2D Elbow Drafting Geometry

[mech5]

I'm trying to draw in AutoCAD a LR 45 elbow in plan view that is rolled to one side at 45 degrees. I need to find out if there are any resources that would explain the geometry or construction sequence associated with drafting such a thing.

 

[BigInch]

You can use some 3D trig, but matrix calculations using vector notation is much easier to program in a spreadsheet.
Read up a bit on vector algebra

here and others,

http://www.allegro.cc/forums/thread/591460

once you describe the angle (45º or any other turn angle) between the incoming pipe and outgoing pipe into and from the elbow's intersection and get an end coordinate, rotation of the plane of the elbow about the incoming pipe axial centerline produces the final coordinates of the end point.




**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic
"Note: Make that 99.99% for pipeline companies" -

http://virtualpipeline.spaces.live.com/

 

[Gator]

Just fake it, it's only going to be 2D, right?

Back many years ago when helping out with the development of an in-house 2D CAD piping program, we worked-out a way to do this by using Autolisp but I forget how we did it. These days I have a goldfish's* short-term memory due to the onslaught of new software, methods, trends and currently-popular ways to replace paper and pencil.

Try creating a torus ("doughnut") in 3D Autocad and chop into sectors.

Paul

*Oooh, look, cool! A treasure chest!
<swim around>
Oooh, look, cool! A treasure chest!
<swim around>
Oooh, look, cool! A treasure chest!
[...]

 

[unclesyd]

How about some old descriptive geometry?

 

[BigInch]

Gator, a 45º Ell rolled 45º in your 2D world turns into a point.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic
"Note: Make that 99.99% for pipeline companies" -

http://virtualpipeline.spaces.live.com/

 

[Gator]

Thanks, BigInch. I wasn't sure if I was explaining thing effectively but at least *someone* recognized that I was trying to make a point.

Cheers,

Paul

 

[BigInch]

Good one.
.. Mission(s) accomplished.

**********************
"Pumping systems account for nearly 20% of the world’s energy used by electric motors and 25% to 50% of the total electrical energy usage in certain industrial facilities." - DOE statistic
"Note: Make that 99.99% for pipeline companies" -

http://virtualpipeline.spaces.live.com/