Sunbeam ALPINE I SERIES: APLINE II SERIES, Workshop Manual

Page: 193 / 413

WSM.124
Section F (Front Suspension)
I
st re-issue
Page 29
FRONT SHOCK ABSORBER
Armstrong Direct-Acting Telescopic Dampers are
fitted.
The body of the shock absorber Is telescopic and
Is mounted more or less vertically through the coll
spring between the suspension cradle and wishbone
spring pan on the front member. It Is ther�fore
direct-acting, no links or levers being required.
SERVICING
Unless proper facilities are available including a
shock absorber testing machine, it is almost in­
variably found that to attempt repairs to the
modern telescopic shock absorbers is neither
practical nor economical.
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 any shock absorbers requiring
attention, it Is strongly recommended that the
faulty unit should be removed and a replacement
shock absorber titted.
Removal and refitting instructions for front
shock absorbers are contained in this section.
CONSTRUCTION
The assembly consists mainly of a piston rod (C)
attached to the upper mounting (A) with a piston
Incorporating the piston valve (M) attached to the
lower end. This is housed in a cylinder (H and P)
with a larger diameter concentric to form a reser­
voir {Q) and a lower mounting (S). In detail the
piston rod has a former and dust shield (B) attached
Immediately below the upper mounting stem, and Is
suitably machined at _the lower end with the piston
to house the piston valve (M). The cylinder is
located at the lower end by a spigot on the piston
rod guide whi�h in turn Is housed In the outer tube.
This piston rod guide forms a bearing for the piston
rod, holds the rebound valve and drain tubes In
position and contains the spring-loaded piston rod
seal (D). The cylinder, piston rod guide and reser­
voir seal are retained in the outer tube. Baffles
(K and N) are sprung on to the outside of the
cylinder (P) to prevent aeration of the fluid in the
reservoir (Q) by the rapid movements of the
suspension.
The cylinder Is completely tilled and the reservoir
about half-tilled with fluid when the piston rod Is
extended.
Operation
The functioning of the shock absorber with its
unique principle of "one-way" oil circulation, is
described below with references to the illustration.
As the wheel rises on fast bump strokes, when the
piston is moving relatively towards the base valve
(R) fluid pressure opens the piston valve (M)
against the coil spring load and fluid passes through
the ports In the piston valve (M) from the lower half
of the cylinder (P) to the upper part of the cylinder
(H). The excess fluid displaced from the cylinder by
the piston passes via the ports (F) in the piston rod
guide (E) through the tilter (G) and down the re­
bound valve tube (L) opening the rebound valve (0)
against the coil spring load Into the reservoir (Q).
On the slow bump strokes, damping Is controlled by
calibrated bleed grooves on the face of the base
valve (R).
On the fast rebound strokes when the piston Is
moving relatively towards the piston rod guide (E)
the piston valve (M) closes and again fluid passes
through the ports (F) In the piston rod guide (E)
through the filter (G) down the rebound valve
tube (L) opening the rebound valve (N) against the
coll spring load and Into the reservoir (Q). At the
same time the lower part of the cylinder (P) is
replenished with fluid as the base valve (R) opens
to allow recuperation from the reservoir (Q).