In indicating the bevel, two methods are used. One is to state the actual rectangular dimensions, and the other is to reduce them so that the larger is 12 inches and the other a proportional part. For example, in Fig. 55 are given four working points and the lines connecting them. The plates are shown in outline. The bevel may be represented by the full dimensions or by taking the longest side as 12 .inches and the other as 9.41 inches, or O inches, since it is unnecessary to get the bevel closer than the nearest six teenth. The value 9.41 is computed as follows: Y 12" " , Y = 9.41" The method of indicat ing the bevel in feet and inches is much used, but indicating it in inches is preferable, since it is suit able to bench work. With the foot-and-inch method the floor of the templet shop has to be used in order to lay it out. The smaller values are advised for all work which can be worked on a bench.
The number of rivets required in the connection plate in any direction must be sufficient to withstand the component of the main member attached to the plate. This can be easily determined by projecting the number of rivets in the diagonal against the line where the required number is to be placed. For example, let it be required to determine the number of rivets in the top of the plate in Fig. 56a, there being as shown 4 rivets in one diagonal and 3 in the other. Draw a diagram, as Fig. 56b, making o-1 and o-2 the same in slant as the diagonals above in 56a. Now with any scale what soever lay off four divisions from o towards 1 and three divisions from o towards 2 and project a line up from the last division mark to the horizontal line. Now measure o-a and o-b to the same scale which was used to lay off the divisions on the diagonal lines. There results 3.1 and 2.3 which means that 3.1 rivets are required for Si and 2.3 for S2, or a total of 5.4 or 6 rivets for both.
It may be that the problem is as is shows in Fig. 56e. In this case the method of procedure is similar. Here, after drawing o-1 to the same slant as the member above, seven spaces to any scale are laid off and the projection made to the top and side. The results show that 6 rivets are required at the top and 3.2, or 4, are required at the side.
Other problems may be solved in a similar manner. The rivet spacing in the sides and tops is so arranged as to be equal awl to fill out the plate, allowing the required edge distance. The plates should be kept rectangular as far as possible.
Tim many cases, as in roof truss or wind bracing work, the com puted number of rivets will he two or less. In such cases three rivets
should be put in in order to have a satisfactory joint which will not loosen under vibrations which are liable to occur.
Detailing of Combinations of Structural Shapes. The general methods to be followed are the same as those which have been given together with those which are exemplified in the discussions which follow. In general, the combinations consist of plates or other shapes held together by angles,. lacing bars, or tie plates, the size and section of the angles being determined in the design since they are part of the section of the member itself, while the lattice bars and tie or batten plates are chosen in accordance with the specifica tions employed. The specifications for lacing bars make their size a function of the distance between rivets. Table XIV gives the thickness of lacing bars for any distance between rivets.
Detailing of Beams. This is for the most part done on "Beam Sheets". These sheets are the size of the shop bills, SlX 14 inches, and have a printed heading and footing as on the shop bills. Between the heading and the footing are printed elevations and cross-sections of I-beams, as in Fig. 57, the number on a sheet varying with the number of dimension lines above and material below, i. e., from two to four. In some eases, those blank sketches are printed lengthwise of the sheet and then two only are placed upon a sheet. In case a channel is to be indicated, the draftsman blocks out one half of the section or end view, sec Fig. 5S, lower cut.
On these blank sketches the draftsman notes the rivets and rivet holes, puts on the connection and other angles, and shows all other information necessary for the complete fabrication of the beam ready for the structure of which it is a part. Figs. 5S, 59, GO, and 61 are beam sheets which have been filled in, arid illustrate very nicely the general principles.
The general rules regarding beam sketches are given in the following: In all possible cases the holes in the end connections to the webs should be according to the standards given in the handbooks. If the connection is standard for that beam, no mention need be made of the fact, and if it is in the center of the web, no dimension is required, see Fig. 58, first view, left end.
If the connection is not in the middle of the web, but it is standard, the location of its center. from the bottom should be given, see Fig. 58, first view, right end.