PDA

View Full Version : What radius is a bend??

lotechman
06-03-2006, 10:11 PM
I have had the odd occasion where I have been given a pile of rolled pipe or beam that has been given a very slight camber.
Trying to quickly figure out which piece is which is frustrating when some are say twenty foot radius and other 22 foot radius. Other times they are a pile of leftovers and management is asking what radius each was bent to.
I am not sure how to figure it out. I have in frustration layed out the radii on the floor but when you don't have room in the shop what can you do? Is there a quick way to calculate chord distance and height other than the old Smoley's tables method I was taught 25 years ago??? Circular functions in Smoley's is busy work and I don't pack a Smoleys like some really old timers did.

smithboy
06-03-2006, 11:11 PM
is this what you are looking for?

http://mathworld.wolfram.com/CircularSegment.html

Oops...I see upon re-reading your post, you already said that, in frustration, you laid out the radius. This is probably no help to you, but I guess others might find it helpful for something.

lotechman
06-04-2006, 12:50 AM
no smithboy, you gave me enough I think I was able to derive a formula from line 9

2R = C squared/4h + h

I think :'))

Sandy
06-04-2006, 12:56 AM
I don't have a clue what you two are going on about :) but this site looks like something in the same realm. Looks like it could be used in field conditions.

http://www.josephfusco.org/Tips/tip0018.html

Sandy
06-04-2006, 12:57 AM
I don't have a clue what you two are going on about :) but this site looks like something in the same realm. Looks like it could be used in field conditions.

http://www.josephfusco.org/Tips/tip0018.html

Sandy
06-04-2006, 12:58 AM
Oooops, I doubled up somehow.

Sorry.

lotechman
06-04-2006, 01:14 AM
Thanks Sandy,
That site confirms my derivation. In most cases I am having to sort out which rolled radius is which when they lengths of pipe have been dumped in a pile by the forklift. Now I can set my steel 50 foot tape across holding it with speaker magnets and measure the chordal height.
I 'm ready for someone next time they jumble the pipes up and don't mark them!

riley mcmillan
06-04-2006, 07:49 PM
This is the way I calculate the radius of an arc when I know the length and height of the arc.

riley mcmillan
06-04-2006, 08:26 PM
I am unable to post the diagram for the calculations. When I tried to attach the scan, there was a maximum of 150 kb and it wouldn't send.

Brett
06-05-2006, 03:08 AM
radius= ((1/2 of cord length squared)+ (cord height squared)) divided by 2x cord height

T.T
06-05-2006, 04:19 AM

Brett
02-06-2007, 04:32 AM
A handy little site:

http://www.1728.com/circsect.htm

pipe fitter
04-03-2007, 01:49 PM
IF YOU ARE LOOKING FOR A 20F 4inch bend 90DEG,MULTiply 242by 90 by `01745 this will be the formula the fitter used to bend the pipe,he will use the centre 240 WE WILL HAVE THE OUTSIDE OF THE BEND

comp
06-13-2007, 10:46 AM

Stuckwldr
06-13-2007, 11:32 AM
I had a similar issue and I had to make several masonite radius gauges. It took an hour or so to make them but after they were made I had them and could just put them against the stock to tell what bend was used.

Tinbasher
09-21-2007, 11:39 PM
Easiest application...lay the two foot side of a framing square along the inside radius, measure the distance, with your tape, from the inside back to the 12 inch mark on the square...this distance becomes 'b' and 12 is used for 'a' in this example. Plug the numbers into the formula and solve for 'R'

12699

William McCormick Jr
10-05-2007, 09:28 PM
Easiest application...lay the two foot side of a framing square along the inside radius, measure the distance, with your tape, from the inside back to the 12 inch mark on the square...this distance becomes 'b' and 12 is used for 'a' in this example. Plug the numbers into the formula and solve for 'R'

12699

Yes, that is a great formula. I just looked up the one in the Machining handbook. It gives a long drawn out version. It is in the link below.

And with old and new mathematicians often in one place, I have found that you have to put everything in parenthesis.

Sincerely,

William McCormick

William McCormick Jr
10-05-2007, 09:53 PM
Easiest application...lay the two foot side of a framing square along the inside radius, measure the distance, with your tape, from the inside back to the 12 inch mark on the square...this distance becomes 'b' and 12 is used for 'a' in this example. Plug the numbers into the formula and solve for 'R'

12699

I checked some more test examples and that formula of yours does not seem to work for all the examples I tried. Just thought I would let you know. And anyone else that is using it.

Sincerely,

William McCormick

Tinbasher
10-06-2007, 04:17 PM
I'll check it out ,but I am pretty sure that it works. Are you performing the order of operations properly? In the denominator 2 and b must be multiplied first before you divide.
13133

Tinbasher
10-06-2007, 04:32 PM
13134

William McCormick Jr
10-07-2007, 12:01 AM
13134

Sorry to leave you hanging there like that. I was mistaken, from habit I was inputting the whole chord length. I did a bunch of example formulas to check out the formula in the machinery hand book. And I got used to the whole chord.

But I did a few correctly using your formula originally and they did work. Later I went back and forgot that your usage is half the chord length.

Really sorry about that. Sorry to anyone else too.

Sincerely,

William McCormick

William McCormick Jr
10-07-2007, 12:21 AM
13134

I did a bunch of example problems with your formula. And checked them against the Cadd programs output. It does work well and is streamlined.

Much easier to remember in the field. Much easier to remember. I was looking at chopping down that formula in the machinery hand book. But, you know you go and change something written in stone, and somewhere someone is going to get upset. Every now and then you miss something and get some off the wall answer as well.

For a sphere volume formula I use, pi D^3/6, and for area I use pi D^2 and I get beat up for that all the time. They say I am not standard.

I was brought up under two math systems. I learned two types of math simultaneously. Sometimes it is a bit hard on my mind.

I learned math addition, subtraction, multiplication and division. So that the in line division symbol had a different meaning then the fractal operator. The division symbol used to have the same meaning as the large division line in those arc formulas you and I posted. When you used it in an in line formula.

Also the multiplication symbol took everything to the left and everything to the right and multiplied it. Years ago if you wanted to multiply something alone, you had to put it in parenthesis. At least where I came from. I learned math like a language rather then something to remember.

But I was a mathematician in the math capital of the world at the time. But the computers changed a lot of stuff. They did away with the division key, backed the order of math we use now.

Thank You for the formula.

Sincerely,

William McCormick