The same principle as applied in the former cases can also be adopted as the method of construction for any kind of a three-way or other connecting-piece, built up wholly with conical pipes, or partly conical and partly cylindrical.
The elevation of an irregular breeches-piece, which is composed of two conical pipes and a cylindrical pipe, is shown in Fig. 23. The joint lines are obtained exactly the same as in the former cases. The only pattern set out is that for the conical pipe "C," as the others can be obtained in a similar manner. To complete the cone of which "C" is a part, the side lines are produced to meet in c, and the cone-base, drawn as shown, being made the same diameter as the dotted circle.
Half of the latter is used as the semicircle for obtaining the required construction lines, perpendiculars being drawn from the division-points down on to the cone-base. The pattern is struck out in the same manner as that shown for Fig. 21. The points E, E, on the pattern have been found without the use of intermediate construction lines, the curves through 1, 2, and 4, 3, being simply produced until they meet in E. No allowance has been attached to the pattern for jointing, as this can be put on according to requirements.
What has been said about allowing for thickness of metal in connection with Fig. 19 will apply equally well in the above class of work. For heavy plate work great care must be taken in this direction if work accurate to dimensions or neat joints is the desideratum.