exhaust-manifold

// Exhaust Manifold
// A welded exhaust header for an inline 4-cylinder engine

// Set Units
@settings(defaultLengthUnit = in)

// Define Constants
primaryTubeDiameter = 1.625
wallThickness = 0.080
plateHeight = 0.125
bendRadius = 3

// Create a function to draw each primary tube with specified lengths and angles
fn primaryTube(n, angle001, length001, length002, length003) {
  // Create an index for the function
  pos001 = n * 2

  // Define a plane for each sweep path defined by an angle
  sweepPlane = {
    plane = {
      origin = [pos001, 0.0, 0],
      xAxis = [
        sin(toRadians(-angle001)),
        cos(toRadians(-angle001)),
        0.0
      ],
      yAxis = [0.0, 0.0, 1.0],
      zAxis = [1.0, 0.0, 0.0]
    }
  }

  // Draw a path for each sweep
  sweepPath = startSketchOn(sweepPlane)
    |> startProfileAt([0, plateHeight], %)
    |> line(end = [0, length001])
    |> tangentialArc({ offset = -80, radius = bendRadius }, %, $arc01)
    |> angledLine({
         angle = tangentToEnd(arc01),
         length = length002
       }, %)
    |> tangentialArc({ offset = 85, radius = bendRadius }, %, $arc02)
    |> angledLine({
         angle = tangentToEnd(arc02),
         length = length003
       }, %)

  // Create the cross section of each tube and sweep them
  sweepProfile = startSketchOn('XY')
    |> circle({
         center = [pos001, 0],
         radius = primaryTubeDiameter / 2
       }, %)
    |> hole(circle({
         center = [pos001, 0],
         radius = primaryTubeDiameter / 2 - wallThickness
       }, %), %)
    |> sweep(path = sweepPath)

  return {  }
}

// Draw a primary tube for each cylinder with specified lengths and angles
primaryTube(0, 0, 3, 6, 5)
primaryTube(1, 1, 3, 6, 5)
primaryTube(2, 24.3, 5, 5, 3)
primaryTube(3, 25.2, 5, 5, 3)

// Create the mounting flange for the header
flangeSketch = startSketchOn('XY')
  |> startProfileAt([3 + 1.3, -1.25], %)
  |> xLine(-2.6, %, $seg01)
  |> tangentialArc({ radius = .3, offset = -40 }, %)
  |> tangentialArc({ radius = .9, offset = 80 }, %)
  |> tangentialArc({ radius = .3, offset = -40 }, %)
  |> xLine(-1.4, %, $seg03)
  |> yLine(segLen(seg01), %, $seg04)
  |> xLine(3.1, %, $seg05)
  |> tangentialArc({ radius = .3, offset = -40 }, %)
  |> tangentialArc({ radius = 1.5, offset = 80 }, %)
  |> tangentialArc({ radius = .3, offset = -40 }, %)
  |> xLine(segLen(seg05), %, $seg07)
  |> yLineTo(profileStartY(%), %, $seg08)
  |> xLine(-segLen(seg03), %, $seg09)
  |> tangentialArc({ radius = .3, offset = -40 }, %)
  |> tangentialArc({ radius = .9, offset = 80 }, %)
  |> tangentialArcTo([profileStartX(%), profileStartY(%)], %)
  |> close()

  // Create openings in the flange to accommodate each tube
  |> hole(circle({
       center = [0, 0],
       radius = primaryTubeDiameter / 2 - wallThickness
     }, %), %)
  |> hole(circle({
       center = [2, 0],
       radius = primaryTubeDiameter / 2 - wallThickness
     }, %), %)
  |> hole(circle({
       center = [4, 0],
       radius = primaryTubeDiameter / 2 - wallThickness
     }, %), %)
  |> hole(circle({
       center = [6, 0],
       radius = primaryTubeDiameter / 2 - wallThickness
     }, %), %)

  // Add mounting holes to the flange
  |> hole(circle({
       center = [
         -primaryTubeDiameter * .6,
         -primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2
     }, %), %)
  |> hole(circle({
       center = [
         primaryTubeDiameter * .6,
         primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2
     }, %), %)
  |> hole(circle({
       center = [
         3 * 2 - (primaryTubeDiameter * .6),
         primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2
     }, %), %)
  |> hole(circle({
       center = [
         3 * 2 + primaryTubeDiameter * .6,
         -primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2
     }, %), %)

  // Extrude the flange and fillet the edges
  |> extrude(length = plateHeight)
  |> fillet(
       radius = 1.5,
       tags = [
         getNextAdjacentEdge(seg04),
         getNextAdjacentEdge(seg07)
       ]
     )
  |> fillet(
       radius = .25,
       tags = [
         getNextAdjacentEdge(seg03),
         getNextAdjacentEdge(seg08)
       ]
     )