This section is from the book "The New Metal Worker Pattern Book", by George Watson Kittredge. Also available from Amazon: The new metal worker pattern book.

In Fig. 714 is shown the design of a right angle elbow of which one end is rectangular, as shown by NOP Q, and the other round, as shown by A B C D. Such an elbow may be constructed in any number of pieces, the elevation for which may be drawn in the manner described in the case of an ordinary piece elbow.

In the present instance the elbow consists of seven pieces. In adjusting the transition from the rectangle to the circle, it is evident that the flat sides of each of the five intermediate pieces must become shorter in each piece as the round end of the elbow is approached; and that the quarter circles forming the corners of each of the intermediate pieces must be of shorter radius as the corners of the rectangular end are approached.

This may be accomplished upon the elevation in the following manner: Through the center of the elevation draw the lines c to m, and divide L l' into the number of parts there are pieces in the elbow subjected to the change in shape, in the present instance five. From k' set off each way four spaces, as shown by k k' and k' k". Set off from j' three spaces, as shown by j' j' and j j'. Continue this operation and connect the points L k j h g f and g" h" f k" L', thus showing in side elevation the change from the rectangle NOPQ to the circle ABCD.

To show a similar shape on the outer curve of elbow, draw any line, as K M, in Fig. 715. From E on E M set off the spaces E F, F G, etc., to L M of Fig. 714. As it is only necessary to show the half shapes, from M and L erect perpendiculars, in length equal to N n of profile, and connect same, as shown by M2 L2 Connect L2 F, and from the points in E M erect perpendiculars cutting F L2 The shapes on inner curve of elbow, as shown in Fig. 716, are obtained in the same manner as described for Fig. 715.

Fig. 714. - Elevation and Profiles of an Elbow to Connect a Round With a Rectangular Pipe.

For the hights of section on c m of the elevation, on any line, as E M, in Fig. 717, starting from E, set off the distances c f, fg', g h', etc., and from the points thus obtained erect perpendiculars, as shown. From E and F set off the distance C B of profile of circular end and draw E3 F3 From M and L set off the distance N n of profile of rectangular end and draw M3 L. Connect L3 with F3, thus completing the section.

The method for obtaining the patterns for sections E F F' E' and LMM'L' is the same as for an ordinary pieced elbow. The method for obtaining the pattern for one of the remaining sections will be shown, which will indicate the method to be followed in the other sections.

In Fig. 718, F G G' F' is a duplicate of the section having similar letters in elevation. The shape F U F' is the half of an ellipse, because F' F of Fig. 714 is an oblique section of a cylinder of which A B C D is the plan, and can be described in any convenient manner.

From G erect the perpendicular G S, equal to G G2 of Fig. 715, and from G' erect another perpendicular, equal to G G6 of Fig. 716. From points g and g' erect perpendiculars equal to G3 G of Fig! 717, and connect T T', as shown. Connect S T and T' S' by a quarter of an ellipse. Divide S T, T' S', F U and

U F' into any convenient number of equal parts, and from the points thus obtained drop perpendiculars cutting G G' and F F'. Connect these points, as shown by the solid and dotted lines in G G' F' F.

Fig. 715. - Shape of Flat Part of Outer Curve of Elbow.

Fig. 716. - Shape of Flat Part of Inner Curve of Elbow.

The next operation will consist in constructing sections upon these solid and dotted lines for the purpose of ascertaining the correct distances which they represent. These sections are shown in Figs. 719 and 720. To construct the sections represented by solid lines in Fig. 718, proceed as follows: Draw the line F G of Fig. 719, in length equal to F G of Fig. 718, and from point G erect a perpendicular, in length equal to G S of Fig. 718. Connect F S, which gives the distance between points F and S. For the second section draw v o, in length equal to v o of Fig. 718, and make the perpendiculars o 6 and v 7 of the section equal to lines having similar letters in Fig. 718. The other sections are obtained in a similar manner. To construct the sections represented by dotted lines in Fig. 718, proceed as follows: Draw the line F o of Fig. 720, in length equal to F o of Fig. 718, and from o erect the perpendicular o 6, equal to o 6 of Fig. 718, and connect F G. For the second section draw vp, in length equal to v p of Fig. 718, and from points v and p erect perpendiculars equal to v 7 and p 5 of Fig. 718. Connect points 7 5, which give the distance between corresponding points in Fig. 718.

Fig. 718. - Elevation of One of the Pieces, Showing Method of Triangulation.

Fig. 717. - Extended Section on Line c m of Fig. 714.

In Fig. 721, G G' F' F is the pattern of part of article shown by similar letters in Figs. 714 or 718. The distances represented by solid lines in pattern are obtained from the sections in Fig. 719, as indicated by corresponding figures, and the distances represented by dotted lines in pattern are obtained from the sections in Fig. 720. The stretchout of G G' of the pattern is obtained from G T T'G' of Fig. 718, as the stretchout of F U F' of the pattern is obtained from F U F' of Fig. 718.

Fig. 719. - Sections on Solid Lines of Fig. 718.

To develop the pattern from the sections above constructed, first draw G F of Fig. 721, in length equal to G F of Fig. 718 or 719, upon which duplicate the triangle G F S of Fig. 719, as shown. From S of pattern as center, with S 6 of Fig. 718 as radius, describe an arc, 6, which intersect with one struck from F of pattern as center, with radius F 6 of Fig. 720, thus establishing point 6 of pattern. Then with radius F 7 of Fig. 718, from F of pattern as center, describe an arc, which intersect with a second arc struck from point 6 of pattern as center, and 6 7 of Fig. 719 as radius, thus establishing point 7 of pattern. Continue this process until the various points indicated in pattern are located. Lines drawn through the points thus obtained, as indicated by G S T T' S' G' and F' U F, will complete one-half of the required pattern. The other half can be obtained by duplication or by a repetition of the above process.

Fig. 720. - Sections on Dotted Lines of Fig. 718.

Fig. 721. - Half Pattern of F G G' F of Fig. 714.

In obtaining the pattern for any one of the remaining pieces first draw a duplicate of its elevation as taken from Fig. 714, upon either side of winch construct the proper section, obtaining the points in the same from Figs. 715, 7l6 and 717 as was done in Fig. 718, after which the subsequent operation is analagous to that above described.

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