Glassy chassis

Clear differences
There are pluses and minuses to using more glass on vehicles

Pluses

  • Better view

  • Feeling of roominess

  • Perception of luxury

    Minuses

  • High cost

  • Weight

  • Lack of privacy

  • At the Detroit auto show in January, Nissan will unveil a concept vehicle designed to provide enticing hints about the shape of the automaker’s next minivan, the Quest replacement due as a 2004 model.

    One of the show car’s most striking features will be its use of glass.

    “There are pros and cons,” Bruce Campbell, director of design at Nissan Design America, says of the increasing use of glass in automotive styling, “and the con list is so long. It’s expensive. It’s heavy. It’s thermally terrible. And then there are the structural aspects.

    “But the reality is, and will be, that there will be more glass.

    “The reasons have a lot to do not just with style but with how people use their cars. It stems from the inside out vs. the outside in,” he continues. “It’s not really being driven by ‘hey, big glass is cool to look at,’ but by an experience, a more commanding view that allows the driver to talk on the phone or to use a PDA (personal digital assistant) or to eat and do all those bad things they’re doing in the car, but still to have the peace of mind, the awareness of what’s going on around them, because of better outward vision.”

    Another reason for using more glass in automotive design, Campbell says, is the way it creates a sense of roominess, and that translates into a perception of luxury.

    Real luxury

    “Luxury is much more than wood grain and chrome,” he says. “It’s the atmosphere you’re in.”

    Campbell doesn’t think designers suddenly will draw cars with glass “halfway down the door.” But “there may be a more intelligent use of how we delegate where the glass area is on the car.

    For example, the minivan concept to be unveiled in Detroit does this, he says.

    “The forward part of the side glass is a little bit lower (for better visibility). To create a more protective feeling for the second-row seating, the glass might be a little bit higher. And in the third row, traditionally occupied by the smallest kids, the glass might drop back down so they can see out.”

    As Campbell notes, there are pros and cons to increased glass use in automotive design, but glass suppliers are working to reduce the con side of the ledger.

    “More glass is being used and at two or three different levels,” says Albert Faraj, business planning and marketing manager for Visteon glass operations.

    “One level has to do with the kinds of vehicles that are coming out today,” he says. “Because of the growth of the truck market, those vehicles tend to have a lot more glass going into them than your standard four-door sedan.

    “There’s also a trend toward an expansion of the vehicle greenhouse (in all vehicle styles) for a more airy environment and more visibility.”

    Another area of growth, Faraj adds, “is the movement toward more complex shaped glass. More rakish windshields or more bend in the windshield means using more glass.”

    Creating options

    Moray Callum, recently appointed manager of design for Mazda, says new glass-bending technologies create new options for designers.

    “An example would be the New Beetle,” he says, “where it uses side (window) glass with a curved plane, actually a double curvature, instead of the conventional, cylindrical, flat in plane. This allows the designer to give much more shape to the vehicle, which helps with the design and the design and the aerodynamics.”

    But doesn’t this increased use of glass add fuel-consuming weight to vehicles and create more opportunity for unwanted solar heating of the vehicle’s interior?

    “The fact that glass has gotten lighter — usually by getting thinner — means there is less of an obstacle,” Callum says. “Weight has always been a factor against glass.

    “Also, the technology in reducing sun loading through new materials and coatings has helped and, therefore, reduces the air conditioning power load.”

    Adds Visteon’s Faraj: “When it comes to the weight, there’s a competing set of tradeoffs. One is a desire for reduction in weight, and the other is a desire to increase the reduction of NVH (noise, vibration and harshness). You can thin up the glass, but one of the trends we’re seeing is the push for reduction in NVH, pushing more vehicles to use (thicker) 4.7-5.0 mm door glass.”

    Faraj says automakers have increased the use of lighter alloys for vehicle chassis and components and things such as multiplex electronic wiring to achieve weight reduction goals.

    One technique to keep glass thick yet strong is to sandwich two thin pieces around a clear vinyl layer, thus maintaining the overall thickness while using slightly less glass. That middle layer also provides insulation from noise, vibration and harshness as well as solar loading.

    “One solution,” says Nissan’s Campbell, “is to follow the lead of some of the architectural solutions: Thermal pains with inert gas between, maybe two very thin layers of glass, structurally sealed with a strong frame.”

    Not as thick

    Tom Throot, vice president for market development for automotive glass supplier AP Technoglass, says that in recent years the average thickness of automotive glass has been reduced by around 20 percent. At the same time, he says, the overall area of the car comprised of glass has increased by 10 percent to 15 percent, so there hasn’t been much weight gain.

    “There are two types of glass in vehicles,” he notes. “The windshield is laminated, two pieces of glass with an inner layer of plastic. The area of technological improvement was in the making of the glass. The glass is thinner but still has the same properties as thicker glass.

    “On the side and back windows, the technology improvements were in how the glass is shaped and tempered.”

    In tempering, he explains, the glass is cooled at different rates on its exterior and interior sides. This causes it to break into small, non-sharp pieces in the event of an impact.

    In regard to solar heating, Visteon’s Faraj notes, “most people think glass is clear, but it has a tint to it and can control the (solar) energy into the vehicle.

    “There’s a limit to what you can do, but glass coatings are coming into play, either on the glass or on the vinyl (sandwiched) in the glass, to better manage the energy into the vehicle (by absorbing it or reflecting it).”

    Glass or plastic?

    Some believe lightweight plastics or composites will replace some automotive glass. But Faraj says “there are many issues with plastic glazing: scratch-resistance, solar management, and it does not meet current government (safety) requirements.”

    Although many agree there’s a trend to increased glass in vehicles, that belief isn’t universal.

    “It depends on the vehicle,” says Mazda’s Callum.

    “In many cases, it is actually doing the opposite. The current trend in sedans and sports cars is a higher belt line, resulting in a shallower side glass.” He offers the Audi TT as an example.

    Ron Hill, retired chairman of transportation design at the Art Center College of Design in California, thinks there’s actually a movement away from larger glass areas, and he also points to the TT.

    “The Audi TT is a design icon these days,” he says, “and it certainly is a movement away from glass.

    “Designers are trying to increase vehicle efficiency, trying to reduce weight, and to reduce heat loading. I don’t see a strong movement toward an enormous amount of glass. Where you do see it is in SUVs.”

    Still, Campbell says new tinted glasses present designers with new possibilities.

    “Traditionally, most of it has been dark gray or a greenish gray,” he says, “but I can see a whole new generation of tinting that could be bold.”

    Glass supplier PPG offers a Solar Color Series that already includes blue-, gray-, green- and bronze-tinted glass that reduces solar heating, blocks ultraviolet rays and provides color to compliment a vehicle’s paint.

    Doesn’t all this complicate the designer’s task?

    “No,” says Campbell, “it adds opportunity for the designer.”

    You can reach Larry Edsall at autonews@crain.com

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