*
Being a stickler for accuracy AND production, i’m curious if anybody can share the mathmatical formula for laying out circular radius arches’ knowing the R.O. width and the height difference between the leg of R.O. and highest point of R.O.?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Fine Homebuilding is excited to be the official media partner of the 2024 Building Science Symposium series! This event offers builders, tradesmen, architects, designers and suppliers to discuss topics ranging…
Featured Video
SawStop's Portable Tablesaw is Bigger and Better Than BeforeHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
*
Well......
An arch top door or window? A radius is just a section of a circle. If the door or window has an arched top, it can be any radius you want. For a round top, the radius is the with of the doorway. I carry around a formula for finding the radius of an existing arch. It goes like this:
Square the cord and divide that by the maximum rise multiplied by 8. Then add that to the rise divided by 2. They say that will give you the radius of the section of circle that is your arch.
Don't stop with me, I always have trouble making that formula work, and there are math wizards around here that know a heck of a lot more about the subject than I do.
You also might check the archives. There have been a multitude of threads on this subject.
Good Luck,
Ed. Williams
*mr. 1/16th,
View Image © 1999-2000"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Mr. 1/16thradius = B squared + 4 (A squared) divided by 8A where B is the width and A is the height. Do the addition first, then divide.
*Mr 1/16, If you hate digging through your truck to find some formula you've written on an old truss layout or napkin, in hopes that your handwriting was actually legible enough that day to make sense of it, buy a Construction Master. It's money well spent, and I find it much easier to tote around in my truck than a filing cabinet full of notes and formulas. And the Construction Master doesn't blow out the window when you're driving. Just a thought...
*The formula I found in a book called Circular work in Carpentry and joinery is simple, gives you exactly what you want and works. It goes like this:Half the chord squared + desired rise squared divided by rise X 2.According to the author, although the rise can be anything less than the radius of the circle, it's usually between 3 and 6 inches. Good luck
*this trick is one of the few Items of Knowledge I retained from my 1/2 semester of college almost 20 yrs ago-
*well I could'nt get it to come up, I'll try again.I jus new I shoolda stuk out that semester
*
Being a stickler for accuracy AND production, i'm curious if anybody can share the mathmatical formula for laying out circular radius arches' knowing the R.O. width and the height difference between the leg of R.O. and highest point of R.O.?