# Fun with Math



## Pipe Rat (Apr 5, 2009)

I'll start with this crude drawing.


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## easttexasplumb (Oct 13, 2010)

http://www.plumbingzone.com/members/bartnc37-938/


I bet this guy can figure it out, he was not scared of old schools math quiz.


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## Tommy plumber (Feb 19, 2010)

People who don't think math is necessary for the plumbing trade have never studied for either a journeyman's or master's license.


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## sheeptown44 (Oct 31, 2010)

Agreed there is more math involved than the outside world knows. We ain't as dumb as we look. i just measure off of the nearest do it your selfer and divide by seven (my lucky number) add 3.14 and there you have it ! all done, no calculator for this guy


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## Pipe Rat (Apr 5, 2009)

easttexasplumb said:


> http://www.plumbingzone.com/members/bartnc37-938/
> 
> 
> I bet this guy can figure it out, he was not scared of old schools math quiz.


There's nothing to figure out east??? The first post is an example of how to figure parralell offsets.


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## easttexasplumb (Oct 13, 2010)

Math is not my strong suit, I had to get math software that started out with 5 th grade when studing for my masters. Just never have been good at math, more like a reading and memorizing type of person.


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## mongo (Jun 26, 2010)

I used to teach math & trig. Not a serious problem at all.


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## SewerRatz (Apr 25, 2009)

There was a post started with the formula's http://www.plumbingzone.com/f2/useful-formula-thread-8539/


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## plbgbiz (Aug 27, 2010)

You also need the formula for calculating the difference in length of the risers above and below the 45's.


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## SlickRick (Sep 3, 2009)

I am more of a physics guru myself.


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## Pipe Rat (Apr 5, 2009)

plbgbiz said:


> You also need the formula for calculating the difference in length of the risers above and below the 45's.


That would be the "A" dimension shown in the drawing.


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## greenscoutII (Aug 27, 2008)

easttexasplumb said:


> Math is not my strong suit, I had to get math software that started out with 5 th grade when studing for my masters. Just never have been good at math, more like a reading and memorizing type of person.


 
Me too..... Math is essential in our profession, but I struggle with it. I can memorize code like a Mo' Fo' though!:thumbsup:


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## CSINEV (Aug 6, 2010)

wouldn't a 
22 1/2 = Known x .199
45 = known x .414
60 = known x .577

your numbers are just a little off or did you round?:whistling2:


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## plbgbiz (Aug 27, 2010)

Pipe Rat said:


> That would be the "A" dimension shown in the drawing.


Isn't the "A" in the drawing is the run between the 45's, not the risers?


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## Epox (Sep 19, 2010)

I had to do that formula on my test been a long time though.:blink:


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## plbgbiz (Aug 27, 2010)

For 45deg with offset of 7"
A=10"
B=13"
C=Offset x 1.414 or 9.898"
D=G-(B+Offset) or 30"
E=Difference in Length compared to D = D-(.414 x A or 4.14") or 25.86"
F=Difference in Length compared to B = B+(.414 x A or 4.14") or 17.14"
G=50"

No guarantee this is right...been a while. :nerd:


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## Pipe Rat (Apr 5, 2009)

plbgbiz said:


> Isn't the "A" in the drawing is the run between the 45's, not the risers?


The "A" in my drawing is the height difference of the risers to maintain the equal spread. Not the run.


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## Pipe Rat (Apr 5, 2009)

Here's a revised version with some added parameters.

My original intent was to simply show the math for determining the height difference "A" of each successive riser to maintain equal spread. We've all seen the Set, Travel and Run formulas a hundred times. 

Looking for some lesser known math tricks you have found useful.


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## plumber666 (Sep 19, 2010)

When I get the apprenti asking me questions about this kinda stuff I say "Let's play Find the Triangle." I always find that's the easiest way to solve these problems. Visualize the triangle. Sketch it out, draw in the imaginary triangle in the spot with the measurement in question, and the rest is Math 101.

My most used work trick is using the old measuring tape as a calculator, but it can only add and subtract.


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## stillaround (Mar 11, 2009)

They got any fancy math for my creditors ????


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## 1703 (Jul 21, 2009)

Fun with math?

Dude, you need to get out more.

:jester:


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## nhmaster3015 (Aug 5, 2008)

Duh I woud jus staple sum pex up and fogets about it. Math is for guys dat don't knows how to get er done


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## PLUMBER_BILL (Oct 23, 2009)

*Are we missing something ???*

Is not the formula for a 45 parallel offset. Assume 10" Centerline Measurement 10" c/l distance x 1.41 = 14.10 Now you must measure the fitt's [45's] from the center line to thread entry point or to the inserted glue joint.
On the job there could be fitt's from different sources. 
IE: on a 2" PVC 45 if the measurement from center was 7/8 of a inch
That would be deducted for each fitting from the 14.10
14.10-1.75= 12.35 rounded to 12-3/8" is the piece you would need
to make the offset fit properly.


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## OldSchool (Jan 30, 2010)

stillaround said:


> They got any fancy math for my creditors ????


Yah.... just tell them they will only get 10% if you go bankrupt right now...

So they might as well settle for 10% now and save them their legal expenses :laughing:


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## ckoch407 (Sep 30, 2009)

Mathematics for Plumbers and Pipefitters. 
Best book on the subject. Has great reference tables with all of the constants for rise, run, offset, rolling offset, volume, you name it.


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## ckoch407 (Sep 30, 2009)

In case you lose the charts or forget the constants, remember Pythagorean theorum for hypotenuse angles: a2 + b2 = c2.


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## PLUMBER_BILL (Oct 23, 2009)

ckoch407 said:


> Mathematics for Plumbers and Pipefitters.
> Best book on the subject. Has great reference tables with all of the constants for rise, run, offset, rolling offset, volume, you name it.


On google books 
http://books.google.com/books?id=DHJDLfaUoywC&pg=PA1&dq=mathematics+for+plumbers+and+pipefitters&hl=en&ei=Y7gDTc38FcP_lgec2oCzCQ&sa=X&oi=book_result&ct=book-preview-link&resnum=4&ved=0CEoQuwUwAw#v=onepage&q=45%20degree%20offsets&f=false

Check out the rolling offset using a framing square.
Click on page 18 then scroll down until you get to page 27

But again you would have to subtract the thread make up from center of the fitt's.
Everbody agree on this? It's how I was taught ...


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## SewerRatz (Apr 25, 2009)

SewerRatz said:


> To find the (T)ravel, (S)et, and (R)un of a 45º offset:
> 
> T= S x 1.414 if set is known to find travel
> S= T x .707 if travel is known to find set
> ...


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