Will it Clear?

Occasionally I’ve been tasked with seeing if a car, truck or aircraft engine cart will make it over a vertical curve without scraping on the pavement. In the past I’ve used a template over a paper set of plans. Today I had some time to see if I could automate the task to not have to create a paper template. I think I came up with a pretty good way of doing it.
The quick method I’m utilizing is drawing a polyline along the profile in a profile view. I’ve hard coded the values I need, but also added the code to prompt the user for the information.

   1:  Sub PerformProfileDemonstration()

   2:      

   3:      ' Always get the objects again since MDI is supported.

   4:      If (GetBaseCivilObjects() = False) Then

   5:          MsgBox "Error accessing top civil objects."

   6:          Exit Sub

   7:      End If

   8:      

   9:      Dim oAcadObj As AcadObject

  10:      Dim vPt As Variant

  11:      

  12:      ThisDrawing.Utility.GetEntity oAcadObj, vPt, "Pick Profile: "

  13:      

  14:      Dim dAxelHt As Double

  15:      dAxelHt = 1.5 ' ThisDrawing.Utility.GetReal("Enter Axel Height: ")

  16:      

  17:      Dim dLength As Double

  18:      dLength = 35 ' ThisDrawing.Utility.GetReal("Enter Length between Axels: ")

  19:      

  20:      If (TypeOf oAcadObj Is AeccProfile) Then

  21:          

  22:          Dim oProfile As AeccProfile

  23:          Set oProfile = oAcadObj

  24:          

  25:          ThisDrawing.Utility.GetEntity oAcadObj, vPt, "Pick Profile View: "

  26:          Dim oProfileView As AeccProfileView

  27:          If (TypeOf oAcadObj Is AeccProfileView) Then

  28:              Set oProfileView = oAcadObj

  29:          Else

  30:              Exit Sub

  31:          End If

  32:          

  33:          Dim dStartSta As Double

  34:          Dim dStaInt As Double

  35:          Dim dEndSta As Double

  36:          

  37:          dStartSta = 250 ' ThisDrawing.Utility.GetReal("Enter starting Station: ")

  38:          dEndSta = 400 'ThisDrawing.Utility.GetReal("Enter Ending Station: ")

  39:          dStaInt = 2 ' ThisDrawing.Utility.GetReal("Enter Station interval: ")

  40:          

  41:          Dim oPoly As AcadLWPolyline

  42:          Dim dPoints(0 To 7) As Double

  43:          Dim dStartElev As Double

  44:          Dim dEndElev As Double

  45:          Do Until dStartSta > dEndSta

  46:              

  47:              dStartElev = oProfile.ElevationAt(dStartSta)

  48:              dEndElev = oProfile.ElevationAt(dStartSta + dLength)

  49:              

  50:              ' Get the points on the profile view, it will account for vertical exageration.

  51:              oProfileView.FindXYAtStationAndElevation dStartSta, dStartElev, dPoints(0), dPoints(1)

  52:              oProfileView.FindXYAtStationAndElevation dStartSta, dStartElev + dAxelHt, dPoints(2), dPoints(3)

  53:              oProfileView.FindXYAtStationAndElevation dStartSta + dLength, dEndElev + dAxelHt, dPoints(4), dPoints(5)

  54:              oProfileView.FindXYAtStationAndElevation dStartSta + dLength, dEndElev, dPoints(6), dPoints(7)

  55:              

  56:              ThisDrawing.ModelSpace.AddLightWeightPolyline dPoints

  57:                  

  58:              dStartSta = dStartSta + dStaInt

  59:          Loop

  60:          

  61:      End If

  62:   

  63:  End Sub

The output looks something like this:

As you can see my vertical curve is too steep for the vehicle. You’ll also notice that I haven’t written the code for the tires to be perpendicular to the profile. In order to get realistic values I probably should revise the code to account for this. Since I don’t have that much time available to day I might leave that for another post or maybe you can come up with a way to do it. The hard part isn’t getting the first tire to be perpendicular, but finding out where the other other tire should sit and be perpendicular to the surface. Fortunately the difference isn’t that much so this method should give a close enough answer. In the picture above the difference was 0.097’.