Drawing an Arc Length

[Anonymous]

Is there any way to draw a precise Arc length using Archicad?

I am working from a surveyor's drawing, and need to input the arc length with a given radius.

(I think I know the answer is "no" or "buy an add-on" but I am posing the question so I can ask the next question: Why not? )

[Stephen Dolbee]

Any arc I have drawn (from a survey) has been in tangent with a line or another arc. I just go 90 degrees from the endpoint to find the center of the radius.

Steve

[Jacek]

"Seiss Wagner" wrote:
I have tried various strategies with the three point circle tool, with no success.[/quote

and Steve wrote: "I just go 90 degrees from the endpoint to find the center of the radius. "

-That's the way I do it

[Seiss Wagner]

Steve or Jacek

I don't follow how you go 90 degrees from the end point to find the center of the radius. Can you give my dim mind a screen shot of what you are doing to get a surveoir's arc.

Seiss

[Stephen Dolbee]

Seiss wrote:
Steve or Jacek

I don't follow how you go 90 degrees from the end point to find the center of the radius

This example might be a little simplistic, but here it is. Hope it helps.

Steve

[Seiss Wagner]

Steve -

Thanks much for the screen shot, it really helped. Which Arc/Circle tool are you using? If I use the Three Point Tool I can draw the cord, constrain 90 degrees with the perpendicular icon, but then I must pull the diameter of the arc to get the radius. Is that how you do it?

Seiss

[Erika Epstein]

Another method is to draw a circle of the known radius at each end of the chord. Where the two circles intersect is the center of the arc you are looking for.

[Stephen Dolbee]

Seiss,
I use the center point circle.

Steve

[Seiss Wagner]

After further investigation, I have found the three point circle tool does not work for a chord arc as I had previously posted. It only seems to work if the radius is large. The three point circle tool will work for a chord arc if you bisect the chord and and graphiclly input the chord rise which equals r-½ the square root of (4r²-c²). But this is more effort then either Stephen's or Erika's posts.

So I guess it is back to drawing circles. ':('

[fuzzytnth3]

Seiss wrote:
Finding the length of an arc (circumference) is of interest, but of limited value. A much more interesting and useful question is how do you draw an arc knowning the cord length and radius without resorting to geometry?

I made a library object that does this. I've attached it below. We found it very useful when setting out a multiple curved building.

Enjoy

[Anonymous]

The character in Scotland made a goodie!

This deserves praise for cleverness, though curses to Archicad for needing it.

Put this one on the Tips and tricks board!