There
are three organisations which lay down stability standards
for fork lift trucks. In the UK we have the British Industrial
Truck Association affectionately known as BITA. The European
standards are promoted by FEM and the Japanese standards are
maintained by JIVA. The capacity plate on the truck will mention
one of these standards although they all use the same criteria!!
There are four tests all of which involve
placing the truck on a tilting platform but two of these are
designed to test tipover at speed and are therefore dependant
upon the trucks top speed. Only the two tests which do not
rely on speed are described on this site. They are numbers
one and three.
No 1 longitudinal stability testing
 As
mentioned, the truck is placed on a steel platform which can
be tilted by means of hydraulic rams. The test states that
the truck must have its full capacity load and it is normal
to chain it to the forks and carriage in case things go wrong!
The truck is placed with its drive, (front),
axle parallel to the hinge of the tilting platform and the
mast is elevated to maximum height. It is this last point
that makes the test a bit dramatic as it greatly increases
the truck's load centre as can be seen in the drawing on the
left.
The actual truck's load centre is defined
as the dimension measured from the front face of the forks
to the centre of gravity of the load and is usually either
500 mm (20"), or 600 mm (24"). The tilt that can
be seen here does not actually alter the load centre in the
sense that the load cannot move away from the forks as it
is secured. The big problem is that the artificial tilt created
in this test gives the same results as if the actual load
centre were moved. This is compounded by the fact that the
mast is fully elevated.
If the truck attains this angle without tipping
it is deemed to have passed the test. If you are an operator
reading this, think about it the next time you hear someone
telling you that you have a large safety factor of stability
built in to your truck- YOU DON'T !!
Trucks are also tested for sideways stability
and a description of this test is
here>>
|
