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V Range 501 l 651 l 801 Maintenance Manual
MA7:8
Chapter - Remove and Refit Procedures
Page Issue B
Checking the condition of the gearbox casing
To determine whether or not a gearbox casing is serviceable
the most important aspect to check is that the rear upper
bearing bore is within tolerance. It should be remembered
that the bore need not necessarily be round, but oval,
triangulated, square, threepenny-bitted or any other shape.
Experience has shown that the bores tend to wear oval
It is important to check the bore by measuring at a number of
positions down the bore & in a number of positions at each
height, not just two positions at right angles to each other
There are different kinds of gauges for measuring the
inside cylinder or bore. A bore gauge is a popular choice
or a telescopic gauge used in conjunction with an outside
micrometer, both of these however require a degree of
familiarity or experience to obtain consistent results. A more
suitable tool for this application is a ‘segmental plug gauge’
(Johnston Part No. 437-321)
Note: This measuring tool requires periodic calibration and
should be included in your normal processes for the control
of measuring tools
The design of this particular type of plug gauge enables the
indication of taper, barrelling & out of round conditions within
upper & lower limits to be determined. This is achieved by
rocking the gauge in the bore being inspected, as described
above.
Provided all the measurements taken lie between the upper
‘maximum’ & the lower ‘minimum’ bore diameter then the bore
is deemed to be within tolerance no matter what it’s perceived
shape.
M02MA-041
Maximum diameter
Minimum diameter
M02MA-042
M02MA-043
VT - Twin Engine
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