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Old 11-29-2006, 06:26 PM
scootluc scootluc is offline
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Default Calculating angles of elbows in multiple fitting offsets

I am wondering if anybody knows the formula for calculating the elbow angles, and length of the filler piece(pipe or duct), when the length of the offset, the distance the line is offsetting, and the radius fo the elbows is known. I have used a formula before, but I cannot remember it, nor find anything in any of my textbooks. I am currently constructing a large mechanical room with many multiple offsets that are too long to construct in one piece, and require definitive lengths and radiuses.


I am a newcomer to this website, and hope to hear from some of my fellow sheet metal workers.

Thanks,
Scott Dimma
Edmonton, Alberta, Canada
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Old 11-29-2006, 07:27 PM
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Hi Scott, welcome to the site..good question, but a bit to involved for a quick answer- PM me your email address...and I'll send you something that may help.
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Old 11-29-2006, 07:50 PM
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You Got Mail.
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Old 11-29-2006, 07:51 PM
bordontn2 bordontn2 is offline
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scootluc............Can you CAD ? I use my CAD program to draw out my duct work to scale and use it to get all my measurements..It's just easier.
Other than that you can use the formula for finding the hypotenuse of
a right triangle which is what you're looking for..The offset squared,plus
the length squared. the square root of the sum of these is the hypotenuse.
Maybe? bordontn
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Old 11-30-2006, 09:36 AM
scootluc scootluc is offline
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I'll give you a example of what I'm up against. I have a 48" dia pipe, that needs to offset 12' over 14', as this is a high velocity duct run, (4" e.s.p, 14ga welded construction) I have to use a 2 times pipe diameter radius, which in this case would be 96" on centre. The length of the offset is non- negotiable, therefore I need to calculate the angle of the elbows(not use one of the more common angles 22.5, 30, 45 etc.) To make this fitting in one piece, (mitred elbows and filler piece), is not desirable, due to weight, and difficulty of joining the mitred end in the field.

Thanks,

scootluc
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Old 11-30-2006, 12:13 PM
tnbndr tnbndr is offline
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If you are indeed locked to 96" centerline radius which is a 72" throat radius, according to my calcs it can't be done. Two 90's would be the shortest and those would take you over in both directions. See file.
If you could get away with 1-1/2 centerline radius which would be 48" throat radius you could do this with two 59 degree bevels and an 86-1/2" filler piece.
Sometimes when you are stuck with certain conditions you can't adhere to all of the standard rules.
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File Type: pdf rd_offset_111.pdf (6.1 KB, 125 views)
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Old 11-30-2006, 12:31 PM
tnbndr tnbndr is offline
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Here is the other layout.
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File Type: pdf rd_offset1_103.pdf (4.5 KB, 141 views)
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Old 11-30-2006, 01:26 PM
scootluc scootluc is offline
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Quote:
If you are indeed locked to 96" centerline radius which is a 72" throat radius, according to my calcs it can't be done. Two 90's would be the shortest and those would take you over in both directions. See file.
If you could get away with 1-1/2 centerline radius which would be 48" throat radius you could do this with two 59 degree bevels and an 86-1/2" filler piece.
Sometimes when you are stuck with certain conditions you can't adhere to all of the standard rules.
I misrepresented what I was dealing with, I am looking more at something like 12' offset over 24', however what I am looking for is the formula you used to come up with the 59 degree elbows, and filler piece. The measurements I used were just a example(not a good one ) off the top of my head. I don't have a CAD program so I have to do this the old fashioned way.

Thanks
scootluc
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Old 11-30-2006, 03:01 PM
tnbndr tnbndr is offline
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http://www.thesheetmetalshop.com/mod...ay-pid-32.html
Try the link above for the formulas, unfortunately they all deal with 45's and 30's. I will search at home for some others but I don't know offhand one that will give you the angles.
I did the layout in CAD.
I do have an excel spreadsheet that may help but if you don't know the angles you have to play a little guessing game. I'll send it to you if you PM me with your e-mail address.
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