Radius help

[Guess who]

That's what he said.

That's what I said, and is what he said, which was clear enough.

[Guess who]

Are my messages not getting through? I'd like to know, since there are other problems [replies with no sign of the original message] and I need to speak to my ISP aobut that.

The "saggita" is the vertical distance from the chord center to the arc. There's a reason Latin was used, and it's political as well as a bit snobbish, and a long story. It's just another word.

I'd rather have the formula and a calculator. Much easier to carry around, and easy to use with practice.

[Duane Bozarth]

Sorry, after posting I regretted what was probably to much of a knee-jerk reaction...

W/ so many automated millwork shops these days and the plethora of CAD designers, it is quite probable a custom mill shop do it that way...

[Walt Cheever]

Another even easier mode is do use the three points on the circle to draw a circle using CAD and measure the radius.

Walt Cheever

[SonomaProducts.com]

I used to be able to do all the geometry and trig stuff in my head. Since using CAD I can't do any of it anymore but I can solve even more complex problems without even thinking about it. I recall when I was just a pup and I solved some nasty hip and valley bracing intersections in about an hour using CAD. It took the seasoned checker 2 days, he built a cardboard model of some parts and still couldn't get every dimension. However, he signed off on the few he couldn't prove because he couldn't find even one error in the ones he could prove.

This was for fabricated steel that was fab'd in California and shipped to Hawaii for installation on the roof of a high rise. It all fit.

[Guess who]

As usual, anything works well in the right hands. My older brother [rest his soul] became wealthy as a consultant correcting structural steel drawings done by young engineers using CAD. I don't know if he could turn on a computer. His background was the old trade school/steel works apprencticeship /drafting office; a good solid on the ground foundation then the theory. Also, he wasn't afraid of the fudge factor, instinctively knowing the limitations from his background.

When he got really stuck, and needed more advanced math or verification, he used me. Remember, I said *he* was the one who got rich. His last job involved deciding whether a bent piece at the NY site was supposed to be that shape. He said I saved him hours and hours of work when I showed it was from his dimensions. I taught math, and can still teach *all* high school math without a computer. They're useful, and I sue one all the time, but base knowledge, not the tool, is the key. That's why I'm here. There are some people with some excellent down-to-earth useful advice willing to share, and I like to listen in.

[Lowell Holmes]

I agree, I use a calculator or AutoCad when I need the sagitta (:-) I might even lay it out if the radius is small.

The Smoleys post was made with tongue in cheek. Smoleys are not used much any more.

[Edwin Pawlowski]

You should be ashamed of yourself. The Smoley family will starve to death because people use cheap $5 made in China calculators from Wal Mart rather than look up the figures in the book for $90. It will be a sad day when there are no more Smoley tables.

[Lowell Holmes]

When I first was introduced to Smoleys (1957), there were only mechanical calculators, Monroe and Marchant comes to mind. They cost hundreds of dollars and of course the big advantage they had was extracting square roots. A slide rule or Smoleys was the state of the art in trig calculations. Initially, I had no use for the segmental tables, but that soon changed. I never heard of a sagitta until yesterday. I suppose an old dog can learn new tricks. Being comfortable with trig, finding a radius is no problem with a $5 calculator. :-)

I do know a fabrication shop that still uses Smoleys, just like I know woodworkers that use hand tools.

[D. J.]

This one is used to find radius in just such a manner in traffic accident investigation.

C squared M ___________ + ________

8 * M 2

Where "C" is chord meaning you measure between two points on the curve.

"M" is middle ordinate which is the distance between the middle of the chord and the end which is the same distance in which your two chord points meet. With those two variables, you can determine the radius.

Don