In another thread I've been posting about the problems I'm having with the gl*** in my car. Here's some questions.... When I installed the safety gl***, everything was OK. When I came out the next day, the gl*** had cracked. Why didn't the gl*** break when I was installing it instead of later? Ordinary sheet gl*** doesn't behave like this, and safety gl*** is just two pieces of gl*** with a adhesive layer in the middle. Will tempered gl*** be less likely to break than safety gl***? How exactly is gl*** tempered after it is cut? Are there shops that do this? How scratch resistant is lexan? I know that plexigl*** isn't worth a **** in this regard. How many of you chop windshields with a high success rate? I've watched some videos and the process looks awfully spooky. Finally, does a waterjet work for cutting laminated gl***?
Chaz, you're probably way more knowledgeable than me but this is my 2 cents worth. No.1: never let the edge of the gl*** touch metal. Anything that touches anything but the flat portion will cause failure. I used lexan for dragster windscreens. Its good but I wouldn't want it to be in something that was used regularly and washed repeatedly. If you feel uncomfortable with gl***, that would be my next choice. I used a verticle band saw to cut it and have bent it in a break as wind wings for a deuce. The last thought is gl*** won't bend. If you straight edge the mounting area, you may find an area that needs addressing. I'm sure that the brain trust that you have in your shop will find the correct answer. Best wishes.
Let me see if I can help you with alot of those. I've chopped a 50 buick and a 50 chevy and thats the extent of my gl*** cutting experience. also ran lexan for side windows in my 50 chevy and can tell you they scratch just as bad as plexi. If/when I wash those side windows I let them air dry because microfiber will haze them pretty well. I also watched those videos you speak of and was terrified. that whole scoring and breaking thing is for the birds. Or people significantly more confident than I am. I used the sandblasting method with 80 grit aluminum oxide at around 100 psi. I used aluminum tape (like ac duct tape) to tape off the lines and just slowly cut back and forth. It worked great. took about 3 inches off the chevy windshield and 4 and a half or so off the buick. A buddy of mine came out the day after cutting curved (windshield) gl*** and it cracked in the corners. he found out later that the window was a little too tight of a fit and the temperature over night shrank the windshield opening and split it. hope that helps some.
Thank you both.... I hope to learn all I can here. I don't recall ever seeing a comprehensive thread here on auto gl***. I sure hope more folks (especially gl*** installers) chime in!
My limited experience: I chopped the compound curved w/s in my '56 Caddy convert with a cheap siphon feed sandblaster after a gl*** shop tried to cut the first one and it cracked. Made a good pattern though. Duct taped off both sides at the cut line, and just blasted through the gl***. Didn't take very long, and it didn't break. I put a Lexan w/s in the '36 (my avatar) and it's narrowed MGB w/s, because I didn't have a gl*** one to cut down. That worked fine, but after 4 years, it was pretty aggravating driving into the sun with the mul***ude of fine scratches, even though I always used micro-fiber towels to wash/wipe down. Don't pinch gl***, and as mentioned, it needs a dead flat surface rest on/against. I've cut a few pieces of flat laminate with a gl*** cutter and razor blade, but it's better, IMHO, to take it to a gl*** shop with a pattern and have the pros do it.
Federal Law says windshields must be made of Safety Gl*** and side windows can be Safety Gl*** or Tempered Gl***. I don't know of any "Plastic" that has a DOT approval for cars.
What are you working on....is it all flat gl***? or is some of it curved? pictures, or at least a few more words about what you're working on, would help folks help you. As mentioned, make sure the mounting flange is straight, so the gl*** is not stressed when it's installed.
I cut the curved windshield in my '51 using a diamond wheel in an air die grinder. I controlled the speed of the cutting wheel by varying the air pressure. I got a cracked windshield from the local windshield replacement place for free. I think that they were giggling a little about how someone actually wanted the trash. I cut that windshield into little pieces for practice. When first starting I used a lot of water for coolant and later found that only a little is needed. The hardest part was cutting the curves at the corners. That required making several p***es in order to get the cut line wide enough that the wheel didn't bind and crack the gl***. I managed to cut out my windshield on the first try. Then since it wasn't ready to install I stored it in a "safe" place. It will now make a nice template for the next one. One of these days when I am feeling ambitious I will write up a tech on the whole process; seriously it isn't magic. If I can do it with no prior gl*** experience anyone can.
Here is what we are working on, the 53 Ranchwagon had sliding windows in the rear. we welded in pieces to the channel to even everything out for the one piece gl***. It was one of these that cracked. http://www.jalopyjournal.com/forum/threads/53-ford-ranchwagon-woodie.816780/page-26#post-11826317 We also chopped the top an inch and a half which is why the questions on cutting a windshield.
I did remove the cracked gl***, and then spent two hours cleaning the silicone from the rubber gasket. After the first window cracked I immediately removed all the shims from the other window so there would be no exterior stress on the gl***. It hasn't cracked... yet. The edges of the gl*** were chamfered. Dana just posted the photo of the car up above. I'd like to say the mounting surface is perfectly flat, but I know it isn't. The gl*** is almost 6 ft in length. Education is expensive. so I'm pretty sure I'm gonna pay a lot for this one! I'll check tomorrow with a straightedge to see how true the surfaces are. They're probably close, but not perfect. That's how we roll
Naw, everything was sitting in a heated shop for days. For those of you that sandblast chopped the windshield, do you blast through the center layer too? or cut it?
I bet the long piece of gl*** has to fill a hole that is not flat. Most cars like that had an angle between the front and rear gl***, slight, but it's there. I would have left it two sections, with a division in between. Like my Suburban, which I know has the two windows at slightly different angles.
Jim,if you look at the side gl*** in my wagon you can see where it is a two piece gl*** with a division bar, the rear gl*** is fixed and the front slides. Chuck opted to do away with the slides and the inherent problems of making the gl*** work due to no one reproducing the correct rubber and slides.
Lexan is tougher than acrylic (being polycarbonate), but is easier scratched. Acrylic will craze after a few years in the sun (or months depending on where you live).If you make your side windows out of Lexan, they won't care if the channel isn't straight, square, Etc. that stuff will go around corners, literally.
This pic shows how far the slider moves....right? If the rear part of the opening was not moved out to match the "line" of the original sliding piece, then the new gl*** will not sit flat. Pretty hard to tell what was done to the car, with the pictures provided.
There was one item of bodywork yet to be completed. We really tried to ignore it, seldom spoke of it, but in the back of our heads it haunted all of us. The rear side gl*** was originally a two piece slider. (like a patio door) That left a notch in the body where the windows slid past each other. We either had to go back to the sliders, or fill the gap. Fill the gap it was...Lotta work, no fun. so we added the long taper to the bodymetal
My experience is of building gl*** rather than automotive, but: Tempered gl*** is remarkably elastic. I won't put it past some manufacturers to have devised sliding arrangements which rely on bending the gl*** slightly. Gl*** has huge thermal movement, far greater than most materials used for buildings or cars. The primary function of window frames in buildings is to accommodate thermal movement. I worked for a guy who thought window frames were irritatingly old-fashioned. On one project he asked, why not just build a 16mm sheet of laminated gl*** right into the brick masonry? I said, on his head be it. It lasted 36 hours before cracking both layers, in different places. And by then the wall was already plastered and primed. Lesson learned: give the gl*** ample space to expand in.
If the opening isn't real straight, you would probably be safer doing a urethane installation. I know its not traditional but then it will be a lot more forgiving . Also silicone sealer isn't a great sealer, not even, or especially with a rubber installation. The difficult thing with a urethane installation is doing the nice careful finish on the urethane so that it looks like a rubber finish. The really bad thing about urethane is if you get it on your hands, next thing its on the side of your nose and in your armpit, and pray you don't have to go to the bathroom suddenly,,,,cause it gets everywhere. It doesn't wash off, it wears off,eventually.
Now we've seen the beginning of the bodywork on the opening for the gl***, we can ask what the finished opening looks like, and how the gl*** is attached to the car.
Two cents from a old gl*** guy (40 years ago), carefully look at the gl*** where the break occurred and be sure that it did not touch any metal with the edge of the gl***. Also look at the edge of the gl*** to be sure that it did not have a small chip/imperfection in it as that will cause a crack if any stress is put on the gl***. I would suggest that the section of the body where the gl*** is going be cleaned very carefully, checked for being straight, Up/Down/Back Forth, the up and down can be off as long as it continues the entire length. I also use a lot of the older type ribbon to install the gl*** as it is forgiving and comes in different thicknesses. Make sure that you block the gl*** with rubber blocks on the bottom and ends so it will not move once you have it sealed against the ribbon. You can make them MAKE SURE THE GL*** IS CLEAN AND THAT YOU DO NOT TOUCH IT WITH YOUR HANDS (WHERE THE SEAL GOES). Once installed you can see the seal on the gl*** from the back side and it will be shiny where it meets the gl***. Then you can use the Urethane tube of caulking to do the detail work. Slow and easy, slow and easy. You can also use a simple U-Shaped gasket that will go all the way around the gl***, set it in the opening, making sure that you have a good fit for the gasket against the body, pull it back and put a small amount of sealer along the edge (body to gasket) and re-install the gl*** making sure the gasket touches the sealer ALL THE WAY AROUND. From looking at your pictures with the wooden blocks holding the gl*** in place you may have caused a pressure point on the edge. I would suggest a longer piece (with rubber on it) to gently hold the gl*** in place while the sealer sets up. If addition questions let me know by PM.
I had a cracked driver's window on my '55 Chevy. I obtained a replacement and took the hardware and cracked gl*** out of the door. The next thought was that it would be cheaper to have a real gl*** guy install the gl*** into the channel than trying to get another replacement. Off to the commercial gl*** folks in town I went. The shop guy took the gl*** from me and cleaned it really well He then cleaned the steel channel really well, too. He put the cork stuff along the bottom of the gl*** and set it onto the channel on his big table. He then picked up a huge leather mallet and pounded the **** out of the gl*** edge. Actually he did install the gl*** into the channel a lot faster than I'm telling the story. When I asked him what I owed him for the labor, he just laughed and said there was no charge. He also stated that the look on people's faces when he pounds the **** out of the gl*** is payment enough.
But LoneJack, your gl*** guy pounded straight down on the edge. Chaz's problem is because he had probable pressure from the side (his track is not as straight as he thought it was). Or he had a chip somewhere on the edge that he didn't notice before installation. Gl*** is strong on the flat plane, but not on the thin plane. I do think I've read that tempered gl*** is a lot more forgiving in the "bending" plane. But it's less forgiving if an edge hits some metal. It will shatter once the pressure point is too much at that single point, whereas plate or laminated will just crack in a line.
Hey Squirrel, Glad to have your input here. The gl*** sits inside a U shaped gasket. Here's a photo That gasket was set with adhesive on one side against the body opening using a sheet of Masonite to keep a straight line. Later the gl*** was inserted with silicone adhesive. So there aren't any places where the gl*** touches the steel. "Now we've seen the beginning of the bodywork on the opening for the gl***, we can ask what the finished opening looks like, and how the gl*** is attached to the car." Here's how we attached the window rubber. You can see it around the opening. We held it in place with the Masonite until the adhesive set. We then removed the masonite "gl***" and installed the real gl***.
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