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RemovingUncle21

Penn Foster civil drafting - Driveway profile help

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RemovingUncle21

Hi, I know there's a lot of info on this forum for this ridiculous project, but I'm having trouble finding any of the threads or posts that answer my questions that haven't been answered by the instructors (despite several tries).

 

I understand that the "profile" line or "cutting" line runs through the centre of the driveway, and that where ever that line crosses a contour line, a perpendicular line is drawn down onto the graph.  However, no where in any of our curriculum does it teach us what to do when that "profile" or "cutting" line has a curve in it.

I have seen the additional info given in post 35 on this thread, but with no explanation of what is going on, it's not very useful to me. https://www.cadtutor.net/forum/topic/41514-penn-foster-civil-drafting-project-plate-3-and-4/?page=2

 

The first two pictures show what i've got so far, however, the cyan plotting lines on the part of the driveway where it curves are obviously not perpendicular like they're supposed to be. Existing- contour lines on the graph are only green for clarity. 

Third picture shows actual perpendicular lines on the intersecting contour lines....but how am I supposed to translate this onto the graph? 

 

I understand what I'm supposed to be doing, but I have no clue how I'm supposed to do it. 

 

 

 

Screen Shot 2018-12-10 at 8.21.23 PM.png

Screen Shot 2018-12-10 at 8.21.36 PM.png

Screen Shot 2018-12-10 at 8.38.27 PM.png

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ReMark

As I have pointed out many a time, P-F is not in the business of teaching students civil, structural, architectural, HVAC, name-a-discipline, drafting/design.  They are teaching AutoCAD and these are just drawing exercises.  For the purpose of this project one could use the chord distance (a straight line) rather than calculate the exact distance on the curve.  However, if you are a stickler for detail you could break the curve at the intersection of each crossing cyan colored line then either click on the curve segment and check its PROPERTIES or invoke the LIST command and obtain the required length of curve data.  The difference between the actual curve data and the chord distance is going to be so small, given the scale of the profile, it will not be noticeable.

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RemovingUncle21

Thank you ReMark. Looking at it that way, it makes much more sense.

Why PF can't add a few more sentences with info like that to the project instructions is beyond me. 

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BIGAL

A little tip with 40 years civil experience when we get curves we would normally do 1/4 pts for small curves and running chainage for large radius, always do tangent points at start and end of curve. Notice in your image the end tp is not square off hence comment.

 

So for small curves we work out the length of the arc / 4 and put this in as a spacing on the curves this produces a cross section at the right point. We have a simple lisp that gives the chainage spacing for the arc so saves a couple of minutes. Like Remark you can use a circle to get intersecting points at 1/4 points its a pretty simple curve calculation to get chord knowing arc length and radius.

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