Many vehicle manufacturers and their engineering departments are often frustrated and challenged when it comes to translating values for shear peel and tensile forces provided by technical data sheets into what this really means for them when designing and manufacturing vehicles.
There are many test standards and engineering norms which are applicable to the automotive industry but few of these directly relate to the manufacture of buses coaches trains and trams. Type approval for whole vehicles was an attempt to rectify this but it only broadly covers the real needs that exist. For adhesives it is common for manufacturers to state drive away times and windscreen glazing air bag requirements but these are not applicable and transferable for bus and coach glazing.
The weight, size and angles of bonding are so different in bus manufacture approval is often obtained by testing once the vehicles are completed and full durability track tested. Joint design and bondline thickness play a major part in successfully bonding any construction but it is critical in glazing due to the flexibility required and the rigidity of glass windows.
A major UK bus manufacturer was approached by an operator who had recently ordered over 100 double deck buses which were a lot larger than previous models and they wanted maximise passenger numbers and achieve a modern look. Direct bonding glass was the only option for them. The ongoing security and
safety of window glazing was of paramount importance to them and so we were approached to come up with a method whereby each window
could be periodically checked and signed off as secure.
We manufactured an aluminium bridge frame that would span the distance from the cant roof rail to the vertical side frame pillar and secured the Formoa® portable test pulling system complete with electronic gauge and Bluetooth phone connection to record the values obtained. A heavy duty vacuum suction cup was secured to the glass window and this was coupled to the pulling device. A force of over 2000Kgs was applied to the window.
This has now become a standard periodic test for the customer to assure them that all windows are secure.
Case Study | Glazing Test