Spiral 1

[ocloner]

Is it possible to draw a true spiral in Acad. The spiral I'm trying to create is a polyline starting from a center point with a groove spacing of 5/32". I've done it with offset circles but that's not a true spiral. Any help on this would be greatly appreciated.
Thanks,
Ron

 

[IFRs]

If you search this forum for "spiral" you will find some solutions. I forget how to paste in the threads so I can't put them here.

 

[smcadman]

Are you trying to draw threads on a screw, or a spring?

Flores

 

[ocloner]

I guess it would be a flat spring.

 

[smcadman]

Good luck with a "flat spring" whenever using vanilla ACAD. Circles can be revolved around a Helix easily, but whenever you revolve another shape, it doesn't extrude correctly because the shape twists as it is extruded.
This will draw a helix path, you will need to draw the shape to extrude.

;  helcon.lsp 
;  mfuccaro@hotmail.com 

(defun C:Helcon() 
  (setq segs 40); segments/turn 
  (setq spin -1); -1=CW, 1=CCW 
  (setq ri (getreal "base radius ") rf (getreal "top radius ")) 
  (initget (+ 1 4)) 
  (setq h (getreal "elevation ")) 
  (initget (+ 1 2 4)) 
  (setq tu (getreal "turns ")) 
  (setq old (getvar "osmode")) 
  (setvar "cmdecho" 0)  
  (setq fi1 (/ (* 2 PI) segs) i 0) 
  (setq points (fix (* tu segs)) 
   h1 (/ h points) r1 (/ (- rf ri) points) 
   s (getpoint "center of base ") 
   end (list (car s) (cadr s) (+ h (caddr s)))) 
  (setvar "osmode" 0 ) 
  (command "line" s end "") 
  (command "chprop" "l" "" "c" 1 "") 
  (command "3dpoly") 
  (setq i 0) 
  (repeat (1+ points) 
    (setq fi (* i fi1) h (* i h1) r (+ ri (* i r1))) 
    (setq x (* r (cos fi)) y (* spin r (sin fi))) 
    (command (list (+ (car s) x) (+ (cadr s) y) (+ (caddr s) h))) 
    (setq i (1+ i))) 
  (command "") 
  (setvar "osmode" old))

Flores

 

[chicopee]

THE WAY I WOULD DRAW A TRUE SPIRAL IS TO CALCULATE X,Y,Z POSITIONS OF SEVERAL POINT UNTIL A FULL PITCH IS DEVELOPED; THEN POLYLINE ALL THE POINTS; THEN ARRAY TO THE LENGTH NEEDED;THEN JOIN AND FIT THE POLYLINES.

 

[ocloner]

Thanks for all the support. It gives me many ways to figure this out. By the way Chicopee was my home town up until about 6 years ago. Small world.

 

[pbergagna]

Hey, I grew up in Springfield!!

 

[pardal]

Pease see the following link.

http://online.redwoods.cc.ca.us/instruct/darnold/calcproj/fall98/darrent/equiangularspiral.html

Is that kind of spiral you want to??



Pardal

 

[Spudnik]

Ron --

Do you want to draw a Spiral? (Each circle is smaller than the previous one, like a piece of thread wrapped around a cone)
Or do you want to draw a Helix? (Each circle is the same size as the previous one, like a piece of thread wrapped around a cylinder.)

Hmmm . . . Rocky

 

[ocloner]

To clarify, it would be like a groove in a record. With each succesive wrap having a consistent 5/32" gap. Thanks for all the responses.

 

[Exxit]

Hi Ron,

;**************************************************************************
; SPIRAL.LSP
;
; Este progrma construye una espiral. Puede ser cargado y llamado
; introduciendo "spiral" o de la manera siguiente:
; (cspiral <num. rotaciones> <centro> <Crecimiento por rotacion>
; <puntos por rotacion>).
;
; Designed and implemented by Kelvin R. Throop in January 1985
;**************************************************************************

(defun cspiral (ntimes bpoint cfac lppass / ang dist tp ainc dinc circle bs cs)
(setq cs (getvar &quot;cmdecho&quot) ; save old cmdecho and blipmode
(setq bs (getvar &quot;blipmode&quot)
(setvar &quot;blipmode&quot; 0) ; turn blipmode off
(setvar &quot;cmdecho&quot; 0) ; turn cmdecho off
(setq circle (* 3.141596235 2))
(setq ainc (/ circle lppass))
(setq dinc (/ cfac lppass))
(setq ang 0.0)
(setq dist 0.0)
(command &quot;_pline&quot; bpoint) ; start spiral from base point and...
(repeat ntimes
(repeat lppass
(setq tp (polar bpoint (setq ang (+ ang ainc))
(setq dist (+ dist dinc))))
(command tp) ; continue to the next point...
)
)
(command) ; until done.
(setvar &quot;blipmode&quot; bs) ; restore saved blipmode
(setvar &quot;cmdecho&quot; cs) ; restore saved cmdecho
nil
)
;
; Interactive spiral generation
;
(defun C:SPIRAL ( / nt bp cf lp)
(initget 1) ; bp must not be null
(setq bp (getpoint &quot;\nCentro: &quot)
(initget 7) ; nt must not be zero, neg, or null
(setq nt (getint &quot;\nNumero de rotaciones: &quot)
(initget 3) ; cf must not be zero, or null
(setq cf (getdist &quot;\nCrecimiento por rotacion: &quot)
(initget 6) ; lp must not be zero or neg
(setq lp (getint &quot;\nPuntos por rotacion <30>: &quot)
(cond ((null lp) (setq lp 30)))
(cspiral nt bp cf lp)
)

;-------- Traduccion AUTODESK AG ESPANA (Barcelona, 419 36 29)-------------




Or

http://www.mymcad.com/tipstricks_question50.html

Lothar

 

[pardal]

This is the lisp as from the previous link , it is english for a better understood.



;; A.Dudek
;;; 3DSPIRAL.LSP
;;; Copyright (C) 1993 by Autodesk, Inc.
;;;
;;; Permission to use, copy, modify, and distribute this software
;;; for any purpose and without fee is hereby granted, provided
;;; that the above copyright notice appears in all copies and that
;;; both that copyright notice and this permission notice appear in
;;; all supporting documentation.
;;;
;;; THIS SOFTWARE IS PROVIDED &quot;AS IS&quot; WITHOUT EXPRESS OR IMPLIED
;;; WARRANTY. ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR
;;; PURPOSE AND OF MERCHANTABILITY ARE HEREBY DISCLAIMED.
;;;
;;; DESCRIPTION
;;;
;;; This is a programming example.
;;;
;;; Designed and implemented by Kelvin R. Throop in January 1985
;;;
;;; This program constructs a spiral. It can be loaded and called
;;; by typing either &quot;spiral&quot;, &quot;3dspiral&quot; or the following:
;;; (cspiral <# rotations> <base point> <horiz growth per rotation>
;;; <points per circle> <start radius>
;;; <vert growth per rotation>).
;;;
;;;
;;; Revision 3/9/95 Anthony Dudek
;;; Fixed problem of not drawing a full 360 degree helix when using only one
;;; rotation of 3dpolyline
;;;

(defun myerror (s) ; If an error (such as CTRL-C) occurs while this command is active...
(if (/= s &quot;Function cancelled&quot
(princ (strcat &quot;\nError: &quot; s))
)
(setvar &quot;cmdecho&quot; ocmd) ; Restore saved modes
(setvar &quot;blipmode&quot; oblp)
(setq *error* olderr) ; Restore old *error* handler
(princ)
)

(defun cspiral (ntimes bpoint hfac lppass strad vfac / ang dist tp ainc dhinc dvinc circle dv)

(setvar &quot;blipmode&quot; 0) ; turn blipmode off
(setvar &quot;cmdecho&quot; 0) ; turn cmdecho off
(setq circle (* 3.141596235 2))
(setq ainc (/ circle lppass))
(setq dhinc (/ hfac lppass))
(if vfac (setq dvinc (/ vfac lppass)))
(setq ang 0.0)
(if vfac
(setq dist strad dv 0.0)
(setq dist 0.0)
)
(if vfac
(command &quot;_3dpoly&quot ; start spiral ...
(command &quot;_pline&quot; bpoint) ; start spiral from ;base point and...
)
(repeat ntimes
;;;
;;; section of revised code

(if (= ntimes 1) ; if the number of
;rotations is 1
(repeat (1+ lppass) ; then calculate points ;one extra time to allow
; for the missing polyline segment at the end of
; the rotation
(setq tp (polar bpoint (setq ang (+ ang ainc))
(setq dist (+ dist dhinc))
)
)
(if vfac
(setq tp (list (car tp) (cadr tp) (+ dv (caddr tp)))
dv (+ dv dvinc)
)
)
(command tp) ; continue to the next point...
);close inner repeat
;;;
;otherwise
(repeat lppass
(setq tp (polar bpoint (setq ang (+ ang ainc))
(setq dist (+ dist dhinc))
)
)
(if vfac
(setq tp (list (car tp) (cadr tp) (+ dv (caddr tp)))
dv (+ dv dvinc)
)
)
(command tp) ; continue to the next point...
);close inner repeat
);close if
);close main repeat
(command &quot;&quot ; until done.
(princ)
);close defun

;;;
;;; Interactive spiral generation
;;;

(defun C:SPIRAL (/ olderr ocmd oblp nt bp cf lp)
(command &quot;.undo&quot; &quot;group&quot
(setq olderr *error*
*error* myerror)
(setq ocmd (getvar &quot;cmdecho&quot)
(setq oblp (getvar &quot;blipmode&quot)
(setvar &quot;cmdecho&quot; 0)

(initget 1) ; bp must not be null
(setq bp (getpoint &quot;\nCenter point: &quot)
(initget 7) ; nt must not be zero, neg, or null
(setq nt (getint &quot;\nNumber of rotations: &quot)
(initget 3) ; cf must not be zero, or null
(setq cf (getdist &quot;\nGrowth per rotation: &quot)
(initget 6) ; lp must not be zero or neg
(setq lp (getint &quot;\nPoints per rotation <30>: &quot)
(cond ((null lp) (setq lp 30)))
(cspiral nt bp cf lp nil nil)
(setvar &quot;cmdecho&quot; ocmd)
(setvar &quot;blipmode&quot; oblp)
(setq *error* olderr) ; Restore old *error* handler

(princ)
(command &quot;.undo&quot; &quot;end&quot
)

;;;
;;; Interactive spiral generation
;;;

(defun C:3DSPIRAL (/ olderr ocmd oblp nt bp hg vg sr lp)
(command &quot;.undo&quot; &quot;group&quot
(setq olderr *error*
*error* myerror)
(setq ocmd (getvar &quot;cmdecho&quot)
(setq oblp (getvar &quot;blipmode&quot)
(setvar &quot;cmdecho&quot; 0)
(initget 1) ; bp must not be null
(setq bp (getpoint &quot;\nCenter point: &quot)
(initget 7) ; nt must not be zero, neg, or null
(setq nt (getint &quot;\nNumber of rotations: &quot)
(initget 7) ; sr must not be zero, neg, or null
(setq sr (getdist bp &quot;\nStarting radius: &quot)
(initget 1) ; cf must not be zero, or null
(setq hg (getdist &quot;\nHorizontal growth per rotation: &quot)
(initget 3) ; cf must not be zero, or null
(setq vg (getdist &quot;\nVertical growth per rotation: &quot)
(initget 6) ; lp must not be zero or neg
(setq lp (getint &quot;\nPoints per rotation <30>: &quot)
(cond ((null lp) (setq lp 30)))
(cspiral nt bp hg lp sr vg)
(setvar &quot;cmdecho&quot; ocmd)
(setvar &quot;blipmode&quot; oblp)
(setq *error* olderr) ; Restore old *error* handler
(princ)
(command &quot;.undo&quot; &quot;end&quot
)
(defun C:3s ()
(C:3dspiral))
;;;
(princ &quot;\n\tC:SPIRAL and C:3DSPIRAL loaded. &quot
(princ &quot;\n\tStart 3DSPIRAL command with 3S&quot
(princ)


Pardal

 

[acaddesigner]

You could try the free spiral program on

http://www.3designersmate.com/download

to make your 2D/3D spiral.

Hope this helps.

Paul

 

[JStephen]

Be aware that "spiral" is not a specific shape, but there are different shapes of spirals, generated by different equations. Contrast your example with the kind in a snail's shell, where the spacing gets wider as you go out. Each is generated by different equations.

I think the short answer to your question, is no, a true spiral such as you describe can't exist in AutoCAD. A polyline is always made up of arcs and straight lines, and a spiral just isn't composed of arcs and straight lines. The radius of curvature continuously changes along the length. Ditto on on a helix, where the curvature doesn't change, but the plane of the curvature does.