Technical Drawing Question

[lrm]

When you make a slice through a tube you are left with an ellipse, the major axis is the width of the tube, and the minor is the height which you can take directly from the front view, (the bottom part of the outer edge would be flat).

 

Actually, it is the minor axis, not the major axis, of the resulting ellipse that is the width of the tube. The minor axis of the ellipse formed by cutting a tube in a direction that is not perpendicular or parallel to the tube's axis is the same for all cuts. The major ellipse axis gets larger as the cut becomes closer to being parallel to the tube's axis.

 

The OP's question is a bit ambiguous as there is nothing explicitly stated to identify the "left" view. I guess we are suppose to assume that the "3D View" is an isometric view that shows the front, left, and top views of the object. Moreover, the country of the OP is not specified so we don't know whether to assume a first or third angle projection!

[steven-g]

Actually, it is the minor axis, not the major axis, of the resulting ellipse that is the width of the tube. The minor axis of the ellipse formed by cutting a tube in a direction that is not perpendicular or parallel to the tube's axis is the same for all cuts. The major ellipse axis gets larger as the cut becomes closer to being parallel to the tube's axis.

Actually it is the major axis, below 45° the width of the tube is wider than the projected height of the cut making it the major axis at 45° both measurements are the same, and above 45° the width of the tube becomes the minor axis (the OP's drawing has a cut angle of 38°). The width of the tube does remain constant no matter how the ellipse is formed, but the major axis of an ellipse is the longest size and depends on the angle.

[danellis]

I am interested to buy the "Advanced Level Technical Drawing by E. Jackson" book. Judging from the title, I assume this book offer and teach more on technical drawing than the books you mentioned above. But, before I spend my money on this book, does anyone here have already read this book? Is it worth? Just to make sure I don't waste my money on this book.

 

TBH, I'd take Remark's recommendation!

 

Actually it is the major axis, below 45° the width of the tube is wider than the projected height of the cut making it the major axis at 45° both measurements are the same, and above 45° the width of the tube becomes the minor axis (the OP's drawing has a cut angle of 38°). The width of the tube does remain constant no matter how the ellipse is formed, but the major axis of an ellipse is the longest size and depends on the angle.

 

Perhaps we can agree on x-axis and y-axis?!?

 

dJE

[ReMark]

I am interested to buy the "Advanced Level Technical Drawing by E. Jackson" book. Judging from the title, I assume this book offer and teach more on technical drawing than the books you mentioned above. But, before I spend my money on this book, does anyone here have already read this book? Is it worth? Just to make sure I don't waste my money on this book.

 

I am not familiar with Jackson's book.

 

Let's get back to the topic of this thread. What's up with the flat edge in the image contained within your first post?

[steven-g]

Perhaps we can agree on x-axis and y-axis?!?

 

Unfortunately not an ellipse has a major and a minor axis, and the major axis does not depend on orientation, it is the longest of the two, except when they are both the same size but then it is no longer an ellipse

[steven-g]

Anybody willing to take on the challenge of drawing the front profile for a tube cut to give this side view (ReMark excluded, I know he can do it)

TIP: it's not an ellipse

[SEANT]

Pretty cool challenge. I won't post any direct spoilers, but I will say that the unrolled surface will look like this:

[steven-g]

+1

Ha Ha, technically I don't think you could classify it as a slice but it does fit the bill of being at 45°

[lrm]

Actually it is the major axis, below 45° the width of the tube is wider than the projected height of the cut making it the major axis at 45° both measurements are the same, and above 45° the width of the tube becomes the minor axis (the OP's drawing has a cut angle of 38°). The width of the tube does remain constant no matter how the ellipse is formed, but the major axis of an ellipse is the longest size and depends on the angle.

 

steven-g, I see now that you are talking about the projection of the cut and not the shape of the cut itself. I interpreted your original statement to be in reference to the elliptical shape of a cylinder cut at an angle. The elliptical shape of the actual cut will have a minor axis equal to the diameter of the cylinder. For a cut of 38° as you reference, the true shape of the cut will be an ellipse with a minor axis equal to the diameter of the cylinder and a major axis width of 1/(cos(38°) = 1.269*diameter. For a 45° cut, the ellipse shape would still have a minor axis width equal to the diameter and a major axis width of 1.414 (1/cos(45°)) Of course, the projected shape of the ellipse could be anything from an ellipse of the true shape to an ellipse that degenerates to a straight line (an edge view of the cut). In the latter case the minor axis of the projected ellipse is zero. As noted by several posters, the projected shape of the 45° cut would be a circle for the "left" view.

[halam]

What's wrong with post #7 REmark made ?

 

 

Supposed forum would be a multi CAD / BIM technical intercontinental horror senario

doomed to disagree more..

[RobDraw]

Fortunately, for the rest of the world, not everyone thinks about the negative aspects of everything.

[halam]

Thanks for speaking for the rest of the world Rob

[RobDraw]

Somebody has to, otherwise the negative people would think they are it.

[basty]

When I was in civil, we drew pipe ends like so:

 

 

Can you please teach me how to draw the pipe ends like above?

Edited January 9, 2018 by basty

[halam]

This routine can be used

 

 

(defun c:pileend (/ )
      
     (Setq pt1 (GetPoint "\nStart: right side -- "))
     (Setq pt2 (GetPoint pt1 "\nEnd: "))
     (Setq ang (angle pt1 pt2)) ; find angle between pt1 and pt2
     (Setq ang1 (angle pt2 pt1))
     (Setq ang2 (- ang1 0.380506377))
     (Setq ang3 (- ang 0.380506377))
     (Setq ang4 (+ ang 0.380506377))
     (Setq dia (distance pt1 pt2))
     (Setq rad (/ dia 2.0))
     (Setq xoffset (/ dia 10.0))
     (Setq yoffset (/ dia 4.0))
     (Setq pt3 (polar pt2
                      ang2
                      (sqrt (+ (expt xoffset 2) (expt yoffset 2)))
               )
     )
     (Setq pt4 (polar pt2 ang1 rad))
     (Setq pt5 (polar pt1
                      ang3
                      (sqrt (+ (expt xoffset 2) (expt yoffset 2)))
               )
     )
     (Setq pt6 (polar pt1
                      ang4
                      (sqrt (+ (expt xoffset 2) (expt yoffset 2)))
               )
     )
     (SetVar "osmode" 0)
     (Command "_.spline" pt2 pt3 pt4 pt5 pt1 pt6 pt4 "" "" "")

 (SetVar "osmode" os)
 (Command "undo" "e") ; ending undo
 (SetVar "cmdecho" 1)
 (Princ)
)

[ReMark]

Can you please teach me how to draw the pipe ends like above?

 

That could easily be done using the Ellipse, Trim and Hatch commands. Or you could get lazy and use a lisp routine.

[CyberAngel]

That could easily be done using the Ellipse, Trim and Hatch commands. Or you could get lazy and use a lisp routine.

 

I do it with a couple of arcs. Pretty lazy.

[ReMark]

Or you could use a "pipe end" block and change the scale accordingly.

[basty]

How do you draw an isometric ellipse that inscribed a rectangle like this?

 

[BIGAL]

Maybe one way ellipse Centre M2P pick the end points for the centre of ellipse then use Perp to pick the edge.