The complete setting out for a swan-neck bend, made up of three conical pipes, is shown in Fig. 20. The double elbow might have been constructed partly conical and partly cylindrical, as in the last case, the same method for obtaining the joint line still holding good. There is no need for very much description in connection with this example after what has been said about the square elbow. The lines that form the cone-bases are indicated in the elevation, those for the parts "A" and " C " being similar to the last case, and that for "B" drawn to the right of the joint, and the radial lines produced through to meet it. It will be noticed that this latter arrangement brings the girth line of the pattern for piece "B" across the pattern instead of at the end, as in the other two patterns. The extras for jointing are added on the same principle as explained for the elbow. In fixing the parts together, it should be noted that "A" fits into "B," and the latter into "C."

Swan Neck Or Offset 25

Fig. 20.