Maintenance
111
AL-KO Safety Ball
AL-KO also recommends fitment of the AL-
KO Safety Ball, this simple plastic ball fits
inside the coupling head (whilst unhitched
from the towball). Used in conjunction with
the AL-KO Safety Device, the Safety Ball is
locked into the coupling area, ensuring the
thief cannot hitch your caravan to a smaller
diameter towball or hook (Fig 19).
The combined use of the AL-KO Safety and
Safety Ball also acts as a very visual theft
deterrent.
Forward Braking
In the free position, with the handbrake fully
forward in the OFF position, the drawshaft of
the overrun device is fully extended and the
shoes are clear of the drum.
As the towing vehicle brakes, or starts to
drive downhill, the drawshaft of the overrun
device is depressed toward the unit being
towed. This action imparts linear motion to
the main shaft of the overrunning device
which is transmitted via the overrun lever,
brake rod and Bowden cable to the
expanding clutch. This mechanism forces
the leading brake shoe and, by reaction, the
trailing shoe outwards into contact with the
drum.
Friction between the brake shoes and the
drum creates a tendency for both shoes and
the expanding clutch to move in the
direction of forward rotation until they abut
against the adjuster box. This ensures that
both remain in the braking position.
Reversing
When the towing vehicle reverses, the
drawshaft is pushed backward, moving the
overrunning device through its full travel.
This movement is transmitted in the normal
manner to the expanding clutch.
The clutch forces both shoes into contact
with the drum. Initial friction between these
creates a tendency for the shoes and
expanding clutch to move in the direction of
wheel rotation i.e. reverse. This movement
imparts pressure to the spring- loaded auto-
reverse lever, causing it to collapse. Thus,
friction between the shoes and drum is
almost eliminated, allowing the trailer to
reverse as one with the towing vehicle.
Fig. 17
Fig. 19
Fig. 18
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