A refuse collection vehicle manufacturer makes novel use of an adhesive
to overcome a problem involving the attachment of sensors to vehicle
chassis
Isle of Anglesey based Faun Municipal Vehicles manufactures a wide range
of street cleaning and refuse collection vehicles. This latter category
includes rear, front, side and front-side loaders - around fourteen
different types to meet the varying demands of local authorities and
other users. In many cases, those demands include a requirement to
measure the vehicle load.
It is important that vehicles are not loaded to beyond their designated
carrying capacity, explains Faun's engineering manager, Paul Godridge.
If a truck is intended to carry, say, 26 tonnes, it is important that
the driver knows when that limit is being reached. If the load exceeds
the designated weight the vehicle can become unsafe and that would result
in a costly fine being imposed. In addition, a number of councils are
now charging by the kilogram to dispose of waste, so an accurate weighing
mechanism must be built into the vehicle's design.
To meet these requirements, some four to eight sensors are strategically
placed around the chassis to take these measurements. Their correct
placement is important because during waste collection the load moves
inside the body. The load information from the sensors is subsequently
displayed inside the cab, enabling the operator to determine whether or
not it is within determined levels. An on-board computer also instructs
the compactor to stop working as capacity is achieved.
The sensors are attached to the vehicle chassis with bolts, but as the
latter is not completely flat at these points, a gap may exist between
the two surfaces - a space that needs to be filled if the sensors are to
function accurately. Faun was already using Loctite products -
particularly threadlockers - on its vehicles, so it seemed natural enough
to see if the company had a product to help solve the problem. Henkel
Loctite sales engineer, David Spence takes up the story.
The answer came in the form of Loctite Hysol 3471, a two part epoxy
adhesive which is normally used for repairing and rebuilding worn metal
parts. However, in this case, the product was able to fill a gap of up to
5mm between the two steel substrates. The types of environment in which
the epoxy has to operate are often exceptional. It has to cope with all
kinds of weather - not just in the UK, but also in more extreme
conditions of mainland Europe. Then there are difficult road conditions
and, of course, the high compression load due to waste payloads.
Loctite Hysol 3471 is a steel putty with a high compression strength of
70N/mm2, very low shrinkage on cure and is easy to apply. The surface is
first prepared with a soft disc hand grinder and the adhesive is then
manually mixed and applied to the bottom of the sub-frame. A plastic
membrane is placed over the epoxy to prevent it from adhering to the top
of the chassis. We put the assembly through many trials to ensure it
would do the job, says Paul Godridge. We were convinced this was the
answer to our problem and, indeed, Loctite's solution has proved to be a
great success.
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