The modern vehicle windshield serves as more than just a transparent glass panel. It plays a critical role in both the structural integrity of the vehicle and the safety of its occupants while on the road.
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A primary function of the windshield is to act as a shield against road debris and flying objects that could strike it with force. To ensure safety, contemporary windshields are designed to be highly resistant to penetration. They are constructed with laminated safety glass, which means that even if the glass cracks, it remains intact, preventing any potential injuries to the driver and passengers.
Apart from its protective capabilities, the windshield is engineered to add strength to the entire vehicle, contributing up to 30% of its overall structural integrity. In case of a collision, the windshield plays a vital role in preventing the vehicle’s roof from collapsing or caving in. Additionally, during front-end collisions, it absorbs and distributes the impact force, offering additional protection to the occupants.
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In some cases, airbags rely on the windshield for support when they are deployed. Therefore, it is essential to have the windshield properly installed by experienced technicians to prevent it from popping out of the frame and compromising its effectiveness.
Stan Bezuidenhout from IBF Investigations, an expert with extensive experience in investigating thousands of Road Traffic Incidents, acting as a court witness, providing training, and specialising in commercial vehicle crashes, shared his insights on the disparities between car and commercial vehicle windshields.
According to Stan, ensuring safety standards is crucial for automotive windshields. Each country, including South Africa, has its own set of regulations and standards that windshields must comply with. For instance, in South Africa, windshields must meet the requirements established by the South African Bureau of Standards (SABS). Similarly, different countries have their own unique standards and testing criteria, although they often encompass similar aspects.
Some of the testing processes may involve:
- Light Stability: Windshields are exposed to various light conditions over time. To test light stability, windshields are subjected to intense UV radiation for extended periods. This simulates years of exposure to sunlight and assesses the windshield’s ability to resist fading, yellowing, or degradation.
- Impact Resistance (Ball/Dart Testing): Windshields must withstand impacts from objects like stones, debris, or hail. Ball/dart testing involves firing a steel ball or a dart at a specific velocity and weight onto the windshield. The test measures the windshield’s ability to withstand the impact without catastrophic penetration.
- Luminous Transmittance: Luminous transmittance determines how much light passes through the windshield. It is measured using a spectrophotometer, which analyses the light transmission at various wavelengths. Standards exist to ensure windshields meet legal requirements for visibility while maintaining optical clarity.
- Humidity Resistance: Windshields are exposed to varying levels of humidity. Humidity resistance tests subject windshields to high humidity and temperature conditions to evaluate their resistance to delamination, fogging, or other moisture-related issues. The windshield is inspected for any signs of distortion or degradation caused by humidity.
- Distortion and Deviation: Windshields must provide a clear and undistorted view for the driver. Testing involves analysing the windshield for any visual distortions, such as waviness, blurring, or optical anomalies which might interfere with a driver’s ability to accurately evaluate traffic risks.
While rigorous testing processes are essential for ensuring windshield safety, vehicle owners must also prioritise regular maintenance to ensure clear visibility, uphold structural integrity and enhance overall road safety. Neglecting maintenance can pose dangers to the driver and other road users.
Among the many types you might encounter, automotive windshields commonly exhibit four types of chips requiring attention and repair.
Understanding these chips is essential to prevent further damage and ensure road safety.
- A Bulls-Eye Chip derives its name from the circular shape resembling the bull’s eye on a dartboard. This chip displays a visible point of impact surrounded by concentric circles. It is crucial not to overlook a bull’s eye crack, as neglecting it allows dust and oil to seep into the crack, exacerbating the damage. Immediate attention and repair are necessary to prevent the chip from worsening and compromising the integrity of the windshield.
- A Star Chip poses particular challenges due to its potential to spread across the windshield if left unattended. This type of chip occurs when an object strikes the windshield, leaving minor cracks that branch off from the central point of impact. Prompt action is crucial to address a star chip, as it can rapidly expand and compromise the structural strength of the windshield. Failure to repair it promptly may necessitate a complete windshield replacement, leading to higher costs and potential safety hazards.
- A Half Moon Chip is another common type, resulting from a blunt impact of small debris. This chip takes on a semi-circular shape, making it relatively easier for a trained technician to clean compared to a bull’s eye chip. While it is not as intricate as some other types, it is still important to address a half-moon chip promptly to prevent it from spreading or becoming more challenging to repair. Timely attention can save costs and ensure the chip is effectively resolved.
- A Combination Chip represents a challenging amalgamation of a bull’s eye and a star chip. When a combination crack occurs, it inflicts extensive damage on the windshield, making it difficult to repair even with modern innovations. Unfortunately, complete restoration of combination cracks is not currently achievable. Thus, it is imperative to address such cracks immediately to prevent further deterioration and explore appropriate solutions with the guidance of a professional.
Promptly addressing repairable chips in windshields is crucial to prevent them from spreading and incurring higher repair costs. By doing so, it helps maintain the windshield’s structural integrity and ensures a safer driving experience. However, comparing truck and bus windshields to car windshields is not straightforward due to their different characteristics, larger size, and emergency design features like being ‘kicked out.’
These are the main differences between car and truck windshields as far as characteristics and design are concerned:
- Size and Shape: Car windshields are typically smaller and have a more compact shape compared to semi-truck and bus windshields. The larger size of semi-trucks and buses necessitates larger windshields to provide optimal visibility for the driver.
- Curvature: Car windshields often have a more pronounced curvature to enhance aerodynamics and reduce wind resistance. On the other hand, semi-truck and bus windshields tend to have a flatter design to accommodate the larger surface area required for better visibility.
- Split Windshield: Some semi-trucks and buses feature split windshields, with a vertical divider down the centre, commonly known as a “split windshield.” This design facilitates easier replacement of individual sections in case of damage, as well as improved visibility in the corners.
- Wipers and Sprayers: Due to their larger size, semi-truck and bus windshields typically have larger wipers and sprayers compared to car windshields. These vehicles require more powerful wipers to effectively clear a greater surface area during inclement weather.
- Reinforcement and Durability: Semi-truck and bus windshields are built with extra reinforcement and durability features to withstand the rigours of long-haul driving and potential impacts from debris on the road. They are typically thicker and made from laminated glass to prevent shattering upon impact.
- Installation: The application process differs between car windshields and those of semi-trucks and buses. Car windshields typically use a single-layer adhesive or sealant applied between the windshield and the frame. In contrast, semi-truck and bus windshields might require a multi-layer sealant system or their windshields might be installed only with a rubber rim to facilitate easier removal (kicking out, by a trapped driver).
While these are general differences between car, semi-truck, and bus windshields, it’s worth noting that specific designs and functionalities can vary depending on the make and model of the vehicle.
Semi-trucks and buses are constructed with stronger metal structures than regular civilian vehicles to handle longer use cycles, heavier loads, and extreme weather conditions. Due to the limited number of doors in semi-trucks, the windshield becomes a crucial escape route in case of a collision or rollover. To allow for escape, many trucks and buses are intentionally designed to facilitate extrication through the glass areas.
This design choice creates challenges for vehicle designers as permanent glass installations using specialised adhesives are not possible. As a result, they need to enhance the structural integrity of the cab or roof, which increases weight and cost. Balancing safety, practicality, financial viability and optimal design is a struggle for manufacturers.
Leading safety brands for semi-trucks and buses invest heavily in glass design, installation and practical application. The windshields of these vehicles undergo rigorous testing and continuous development due to the higher forces, weights and severity of potential collisions, emphasising the utmost importance of safety in their design.
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Picture: Supplied