so satisfactory that

the company has since had five more of the same type constructed.

Gusset stays are used mainly in boilers of the Lancashire model and

are triangularshaped plates sheared to the

proper form and having two angle irons riveted to the edges that come against the shell and the head. The angle irons are then riveted to the shell and the flat head. This form of brace is simple and solid, but its chief defect is,

that it is very rigid

and does not allow for the unequal expansion of the internal furnace flues and the shell. Fig. 106 illustrates a gusset stay and the method of applying it.

Coming now to through stay rods, it is safe to say that whenever and wherever it is possible to apply them they should be used. In all cases they should

be placed far enough apart to allow a man to pass between them for the purposes of inspection and washing out of the boiler. Through stay rods are usually spaced 14 in. apart horizontally and about the same distance vertically. The ends, as far back as the threads run, are swaged larger than the body, so that the diameter at the bottom of the thread is greater than the diameter of the body. There are severa)

methods of applying through stays. One of the most common, especially for land boilers, is to allow the ends of the rod to project through the plates to be stayed, and holding them in place by a nut and copper washer, both inside and outside the plate. Another and still better plan is to rivet 6-in. channel bars across the head, inside above the tubes, the number of bars depending upon the height of the segment to be stayed.

FIGURE 106.

The channel bars are drilled to correspond with the holes that are drilled in the

plate to receive the stay rods, which latter are then secured by inside and outside nuts and copper washers.

These channel bars act as girders and serve to greatly strengthen the head or flat plate. Fig. 107 will serve to illustrate this method.

Sometimes a combination of channel bar and diagonal crow foot braces is used, as shown by Fig. 108. A good form of diagonal crow foot stay is obtained by using dou

this secures the forked end of the stay.

Another method of securing through stays to the heads is shown by Fig. 110 and is applied where too many stay rods would be required to connect all the points to be stayed. A tee iron is first riveted to the flat plate to be stayed, and two V-shaped forgings are bolted to it as shown. The through stay is then bolted to the forgings, and thus two points in the flat head are supported by one stay. It will readily be seen that this method will reduce the number of through stay rods required.

FIGURE 109.

Calculating the Strength of Stayed Surfaces. In calculations for ascertaining the strength of stayed sur

faces, or for finding the number of stays required for any given flat surface in a boiler, the working pressure being known, it must be remembered that each stay is subjected to the pressure on an area bounded by lines drawn midway between it and its neighbors. Therefore the area in square inches, of the surface to

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FIGURE 110.

be supported by each stay, equals the square of the pitch or distance in inches between centers of the points of connection of the stays to the flat plate. Thus, suppose the stays in a certain boiler are spaced 8 in. apart, the area sustained by each stay = 8 × 8 = 64 sq. in., or assume the stay bolts in a locomotive fire box to be pitched 41⁄2 in. each way, the area supported by each stay bolt = 42 × 4% = 204 sq. in. Again taking through stay rods, suppose, for example,