with Saw tooth Roof of Steel Construction.

Fig. 17. Transverse Section of Machine Shop with Saw-tooth Roof of Steel Construction.

The essential feature of the saw-tooth construction consists in forming the roof in broken sections, the roof proper having an inclination of about fifteen degrees, and the glazed portions an inclination of about sixty degrees.

Fig. 16 is a longitudinal section and Fig. 17 a transverse or cross-section of a machine shop with this type of roof, the construction being of steel. Fig. 18 and Fig. 19 represent a similar roof with wood used in its construction instead of steel. In Fig. 20 is given a perspective view of the machine shop when finished, showing the general arrangement of the high central portion and the lower portions at each side.

The side walls are built in the usual manner, with pilasters to strengthen them. They are pierced for windows on the same general plan as in the previously described buildings.

The plan of the building is the well-known one wherein a high central space is provided for an erecting floor, over which a heavy traveling crane is mounted, covering every part of this floor. The sides of this building, where it reaches above the side portions, may be planked up and covered with tarred paper and then tin, or, still better, with the specially stamped sheet steel. Corrugated steel or iron is sometimes used. Either of these plans will answer the purpose.

The side portions are built considerably lower as the same height is not here necessary or desirable. These portions are provided with smaller traveling cranes, running upon I-beams or girders which project into the central space, as shown in Fig. 17, so that these cranes are capable of depositing their loads within the reach of, and under, the main crane.

If much heavy work is to be done, each of the bays, on both sides of the central portion, is supplied with one of these cranes, as shown in Fig. 16 and Fig. 17. By this means any load may be quickly and conveniently transferred from any one point, within any one of the bays to any point within any other bay, or to any point in the central erecting space, by the combined use of the main and secondary cranes.

In many cases it will be necessary to have these secondary cranes on one side only of the central space, the other side portion being reserved for machines and work of a lighter description. So, also, it may not be necessary to equip all the bays on one side, even, with secondary cranes, while it may be necessary, and very convenient, to so equip several bays in this way. The nature of the work may be such that it will be convenient to equip several bays on each side and at one end with secondary cranes so as to arrange all the heavy work across the end of the shop instead of along the side.

As a matter of course, if traveling cranes are to be used over the bays we must provide such a system of driving power as not to interfere with them. Shafting may be used near the side walls for driving machines under it or near to it, but the main dependence will have to be the electric system, which, with separate motors for each machine, or one motor for a group of machines located closely together, seems to be the favorite method of driving.