Sunbeam ALPINE I SERIES: APLINE II SERIES, Workshop Manual

Page: 237 / 413

3rd re-issue
Page 10
WSM.12,f
Section H (Rear Suspension)
SHOCK ABSORBERS
RAPIER
Girling Direct-Acting Telescopic Dampers are
titted.
The body of the shock absorber is telescopic and
is mounted more or less vertically between the
spring pad brackets and the body. It is therefore
direct-acting, no links or levers being required.
Servlcin1
These units are completely sealed, no topping
up, adjustment, or other service is required apart
from periodical checks of mountings and rubber
bushes, which can be carried out without the aid of
special tools.
In the event of the shock absorbers requiring
attention, it is strongly recommended that the
faulty unit should be removed and a replacement
shock absorber fitted.
Construction
The assembly can be divided into two main moving
parts, the upper one consisting of the piston
rod with the piston attached to Its lower end and
the outer tubular shroud attached at the top just
below the stem. The lower part consists of a
cylinder and an outer reservoir tube which termin­
ates In a base cup and Is welded to the stem, and at
Its upper end Is a welded cap. This cap forms part of
an assembly which houses the seal on the piston
rod, compresses the static seal rubber, and locates
the piston rod bearing-usually referred to as the
piston rod guide. The piston rod seal Is of synthetic
rubber and has multi-wiping lips and all except one,
face Inwards. The outer lips act to exclude dirt,
etc., and faces outwards.
Any fluid which exudes past the guide bearing is
prevented from escaping further by the seal and a
port below the seal allows fluid to return into the
reservoir tube via a closed circuit drain tube fitted
to prevent frothing and aeration.
The operating cylinder is normally completely
full of fluid and the reservoir tube Is about half full
when the piston rod Is extended.
A baffle, In the form of a pressed steel collar
anchored to the drain tube is fitted between the
outside of the operating cylinder and the inside of
the reserve tube just above the level of the fluid, to
prevent the fluid in the reserve tube being shaken
about by movement of the suspension.
Operation (See Fig. 6)
Assume that the damper is in the midway position
and that the car passes over a bump in the road.
The road springs flex and the damper Is compressed
and shortened. The piston in
effect
moves down­
wards In the cylinder applying pressure to the fluid
beneath It.
If the movement Is slow the fluid passes through the
metering restriction in the valve disc (A) and enters
the upper part of the cylinder.
If the movement Is fast the fluid passes through
the spring-controlled compression valve also at (A)
which is quite lightly loaded. The ported sleeve
in the piston remains closed.
Downward movement of the piston displaces a
greater volume of fluid than the lesser volume
above the piston. Hence during a slow movement
the excess can find a restricted way out to the
reservoir via a groove machined in the valve disc
of the compression valve assembly (B) In the base
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