True Length

[Ryuk1990]

In my engineering class we are learning about finding the true length of a line. I don't understand it at all. We basically work with 2D views of a line in either the profile, front, or horizontal view. I don't understand how to get from one view to the next. Does anyone know of any good internet resources to help me understand this concept? I tried googling it but I couldn't really find anything too good.

[CarlAK]

Imagine a toothpick frozen in an ice cube. Look at it from the top, the front, and the left side. How do you determine the toothpick's length? Picture the the toothpick being the diagonal (hypotenuse) of a right triangle resting on the bottom of the cube. The length of the base of the triangle (B) is the same length you see in the top view. The height of the triangle (H) is the height you see in any side view. The length of the triangle's hypotenuse (the toothpick length) is the square root of A squared + B squared, which is the familiar Pythagorean formula.

[FredGarvin]

Did you try doing a search for "descriptive geometry?" I found a lot of hits.

http://en.wikipedia.org/wiki/Descriptive_geometry
http://en.wikipedia.org/wiki/File:Descriptive_geometry_-_skew_lines_appearing_perpendicular.png
http://www.amazon.com/Problems-theorems-examples-descriptive-geometry/dp/1418182486

This is an older book but you can download it in PDF form:
http://books.google.com/books?id=r6P2R3-GhzgC&pg=PA1&lpg=PA1&dq=descriptive+geometry+examples&source=bl&ots=GZ3hdBC1SM&sig=JIkbVjx9jPbqLwYU_fnk8w9gdMw&hl=en&ei=T8G4SsOTKMLOlAeNqNjMDg&sa=X&oi=book_result&ct=result&resnum=8#v=onepage&q=&f=false

[hhn2002]

In my engineering class we are learning about finding the true length of a line. I don't understand it at all. We basically work with 2D views of a line in either the profile, front, or horizontal view. I don't understand how to get from one view to the next. Does anyone know of any good internet resources to help me understand this concept? I tried googling it but I couldn't really find anything too good.

are each three of the views on different planes that are perpendicular to each other, for example: top, front, side?

if they are then find lengths of the lines in each view. say L1,L2, and L3
to find the true length the formula is: sqrt[(L1^2)+(L2^2)+(L3^2)]
this is the 3D formulation of the pythagorean theorem.
if 1 or more of the view planes are not perpendicular to the other two and the line is not parallel to at least 1 plane then you'd need to find the angle at which the planes intersect each other and through a more tedious calculation you find the true length.

what program are you using?

[FredGarvin]

If they're learning the way they should, the program is called a pencil-paper-tsquare v1.0.

[hhn2002]

If they're learning the way they should, the program is called a pencil-paper-tsquare v1.0.

lol, i actually googled that.
i only asked because i dont know how profile, horizontal, and front relate to each other.

[FredGarvin]

Did anything come up? Google is awesome.

[hhn2002]

well what do you think came up? this page is the first on the list!

[CarlAK]

Try this:
http://www2.bakersfieldcollege.edu/mrozell/documents/Engr%20B24/Ch16_1.pdf

full course at:
http://www2.bakersfieldcollege.edu/mrozell/