May 9, 2019 -- Toronto, Ontario -- In 1904, the first windshields—at least as we would recognize them—began to appear on vehicles. While internal combustion engine-powered automobiles had existed for about twenty years by the time of this innovation, earlier motorists had not been terribly concerned about wind protection. Older automobiles were not able to travel quickly enough for the wind to be troublesome for drivers and passengers.
When windshields did arrive, they were, essentially, made of window panes, and thus not particularly aerodynamic. They were also constructed using untempered glass, making them prone to shattering.
History, however, has a sense of humour. It would not be too long before the construction of windshields was entirely changed as a result of one man’s misfortune. That man was the appropriately named William Pane.
In 1917, Pane sued Ford after he was injured by the shards of the windshield in his Model T Ford. While the lawsuit was eventually won by the OEM, it did raise concerns.
Manufacturers quickly changed their approach. Rather than simple window glass, OEMs began heat treating them to turn them into toughened glass. In order to prevent any shocks to send vibrations through the windshields, a rubberized seal was added between the glass and the frame.
By 1919, Ford adopted a new technology to prevent shards from causing drivers and passengers injuries—glass lamination. By adding a thin sheet of clear plastic between two layers of glass, Ford ensured its windshields would shatter into harmless chunks.
In the 1930s, many manufacturers became increasingly conscious of the streamlined designs of aeroplanes. In order to decrease wind resistance, some vehicles actually adopted a two-pane windshield, with both halves angled out towards the front of the vehicle.
With the end of World War II, techniques for making the rounded glass in aeroplane cockpits began to be used in consumer vehicles. By the mid-1950s, aerodynamically curved glass became the norm for automobiles. Glass-curving is accomplished during the toughening stage of the manufacturing process, with both layers of glass, one on top of the other, heated to the point that they sag into molds.
By the 1970s, the public became more aware of the dangers posed by bodies flying through windshields during traffic accidents, causing OEMs to invest in ways to make windshields less easily punctured. The answer was to change the plastic used between the layers of glass. Since then, polyvinyl butyral has served as the inner layer of windshield glasses.
By the early 1990s, the struggling American auto industry began to redesign their vehicles in order to make them more appealing to domestic consumers. One choice made was to increase the curvature of the glass used in vehicles. While initially seen as a response to consumer tastes, the aerodynamic benefits of these smoother shapes served to improve gas mileage.
In the 2000s, as more and more consumers became interested in gas mileage, OEMs began to incorporate more smooth glass and less metal in their vehicles.