This question appears in our local forum. **Is there any way we can create an arc by defining the arc length**? There is no direct way to do this. There are some methods that seem to allow you define length. For example start, center, length. But this is defining the chord length, not the arch length.

There is a suggestion to calculate the angle using simple mathematic calculation, comparing the arch radius and arch length. After you get the angle value, then you can draw it. But it is not easy.

One of our member, Ast, suggest a better solution: draw the arch, then modify it using **lengthen tool**.

Lengthen tool allows you to define the object total length, including an arch. Select the **total length** option, then type the distance you want.

Command: LENGTHEN

Select an object or [DElta/Percent/Total/DYnamic]: TSpecify total length or [Angle] <1.0000)>: 1000

Select an object to change or [Undo]:

Now if I try to inquiry or see the arc properties, I will see the arch has the exact length I wanted.

I never need to draw arch by defining it’s length. Any body knows why we would need to do that?

Hello, how do i create arches like three-centred arches segimented arches while using AutoCAD

Hi Edwin, Concerning your question at the end of this article, I design theater seating, and oftentimes the theater is already built and I need to adapt the seats to the layout. in cases when the stands are arcs, I need some way to define such arcs, so I measure the length of the chord and then the perimeter because its easy to measure with a measuring tape and is very precise. You could say that if you measure the chord, divide it by two and then measure the length between the middle of the chord and the arc would… Read more »

Thank you very much, Nicolas.

I’ve never needed to create designs like that. So I was always wondering. I just learned something!

Any body knows why we would need to do that?

I need a ramp with 8% inclination.

I have to cover 3.5m height

Ramp needs to be 43.75m long

Around a circular building.

There :)

Thanks for answering there question, it helped us as well. I am one of the people who needs to draw an arc at a define length. We roll angles which generally start out at 20’0″ long and we need to know what the chord length is going to be so we can check the dimension when the angle is being rolled. This allows us to leave the angle in the machine longer, before pulling it out and putting it on the floor against the arc we drew on the floor. The angles we roll weigh between 64# and 250#. Thanks… Read more »

bang,,kayaknya ini versi inggris dari situs autocad indonesia yah ???

wah ,,,,mantapp salut sama abang .. :) rejekinya melimpah nih

Here’s a little LISP file I pulled from my library. Enter the length a positive for CCW and negative for CW. (defun c:abl (/ |cmdecho| p1 p2 len delta) (setq |cmdecho| (getvar “cmdecho”)) (initget (+ 1 8)) (setq p1 (getpoint “\nCenter point: “)) (initget (+ 1 8)) (setq p2 (getpoint p1 “\nStart point: “)) (initget (+ 1 2)) (setq len (getdist “\nArc length: “) delta (cal “r2d(len)/dist(p1,p2)”) ) (setvar “cmdecho” 0) (command “_.arc” “_c” p1 p2 “_a” delta) (setvar “cmdecho” |cmdecho|) (princ) )

Your routine not working, I ask a friend to fix it, now is working.

(defun c:abl (/ |cmdecho| p1 p2 len delta)

(setq |cmdecho| (getvar “cmdecho”))

(initget (+ 1 8))

(setq p1 (getpoint “\nCenter point: “))

(initget (+ 1 8))

(setq p2 (getpoint p1 “\nStart point: “))

(initget (+ 1 2))

(setq len (getdist “\nArc length: “))

(setq delta (r2d (/ len (distance p1 p2))))

(setvar “cmdecho” 0)

(command “_.arc” “_c” p1 p2 “_a” delta)

(setvar “cmdecho” |cmdecho|)

(princ)

)

;;*********************************

(defun r2d(r)

(/ (* r 180) pi)

)

In a mete & bound description, sometimes you’d see something like “THENCE westerly on a curve to the right having a radius of ___ feet, a distance of___ feet”, in this case I think knowing how to draw an arc with specified arc length is helpful (:

My example of use: I design heat distribution systems in AutoCAD and we use steel pipes of standard 12 m length. Sometimes we need to bend the pipes a bit if the street is not straight. Then I need to draw an arc which is exactly 12 m long and has a certain radius (same as the street).

Thank you for sharing Mary.

I learn something new today!

I have to desing arcs using defined material lengths like pipes based on specific dimensions of the project area. Price vs desing. Ej, 20 feet of pipe bended to a certain ° that makes it to 17 feet

How can you make a pipe shorter just by bending it?

This subject is confusing off topic and useless

I just want to know how to draw an specific arc length in autocad where is the rocket science?????

I have an instance where I need to draw an arc by arc length and chord length. I’m trying to help the field confirm that a fabricated part is the correct radius. Since we don’t know what the radius is, but we are able to measure the chord length and arc length. They could possibly measure the height of the arc by stringing from the chord length to the center of the arc, however, I don’t think they can do this very accurately. It would be nice if you could specify an arc with a start and end point (chord… Read more »