7 Multi-piece Tapering Elbows-4 or More Pieces
- Unlike 3 piece tapering elbows, the elevation view cannot be drawn immediately. We do not know how the shape of the fitting will change between the pieces, so we must use a different technique to create the elevation view
- Draw a center line arc of the elevation view of the fitting
- Using the elbow rule, draw in the miter lines
- Draw both end gores based off the centerline. Make sure the heel, throat and centerline have been squared up.
- Next, we must turn the arc of the centerline into straight segments. Using a straight edge, draw a line on each middle gore representing the seam. These lines will hit the curved centerline only with 1 point of tangency. It should create a straight centerline through each gores center
- Next, we will create a vertical representation of the fitting. Take the seam height of each gore with your dividers and stack them vertically as a centerline
- Then draw in the end gores. For a square to round elbow, a round profile and element lines must be included as well
- Connect the end gores with straight lines from top to bottom.
- Extend horizontal lines from each miter line (seam height) of the vertical representation. This gives us the width of each gore at the miter lines. This width can now be transferred to the elevation view. For a square to round, transfer all widths that the element lines created. This shows how the round portion slowly changes to square
- From the vertical representation pick up this width, from center to the outside edge, at each miter line and transfer that distance to both sides of center of the elevation view
- Connect the outside edges of the elevation view. For a square to round, connect all the element line widths as necessary
- Complete any profiles and element lines on the elevation view
- Now that the elevation view is complete, we can start the pattern. Start by laying out the 2 end gores, using parallel line
- For the middle gores, we will copy and redraw them separately from the elevation view using triangulation
- For the middle gores, take the miter line and draw it as a baseline
- Pick up the throat and heel distances and swing them from each end of the baseline
- Pick up the diagonal lines in the gore and swing them from the corresponding ends of the baseline
- Finish the gore by drawing lines between the points created
- If one miter line of this middle gore was attached to an end gore, no sector is required, but for the end which was attached to another middle gore, we need a sector. Draw the sector on this end. If you choose, sectors can be drawn at both ends of the gore and the pattern developed using standard difference in profile method. But it is important to recognize that those sectors are not required.
- On an end which was attached to the end gore, transfer the element line locations along the miter line of the individual gore. If no miter line of this gore was attached to an end gore, sectors are required for both ends
- Now we can draw all the element lines into the gore
- Using difference in profile, we will now triangulate the gore pattern
- For any miter line which was attached to the end gore, follow the same procedures as a 3 piece tapering elbow for that edge
- For any miter line which was attached to a middle gore, use standard triangulation using the sector drawn
- Continue this process until all gore patterns have been developed