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Panoramic (wrap-around) windscreen on a 1959 Edsel Corsair.

The windscreen (English terminology) or windshield (American terminology) of an aircraft, car, bus, motorbike or tram is the front window. Modern windscreens are generally made of laminated safety glass, a type of treated glass, which consists of two (typically) curved sheets of glass with a plastic layer laminated between them for safety, and are glued into the window frame.

Motorbike windscreens are often made of high-impact acrylic plastic. As the name implies, their main function is to shield the driver from the wind, though they do not do so as totally as those of a car, whereas on sports and racing motorcycles the main function is improving the drag coefficient when the rider assumes the most aerodynamic optimal configuration of his or her body in unison with the machine and does not shield the rider from wind when sitting upright.

Contents

Usage

In daily use, windscreens mainly protect the vehicle's occupants from wind, temperature extremes, and flying debris such as dust, insects, and rocks, as well as providing an aerodynamically formed window towards the front. UV Coating may be applied to screen out harmful ultraviolet light.

Safety

Early windscreens were made of ordinary window glass, but that could lead to serious injuries in the event of a crash. A series of lawsuits led up to the development of stronger windscreens. The most notable example of this is the Pane vs. Ford case of 1917 that decided against Pane in that he was only injured through reckless driving. They were replaced with windscreens made of toughened glass and were fitted in the frame using a rubber or neoprene seal. The hardened glass shattered into many mostly harmless fragments when the windscreen broke. These windscreens, however, could shatter from a simple stone chip. In 1919, Henry Ford solved the problem of flying debris by using a new technology founded in France called glass laminating. Windscreens made using this process were actually two layers of glass with a cellulose inner layer. This inner layer held the glass together when it fractured. Between 1919 and 1929, Ford ordered the use of laminated glass on all of his vehicles.[1]

Split and raked windscreen on a 1952 DeSoto. Note the panes of glass are flat.

Modern, glued-in windscreens contribute to the vehicle's rigidity, but the main force for innovation in windscreens has historically been the need to prevent injury from sharp glass fragments. Almost all nations now require windscreens to stay in one piece even if broken, except if pierced locally by a strong force. Properly installed automobile windscreens are also essential to safety; along with the roof of the car, they provide protection to the vehicle's occupants in the case of a roll-over accident.

Other aspects

In many places, laws restrict the use of heavily tinted glass in vehicle windscreens; generally, laws specify the maximum level of tint permitted. Some vehicles have noticeably more tint in the uppermost part of the windscreen to block sunglare.

In aircraft windscreens, an electric current is applied through a conducting layer of tin(IV) oxide to generate heat to prevent icing. A similar system for automobile windscreens, introduced on Ford vehicles as "Quickclear" in Europe ("InstaClear" in North America) in the 1980s, uses very thin heating wires or conductive-film layer embedded between the two laminations.

Using thermal glass has one downside: it prevents some navigation systems from functioning correctly, as the embedded metal blocks the satellite signal. This can be resolved by using an external antenna.

Automobile windscreen displaying "spiderweb" cracking typical of laminated safety glass.

Terminology

The term windshield is used generally throughout North America. The term windscreen is the usual term in the British Isles and Australasia for all vehicles. In Japanese English, it is called "front glass". In the USA, windscreen refers to the mesh or foam screen placed over a microphone to minimize wind noise, while a windshield refers to the front window of a car. In the UK, the terms are reversed, although generally, the foam screen is referred to as a microphone shield, and not a windshield.

Today’s windscreens are a safety device just like seat belts and air bags. The installation of the auto glass is done with an automotive grade urethane designed specifically for automobiles. The adhesive creates a molecular bond between the glass and the vehicle. If the adhesive bond fails at any point on the glass it can reduce the effectiveness of the air bag and substantially compromise the structural integrity of the roof. (Raymond Clough)

Brookland aeroscreen on a 1931 Austin Seven Sports.

Auto windscreens less than 20 cm (8 inches) in height are sometimes known as aeroscreens since they only deflect the wind. The twin aeroscreen setup (often called Brooklands) was popular among older sports and modern cars in vintage style.

A wiperless windscreen is a windscreen that uses a mechanism other than wipers to remove snow and rain from the windscreen. The concept car Acura TL features a wiperless windscreen using a series of jet nozzles in the cowl to blow pressurized air onto the windscreen.

Stone chip and crack damage

Many types of stone damage can be successfully repaired. Bullseyes, cracks, starbreaks or a combination of all three, can be repaired without removing the glass, eliminating the risk of leaking or bonding problems sometimes associated with replacement.

Repair

Windscreen repair is a process that combines modern technology and skill to fill a damaged area on a windscreen with special clear adhesive resin. The resin is then cured with an ultraviolet light. When done properly, the damaged area’s strength is restored, as is most of the clarity.

When repairing a windscreen, it is important to start with a clean work area. Any dust, dirt, or contaminants in or on the glass can result in scarring or trapped particles that will permanently be visible in the final repair. Any moisture can cause future cracks when the glass cools or heats. Many chips in automotive safety glass will never grow but insurance companies in the United States often waive the deductible to ensure they do not have to pay for the replacement of the auto glass.

See also

References

  1. ^ [1] National Glass Association - "Your Windshield is Not Just a "Wind-Shield" Any More"

Manufacturing Processes Reference Guide: Robert H. Todd, Dell K. Allen, and Leo Alting How It's Made: Windshields

External links

  • Long crack repair A video of the crack repair process.
  • UNECE Reg. 43 Safety glazing material
  • BS 857:1967 Specification for safety glass for land transport
  • [2] National Glass Association
  • [3] Auto Glass Replacement Safety Standards Council
  • [4] How It's Made: Windshields
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