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The 5 Pipe Intersection is the flat pattern (development) for one pipe of a junction where five pipes of the same diameter meet at a single point. All five pipe centrelines lie in one plane and radiate from a common centre point; you set the angle between each pipe and the next. Each pipe is cut back where it meets the other pipes, and the shape unrolls one chosen pipe into a flat outline. Cut the pattern from thin plate, roll it along its bend lines into a tube, and repeat for each of the five pipes to make the junction.

It appears in the shapes library under Thin Walled Developments. The shape is defined in 3D; the property page shows the 3D junction, and the part that is cut is the 2D flat pattern of the pipe selected in Dev. Pipe.

How the junction is defined

Every pipe has diameter Pipe D, and its centreline runs from the common centre point out to its free end, a distance of Pipe Length. Pipe #1 is the reference; the other pipes are turned about an axis through the centre point, square to the plane of the pipes:

•Pipe #2 is 1-2 Angle from Pipe #1.

•Pipe #3 is 2-3 Angle beyond Pipe #2, Pipe #4 is 3-4 Angle beyond Pipe #3, and Pipe #5 is 4-5 Angle beyond Pipe #4. The angles add up, all in the same direction.

•There is no angle for the gap between Pipe #5 and Pipe #1; it is whatever is left of 360°. With the defaults (120°, 40°, 40°, 40°) the pipes are at 0°, 120°, 160°, 200° and 240°, leaving 120° between Pipe #5 and Pipe #1.

Each pipe is trimmed by the walls of the other four pipes, so the end at the centre becomes the intersection (saddle) edge where it meets its neighbours. The free end of each pipe is cut square.

In the 3D view the pipe selected in Dev. Pipe is drawn in green and the other four in grey.

How the pattern is laid out

The selected pipe is divided into Dev. Segs flat strips round its circumference and unrolled into one closed outline. The pattern has one seam, the straight line where the rolled pipe closes. Dev. Angle sets where the seam lies round the pipe. At 0° the seam lies in the plane of the pipe centrelines.

The insert point (0, 0) is the intersection end of the seam. The seam runs along +X from there to the free end. The strips are laid side by side across the pattern, at right angles to the seam, so the pattern is about π × Pipe D across in total. The free end of the pipe is a straight edge; the intersection end is the shaped edge that fits against the other pipes. Because the intersection end is trimmed back, the pattern is shorter than Pipe Length along most of its width.

Bend lines

With Show Bends on, a bend line is added on every fold between two strips – Dev. Segs minus 1 lines. They are marking entities, not cuts, and alternate lines run in opposite directions so the marking tool zig-zags across the pattern. If Bend Length is more than 0, each bend line longer than 2.1 × Bend Length is shortened to two marks of that length, one at each end, instead of a full line across the plate.

Properties

The property page lists the junction properties first, then the development properties, then the Transform group. Default lengths are shown for metric and (inch) settings.

The dimensions drawn on the 3D view are Pipe Length, Pipe D and the four angles.

Notes and limits

•All five pipes have the same diameter and length, all centrelines lie in one plane, and all of them meet at one point. Pipes of different sizes, or pipes whose centrelines are offset from each other, cannot be made with this shape.

•The pattern is built on the surface of diameter Pipe D; there is no plate thickness or neutral-axis allowance. Enter the diameter you want the pattern laid out on (for example the mean diameter for a part rolled from thick plate).

•The pipes are trimmed against each other as many-sided prisms (Dev. Segs sides), not true cylinders, so a low Dev. Segs value gives a visibly faceted intersection edge.

•The property page only stops Pipe D and Pipe Length going below 0; the four angles have no limits. The shape does not check the angles against each other: an angle of 0° puts two pipes on the same centreline, and nothing checks that the four angles add up to less than 360°. Check the 3D view before cutting.

•If the shape cannot be built from the values entered, the 3D view is cleared and the property page shows Warning: Cannot build shape from these parameters. Change the values until the warning goes away.

•The shape has no aliases (no former names).

The 5 Pipe Intersection also has the Transform properties (Base X, Base Y, Rotation, Scale, Mirroring X), listed after its own properties. It is a 3D shape, so it has no Polar Array properties.