Confused about a simple offset, any help appreciated.

[pdean712]

Hey everyone im confused about a simple offset, i made a drawing if anyone could tell me its right or wrong i would really appreciate it. Thank you

[Tensaiteki]

I don't know what you mean by "take out," but the problem would be easier to solve if we knew the centerline radius of the elbows and whether or not they are simple sections of a torus or if they have any straight segments (and, if so, how long).

[pdean712]

im not sure what that means, by "take out" i mean how much the factory 45 degree elbow takes out of the total length.

[kazlx]

Why don't you just install the two 45s on the other two pipes, then measure for the diagonal?

[rvpc]

pdean, 8" vertical distance [i call rise] x 1.4 [multiplier for 45*] =11.2" is center to center distance between the bends. [measured from the center of first radius to center of the second radius] . this is larger than your 6" measurement. can you increase your horizontal distance to accommodate the larger distance.

[aevald]

Hello pdean, I will include an image here that might explain a bit of what you are trying to do. As one of the other posters mentioned, your use of 45's might entail changing the other dimensions to accomodate 45's only, otherwise you will need to cut the elbows to specific degrees to accomodate the offsets that you are trying to use. The red triangle in the image that I am including takes into account the vertical and horizontal offset being 45. The other triangles are formulated based on the centerline of the elbow radius and figured using the hypotenuse of the purple elbow x's the angle(45) sine of the pipe elbow. I'm hoping looking at the sketch will provide a bit of direction for a mathematical answer to your question, I don't have the time to properly complete this in a very timely manner. Good luck and best regards, Allan

[tanglediver]

Nice job Allan.
~~~~~~~~
I was about to post this....
~~~~~~~~
...
I laid it out on graph paper.
Without any connection between the 2 horizontal pipes, I measured 53 degrees of angle between the ends of the 2 pipes, centerline to centerline.
I expect your angles are not going to be 45 degrees.
Stretch the horizontal distance between the 2 pipes, then 45's might do it.

[Oldiron2]

Let me put the problem you have with the setup in simpler terms than Allan did;

because the two lengths ( 6" and 8" ) are not the same, the angle between the ends of the two pipes is not 45 degrees. Even if you have slightly different lengths due to the fittings, the two distances (rise and run) will still be different. Because the fittings only come in these fixed angles, something else needs to change...or you need to bend something, make special fittings, or use flexible tubing (still bending something though).
These last are probably not good options.


If that didn't matter and you still needed to know the length of the diagonal, it is given by the formula

(A x A) + (B x B) = (C x C)

[Sorry that I don't have mathematical symbols on this computer]

where A and B are the rise and run and C is the diagonal.

Here, using the lengths given in your diagram, we have:

( 6 x 6 ) + ( 8 x 8 ) = 36 + 64 = 100 and 100 = (10 x 10) so C = 10

Please pardon this explanation if you know this already; not everybody here does.

[phyisisist777]

you peaked my interest so i had to draw it up before i could sleep...

using data from engineering toolbox, the 2" elbow has a 4" radius and is 1.375" from face to center of radius.

honestly, drop the elbows because I see no way to utilize them without being a PITA.

just lay it out on the floor of your shop in chalk and arbitrary miter the corners so it looks good

[Baila La Pinza]

As said Its worked out by centre lines, a simple way to work it out is....

You've got 8" (203mm) between centres multiply this by 1.4142 = 287.1mm(11.3") to give you the diagonal.

Now to subtract the fittings, a 2" elbow should have 110mm (4.3") centres, multiply this by 0.141 = 15.5mm (0.6"), giving you the "take off" (as you put it) for one elbow.

Now multipy this by 2 ('cus you've got 2 elbows) =31mm(1.2") and subtract this from the first calculation you made (the diagonal) = 287.1mm - 31mm = 256.1 mm (10.1")

However, If you want to use 45 degree elbows then you're locked into this formular and you can't make them 6" apart. To make it work how you want you would need to change the angles of the elbows. To find the diagonal Instead of multiplying by 1.4142 you would need to change it to (there are more, but these are the ones I can remember off the top of my head);

60degrees = 1.15
30 degrees = 2.00
22,1/2 degrees =2.61
11,1/4 degrees = 5.12

Draw out a the triangle on a scrap of paper, then measure the angle to work out what's closest to what you want. There is a formular, or at least a chart for the "take off" of elbows that arn't 45 or 90 degrees but I haven't got it to hand.

Hope this helps!

[Baila La Pinza]

Originally Posted by Baila La Pinza

As said Its worked out by centre lines, a simple way to work it out is....

You've got 8" (203mm) between centres multiply this by 1.4142 = 287.1mm(11.3") to give you the diagonal.

Now to subtract the fittings, a 2" elbow should have 110mm (4.3") centres, multiply this by 0.141 = 15.5mm (0.6"), giving you the "take off" (as you put it) for one elbow.

Now multipy this by 2 ('cus you've got 2 elbows) =31mm(1.2") and subtract this from the first calculation you made (the diagonal) = 287.1mm - 31mm = 256.1 mm (10.1")

However, If you want to use 45 degree elbows then you're locked into this formular and you can't make them 6" apart. To make it work how you want you would need to change the angles of the elbows. To find the diagonal Instead of multiplying by 1.4142 you would need to change it to (there are more, but these are the ones I can remember off the top of my head);

60degrees = 1.15
30 degrees = 2.00
22,1/2 degrees =2.61
11,1/4 degrees = 5.12

Draw out a the triangle on a scrap of paper, then measure the angle to work out what's closest to what you want. There is a formular, or at least a chart for the "take off" of elbows that arn't 45 or 90 degrees but I haven't got it to hand.

Hope this helps!

Just to be clear the underlined part in your case would be multipling 6" (the offset) which in the first formular would have had to be 8" (as the 'rise' and 'offset' were the same). The distance that the tubes are apart 'rise' would then be determined by the angle that you used in the formular, or vice versa.

At the end of the day, for something like this as a 'one off' it's probably easier, as said, to just draw it out.

[pdean712]

wow, you guys were a great help, i dont know what i was thinking, you guys really cleared the air, so in order for a 45 degree offset both of my lengths would have to be the same, either 8 rise and 8 run or 6 rise and 6 run and so forth.

[Scott Young]

Originally Posted by pdean712

wow, you guys were a great help, i dont know what i was thinking, you guys really cleared the air, so in order for a 45 degree offset both of my lengths would have to be the same, either 8 rise and 8 run or 6 rise and 6 run and so forth.

you got it

[coreshield8]

I agree with post 4, keep it simple and moveing.

[slim83]

the way I do take off for 45s buttweld fittings is 5/8 multiplied by pipe size

[drafterx]

Originally Posted by slim83

the way I do take off for 45s buttweld fittings is 5/8 multiplied by pipe size

right on!

[biker trash]

whats up guys newb here. Just thought I'd throw my 2 cents in. It comes out picture perfect every time when I do it like this. Like every one else I use the 1.4142 formula. Just multiply the offset by 1.4142 and that will give you the length of pipe you need between the two 45's, minus the throat of the 45's. you don't even have to get technical about it. just 1.4142 times the offset = the length of the travel piece between the 45's.

[epadrigo]

Originally Posted by slim83

the way I do take off for 45s buttweld fittings is 5/8 multiplied by pipe size

You can also use: Nominal pipe size x .625

[epadrigo]

Originally Posted by biker trash

whats up guys newb here. Just thought I'd throw my 2 cents in. It comes out picture perfect every time when I do it like this. Like every one else I use the 1.4142 formula. Just multiply the offset by 1.4142 and that will give you the length of pipe you need between the two 45's, minus the throat of the 45's. you don't even have to get technical about it. just 1.4142 times the offset = the length of the travel piece between the 45's.

1.4142 is the Cosecant of 45 degrees ( Check your trigonometric table)
It is always use for solving the travel of two 45 degrees elbow. The formula is:

Run x Cosecant (1.4142) =

[MarkBall2]

I has headache............................

In other words, math is not my forte!

[slim83]

Originally Posted by epadrigo

You can also use: Nominal pipe size x .625

.625 is 5/8ths

[Oldiron2]

Originally Posted by MarkBall2

I has headache............................

In other words, math is not my forte!

I thought you flew our of a hanger, not were playing Fort.

[MainePiper]

If all else fails there are android and iphone calculators available for this

Pipe Fitter Calculator
https://play.google.com/store/apps/d...fittings.kevin

Lateral Pipe Calculator
https://play.google.com/store/apps/d...y.trigonomitry

Mitered Pipe Calculator
https://play.google.com/store/apps/d...lculator.miter

[66mynd]

I never work with pipe but this is good info. If you can, why not just figure for an 8" rise and run and just cut off what you need and weld it up?

[pipefitter72]

simple way to find takeoff of standard 45 degree fittings. take pipe size and divide by2 then divide by 2 then divide by 2..add the second number and last number it will give your takeoff.

ie.

10
5
2.5
1.25
takeoff= 6.25