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Restorer32

Followup to having curved glass windows made

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Some time ago I posted looking for suggestions as to who could make 4 curved glass windows for a 1918 Rauch and Lang Electric we are restoring. Despite assurances that it would be easy to have them made it turned out to be anything but. After a thorough Google search and many phone calls we found a company in Philadelphia that agreed to take on the project. Their specialty is curved architectural glass using laminated safety glass, exactly what we wanted. The process is fairly straight forward. A steel mold is made replicating the inside curve of the window. The flat glass is then mounted above the mold in a furnace and the glass and mold are heated until the glass slumps to the shape of the mold. The mold and glass are then allowed to cool in the furnace very slowly before the glass can be removed and cut to size and shape. One of the pieces we need has the same radius top and bottom so the same mold could be used to form both pieces. The other piece, because its radius is different top and bottom, required 2 molds, one for each side, right and left. Bottom line, our cost for 4 curved windows about 2' by 2'  in laminated safety glass was $4050. A lot of money but after understanding the process and touring the factory the price is justified by the amount of skill and labor required to make the molds and produce the windows with a margin of error of 1/16". Before anyone asks we thought doing them in tempered safety might be cheaper but not so. In fact we couldn't find anyone who could or would make them in tempered.

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Curved glass definitely isn't easy.  I work in the architectural glass and aluminum industry and back in the winter of 2015/2016, we had to do curved glass on a spiral staircase - not only are you dealing with the curvature of the glass, you're also dealing with the twist of the staircase.  Not fun.

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I congratulate you on having the fortitude, and money, to do it right. If anyone else is in a similar situation and doesn't want to spend the time and money,  plexiglass or lexan windows can be bent to shape and they are much cheaper.

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Maybe a guy could make a template of sorts to match the curve, then tour a good windshield warehouse and match up that template with various windshield curves.

Buy a few windshields and cut the needed pieces from them.

Could cost less than 4K.

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3 minutes ago, Rusty_OToole said:

I congratulate you on having the fortitude, and money, to do it right. If anyone else is in a similar situation and doesn't want to spend the time and money,  plexiglass or lexan windows can be bent to shape and they are much cheaper.

 

We were hired to restore the car.  It had Lexan in it when it came in.  Our client is very picky about originality though he did specify safety glass in place of the original simple plate glass. He intends to use the car at his Summer home in Normandy where electrics were the norm before WW II.  We hoped to have it at Hershey in a few weeks but it isn't going to happen. This particular electric was still on the road in NJ in 1937 as evidenced by a registration decal on the windshield.

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7 minutes ago, JACK M said:

 

Wouldn't take too much time touring windshield warehouses at our shop rate to add up to having them made from scratch.  I actually considered that approach but these windows are curved too tightly to match up to any windshield I can envision.

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On the other hand the molds now exist so if anyone else wants windows for an R&L electric they should get them a lot cheaper. Do the molds belong to you, the glass company, or the car owner?

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Good question. We actually have not yet picked up the windows so I will have to ask. Supposed to be done this week.  The molds accounted for roughly 1/2 the total cost. I still do not understand how they can heat glass to its bending temp without affecting the plastic laminate in the safety glass.

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I understand that they make 2 pieces of thin glass and laminate them together with plastic in between, squeezing the glass back and forth between rubber rollers until all air is removed and the glass is clear.

 

If you paid for the molds they should belong to you or to the car owner who paid for them. It should be spelled out in your contract.

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I would definitely check on the ownership of the molds.  They're valuable and you paid for them! 

 

And by owning them, you can potentially earn back the cost of those molds.

 

For example (assuming you have possession of the molds) you could ask the glass company what they'd charge to produce one of the curved glass windows if they had the mold.  Then, advertise the glass for sale (in the "Rauch and Lang Club Bulletin?") at the company's price per unit, and add in -- let's say -- $50 per window to partly cover your mold costs.  You could handle each transaction yourself so you get the "mold portion" of each order, and then pay the glass company to make the window using your mold. (Be sure to get a down payment up front!)

 

With any luck, a number of R & L owners would see the wisdom of buying extra windows "just in case", and --- as each window is sold --- you'll make back more and more of your mold cost.  It's gonna be a lot cheaper for a R & L owner to buy your glass than to go out and pay $2,000 for his own glass mold!

 

 

 

 

 

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A few years back I talked to an owner that had 2 Compound curved glass windows made for his car. He said the first one was $5000 the second was $500..........Bob

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3 hours ago, JACK M said:

Maybe a guy could make a template of sorts to match the curve, then tour a good windshield warehouse and match up that template with various windshield curves.

Buy a few windshields and cut the needed pieces from them.

Could cost less than 4K.

 

I saw somebody do exactly this on one of those Velocity Channel shows.  He went to a glass warehouse somewhere in California, showed the man the glass he wanted to replace (can't remember what it was for, something rare and exotic, though), and the fellow went out into the warehouse and pulled two or three donor candidates from his inventory of several thousand, and ended up cutting down a rear window from a Ford Taurus or something like that to make a perfect replacement.  Not saying it would work for a quarter window on a Rauch and Lang, but I was impressed with the whole idea of it...and the man's expertise to pull the right donor candidates by memory was impressive.

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Windshields are normally laminated by placing a thin layer of polyvinyl butyral (PVB) between the two glass sheets, placing the assembly in a vacuum bag made of high-temperature plastic film and breather sheets of non-woven material.  The bag is placed in a large autoclave where each bag is connected to a vacuum pumping port.  The air in the bag, especially between the glass and PVB layer, is removed while the glass is cold.  The autoclave is then heated to about 285 degrees F and the pressure raised to about 225 psig for 20 minutes or so, then allowed to cool.  This should produce a highly adherent assembly without bubbles.  The bag/autoclave process works on any shape glass, whereas heated rollers might not be able to cover all the surface of a complex shape.  An autoclave is typically a large cylinder, say 6-10 ft diameter x 10-20 ft long, made of heavy steel.  Be prepared to spend $500,000 or more to have one in your garage.

 

About 40 years ago, I was responsible for developing a process to dye the PVB material specific colors for filtering the light from very large TV tubes used for FAA radar displays, early computer screens, and similar applications.  The FAA tubes needed laminated glass so that an exploding/imploding tube wouldn't send the electron gun into the face of the guy staring at the tube.  It took special dyes to obtain the right colors without non-uniformity, similar to the dyes used for the dark bands at the top of windshields.  The consultant who helped most was the guy who developed the process for making Technicolor movie film.  He got very wealthy from this, had a big mansion in San Marino, CA.  I developed the basic dyeing process in my home washing machine, didn't make the (ex) wife happy. Unfortunately, I didn't get rich from this, but it sure was fun!

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