Drawing a circle in 2d based on a 3d picture where circle is on an angle

[Anonymous]

Hello,

So I'm in intro to autocad and my professor isn't willing to help us at all. He believes we should figure out how to use it because that's the way he learned autocad. I am struggling with the concept of representing a circle in 3d onto a 2d platform. Could somebody help me and tell me how to do this? I realize this question is not clear so I posted 2 pictures (1 with the figure, the next with the answer) to better identify my question.

My question is how do I determine the width and length of that oval representing the circle in the 3ds picture? Thanks for any help in advance!

Bonus question: For the hidden circle in light blue on the top angle representation, why is it an oval? Wouldn't you be looking straight down so it should be a circle?

[Kent1Cooper]

Welcome to these Forums!

If as it appears you're just drawing it in 2D, use the Ellipse command, give it two points in the side-to-side-on-the-sloped-surface direction to define the ends of the major axis [easy if you do it all with Snap on and set to 1 drawing unit], and use its Rotation option.  Give that a rotation of 30 in the top view and 60 in the end view.  The precise horizontal position of the Ellipse in the top view, and its vertical position in the end view, could be calculated with a little trigonometry, or you can get it by projection from the side view -- one way would be to draw a Circle in the side view with its center at the bottom of the slope and a radius of 28, and where that intersects the slope is the center of the circle on the sloped surface, which you can project into the other views, then draw the Ellipses centered there, or move them thus if drawn beforehand.

If you're going to need to draw/build a solid model in 3D, you'll need to get into changing the User Coordinate System so you can draw a true Circle on that sloped face -- write back if that's what you need to do.

[By the way, since this is not a version-specific issue, you would do better to post such questions in the Drafting Techniques Forum.]

[Patchy]

2d dimensions use your calculator, or draw it out and list it.

[JDMather]

I think I would change to a school where the professor actually teaches.

You don't need any calculations for this.

If I follow the problem statement correctly - this is a simple exercise in orthographic projection.  Drafting 101.

Back in a few minutes with solution derivation.

Well, give me more than a few minutes - it is supper time.

[Patchy]

[nestly2]

... and for those of us that have forgotten most of what we knew about isometric drafting... (both demos are real-time)

[JDMather]

There is sound with the tutorial below.

And be sure to check the right side view - I forgot to finish it during thee video and your view wasn't correct.

You should also let your instructor know that you, your instructor, classmates and school can get the latest Autodesk software for free http://www.autodesk.com/edcommunity

[JDMather]

How are you making out on this assignment?

You might invite your instructor to join the discussion in this thread. 

[JDMather]

Are you having trouble communicating with your professor too?