Swift caravan Owner's Handbook Manual page 115

Maintenance
The AL-KO parking brake system comprises
a handbrake lever mechanism actuating a
Bowden cable which operates a brake unit
assembly contained within the wheel hub.
AL-KO provide two types of parking brake
system on their trailers, with the Bowden
cable and the wheel hub brake unit being
common to both types.
The difference between the systems is the
handbrake mechanism used to actuate the
Bowden cable.
AL-KO's unique parking brake system
requires a source of stored energy to lock
the wheel brakes should the trailer start to
move after it has been uncoupled from the
towing unit.
This energy source can be provided by either
a spring cylinder charged by hand or by a
gas filled cylinder acting as an energy store.
Each system requires a slightly different
method of operation when parking the trailer,
though they both operate in the same manner
when forward or reverse braking is applied.
Spring Cylinder Type
A spring system is attached to the link
between the handbrake lever and the central
brake rod. Full application of the handbrake
lever (such that the lever is vertical) to the
last tooth of the ratchet compresses a steel
spring inside the steel cylinder and energy is
stored.
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The action of the brake lever imparts motion
to the brake rod, the Bowden cable and the
expanding clutch. This mechanism forces
both shoes into contact with the drum.
At this stage, the brake unit is latent, the
mechanism waiting to see in which direction
the trailer will start to move.
If the trailer starts to move backwards, the
stored energy in the spring will be released.
The trailing brake shoe and by reaction, the
leading shoe together with the expanding
clutch will tend to move in the direction of
rotation (reverse) and abut against the stop.
Thus the trailer is braked.
However, if the handbrake is NOT fully
applied to the last tooth (i.e. vertical) and is
set to some lesser position than the full
vertical, then problems will almost certainly
arise after the trailer has been uncoupled
from the towing unit.
If the trailer is parked on a reverse slope or if
it is pushed backwards, then the brake
mechanism will act as though the trailer is
being reversed by the towing unit. The shoes
and expanding clutch will tend to move with
the direction of rotation (reverse) which
imparts pressure to the spring-loaded
reverse lever, causing it to collapse. Thus,
friction between the shoes and the drum is
almost eliminated and the trailer will run
away.
Operating the Handbrake
Some people may find it difficult to set the
handbrake lever to its full vertical position
without a great deal of physical effort.
However, AL-KO have designed their system
so that the average user need not do so.
For successful parking on a reverse slope or
steep hill, the operator need only apply the
handbrake with one hand while gently but
purposefully inching the caravan trailer a
small distance backwards with the other.
The user must supply this small but essential
backward movement to ensure that the
fulcrum of the transmission lever moves past
the point of reverse, thus preventing the
lever from collapsing as it would normally do
when reversing.
Most users will find it easier to stand facing
the towing unit while applying the hand
brake and at the same time gently push the
caravan an inch or two backwards with their
posterior.
Gas Cylinder Type
A gas cylinder, acting as an accumulator of
stored energy, can be fitted to the handbrake
lever to provide the same effect as a spring
cylinder.