Simple Transition -

[SEANT]

 

One interesting thing about that file, though, is that the base

diameter is dimensioned from the outside and the top (smaller) diameter is dimensioned

to the inside.

 

[ReMark]

You can always fall back on the "tried and true" resource: books.

 

Go to your local library and find Thomas E. French's book entitled Engineering Drawing. Open this to page 441 and look at Fig. 20-9 Development of a truncated right circular cone. Read section 20-11: To develop a truncated right circular cone. This will tell you how to do it exactly.

 

If you can't find that book then look for Spencer's book entitled Basic Technical Drawing. The development of a cone is covered on pages 302-303.

 

And if either of those very fine books are too old fashioned for you then pick up a copy of Technical Graphics Communication by Bertoline & Wiebe. Development of a truncated cone is covered on pages 621-622. Bonus: page 627 discusses developments and CAD techniques.

 

Now go forth and develop.

[paulmcz]

Here is a quick lisp for those who don't want to learn about the cone development.

 

;;; draws cone development
(defun c:cnn (/ rl rs h ip ha rdl rds u ra p1 p2 p3 p4 p5 p6 osn)
 (initget 7)
 (setq	rl  (/ (getdist "\n Larger cone diameter: ") 2.0))
 (setq rs  (/ (getdist "\n Smaller cone diameter: ") 2.0)
h   (getdist "\n Cone height: ")
ip  (getpoint "\n Insert cone development: ")
ha  (/ (* h rl) (- rl rs))
rdl (sqrt (+ (expt rl 2) (expt ha 2)))
rds (sqrt (+ (expt rs 2) (expt (- ha h) 2)))
u   (/ (* pi rl) rdl)
ra  (* pi 0.5)
p1  (polar ip (- ra u) rdl)
p2  (polar ip ra rdl)
p3  (polar ip (+ ra u) rdl)
p4  (polar ip (- ra u) rds)
p5  (polar ip ra rds)
p6  (polar ip (+ ra u) rds)
osn (getvar "osmode")
 )
 (setvar "osmode" 0)
 (cond	((> rs 0)
 (command "arc" p1 p2 p3)
 (command "arc" p4 p5 p6)
 (command "line" p1 p4 "")
 (command "line" p3 p6 "")
)
((= rs 0)
 (command "arc" p1 p2 p3)
 (command "line" p1 ip p3 "")
)
(t nil)
 )
 (setvar "osmode" osn)
 (princ)
)

[JD Mather]

...One interesting thing about that file, though, is that the base

diameter is dimensioned from the outside and the top (smaller) diameter is dimensioned

to the inside...

 

Oops, didn't notice that. It is also highly irregular to dimensions the aligned length of the cone side rather than the height.

Looks like the entire example is a disaster.

 

Good exhibit of why we need to leave behind the old methods and adopt modern techniques - in my experience only about 10% of users actually knew what they were doing anyhow. Something like this would get out to the shop floor - the guys out on the shop floor would realize it was wrong (probably after scrapping a couple) and make whatever adjustments needed, often not getting documented.

 

The 3D model is the single source of truth. The guys on the shop floor will be making a real 3D model - the designers in their offices should be making a virtual 3D digital model before it goes to the floor. Our job is to get correct drawings out to the floor and correct products out the door. Modern tools do that more quickly and more reliably.

[scj]

Informations on unfolding General 3D surface areas you can get at

http://www.ant-ares.de

Regards

Jochen