Lines tangent to circles

[Glenn Taylor]

I am new to Autocad. I'm using 2002. I have two different sized circles. I need to construct a line that is tangent to both circles (along the circumference).

[hyposmurf]

You'd be wanting to use your OSNAPS I guess :) .I'm using CAD2K but I'm sure its much the same.When your drawing is open look at the boxes under you comand line(where you enter text).Now right click the OSNAP box and select settings,then tick the box called tangent.You can also use the quadrant box that will snap to four corners of your circle(N,E,S & W).Now come out of the settings and make sure your OSNAP button is selected(it will be pushed in for on)

[hyposmurf]

Just realised your post too Fuccaro,two different answers to the same question.The diversity of CAD I guess!

[Flores]

Hyposmurf, diversity is a good thing...I have worked with some who complain that ACAD has too many options and is too complicated. I say that is what makes ACAD great. There are some things that I type faster than clicking a button, other times I just use buttons. Whenever I go to another computer to help someone on ACAD, I usually type commands because it is faster than searching there screen for buttons because of their customization...but then again, some say the way I have my buttons set up is too weird...
Anyway...usually when I put lines tangents on both sides of a circle, it is because I am drawing a slot or cam shape, and I delete the parts of the circle between the lines. Glen, tell me if I am correct on assuming that this is what you are doing. Here is a routine to do just that.


;| cam.lsp
Draws cams or slotted holes
|;

(defun c:cam ()
(setq c1 (getpoint "\nPick center of first radius: ")
r1 (getdist c1 "\nEnter first radius: ")
c2 (getpoint c1 "\nPick center of second radius ")
r2 (getdist c2 "\nEnter second radius ")
a (angle c1 c2)
d (distance c1 c2)
p (- r1 r2)
l (sqrt (- (* d d) (* p p)))
a1 (atan l p)
pt1 (polar c1 (- a a1) r1)
pt2 (polar pt1 (+ (/ pi 2.0) (- a a1)) l)
pt3 (polar c1 (+ a a1) r1)
pt4 (polar pt3 (- (+ a a1) (/ pi 2.0)) l)
)
(command "ARC" "C" c1 pt3 pt1 "ARC" "C" c2 pt2 pt4)
(command "LINE" pt1 pt2 "" "LINE" pt3 pt4 "")
(princ)
)


Flores

[Mr T]

Tools menu, Drafting settings then OSNAP tab, check the tangent box.

Nick

[fuccaro]

Just realised your post too Fuccaro,two different answers to the same question.The diversity of CAD I guess!
- Or just the diversity of the places of this post?

[The Aggie]

Flores,

Thanks for the cam lsp. Its very useful. I draw transitions for left and right turn lanes often and your tool also helps me draw cross tangent, or the two tangents which fall between the circles. Glenn, if these are the tangents you need to draw, just use Flores' cam lsp then connect teh end points of two of the outside tangents with a line, then draw a line from teh center point of that line to the tangent of one cirle (using OSNAP) then another on the other side. If these two are parallel then you have corectly drawn the cross tangent you are looking for.

Hope this helps,

The Aggie

[fuccaro]

The Aggie
You just answered a *very* old post and as you can see Flores and Glenn Taylor are called guests, not members. That's it: people come and people go.
However we like to receive feedback for the stuff posted on these pages. Thank you and welcome in the forum. I hope you will enjoy!