# For the sake of Accuracy.!!!

Discussion in 'Architecture & Engineering' started by cluelusshusbund, Nov 3, 2018.

1. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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Problem:::
To make a rain gauge that woud measure at least 4” of rain in 1” increments... from a cylinder shaped plastic container which has an irregular shaped bottom... how woud you determine whare to put the 1” mark on the bottle.???

The container to be used is around 12” tall an woud be much like a plastic soda bottle wit the top part cut off like the example shown below.!!!

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3. ### billvonValued Senior Member

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Calculate the area of the top of your container. Multiply by 1 inch. (Easy math!) That is the number in cubic inches that 1" of rain will give you.

Now measure that amount with a measuring spoon (or cup, or scale, or whatever.) Add it to your container. Draw a line where the water level is. That's 1 inch.

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5. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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I woudnt have thout of that way.!!!

My way dont use math... an i wont post it yet in case sombody else figers it out an wants to post how its done.!!!

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7. ### DaveC426913Valued Senior Member

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I would have done it without calculations too - I'm an analog guy - I wouldn't trust the measured area of such a wobbly object.

Fill a second bottle B part way. Make a mark at the water level and another one inch below it.
Pour water in small amounts into the first bottle (A) until you've poured out that one inch from bottle B.
Make your mark on bottle A where the water level is.

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8. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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Yeah thats my way.!!!

But now ive determined that the egg-holder shape of the bottom of the bottle will cause inaccurate measurments when the rain falls at an angle… so the bottom will have to be made level :-(

9. ### DaveC426913Valued Senior Member

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No, you're overthinking it. The shape of the bottom will have no effect.
Once the rain is inside the body of the cylinder, it matters naught what shape the bottom is.

10. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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Yeah it wont mater when the rain level is above the irregular shaped part of the bottle… but below the 1” level i also want marks at ¼ “ increments… an the rain level measurements in the irregular shaped part of the bottle will likely be inaccurate when the rain falls at an angle.!!!

Edit:::

Just thout of a fix:::

Cut off the irregular bottom part of the bottle... an use the bottle upside down to catch the rain water... then any 1/4 inch measurements in the lower part of the bottle will be accurate.!!!

Last edited: Nov 3, 2018
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11. ### billvonValued Senior Member

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Nope. Angle doesn't matter.

12. ### JeevesValued Senior Member

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Why not use a graduated measuring cup instead?

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13. ### DaveC426913Valued Senior Member

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Never really understood how a gentle widening made any difference.

But, at the risk of speaking for CluelessH, I'd say his materials are what they are.

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15. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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When the rain comes down at a angle some of the low areas at the botom portion of the bottle woud fill faster... causin measurements taken in the irregular shaped area to be inaccurate.!!!

16. ### DaveC426913Valued Senior Member

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No.

You marked how much one inch of rain will fill.
The rain comes in from the top. It doesn't matter what shape the bottom is.

17. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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Yes... an that 1" mark will be accurate in all rain situations as long as that mark is above the irregular shape in the lower part of the bottle.!!!

It maters when it rains at an angle an you are takin a measurement in the irregular area of the bottle... cause some of the "egg-holders" in the irregular portion of the bottle will fill faster than others.!!!

18. ### DaveC426913Valued Senior Member

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That part's true. Your Coke bottle device cannot measure an amount of rain less than that which will fill the irregular portion of the bottom - regardless of the angle of the rain.

If changing to a different bottle is impractical, you can simply fill up the irregular space. You could put an inch of epoxy in there, or just a big glob of hot glue from a glue gun. You could even use marbles. (You'll want to glue them down, so you can empty the bottle of water for the next rainfall.)

Whatever you fill it with doesn't have to be level - it doesn't even have to completely fill the space. All you want is to use up volume. Your first inch of water will fill to the same level every time regardless of the shape. It would just alter where you put your "one inch" calibration.

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Last edited: Nov 3, 2018
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19. ### billvonValued Senior Member

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Nope. We measure rain by inches on the ground, not by how much rain passes through an area perpendicular to the raindrops. It doesn't matter what the angle is.

Look at any rain gauge if you don't believe me.

20. ### DaveC426913Valued Senior Member

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That's what I thought he was saying too, at first.

What he's saying is that slanted rain will fill some of the indentations and not others, leading to a non-level surface, resulting in an inability to get a proper reading.

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He wants the rain to fill the indentations evenly. That's not likely to happen.

His first tick mark must be above the lowest possible level at which the water surface can be level.

Last edited: Nov 3, 2018
21. ### geordiefValued Senior Member

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Funny thread.Have you thought of script writing for the Simpsons?

22. ### billvonValued Senior Member

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Ah, I see what you are saying. (Although it would probably be fair to say that you will _never_ get a good reading until all the depressions communicate, due to poor averaging, splashing etc.)

23. ### cluelusshusbund+ Public Dilemma +Valued Senior Member

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Thout about it... but i turned 'em down.!!!

Well... they will fill evenly when the rain falls at 90 degrees… but sinse that ant gonna hapen often i realized that i had a BIG prollem in my design... cause i wanted to make smaller measurements that woud fall into the... Irregular Zone.!!!

That woud work but im goin wit cuttin off the irregular part an turn the bottle upside down... then it will be easy to read the water level even at 1/8" of rain… much like the cone shaped rain gauge pic i posted.!!!

The accumulated water in each of the indentions woud be a level surface… but not necessarily wit each other… lol.!!!

Not so much what i “want”… i was just pontin out that they woudnt fill at a even rate wit rain at an angle.!!!

I rest my case

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I will take a picture of my cola bottle rain gauge when i get it done… but that may take a while sinse i dont drank colas… haha.!!!