Triangulation

# 25 On-Centre Round to Taper

1. Draw a full plan view complete with all element lines and labeling. Label one half of the plan view, travel from large end to small end, zig-zagging back and forth with the numbering 1-14. Notice the lines of symmetry in the plan view. Every round to round will be on centre one way, but it is always worth drawing the whole thing.
2. Create a TLD and label all the element lines. Remember, any element line which travels from one end of the fitting to the other, will need to be put into a true length diagram.
3. Draw a vertical line equal to the true length of line 1-2. Square to rounds always start with a horizontal line and round tapers always start with a vertical line. We are now ready to triangulate.
4. From the TLD, pick up the true length of line 2-3 and swing it from point 2, back towards point 1. Remember to work both sides at the same time.
5. Next, pick up step-off 1-3 and swing it from point 1, to complete point 3. When we look at our plan view, we have labeled it in a way that odd numbers are at one end and even on the other. So, when we go from one end to the other (odd to even), we need to find the true length, but when we go from even to even or odd to odd we don’t have any elevation change involved. We are just going horizontally along the end, which means it is a true length in the plan view.
6. Pick up line 3-4 from the TLD and swing it from point 3 back towards point 2.
7. Pick up the step-off and swing it from point 2, to complete point 4.
8. Follow this same procedures, swing a true length of an element line and a step-off to create the next point until you reach point 14.
9. Draw in the all the element lines and outside edges, use a flexible curve for the round ends. Because this is a fitting that could be done in radial line, although maybe not practical, the pattern will follow the same shape, having a common radius point and parallel arcs.

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