Making a Volume Measuring Stick - Home Brew Forums

 Home Brew Forums > Making a Volume Measuring Stick

11-12-2011, 03:48 AM   #1
Rcole

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Jan 2011
Providence, Rhode Island
Posts: 88
Liked 10 Times on 8 Posts

Hi,

I'm sure this formula is on the boards here somewhere, but thought I would post the formula for marking a stick to measure the volume of liquid in a round container as a function of the height of the liquid. So, here is how to figure out where to mark your dowel to indicate number of gallons:

Formula to Calculate Height Based on Volume is

h = v/pi r^2

Where h is height, v is volume, pi is 3.1415, and r^2 is radius squared

Note: 1 gallon = 231 cu inches

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Here is an example of how to solve for height in inches of a given volume, in a given pot diameter, say

4 gal. in 14" pot

h = v / (pi)(r^2)

h = 4*231/(3.1415)(7^2)

h = 924/(3.1415)(49)

h = 924/153.93

h = 6" for 4 gallons in 14" pot

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11-12-2011, 04:35 AM   #2
Dilligans
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Jun 2011
Acworth, Ga
Posts: 89
Liked 5 Times on 3 Posts

all I did was pour a gallon of water in a pot then mark it... then poured two gallons then marked it ... 3. 4.. etc... I dont know about using a formula... but then again I forgot everything in learned in high school and college.

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11-12-2011, 04:41 AM   #3
franklinswheat
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Jun 2010
new york
Posts: 151

At first I thought this thread was funny because I thought it was somebody's sarcastic response then I realized it was 100% serious. That formula makes baby Jesus cry.
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11-12-2011, 04:58 AM   #4
day_trippr
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May 2011
Stow, MA
Posts: 18,866
Liked 3372 Times on 2512 Posts

It better be one hell of a fancy stick...

Cheers

11-12-2011, 11:31 AM   #5
SwampassJ

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Mar 2010
Coral Springs, FL
Posts: 2,163
Liked 39 Times on 35 Posts

Take the largest accurate measuring cup you have and measure out a gallon in a pitcher or something. Mark the pitcher and then began filling the kettle from the pitcher. Ever addition mark or knotch a spoon or a spare plastic racking tube. The people at the brew store thought it was the neatest thing when I broke out the measuring stick.
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11-12-2011, 11:38 AM   #6
Pappers_
Moderator

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Jan 2009
Chicago
Posts: 14,638
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Quote:
 Originally Posted by Dilligans all I did was pour a gallon of water in a pot then mark it... then poured two gallons then marked it ... 3. 4.. etc... I dont know about using a formula... but then again I forgot everything in learned in high school and college.
This is what I did, too

11-12-2011, 12:32 PM   #7
tmurph6
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Dec 2010
katy, tx
Posts: 409
Liked 30 Times on 17 Posts

Pouring in water is more accurate than measuring and calculating. With every measurement you introduce error. Also pots aren't always perfect cylinders. The error may be minimal, but when you can get it just about perfect with the volume method, why not? There's a time and place for calculation.

Example, you want to figure out the optimal place to put a floor drain. Do you shoot elevations and measure grade to find out where the low point is? No, you spray water on the ground and see where it collects. Easiest answer is usually the best.

11-12-2011, 12:44 PM   #8
MichaelBrock

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Jun 2011
Alachua, FL
Posts: 498
Liked 35 Times on 30 Posts

When I first started brewing I set out to take the scientific approach to measuring my volume. The plan was to measure the height of the water with a nice stainless steel ruler and calculate the volume. Unfortunately, my pot has a bowed bottom and that wasn't going to work. So I fell back to pouring water in the pot in set volumes and marking a piece of pvc. The math is pretty but not always practical (and this from a physics degree carrying computer programmer).

11-12-2011, 12:45 PM   #9
emjay

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Jan 2011
Toronto, Ontario
Posts: 12,792
Liked 1719 Times on 1606 Posts

GL using this formula in a Blichmann kettle...

Then again, it already has a calibrated sightglass, so I guess it doesn't matter.

11-12-2011, 01:17 PM   #10
chezhed
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Dec 2010
Mission, TX
Posts: 676
Liked 65 Times on 57 Posts

There's a time for common sense/practicality and a time for science.
The smart individual knows when to use what, no matter which
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