Eye Bars. These are used in pin connected trusses and structures to take care of tensile strains. The heads at each end are formed by upsetting machines and the pin holes afterward bored out. See page 331 of Cambria Handbook for dimensions, etc., of standard eye-bar heads.

Steel Construction Definitions And Abbreviations C 0500204

Fig. 188.

Batten Plates. In Fig. 225 a batten plate is placed at each end of the strut, on the top and bottom of the flanges. It is used merely to tie together the two parts of the strut. Batten plates (also called tie plates) are used generally wherever lacing is used in order to tie the parts of a member together at each end of the lacing. The Pencoyd Iron Works specifications for railroad bridges gives the following in regard to tie plates:

"All segments of compression members, connected by latticing only, shall have tie plates placed as near the ends as practicable. They shall have a length of not less than the greatest depth or width of the member, and a thickness not less than one-fiftieth of the distance between the rivets connecting them to the compression members".

Chas. Evan Fowler, in his Specifications for Roofs and Iron Buildings, refers to tie plates as follows:

"Laced compression members shall be stayed at the ends by batten plates having a length equal to the depth of the members".

The rules given in various specifications are somewhat different as regards the length and thickness, being determined by each authority merely on his own judgment of what will prove satisfactory. There is no method of proportioning batten plates except in accordance with such specifications as may be furnished in relation to the particular job of work in hand.

Lacing. Single lacing is used on the girder shown in Fig. 225, but if two systems of lace bars are used crossing each other and riveted at their intersections, it is called double lacing This is only used on very heavy members. Single lacing is usually placed at an angle of about 60 degrees with the axis of the member, while double lacing is placed at about 45 degrees to the axis.

The size of lace bars to use is somewhat a matter of judgment, but certain rules have been established by common practice and experience which it is well to observe when practicable. Chas. Evan Fowler's specifications give the following:

The sizes of lacing bars shall not be less than that given in the following table. When the distance between gauge lines is

6

in.

or

less

than

8

in.............

1 1/4

in.

x

1/4

in.

8

in.

,,

,,

,,

10

in.........

1 1/2

in.

x

4

in.

10

in.

,,

,,

,,

12

in........

1 3/4

in.

x

5/16

in.

12

in.

,,

,,

,,

16

in........

2

in.

x

3/8

in.

16

in.

,,

,,

,,

20

in.......

2 1/4

in.

x

7

in.

20

in.

,,

,,

,,

24

in..........

2 1/2

in.

x

1/2

in.

24 in. or above, use angles.

They shall generally be inclined at 45 degrees to the axis of the member, but shall not be spaced so as to reduce the strength of the member as a whole. Where laced members are subjected to bending, the size of the lacing bars shall be calculated, or a solid web plate used.

Shop Drawings. In making shop drawings, the outlines of the member (in other words, the "picture" of it) should be done in fairly heavy lines, so as to show up clearly on the blue prints, and the dimension lines should be very light so that they will not be confused with the outlines of the members. All distances should be given from center to center, wherever possible. Dimensions from the edge of an angle, beam, or plate, should never be given unless there is a special reason for so doing; because all rolled shapes vary in the width of the flanges, and Z-bars also vary in height. The reason for this variation is that different sizes are rolled by the same set of rolls and the difference is made in the spacing of the rolls. See Figs. 25, 26, 27 of Part I. Also, angles of a thickness of one-half inch or more vary somewhat in the length of legs unless they are given what is called a finishing pass or rolling which is not always done.

Make all drawings on the dull side of tracing cloth with a No. H H or a No. H H H pencil. After the drawing is completed the pencil marks are easily removed with a piece of sponge rubber.

Do not draw out your work on paper first and then trace it. You will find that this is a waste of valuable, time. Learn to draw directly on the tracing cloth, as you will be expected to do when you begin work in an office. You will need the following outfit in the way of drafting instruments and equipment:

1 T-square, at least 20 in. long.

2 Triangles, 1 of 45°, the other 60°.

1 Small drawing board, about 18 by 24 in.

1/2 dozen small thumb tacks.

1 Ruling pen.

1 Circular pen or spring bow pen.

Tracing cloth.

1 Triangular boxwood Architect's scale 12 in. long.

1 Bottle of Higgins' American drawing ink.

1 1/2 dozen Gillot's pens No. 303.

1 No. H H pencil.

1 No. H H H pencil.

1 Copy of Cambria Handbook, Edition 1904.