Cab Glazing Methods
Earth moving machines tend to be simple in cab design, especially when it comes to windscreens and their glazing methods.
However, new designs are becoming more complex from a glass point of view, but is this really for the best?
Older Machinery Cab Designs
Older type machinery cab designs tend to have simple glass shapes and basic glazing methods. In most cases the windscreens are held in by “H” style rubber gaskets (rubber seals) that sit on the body (see image below).
Glass is then inserted into the opposite end of the rubber and locked into place with with what’s know as a lock strip rubber (zip rubber).
It’s a simple method that works every time and has served us well to this point, however, it does have many limitations.
The problem with this kind of cab glazing is the rubber seals wear out in harsh Australian conditions (UV light).
Once the rubber seal is sun damaged they often leak as the seal shrinks and cracks. Worse still, the rubber gaskets no longer seal and allow dust to enter the cabins. This can be a safety issue if operators are exposed to dust particles which are harmful.
Modern Cab Glazing With High Performance Adhesives
Modern earth moving machines are favoring to larger more complex shaped glass. This in turn provides much improved visibility for operators. Windscreens are often curved, have cut out shapes and holes that allow for door latches, handles, windscreen wipers, etc.
Unlike the older flat laminated glass windscreen, these complex shapes cannot be custom cut onsite However, there are some big advantage of these newer designs.
By bonding the glass in place with adhesive provides good soundproofing through better seals.
In addition, better seals reduce dust, allowing machinery cabs to be pressurised.
Other benefits are more efficient air conditioning and from safety point, more driver protection.
Bonding the glass in place also allows for more glass type options to be installed. Old style rubber seals limit the glass thickness to 6/8mm, as they are not able to accommodate thicker glass.
In addition, the extra glass weight limits the size of the glass that can be installed securely into an H Rubber Seal.
This is why older style machinery cabs have smaller windows, rather than one or two larger ones.
However, many smaller windows do have a disadvantage as they create many blind spots.
Having larger more complex windscreen shapes like the Rosenbauer Aviation Fire Truck (see image below) does have benefits when driver visibility is a priority.
However it does make the installation process more challenging. With today’s health and safety requirements, lifting equipment such as cranes must be used to lift larger glass.
The Rosenbauer fire fighting truck is nearly 3 meters wide and 2 meter high, it can’t be safely lifted by hand.
Safety & Escaping From A Cab In An Emergency
Something often overlooked when glazing machinery cabs is operator safety. Suppose an operator is trapped in a cab and needs to escape?
A cab window installed in a rubber seal can easily be kicked out in emergency, however, bonded windows cannot. Further more, if a bonded windscreens is made from laminated glass it will be almost impossible to kick out.
This is why machinery cabs should always have at least one emergency exit window. This window should be is easy for an operator to fit through and easy to kick out.
However, a better idea would be to keep a hammer in the cab to allow an operator to escape from multiple windows in an emergency.
Unbreakable plastics also have the same risk. In an emergency plastics cannot be broken or kicked out if bonded to the cab body.
This is often overlooked by machinery owners who are looking for a cost effective solution.
Service 8® advises against plastics in most cases for this reason. In addition plastics are a fire risk.
For information about glazing methods for your machinery call Service 8® Auto Glass. We offer free advice from experienced technicians.