3D modelling (extrude)

[1001955166]

I don't know how to get started with the main object. Extruding a 2D triangle doesn't work and I tried to fillet a pyramid but realised that I can't smoothen the top vertex. And I'm not sure what the height of the main object is to begin with. 

 

[Cad64]

This is a very odd drawing to look at. It's like an isometric and plan view drawing combined in the same drawing.

 

The height of the main triangle is 12. It's shown on the side edge.

 

I would probably start by drawing the 127 dia. centerline circle, then draw the three small dia. holes, then offset the holes to get the rounded corners of the triangle. Then you can draw the lines for the edges of the triangle using the Tangent Osnap. Then Trim everything and run the Polyedit command to join all the segments of the triangle into one continuous polyline.

 

That should get you started. Let us know if you get stuck.

[ammobake]

Yeah it's a little wacky.  But love these old hand-drawn ones from back in the day.

Like the guy's boss was like - do it all in one drawing we don't have time.

 

How I would start is draw the center circles as a reference point.  array 3 lines around the circle and offset each 5 mil to each side for the webs, then offset again 19 mil to finish the webs.

from there I would draw the larger 127 mil circle.

Draw the 12 mil circle holes (array if u want).

 

offset the drill holes 15 mil to get outside of each corner.

tangent osnap would clean up the rest.

 

 

[lrm]

"This is a very odd drawing ..."

 

It's an oblique projection.  It's a form of a parallel projection but unlike an axonometric projection (i.e., isometric, dimetric and trimetric) the projection lines are not perpendicular to the viewing plan (although parallel to each other).  We made them back in the day because you could draw a circle as a circle if the circle was in a plane parallel to the viewing plane.  Axonometric projections require drawing an ellipse to represent a circle.  If the third axis is scale by a half then it is called a cabinet projection. 

[Cad64]

19 minutes ago, lrm said:

"This is a very odd drawing ..."

 

I didn't say "this is a very odd drawing". I said it's a very odd drawing "to look at". It plays tricks on the eyes.

[lrm]

22 minutes ago, Cad64 said:

 

I didn't say "this is a very odd drawing". I said it's a very odd drawing "to look at". It plays tricks on the eyes.

 

Your statement "It's like an isometric and plan view drawing combined in the same drawing" made it sound like you were not familiar with oblique projections.  I was trying to shed some light on the type of drawing as others also found the image unusual even "wacky".

 

[Cad64]

I appreciate the explanation, but I have seen these types of drawings before and I always find them a little difficult to understand. It's like a drawing of an impossible object. You're trying to find something that makes sense, but as your eyes move across the drawing it changes and doesn't make sense anymore. I'm glad I don't have to create or deal with drawings like this in my line of work.

[1001955166]

@Cad64 @ammobake yes that definitely helped! I don't know why I find it so hard just to figure out how to start haha. Thank you.

[lrm]

Oblique and cabinet projections were a common way of making pictorial drawings for engineering graphics books more than 50 years ago.  I agree, they can be confusing.  It is a bit disheartening to see them used in 2020 for CAD course exercises.

[ammobake]

1 hour ago, lrm said:

 

Your statement "It's like an isometric and plan view drawing combined in the same drawing" made it sound like you were not familiar with oblique projections.  I was trying to shed some light on the type of drawing as others also found the image unusual even "wacky".

 

 

It's not exactly what I would call common practice nowadays.

 

Small components like this are likely better suited for inventor or solidworks than autocad, specifically.

 

I've done 1 set of projections like this before in Autocad with a custom view, display style and dimensions.  I designed a pole barn in 2008 for strykers and showed projections of each steel saddle alongside the details.

 

But only because I had already modeled the entire project in 3D and it made sense at the time. I had to create a custom display style for it to display correctly.

Also wanted it to look impressive for the client.

 

Might still have that somewhere.

 

-ChriS

[Cad64]

3 hours ago, 1001955166 said:

@Cad64 @ammobake yes that definitely helped! I don't know why I find it so hard just to figure out how to start haha. Thank you.

 

It's a learning process. You just have to keep practicing and eventually you will get to the point where you can look at a drawing and visualize in your head how to start and how to create the 3D model.

[Dadgad]

On 7/18/2020 at 8:15 AM, ammobake said:

 

It's not exactly what I would call common practice nowadays.

 

Small components like this are likely better suited for inventor or solidworks than autocad, specifically.

 

I've done 1 set of projections like this before in Autocad with a custom view, display style and dimensions.  I designed a pole barn in 2008 for strykers and showed projections of each steel saddle alongside the details.

 

But only because I had already modeled the entire project in 3D and it made sense at the time. I had to create a custom display style for it to display correctly.

Also wanted it to look impressive for the client.

 

Might still have that somewhere.

 

-ChriS

 

If I had to do this in Autocad, and already had it 3D modeled I would just use VIEWBASE, very quick and painless, although it wouldn't do the OP any good.

 

As far as modeling this in 3D hopefully this progression of images will help the OP sort of think it through, so many different ways to approach it.