Tangent to curve

[Interior]

Hi, How do you place tangent lines on the curve so the lines (stairs) are at right angles. The curve is a spline i have tried lots of different ways including making it a poly line but the lines at tangents are the issue. Image belows shows the problem

 

thanks

 

[rkent]

Using the ARC command, after picking the third point of the first arc, hit enter or space-bar to go back into ARC, the following arc will be tangent to the first, hit enter again and keep picking arcs

[lpseifert]

You could try the Measure command using a block (stair tread).

or maybe this will help

;;  PLPERP.lsp starts a polyline perpendicular to any 2D curve at
;;    the point picked.
;;  Allows direct distance entry for first polyline segment, then
;;    restores previous ortho setting and snap angle (if any).

;;  by Bill Gilliss  bill dot gilliss at aya.yale.edu
;;  3/20/2008
;;  Comments and suggestions always welcome.

(defun c:plperp ( / e en obj param p1 p2 wp1 sa oldortho oldsnapang oldosmode olderror)

 (setq oldortho (getvar "orthomode") 
       oldsnapang (getvar "snapang")
       oldosmode (getvar "osmode")
       olderror *error*
       )
 (setq e (entsel "Select curve at point to start perpendicular (OSNAPS welcome):"))
 (setq en (car e) p1 (cadr e))            ;UCS point
 (setq p1 (osnap p1 "_nea"))
 (setq obj (vlax-ename->vla-object en))
 (setq param (vlax-curve-getParamAtPoint obj (trans p1 1 0)))  ;WCS point
 (setq fderiv (vlax-curve-getFirstDeriv obj param))
 (setq sa (+ (* pi 0.5) (angle (trans '(0.0 0.0 0.0) 0 1) (trans fderiv 0 1))))
 (setvar "snapang" sa)
 (setvar "orthomode" 1)
 (setq p2 (getpoint p1 "\nNext point:"))
 (setvar "orthomode" oldortho)
 (setvar "snapang" oldsnapang)
 (setvar "osmode" oldosmode)
 (setq *error* olderror)
 

 (command "pline" p1 p2)
);defun


(defun *error* (msg)
 (setvar "orthomode" oldortho)
 (setvar "snapang" oldsnapang)
 (setvar "osmode" oldosmode)
 (setq *error* olderror)
 ) 

(prompt "PLPERP loaded.")
(princ) 

[Organic]

Use tangential circles, not splines.

[Arizona]

When attempting to draw a line perp to an arc or curved segment of a polyline, I often start my line at the "Center" of the arc segment, then end it where I need it and trim it later. That insures that the line is perpendicular to the arc.

[Interior]

is it possible to explain it a little bit simpler as I'm not great at cad and created what i have by trying. I was recommended to use the spline as it would create the best smooth curve the same as my hand drawings. sorry i should know how to do this but your help is greatly received. thanks

[lpseifert]

draw a vertical line the length of the stair tread (e.g. 4')

make a block out of the line using the bottom endpoint the base point. Call it TREAD

use the measure command as below

Command: measure

 

Select object to measure: select the spline

Specify length of segment or [block]: Block

 

Enter name of block to insert: TREAD

 

Align block with object? [Yes/No] : Y

 

Specify length of segment: 1 this will insert treads 1 unit apart along the spline

[Interior]

Thank you very much fixed it straight away