A welded exhaust header for an inline 4-cylinder engine

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

// Set units
@settings(defaultLengthUnit = in, kclVersion = 1.0)

// Define parameters
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 = {
    origin = [pos001, 0.0, 0],
    xAxis = [sin(-angle001), cos(-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)
    |> startProfile(at = [0, plateHeight])
    |> line(end = [0, length001])
    |> tangentialArc(angle = -80deg, radius = bendRadius, tag = $arc01)
    |> angledLine(angle = tangentToEnd(arc01), length = length002)
    |> tangentialArc(angle = 85deg, radius = bendRadius, tag = $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)
    |> subtract2d(tool = 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(
  n = 0,
  angle001 = 0,
  length001 = 3,
  length002 = 6,
  length003 = 5,
)
primaryTube(
  n = 1,
  angle001 = 1deg,
  length001 = 3,
  length002 = 6,
  length003 = 5,
)
primaryTube(
  n = 2,
  angle001 = 24.3deg,
  length001 = 5,
  length002 = 5,
  length003 = 3,
)
primaryTube(
  n = 3,
  angle001 = 25.2deg,
  length001 = 5,
  length002 = 5,
  length003 = 3,
)

// Create the mounting flange for the header
flangeSketch = startSketchOn(XY)
  |> startProfile(at = [3 + 1.3, -1.25])
  |> xLine(length = -2.6, tag = $seg01)
  |> tangentialArc(radius = .3, angle = -40deg)
  |> tangentialArc(radius = .9, angle = 80deg)
  |> tangentialArc(radius = .3, angle = -40deg)
  |> xLine(length = -1.4, tag = $seg03)
  |> yLine(length = segLen(seg01), tag = $seg04)
  |> xLine(length = 3.1, tag = $seg05)
  |> tangentialArc(radius = .3, angle = -40deg)
  |> tangentialArc(radius = 1.5, angle = 80deg)
  |> tangentialArc(radius = .3, angle = -40deg)
  |> xLine(length = segLen(seg05), tag = $seg07)
  |> yLine(endAbsolute = profileStartY(%), tag = $seg08)
  |> xLine(length = -segLen(seg03), tag = $seg09)
  |> tangentialArc(radius = .3, angle = -40deg)
  |> tangentialArc(radius = .9, angle = 80deg)
  |> tangentialArc(endAbsolute = [profileStartX(%), profileStartY(%)])
  |> close()

  // Create openings in the flange to accommodate each tube
  |> subtract2d(tool = circle(center = [0, 0], radius = primaryTubeDiameter / 2 - wallThickness))
  |> subtract2d(tool = circle(center = [2, 0], radius = primaryTubeDiameter / 2 - wallThickness))
  |> subtract2d(tool = circle(center = [4, 0], radius = primaryTubeDiameter / 2 - wallThickness))
  |> subtract2d(tool = circle(center = [6, 0], radius = primaryTubeDiameter / 2 - wallThickness))

  // Add mounting holes to the flange
  |> subtract2d(tool = circle(
       center = [
         -primaryTubeDiameter * .6,
         -primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2,
     ))
  |> subtract2d(tool = circle(
       center = [
         primaryTubeDiameter * .6,
         primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2,
     ))
  |> subtract2d(tool = circle(
       center = [
         3 * 2 - (primaryTubeDiameter * .6),
         primaryTubeDiameter * .6
       ],
       radius = 0.25 / 2,
     ))
  |> subtract2d(tool = 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)
       ],
     )


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exhaust-manifold