Thwaites SPRITE NIMBUS, Manual

Page: 46 / 54

EXAMINE AND CHECK FOR WEAR
The parts most likely to show signs of wear after long usage are bearing races and
spider journals. Should looseness in the fit of these parts load markings or distortion
be observed, they should be renewed complete as a unit, i.e. because worn needle
bearings used with a new spider journal, or new needle bearings used with a worn
spider journal, will wear more rapidly, making another replacement necessary in a
short time.
It is essential that bearing races are a light drive fit in the yoke trunnion.
In the rare event of wear having taken place in the yoke cross holes, the holes will
most certainly be oval, and the yokes must be removed.
In the case of wear of the cross holes in a fixed yoke, which is part of the tubular
shaft, yoke and tube or yoke and shaft assembly, only in cases of emergency should
these be replaced in the field. They should normally be replaced by a complete
assembly.
The other parts likely to show signs of wear are the splined sleeve yoke, or splined
stub. A total of .004" circumferential movement, measured on the outside diameter
of the splined, should not be exceeded. Should the splined stub shaft require
renewing, this must be dealt with in the same way as the fixed yoke, i.e. a
replacement tubular shaft assembly fitted.
RE-ASSEMBLY
Insert journal in yoke holes and using a soft round drift with flat face about 1/32"
smaller in diameter than the hole in the yoke, tap the bearing into position. Repeat
this operation for the other three bearings. Replace snap rings or bearing caps,
bearing cap screws, locking plate and split pins as fitted. With the bearing cap type
make sure that bearing races are replaced with the slot in the top of the race in line
with the bearing cap screw holes, so that they are prevented from rotating by the
key in the bearing cap. If joint appears to bind, tap lightly with a wooden mallet,
which will relieve any pressure of the bearings on the end of the journal. When
replacing a sliding joint on shaft, be sure that trunnions in sliding and fixed yoke are
in line.
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