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45 Rolling Offset Formula ??

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piping offsets
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#42 ·
Your actual piece will be shorter than your calculated traveler. I don't know of any fittings that make up all the way to center.

You guys already know this, some might not though....:)
 
#43 ·
Fitting Allowance

There's also a formula for fitting allowance, "the distance the fitting takes up in the center to center measurement"
FA = CF - TE CF = center to face measurement of the fitting
TE = thread engagement of thread (or socket)
FA is deducted from c-c measurement and that equals your end to end measurement. Here's the problem: A black (galv.) screw pipe fitting is suppose to screw on a threaded end (nipple or pipe) 3 - 3 1/2 turns then engage and use the PROPER size pipe wrench to make up fitting. The measurement comes out nearly perfect every time. However, when using screw pipe fittings made oversea's your lucky if they screw on one complete turn before you need a 18" wrench on a 3/4" fitting. I always insist on "AMERICAN' made pipe & fittings. There is a difference.
In PLUMBING there's a formula for everything. I use them all the time and it does save time and waste (money). I just need to remember not to use a black magic marker on newly installed sheetrock, painter's have hard time covering over.
 
#45 ·
Double-A said:
Um... you folks are making things complicated and Killer, I'm not sure what the heck Spread and Advance refer to.

Think of a right triangle, 45, 45, 90. The two short sides are equal. The long side is calculated by using the
Pythagorean theorem. The three sides are A, B, and C, so A squared, plus B squared is equal to the square root of C.

Now, think of a vertical pipe that needs to offset 6 inches. You use the 6 inches and multiply by 1.4142, and that will give you the center line to center line distance between the two pipes along the path of your angle, or 8.48 inches, which rounds to the nearest 1/16th of an inch, or 8-1/2". You have to compensate for the fitting make up distance, which is subtracted from that length.

BTW, your offset will always equal your rise and visa versa in a 45,45,90 triangle.

A picture is worth a thousand words so...

If you were to do as Killer says, 6x6=36, 36+36=72, the square root of 72 = 8.48528. If I then multiply that by 1.4142, I come out with something just under 12. That won't work, even after I subtract for the fitting make up. That's why I got lost.

Just multiply the offset by 1.414 and then knock off the fitting allowances or make up and it'll fit like it was made to go there.
Click to expand...
There is an error in your calculation. A sq x B sq = C sq is the correct formula. You do not need to multiply 8.48528 by pi. 8.48 minus the make in is the answer.
 
#46 ·
Rolling Offsets

You need to find the true offset

True offset = square the rise
square the offset
add the results together
square that number

Constants for rolling offsets Travel = true offset X 1.413 45 degree

Setback = True Offset X 0.577 45 degree
 
#48 ·
That's why you keep a cheat sheet with all of your fitting allowances in your tool bag.

Matt said:
Your actual piece will be shorter than your calculated traveler. I don't know of any fittings that make up all the way to center.

You guys already know this, some might not though....:)
Click to expand...
 
#51 ·
Plasticman said:
Worked for a guy who said he fired his leed plumber for trying to hold up 2, 4 inch no hub 1/8 bends and measure between them at the same time. AND was on a ladder.
Click to expand...
Nothing wrong with that if you are really fast:rolleyes:

I had a plumber working with me that was trying to plumb a vertical line that wasn't hooked solid to anything, he wouldn't believe me that it couldn't work:eek:
 
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#52 ·
In all this talk about 45 degree offsets and the constants used to figure them out. We missed something projection constants. ??? The amount of measurement the offset will add to the forward measurement. E.G is there enough room from the first fitting to get the offset in.

I'm sure NH-Master will look at this. Maybe some others!
http://books.google.com/books?id=Ec...A54&dq=plumbing+1916+offsets&ei=YV4JTIuNB4m-zgTRzcjKAg&cd=2#v=onepage&q&f=false

This will probably open on page 54 -- use the arrows go back to page 53
chapter ends on page 57!
 
#53 ·
i think its cool to lay out a entire system and cut everything and have it ready like a puzzle. i had just recently installed 15" iron system. i would like to see someone hold a 1/8 or 1/4 bend up for a measurement.

ya got to know the math.
 
#54 ·
I would love for you all to believe that I have all them formulas stored in my teeny little brain but reality is very different. At my age, remembering where the hell I left my shoes is an every morning dilemma. They came from a text book called math for plumbers, which I may add is a must text for anybody taking the journeymans exam in any state.
 
#55 ·
Plasticman said:
Worked for a guy who said he fired his leed plumber for trying to hold up 2, 4 inch no hub 1/8 bends and measure between them at the same time. AND was on a ladder.
Click to expand...
Hire the handicap...
They are fun to watch...:whistling2:
 
#56 ·
The book to use is Mathmatics for Plumbers as stated in previous links. If I'm understanding correctly the distance of the upward path in an offset is called the rise measurement. "The actual distance the travel moves upward as it moves over to the new location" The offset or set as some call it, is "the distance the pipe line moves over" On a 45 degree offset - the rise and the offset are the same. If your offsetting 7" - you will also be rising 7" -(all c-c measurements). the above mentioned book is good and is illustrated. The only thing that needs to be mentioned is that there is a formula and constant for everything dealing with angled fittings in plumbing. It sounds confusing, but there is a chart that gives them all in a small amount of space. I use these calculations not only in my plumbing installations but in my duct work as well (HVAC) I'm the one that usually makes the mistakes, not the calc's. you really need to use them frequently in order to feel comfortable with them. but once you do, you'll always use them. I teach the journeyman's/Master plumbers exam and math is a major portion where I teach. http://www.plumbingzone.com/images/smilies/thumbup.gif
 
#57 · (Edited)
" The offset or set as some call it, is "the distance the pipe line moves over" On a 45 degree offset - the rise and the offset are the same. If your offsetting 7" - you will also be rising 7" -(all c-c measurements). the above mentioned book is good and is illustrated.
 
#59 ·
Fitting measurments

Bayside500 said:
does anyone have take off the measurements for pvc fittngs, i used to have a little book from charlotte pipe, but lost it many years ago.
Click to expand...
Charlotte Pipe company has cast iron and plastic DWV fitting books have all the measurments for their fittings Oso:thumbsup::thumbsup:
 
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