Advanced geometric pattern development · Lesson 3 of 4

Advanced geometric pattern development: methods and worked application

The parallel line, radial line and triangulation procedures step by step, each worked through on a real part with every number shown, elbow cut angles, and how one manufacturer laps a pipe flashing into a shingle roof.

You will be able to: Develop a sloped-cut pipe sleeve by parallel line, a cone frustum by radial line and a square-to-round by triangulation, recording every input, unit and check point.

12 min · 11 slides · 8 questions

All lessons in this module

Slide 1 of 11

Parallel line, step by step

The Navy Steelworker manual's order for a cut cylinder:

Draw the plan and elevation views.
Divide half the circle into equal parts and draw the elements.
Divide the stretch-out line into twice as many equal parts as the half circle.
Draw perpendiculars at each division and project each element length across.
Join the points with a smooth curve, then add the allowances.

Sources

Steelworker Volume 2, NAVEDTRA 14251 (November 1996), Chapters 2 and 3 and Appendix II - U.S. Navy, Naval Education and Training Professional Development and Technology Center

Glossary

Frustum: The part of a cone left when its top is cut off; its pattern is the whole cone's sector minus the sector of the removed top.
Template angle: In the US Navy Steelworker manual, the cut angle on each end of a two-piece elbow: one half of the angle of turn, so 45 deg for a 90 deg turn.
True-length diagram: A separate construction beside the elevation holding many right triangles, each giving the true length of one line from its plan length and height.
Transition piece: A fitting that joins two different shapes, such as a square duct to a round one; usually developed by triangulation.
Sector angle: The angle of the flat sector a right cone unrolls into: the base radius divided by the slant length, times 360 deg.