BOGIES AND SUSPENSION - South Central Railway

CHAPTER 6 – BOGIES AND SUSPENSION
WAGON MAINTENANCE MANUAL
Page 77 of 121
Axle boxes having key plate have been provided with lugs in the front and
back as well as on both the sides. The key plate is kept in position by these lugs. The
bearing brass gets suitably locked with the key plate and thus the former is prevented
from having undue movement longitudinally and transversally in relation to axle box.
It is, therefore, very important that machining of the lugs should be correctly done,
otherwise, there will be undue movement of the brass in relation to the axle box. The
front, back and side lugs are fine-finish machined. The inner top surface of the axle
box, which comes in contact with the top surface of the key plate should be fine
machined. The surface on which the faceplate sits should be rough machined. The
machining tolerance between the front and back lugs and side lugs is +1.0/ - o.5 mm.
In addition to machine tolerance, 1 mm wear is allowed on the lugs. These
dimensions should be very strictly followed at the time of manufacture as well as at
the time of POH and at the times of re-packing in sick lines.
It has been the experience that the initial machining at the time of manufacture
is not always satisfactory and, therefore, 1 to 2% of the new axle boxes should be
checked in the workshops to ensure that –
The crown inner surface has not been machined out of square.
The lugs are of equal depth and also at an equal distance from the centre
line of the axle box and
The machining of the guides is not on a taper or in other words, guide
surfaces must be parallel to each other along the full length.
In service, the inside crown of the axle box wears. It should be checked for
wear at the time of POH and re-packing. Concave wear on the inside crown should
not be permitted under any circumstances. If worn, the inside crown should be fine
machined to ensure proper flatness. The thickness of the crown may be reduced to
the extent of 2 mm by machining.
IRCA axle boxes have not been provided with key plates. On such axle boxes
instead of front & back lugs, the top inner surface have a downward projection.
These axle boxes have side lugs. The bearing brass has upward projections at the 2
ends at a distance corresponding to the downward projected portion of the axle box.
The projected portion rests on the top recess of the bearing brass. The raised portions
of the brass do not permit its movement along the centre line of axle. The side
movement is prevented by the side lugs. It is, therefore, important that the projected
portions should be machined accurately. The distance between the edges should be
correct. If it is more, it will infringe with the brass and if less, it will give excessive
movement of the brass in relation to the axle box.
a) AXLE BOX COVER PLATE (TOP AND BOTTOM)
The back opening of the axle box is covered with cover plates/plate. In IRS
boxes the cover plate is used in two half. It is known as ‘Cover plate top’ and ‘cover
plate bottom’. In IRCA axle boxes, one complete plate is used. It is secured with
axle box by welding.