Spring 2021

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Darryl Nanka, Director of Maintenance, Payne Transportation Ltd.

Having to write these articles four times a year presents certain challenges. What is a good topic to cover? Is it relevant? Fun? Or might something be mentioned the reader hasn’t seen for quite some time? For our purposes I decided to go with something that was right in front of me, staring me right in the face in fact: windshields. What do you know about your commercial vehicle’s glass?

Windshield Manufacturing

As most things on your commercial truck, the windshield is technologically advanced. It may look simple but is made to extremely high OEM standards with precise measurements and tolerances. The typical windshield is two layers of glass adhered to a vinyl middle layer. The windshield, before it becomes the specialty item it is, is made from several ingredients. Fine silica sand, soda ash, dolomite, cullet, and limestone are used in formulations. Additional materials such as potassium oxide and aluminum oxide can be used. Silica, however, is the main component, taking up as much as 70% of the formula. Some of these substances will lower the melting point of the mixture, make the glass more pliable, easier to shape and work with. Durability is also key so that is always taken into consideration by windshield manufacturers for safety and longevity.

Once blended with water and heated to extremely high temperatures, the mixture fuses and becomes a single entity – the glass. Several steps are involved that use float chambers, sheets of molten tin, and treatment chambers to allow annealing. Bet you’ve never heard of that! It means to allow the glass to cool gradually, which allows it to strengthen and remove any internal stresses. This process is truly a craft involving very sophisticated machinery.

Depending on processes used, the glass will be kept warm and placed in a cast where it will take on the shape an OEM wants. Once the shape is achieved, the infant windshield will be cooled with jets of air, which tempers the glass and subsequently strengthens and hardens. Then comes the lamination stage where two pieces of glass are placed on either side of something called poly-vinyl butyral (PVB). An autoclave heats each component and are pressed between rollers. This is called the “see-through” stage as all the layers become a single mass of “vehicle safety glass.” As technology grows this is the point where sensor and other goodies are added into the glass. Volvo, as an example, are leading innovators and we’ll touch base with that soon enough.

General Purposes of a Windshield

Besides the obvious – being a barrier between the driver and elements – a windshield provides structural support for the cab body. In the event of a rollover event, the windshield provides strength to the cab frame and can help prevent roof crush. Preventing ejection from a vehicle in an accident is another purpose a windshield serves; however, I’d recommend wearing a seatbelt.

Ever notice that a windshield will crack and not split into thousands of tiny pieces, and side windows will? This is due to that PVB layer. In the event of an accident where a driver is facing forward, the windshield will not break into pieces causing injury. Side and rear windows are made of tempered glass. These windows are heated to over 1,000 degrees F° and rapidly cooled. This makes side and rear glass comparatively stronger than untampered and, if broken, is made to fragment into small pieces about the size of aquarium gravel. This is a safety feature whereby a driver will not be cut by large shards of glass with a jagged edge. It also allows first responders, if needed, to break the glass and reduce the chance of injury to a cab occupant.

Basic Windshield Care

Like anything else, you need to care for your vehicle glass. Make every attempt to keep your windshield free of debris. Your wiper/washer system should be checked often for fluid level. As well, worn or torn wipers, depending on the degree of degradation, can potentially scratch the windshield you look through. Dry wiping can also prematurely scratch or etch your glass. This is when sand or other debris collect on a windshield and are wiped away without the help of washer fluid. During most basic PM inspections, take note of your wiper spray pattern to make sure the parts of your windshield that need to be cleaned are taken care of evenly by your wiper sweeps.

Glass, as it gets older and is continuously exposed to the elements, may become pitted and (in certain situations) throw a glare to the driver inside the cab. This is called “sandblasting” and can literally blind a driver, for example, in a situation where they are headed toward the sun while driving on a roadway.

Windshields can discolor over time so keep a particular eye on the driver’s field of view. Of particular concern are stone chips and cracks which can easily take a windshield out of service (see criteria later in this article). Chips can be dealt with before they become cracks, but this must be done as soon as possible and before any contaminates affect the distorted area. Furthermore, is has been proved through controlled experiments that any distortion on a windshield can increase reaction time for a driver in an emergency. This, in turn, can become deadly.

What Does the CCMTA NSC Standard 11
Have to Say About Windshields?

Windshields, like anything else on a commercial vehicle, are subject to inspection and failure criteria as just mentioned.

A good technician will be familiar with what fails a windshield. Taken directly from the standard, the criteria given below and is worth a read. The section that deals with windshield safety criteria is found under Periodic Commercial Motor Vehicle Inspections (PMVI) Section 8 – Body, Subsection 13 A-G. Further information regarding side glass and passenger buses can be found in other Sections of the vehicle standard.

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The Driver/Windshield Relationship

Since the onset of the automobile, researchers have been involved in making vehicle better and safer. This is no different for the commercial vehicle. Due to the profession itself, long hours behind the wheel affect a driver differently than the casual commuter. Some commercial vehicles have dashboards that resemble an airplane. There is a lot going on for the professional driver to handle.

It may not be an obvious circumstance but there is a human-machine relationship when it comes to the operation of a motor vehicle. If a driver is looking out toward the highway, they are periodically looking down at gauges and in their rear facing mirrors. For hours on end, our commercial drivers are maintaining control of their vehicles and the cargo they are pulling. Their field of view, both forward and back, are remarkably different than the average car driver.

Therefore, a great deal of effort has been put into the environment of the professional truck driver. Cab ergonomics and technological innovation are primary considerations when building a commercial vehicle. Did you know that the head’s up display (HUD) has been around for some time in passenger cars? Some believed it would be impossible to adapt these displays for the commercial industry. The challenges of HUDs for the commercial industry come in the form of different angles for the drivers, cab vibration and the overall increase of abuse the commercial vehicle takes. Physical location of the driver, the field of view and the overall size of a commercial vehicle’s windshield created problems to overcome.

And what exactly should a HUD give a driver? We are in an age of information overload. We already know what the commercial truck driver needs to pay attention to: their truck, trailer, other drivers, roadways, road hazards and weather. To inundate a driver with even more information on a head’s up display may not be the safest avenue to employ. This may distract a driver; not good.

Volvo trucks can be considered the industry leader in HUD display technology. Their research is focused on developing HUD information strategy. Without being too complicated, this involves providing a driver critical information and when this information should be given. Their goal is to support and not distract a driver. For example, the information given to a driver on a busy city street would be different on an open interstate highway. There are so many considerations to evaluate.

Not only is the HUD something to use, it must interact with the way one behaves. Research includes how a driver is distracted, what causes one to focus on one thing and not something else in a variety of everyday situations. An excellent read can be found here: https://insight.shrp2nds.us/documents/shrp2_background.pdf.

This involves the SHRP2 study, where Volvo has been involved in the data analysis of 3,000 years of driving data. No doubt Volvo takes this seriously and we can be sure that in the years to come, technological advancements in driving technology will transform the commercial driving experience. As always, what is learned in one area of the driving experience will overflow to other industries, such as construction or passenger bus travel, and who knows where else or how far we will come to see things?

One snippet from Volvo involving their HUD technology is worth printing:

            “[Our head’s up] display projects a warning signal onto the windshield, instantly alerting drivers to critical messaging without taking their eyes off the road. Volvo Enhanced Cruise uses heads up display to warn if the truck is too close to the vehicle in front of it – and will de-throttle the engine and actively brake to help prevent a collision.”

And from Continental, another industry innovator:

            “The head-up display makes a significant contribution to road safety. The driver can monitor events without getting tired because his eyes don’t have to continually switch back and forth between long-distance and short-range focusing. The HUD keeps him up-to-date about what’s happening in his vicinity, providing him with information like distance from the vehicle ahead, a traffic jam or sudden weather events like heavy rainfall,” explains Dr. Michael Ruf, Head of Business Unit Commercial Vehicles and Aftermarket. “The HUD is also an important technology in terms of the progressive automation of driving, because in its role as a human-machine interface, it can ideally provide the driver with information about the current automation mode. The driver must believe in the efficiency and performance of the machine and getting this information boosts his confidence.”

It is indeed an exciting age in trucking. While we may hearken back to a simpler time where trucking was raw and brute, we must constantly look ahead (at and through our windshields) at what trucking can be. Innovative, technologically driven, and safer than ever.


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