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Opeler
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Discussion Starter · #1 ·
Ok I need some advice. My son and I are trying to complete his GT build and we put the doors all together and windows went up and down seemingly without issue. Then a couple days later the passenger window exploded just sitting there. I figured maybe that window had some stress crack or something else. Cleaned the mess up and installed another spare glass I happen to have. This time I kept all the regulator and top metal trim screws loose until the glass was installed. Then I put the window all the way down and tightened the lower screws. Put the window up and tightened the top screws. It has been fine for 4 days and this morning we go out and the window is exploded again. WTF!>>>>>

Any advice would be extremely appreciated.
 

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Be sure when installing the glass you have good nylon where it bolts in the bracket, that’s the first place I’d look. Don’t be afraid to overdo it as far as insulating the glass from the metal. Assuming you have smooth operation of the carrier to the top. Adjustment bolts are also on the bottom and top of the guide.
 

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Just Some Dude in Jersey
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I had this happen to a window also. One thing for sure DO NOT PUT THEM ON A HARD CEMENT SURFACE. ALWAYS put cardboard or something under them . I carefully removed the windows on my Red Baron car when I was fixing it up and very gently set it down on my basement floor and it detonated. Apparently they are tempered glass and can't be ground or drilled.
 

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Hopefully the car is locked up in a garage and not in the open where some bozo can smash them.
 

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Opeler
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Discussion Starter · #6 ·
Hopefully the car is locked up in a garage and not in the open where some bozo can smash them.
Both times car was in the garage. First time we were there when it detonated. Second time was overnight in the garage.

So these windows didn't have the round nylon washers like the later years but have the metal sleeve that fits over the window prior to it installing in the regulator. Could it be that metal sleeve is causing too much tension?
 

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Just Some Dude in Jersey
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Absolutely! The nylon washers/bushings are essential to be in place. There's also some sort of tape or paper inside the metal sleeve as an added buffer between the glass and the steel. Basically, you don't want hard contact between any part of the metal sleeve AND THE BOLTS with the glass. I have used masking tape to replace the paper-in-the-metal-sleeve. Make sure that you have the nylon washers at both holes and both sides of the glass.
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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I have removed the windows more times than I care to remember and have never had an issue. Mine is a 70 model but pretty sure I replaced at least one of the pieces of glass way back when due to scratches. One of the windows had larger holes and I was able to find grommets that fit and the other window the hold are the same size as the bolts. Both of the windows have the plate/holder that the window sits in and then attaches to the slide unit. I have always been careful not to over tighten them with the thought it could lead to breakage and the possibility of them coming loose seems somewhat remote. If your windows roll up and down without effort I can think of nothing else other than over tightening the screws that hold it on the slide unit. But seems odd the destruction did not happen right away during the tightening process or later perhaps when you hit a big bump when out for a drive. Gremlins perhaps?? Good luck on the third window.
 

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The same thing happened to me once. I found a small chip of the original broken side window lodged in the window track. I surmised that the chip was jammed against the new glass, and with sufficient force, it cause the 2nd window to break. Might be something else, but worth checking the door tracks very carefully
 

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Just Some Dude in Jersey
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When I was looking into shortening the window glass on the gullwing car, so that they could roll all the way down, I was told that they are tempered glass and you can't drill or cut them in any way, or they will self destruct. They appear to be a different form of glass than what the windshields are made of, which often CAN be ground.
 

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Tempered glass is extremely strong but very weak at edges, including the edges of holes. I restore pinball machines that use tempered glass. In a machine you can beat on it and it won't break, but when removed with the edge exposed a tiny tink on the edge will result in a spectacular explosion.
 

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1970 Opel Gt - Purchased July 1972 - Chartreuse - restored - 3000 miles as of 02-16, 2021 -
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I also like Keith's idea that something in the track, that is the small metal track with the two holes, could in conjunction with tightening certainly cause a break. Still seems odd that it did not happen while tightening. There could even be a small dimple/ manufacturing defect, on the inside of the metal track with the two holes that is responsible acting as a sharp point that contacts the glass first and bingo, that would certainly do it. So perhaps a foreign body or a defect in the metal track. Another mystery and as we all know this forum collectively solves all mysteries, eventually.
 

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The tempering in tempered glass has to do with the way the glass is cooled. The outside is cooled first, and the inside is then restrained from expanding like it wants to. This tension in the glass is what gives it its strength.

But it also means that if anything breaks that outside edge, the thing that holds the tension in place will become untense, and allow all that energy mechanically stored (like of like a spring made out of crystal) to escape, causing the instant shattering of the entire piece. It doesn't matter how slowly you do this or how carefully. Even if you gradually tried to abrade the edge away over a week, at some point, it stops holding the tension and the whole thing explodes.

I have scored 3/16" glass with a glass cutter, suspended it between two cinderblocks, and jumped on it, and it taken my full bodyweight and it deflecting an inch multiple times to shatter. It's super tough.

Glass fractures generally happen at one temperature, and then damage is done, but hidden until the temperature changes. This pushes or pulls on the fracture which causes it to rip apart. This is like how you can cut glass with a hot string, and then put the glass under cold water. It shatters along wherever the string was.

It's hard to say what caused this glass to fracture, could've been some damage it picked up years ago. But, my guess is the lack of nylon. Anything hard that could cause a pinpoint pressure is all it takes.

Windshields are laminated with plastic, but they're not tempered. If they were tempered, the first stone chip would make the windshield explode like the passenger windows. The plastic would still stop the pieces from flaking off, but, it would be fully cracked.
 

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Just Some Dude in Jersey
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The tempering in tempered glass has to do with the way the glass is cooled. The outside is cooled first, and the inside is then restrained from expanding like it wants to. This tension in the glass is what gives it its strength.

But it also means that if anything breaks that outside edge, the thing that holds the tension in place will become untense, and allow all that energy mechanically stored (like of like a spring made out of crystal) to escape, causing the instant shattering of the entire piece. It doesn't matter how slowly you do this or how carefully. Even if you gradually tried to abrade the edge away over a week, at some point, it stops holding the tension and the whole thing explodes.

I have scored 3/16" glass with a glass cutter, suspended it between two cinderblocks, and jumped on it, and it taken my full bodyweight and it deflecting an inch multiple times to shatter. It's super tough.

Glass fractures generally happen at one temperature, and then damage is done, but hidden until the temperature changes. This pushes or pulls on the fracture which causes it to rip apart. This is like how you can cut glass with a hot string, and then put the glass under cold water. It shatters along wherever the string was.

It's hard to say what caused this glass to fracture, could've been some damage it picked up years ago. But, my guess is the lack of nylon. Anything hard that could cause a pinpoint pressure is all it takes.

Windshields are laminated with plastic, but they're not tempered. If they were tempered, the first stone chip would make the windshield explode like the passenger windows. The plastic would still stop the pieces from flaking off, but, it would be fully cracked.

Prince Rupert's Drops
These scientific curiousities demonstrate Matt's point:

 

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Ok I need some advice. My son and I are trying to complete his GT build and we put the doors all together and windows went up and down seemingly without issue. Then a couple days later the passenger window exploded just sitting there. I figured maybe that window had some stress crack or something else. Cleaned the mess up and installed another spare glass I happen to have. This time I kept all the regulator and top metal trim screws loose until the glass was installed. Then I put the window all the way down and tightened the lower screws. Put the window up and tightened the top screws. It has been fine for 4 days and this morning we go out and the window is exploded again. WTF!>>>>>

Any advice would be extremely appreciated.
 

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Ok I need some advice. My son and I are trying to complete his GT build and we put the doors all together and windows went up and down seemingly without issue. Then a couple days later the passenger window exploded just sitting there. I figured maybe that window had some stress crack or something else. Cleaned the mess up and installed another spare glass I happen to have. This time I kept all the regulator and top metal trim screws loose until the glass was installed. Then I put the window all the way down and tightened the lower screws. Put the window up and tightened the top screws. It has been fine for 4 days and this morning we go out and the window is exploded again. WTF!>>>>>

Any advice would be extremely appreciated.
You must use the insulators (nylon washers with extended centers) AND either heavy masking tape or heavy duct tape on the metal parts so no metal is touching the glass. If the nylon washers no longer have the extended centers (which go INTO the bolt holes on the glass) you will need to get new ones. Finally do not over tighten the bolts holding the glass onto the metal bracket. If you have an outside mirror, you need to verify the bolts holding the mirror are not touching the glass and allowing enough room to not touch the glass from normal movement while driving. If either the bolt holding the mirror on or the bolt holding the window onto the guide rail comes into contact with the glass it can shatter. You also need to verify that there is -0- ceramic pieces such as a broken spark plug, some blasting media, some grinding media anywhere on your felt window track. Even ceramic dust on the window track can shatter tempered glass if it comes in contact with the edge or impacts with the surface of the glass. Some sanding disk, and grinding disk use ceramic particles as the abrasive. Most likely the bolts at the bottom are your culprit, during temperature changes thru the night the metal is expanding or contracting and causing the breakage. (too tight)
 

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Opeler
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Discussion Starter · #19 ·
Thanks everyone. We did take the window track out and thoroughly clean it as well as the metal frame that holds the rubber track. I did find a couple of small metal burs inside the metal track and knocked those down with a small chisel. I doubt those were the factor as they were probably there since the car was new. Replaced the older style metal window sleeve with good plastic washers with the extended centers and reassembled. Did not overtighten and made sure there was no pinching of the glass up and down the channel by moving it by hand several times. Also made sure no screws or otherwise interfered with the glass. It's been several days and no detonation! Hope this is good to go now.
 
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