Water Pressure - Laws and Calculator

[borderraider]

thankyou for this! im having an all glass tank made for me at the moment (not brave enough to do it myself) its nice to be able to do maths to see if it was such a bargain after all lol! and thanks out of mathematical curiosity!

 

[apisto]

thanks for posting the calculator, however, where can I see the standard thickness? I tried 79*23*23 and get glass thickness of 10.74 mm sf 3

 

[Jgray152]

MM to Inch
http://tinyurl.com/l4ufla

 

[apisto]

not what I meant. 10.74mm isn't a standard glass thickness

 

[Rivermud]

The calculator had a stand glass size field in it to begin with. However, it was removed for a several reasons. First, it automatically rounded up to the next nearest size. 10mm Glass is 3/8's and 12mm glass is 1/2. It's up to you as the user of the tool to decide what is appropriate for your build. I had already heard several complaints where people were getting a recommendation for 19 mil glass and they were just a shade of 15mils on the calculator. sincce there is not common glass between 15 and 19 it rounded up to 19. Granted, people should use their own judgement, it caused more confusion than it solved. Now it's not part of the calculator and people will have to use their own smarts to figure out what is appropriate for them. The calculator is a guide, not gospel.

 

[toffee]

This is the most fantastic thread, Rivermud you ROCK!

Thank you thank you thank you.

 

[Rivermud]

I am happy people have found it useful. I have taken a lot of pride in fixing the standard calculators out there with the proper formula. The funny part is that the math was there, the formulas in the calcs they used were wrong. It was probabl a simple error.. Either way it provides a tool for people to use that gives them direct feedback for their projects, and that was the itended purpose of this thread.

 

[Josh the Happy]

Wow, thank you, this was most useful. (and i wont complain if the numbers end up being wrong - after all it is not gospel as you said!)

 

[Griller]

Fabulous tool! Is it possible to modify the calculator to calculate supported aquarium windows at various depths? I'm planning on having multiple windows in a steel frame below the waterline at servel different depths and I can't find good information! I know the water pressure at each depth, but not the load that the glass can take.

 

[Griller]

Further to my last:

I found a formula for calculating the weight that a piece of glass can hold and converted it for PSI to determine window size.

Formula used for glass strength:
Weight load=Strength of Glass*2*Length*thickness^2/(3*Width)
Then /4 for safety
Strength of glass = 10,000 PSI (normal glass, conservative estimate)

Do these results look acceptable to guys with experience with glass tanks???

1st window
Unsupported dimensions: 94"x 22.4"
Thickness: 12mm
This glass can bear 6264lbs when supported by a frame
Divide by 4 for safety = 1566lbs
Area of glass is 2120 cubic inches
Therefore max PSI load is 0.74 PSI
Depth at top of glass: 7.9"
Actual PSI load on glass: 0.70 PSI

2nd window
Unsupported dimensions: 94"x 14.5"
Thickness: 12mm
This glass can bear 9648lbs when supported by a frame
Divide by 4 for safety = 2412lbs
Area of glass is 1376 cubic inches
Therefore max PSI load is 1.75 PSI
Depth at top of glass: 38.2"
Actual PSI load on glass: 1.67 PSI

3rd window
Unsupported dimensions: 94"x 11.8"
Thickness: 12mm
This glass can bear 11504lbs when supported by a frame
Divide by 4 for safety = 2876lbs
Area of glass is 1116 cubic inches
Therefore max PSI load is 2.67 PSI
Depth at top of glass: 60.6"
Actual PSI load on glass: 2.44 PSI