sagulator for glass?

Ok, I know that glass doesn't sag (perceptibly), but does anyone have a source for a load/span calculator for glass?
tia,
jc
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May want to check the Corning Glass web site http://www.corning.com/index.aspx as one possibility
Bob S.
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Tell that to the guys who build big telescopes.
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Joe wrote:

http://www.woodbin.com/calcs/sagulator.htm
Choose glass from the materials list.
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Again, pretty neat software. Thanks. It is in my bookmarks.
Only concern is it provides sag but not breaking strength. I have used 1/4" glass panels for some 16"x12" curio cabinet shelves but no weight to speak of. I also built a small A/V cabinet years ago that had 16" x 20" 1/4" glass shelves holding some pretty beefy stereo amps and tuners (20 pounds+); but load points were cloe to the ends of the shelfs. In both cases, I talked to the local glass shop and they gave me size and strength guidance.
RonB
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RonB wrote:

IIRC, They do give you a "target sag" recommendation, which anything over you would think would be bordering on failure for glass, which is better than nothing. But it is the closest thing I could find that answers Joe's question, if only partially.
I let my glass guy make the recommendation when I give him the shelf template, or the dimensions I need and specify the use ... and most of the time I end up with tempered glass in 1/4" thickness for china cabinet shelf use.
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Geez, Swing. I even *went* there! I just scrolled down the the G's, didn't see it and stopped.
Not feeling particularly smart at the moment.
jc
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Go all the way to the bottom of the list. Tom
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tom wrote:

Here's a South African glass industry standard http://www.aaamsa.co.za/images/Technical%20Publications/SAGGA/Selection%20Guide%20for%20Glass%20in%20Furniture%20New.pdf or http://tinyurl.com/yzpmlpz . Note that it is metric.
Just for hohos I ran a 1x1 meter by 4mm piece of glass through the sagulator with the standard's maximum recommended 17kg/square meter load and it came up with .068 in/ft sag, so if you go by the .02 recommendation that the sagulator uses you may be safe, but I'd check both the sagulator and the standard to make sure that it will both hold the load and not sag--glass doesn't usually warn you before it lets go.
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Most glass is a liquid and sags. In an old house you may see the bottom of the windowpane is thicker than the top portion. Quartz glass is a solid--probably less sag over time and transmits more lightwaves than regular glass.
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I believed that for a long time until it was pointed out to me that there are intact glass windows in Roman and Egyptian buildings which would belie the flowing glass myth. If the glass sagged enough to be noticeable in a two hundred year old house, the sag in two or four thousand year old glass would be very noticeable, and it's simply not.
http://www.glassnotes.com/WindowPanes.html
http://dwb4.unl.edu/Chem/CHEM869A/CHEM869ALinks/www.ualberta.ca/~bderksen/florin.html
R
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RicodJour wrote:

http://dwb4.unl.edu/Chem/CHEM869A/CHEM869ALinks/www.ualberta.ca/~bderksen/florin.html
I've seen lots of old, wavy glass - new wavy glass too, especially in China - but have always attributed that to lousy glass making. Never seen any thicker at the bottom though.
There appears to be no argument about glass being an amorphous (non-crystalline) material. When I was a geology student more than 50 years ago we were taught that there is no such thing as glass beyond a certain age (some multi-millions of years) because it ultimately crystallizes. Now, humans haven't been making glass long enough for it to crystallize but there are naturally occuring glasses - obsidian, for example - and it was/is those that were not found beyond a certain period in the past.
OTOH, the profs all po-pooed poor old Alfred Wegener and his silly continental drift idea :)
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dadiOH
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On Thu, 10 Dec 2009 06:56:35 -0800 (PST), the infamous RicodJour

I scratched the windows in the new door I put in the utility room 7 years ago. It's a halflite and the scratch was right next to the door knob. I was taking the label off with a scraper. Fingernails, water, soap, and several chemical solvents proved that it wasn't just glue, it was a scratch, and I fumed for weeks about it.
A few months later, I was cleaning that window and couldn't find the scratch. To this day, there is no scratch on that lite. This leads me to finally believe in that "liquid glass" thang, KWIM,V?
-- To know what you prefer instead of humbly saying Amen to what the world tells you you ought to prefer, is to have kept your soul alive. -- Robert Louis Stevenson
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Phisherman wrote: ...

This is commonly heard but...
Corning Museum of Glass Research Scientist's discussion is at-- <http://www.cmog.org/dynamic.aspx?id )4>
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dpb wrote:

Probably because public school "science" teachers are taught it and pass it along and while kids don't get anything _useful_ out of those "science" classes they do get the notion that glass is not a solid. I recognized that as bullshit the first time I heard it--the teacher gave a definition of "solid" which glass met in every particular and then said "glass is not a solid", but could not explain why it was not a solid and could not explain what it was other than "glass" like "glass" is some fifth state of matter.
The notion that it's not solid is really a philosophical debate about the definition of "solid" and has little do to with the realities of structural design.

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glass is amazingly flexible in long pieces. watch them unload 12'x4'x1/2" glass sheets from the case sometimes. they'll flex back and forth by multiple inches. i have some double pane windows in my house that are 10'x6' of normal strength 1/8" glass, and i can press in the middle of the pane to see the sheet flex.
regards, charlie http://glassartists.org/ChaniArts
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Fair warning -- that's going to be a _complex_ issue. There are many, *many* moree varieties of 'glass' than there of 'wood'. And they _all_ have different characteristics.
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wrote:

but for shelving purposes, almost all float is interchangable.
regards, charlie http://glassartists.org/ChaniArts
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Slightly OT, but of interest, I bet:
Long, long ago in this NG, there was a discussion about where to locate lifting straps to hoist a flat panel. It was one of the better discussions I can recall, and brought out some of the best of the engineering types from even other NGs to get an answer. I even passed along the discussion to a nephew, who worked for a concrete panel company. What I remember most was to "lift on the 5ths." In other words, you divided the panel (or shelf or retaining wall etc) into 5 parts, using 4 lines and then support it at the first points in from the end. It assumes that the panel is of uniform thickness and strength. It's counterintuitive in many respects, but recognizes that the interior sections lend some mutual support and also the outer panels "lift" as they pivot around the point of attachment.
I assume that this would also apply to an UNLOADED glass, wood or shelf of other material. Of course, with an uneven distribution of load, such as a big weight in the center, this might not be correct.
YMMV and also this is based upon my poor, addled brain thinking back many years.
--
Nonny

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lovin' the sig line.
jc
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