Math problem (geometry)
 

I am trying to find the radius of this piece I need to cut out of a 24" glu lam beam. Can anyone help? Is there even enough info to get the radius? I hope my crappy drawing is decipherable.

Thanks for any help.

If the drawing doesn't make sense, I have a 24"X109" beam. I need to cut a 10 1/2" wide radius out of it.

Thanks for any kind of response.

D = 2r

D = Diameter
r = radius

2 (10.5") = 21"

I'm pretty sure that's wrong w. I don't have a formula. But I would lay the beam on the ground. Have another person hold the end of a string and move far enough away until you can achieve the arc you want. The length of th string is your radius

Pretty sure I'm wrong????? Look it up in your Geometry book, Einstein!

From that picture 10.5" is only a piece of the radius..... just the portion of the radius of 109" of the circle.... the radius in fact would be much much larger.


On the drawing - are you cutting out a 10.5" wide piece (e.i. - 2 cuts -top and bottom)? or just one cut 10.5" from the base of the board?


@ W - 1st post he is looking for the radius, so you have a equation - that is no help. good job.

Outside = 157.1905"
Inside = 146.6905"

You could calcute it from the 3 point math...

http://local.wasp.uwa.edu.au/~pbourk...y/circlefrom3/

I need to make both the top and bottom cuts.

I found this equation which apparently will give me the radius, but I'm not sure how the math works.

http://mathforum.org/library/drmath/view/69144.html

inside r = [(109 / 2) **2 + 10.5 **2 ] / 2 * 10.5 = 146.69

outside r = 146.69 + 10.5 = 157.19

Thanks everybody. I'll let you know how it turns out.

Here is the final outcome. Thank you all for your help. I really appreciate it.

Before, during and complete.

Did someone call the cops on you?

They must have heard you had doughnuts.

No, I have a Sheriff's Deputy that lives across the street. I do think I piss him off sometimes when I am working in the garage and he is on night shift. Oh well.

So what's it going to be?

And what did you use to make the cut? That's a pretty mondo cut regardless of the tool.

It's going in between two entry columns on a custom home. I cut it for a local builder.

I made a template out of 1/2" ACX plywood and used a 2hp plunge router with a collar. I took about 1/8" of depth per pass. The sketchy part was I could only rout 2 1/2" deep and then I had to flip it and get the template lined up exactly to rout the other side.