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how to calculate 45 and 90 elbows
Reply:Are you talking about square, round, one piece, or multiple gore elbows?Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:This is what we call a three gore elbow, it actually has two full gores and two half gores, however it seems to be a more sane stronger design. It is the norm now when talking three gore elbows. It really is easier than it looks to lay this out. You do have to add over lap if you are dealing with sheet metal and you are going to rivet or press form bond them.

Square elbows are super simple. Sincerely, William McCormickLast edited by William McCormick; 12-04-2016 at 09:23 PM.If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:

Originally Posted by BootsyHandy

how to calculate 45 and 90 elbows
Reply:Good point, I believe most people never start because they do not know where to start. Or they are missing information. Most of the time for an elbows inside radius we just make it half the diameter of the pipe. This has worked well for us. I have seen guys that have hammered duct together for years not know where to start when making a square duct elbow. Things like the throat, what depth, should it be square or have a radius? This has caused them to get stopped. Should it have an outside radius or turning veins? Half the problem is not knowing what they want to build rather than worrying about how to build it and fifty other types of duct. I have found once I have an actual task I will find out how to make it if I do not know. If it is not a welded round or square duct, allowances have to be made for a pittsburg or ACME seam, often these allowances work in an opposite way the mind normally thinks. So again they never get started.

In the shop if I am making some elbows I make a 30 degree pie slice, by using dividers (a bar compass) for lack of a better description. I make a circle and then create an arc with the pivot point at the lower quadrant of the circle. I start the arc from the center of the circle to the edge of the circle and well beyond. The radius of the arc is the circle radius. And then where the arc intersects the circle I make that the pivot point and I just swing another arc through the center of the circle and outside the circle to where the two arcs intersect. That intersection point the center of the circle and the lower quadrant of the circle point create a 30 degree angle. Looking at the picture I attached, you basically draw a line A,B then draw a circle with its center C, on A,B. Put your dividers on B and swing an arc from C to H and well beyond because you do not know where H is yet. Then put your dividers on G and swing an arc from C to H and where they intersect is 30 degrees. B,C,H creates a 30 degree angle. You can also cut one in half to make 15 degrees too. B,C,G is 60 degrees. Good thinking. Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:I usually know the number of joints ahead of time. So if it is a ninety degree elbow, I just divide by the number of joints. If there are three joints I divide 90 by 3 making each joint a 30 degree angle. So each piece at a joint is on a 15 degree angle. If it was a 45 degree elbow each joint would be 15 degrees and each piece at the joint would be half of that 15 degrees or 7.5 degrees. Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:On a 90, multiply your pipe size by 1.5.     6 inch 90 takeoff = 9 inches.............    12 inch = 18 inches, etc.On a 45, divide your pipe size by 2, three times.     6,3,1-1/2,3/4. then add the second and last numbers. 6 inch 45 takeoff = 3-3/4"12 inch -   12, 6, 3, 1-1/2.....  12 inch 45 takeoff = 6-1/2"I believe you can also multiply pipe size by 5/9 to get a 45 takeoffLast edited by TimmyTIG; 12-06-2016 at 08:39 PM.
Reply:Dividing by 2, three times....=Just divide it by 8..... Why does everybody always say 2, three times?-Everlast PowerArc 280 STH

-Hypertherm Powermax 30 XP


Reply:In real life or on big jobs the office would not allow us to make four piece elbows if they are only 45 degree elbows. They would take out a full gore for sure. On big jobs they just program it into the plasma table so there is no calculating. I have even done jobs where they just programmed and cut pipe so the ends of the pipe are on an angle and that was it. I just supplied them with the angle I needed. What ever angle five feet of pipe would allow to get us tight to a large round wall. Five feet is because it is the maximum length we could get into the roller. Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:

Originally Posted by TimmyTIG

On a 90, multiply your pipe size by 1.5.     6 inch 90 takeoff = 9 inches.............    12 inch = 18 inches, etc.On a 45, divide your pipe size by 2, three times.     6,3,1-1/2,3/4. then add the second and last numbers. 6 inch 45 takeoff = 3-3/4"12 inch -   12, 6, 3, 1-1/2.....  12 inch 45 takeoff = 6-1/2"I believe you can also multiply pipe size by 5/9 to get a 45 takeoff
Reply:butt weld 45's are either the 1/2 of diameter 4 times and taking 2nd and last or 5/8 the pipe size, as said above. handy to know the 5/8 trick when working on a calculator. (.625 x 6 = 3.75)as with 6", you would say 6, 3, 1-1/2, and 3/4, so you are whole, half, quarter, and one eighth the original diameter. taking the proven 2nd and last number added together means the takeoff is 1/2+1/8 the original diameter, which is 5/8. 5/8 of ("of" is a short way to say "multiplied by" but if you say "out of" think division) 6 = 3-3/4i have found pipe 3" and under to not follow the rules. i have to look those up to get perfect fit. i know a 3" 45 is a 2" takeoff. weird.90's are, as stated above, 1.5 diameters. in sch pipe, that is long radius, and is common. short radius is 1 diameter. tubing (like process tube or conduit) can get odd cause they have huge radius elbows, or elbows with strait tails on them that can make fitting difficult if the guy ordering didn't tell you what he bought.Last edited by 92dlxman; 12-06-2016 at 10:01 PM.bosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:

Originally Posted by William McCormick

What application are you making them for? That would be a nice elbow you are describing, but nowadays there is just no room for it in most HVAC jobs I see.Sincerely, William McCormick
Reply:

Originally Posted by rtlflat

Dividing by 2, three times....=Just divide it by 8..... Why does everybody always say 2, three times?
Reply:but six divided by 8 would be 1/8 of 6 which is .75, added to half of six (totaling 5/8 of six) = 3.75bosses stuff:trailblazer 325maxstar 200my stuff:sa 200fronius transpocket 180100 amp Lincoln w/f97 f350 DITKevin
Reply:so you would have to say:  x/8 + x/2 = 2 much algebra for this old welder.


Reply:

Originally Posted by 92dlxman

butt weld 45's are either the 1/2 of diameter 4 times and taking 2nd and last or 5/8 the pipe size, as said above. handy to know the 5/8 trick when working on a calculator. (.625 x 6 = 3.75)as with 6", you would say 6, 3, 1-1/2, and 3/4, so you are whole, half, quarter, and one eighth the original diameter. taking the proven 2nd and last number added together means the takeoff is 1/2+1/8 the original diameter, which is 5/8. 5/8 of ("of" is a short way to say "multiplied by" but if you say "out of" think division) 6 = 3-3/4i have found pipe 3" and under to not follow the rules. i have to look those up to get perfect fit. i know a 3" 45 is a 2" takeoff. weird.90's are, as stated above, 1.5 diameters. in sch pipe, that is long radius, and is common. short radius is 1 diameter. tubing (like process tube or conduit) can get odd cause they have huge radius elbows, or elbows with strait tails on them that can make fitting difficult if the guy ordering didn't tell you what he bought.
Reply:

Originally Posted by TimmyTIG

6 divided by 8 does not equal 3-3/4.
Reply:

Originally Posted by rtlflat

It does if your a pipefitter
Reply:I've worked with some pipefitters that couldn't spell pipe, much less fit it.
Reply:

Originally Posted by TimmyTIG

This is for piping systems, refineries and power plants, etc. Forged fittings, not hand made. The fitting takeoff is used for finding piping cut lengths on isometric drawings that usually just give you center to center dimensions.So, for example: You have an iso drawing that you have to build, it shows a a run of  6 inch pipe with 90s on each end, and gives you a dimension of 6 feet from center of 90 to center of 90. You takeoff for two 90s, 9"+9" =18" - and that gives you a cut length for your pipe of 4'6".
Reply:

Originally Posted by TimmyTIG

Care to show your work, Mr. Pipefitter?