MAINTENANCEAUSTRALIANEARTHMOVING.COM.AU 64In past times we often connect shock or vibration
to large solid tyres working in scrap metal or waste
yards. However as earthmoving equipment evolves
to become larger, faster and more versatile the
“operating comfort factor” starts coming into play.
Risk to Earthmoving Machinery Operators.
Whole body vibration (WBV) occurs when
vibration is transmitted through the entire body
via a supporting structure. Earthmoving machinery
operators are exposed to WBV through the seat or
floor of the machinery they are operating. When it
comes to tyre and rubber track related vibrations
the effects can also cause lack of confidence in
driving and operating the equipment. Normally this
is justified as the operator can feel the diminishing
responsiveness of the unit in service when braking or
turning.
For earthmoving equipment to run smoothly it
requires transmission of contact forces between the
surface (roadway) and tyre to be achieved within
very tight tolerances. Soft surfaces can minimise the
impact of general vibrations (for pneumatic tyres)
where as a hard surface may generally increase the
vibration level.
Is it just the tread?If it never rained, we could build perfectly smooth
roads and tyres without tread design. Tyres in
contact with the road would produce a lot less noise
and fewer vibrations. However, the need for grip on
wet ground requires more open surface roads and
tyre tread patterns that drain away water to retain a
dry contact patch. Tyres are flexible objects which
are never perfectly round and which need to be
distorted to grip on road surfaces. The combination
of the tyre's distortion and road surface irregularities
produces small shocks in the contact patch, which
can make the tyre and the vehicle vibrate. When
propagated to people inside machine, these
vibrations can be most disturbing and also induce
fatigue.When it comes to load and shift and haul
applications most vibration problems are caused
by the wheels or tyres being out of tolerance in
some way. Either the wheel is bent or the tyre is
not completely and truly round (steel belts are
improperly aligned, there is hidden delamination,
damage from a pothole, etc). Basic diagnosing of
vibration issues begins by determining which of
these is actually happening, or whether some otherAUTHOR: GLEN WOLFENDENVibration
from the ground up