ELECTRICAL EQUIPMENT—Q.16
(b) DRIVE END BEARING
1.
Press out the old bearing bush from the inside of
the end-shield.
2.
Press in new bush taking care to keep the
lubricating wick away from the bore by using a
split dolly. Finally set up the end-shield on a
lathe and turn the bore using a spigot diameter
as a register, to 1.126—1.137 in (28.6—28,62
mm).
PINION
If the pinion teeth are badly worn, obtain a
replacement and offer this up to the shaft to ensure
freedom of movement. Should it be necessary they can
be lightly lapped together.
SOLENOID AND OPERATING MECHANISMS
Examine all moving parts for wear. Inspect the
electrical leads for chafing and impaired insulation.
Examine the springs for possible fracture and replace
as necessary. After any removal, the spring pressures
should be checked before re-assembly In accordance
with the following:-e
Ball-lock spring (18) (Fig Q.9)—11 lbf/in (1,97
kgf/cm)
Pinion return spring (4) — 8.6 lbf/in (1.54
kgf/cm)
Main contact (plunger) spring (14) 91/2 — 12 lbf
(4,31—5,44 kgf) when compressed to 3/16 in
(4,76 mm).
Contact return spring (42) 6—7 lbf (2,72— 3,18
kgf) when compressed to 1/4 in (6,35 mm).
CONTACTS
Examine the "fixed " and "moving " contacts, and clean
them with spirit or very fine carborundum paper.
If the contacts are badly burnt and pitted, they should
be replaced. As replacements are not supplied ready
machined, it will be necessary to face them when in
position.
It is essential, when facing the "fixed" contacts, that
they are kept to the angle shown in Fig. Q.12.
Fig. Q.12.
This can most easily he done by placing a 1/16 in (1,6
mm) shim behind the end-plate and the faceplate on the
lathe. This will provide the required 2 angle.
Make sure that the shim is placed on the correct side.
Alternatively, if a number of refacing operations are
likely to be dealt with, a suitable face-plate can be made
up for attaching to the lathe. This should have one side
machined to the 2 angle, as shown in Fig. Q.13. The
end-plate of the solenoid can then be secured to it, and
the contacts skimmed.
In facing the "moving" contacts, it is essential to keep
to a dimension within the limits 0.250 in to 0.247 in (6,35
to 6,27 mm), between the rear side of the back-plate and
the contact face.
