cases, it may be necessary to fabricate a special
frame to mount the drive unit. It should be noted
that chain tension can exceed
and
thus
an extremely rigid mounting structure is
vital to maintain good chain alignment. Installation
failures frequently occur in this area and as a
general rule, it is desirable to ‘over engineer’ the
drive unit mounting. All fastenings should be
secured by lock washers.
Provision must also be made for chain
adjustment which is most easily achieved by
removable shims placed under the mounting foot
or by elongated clearance holes in the mounting
frame as illustrated in Figs. 20 and 21.
Both sprockets must be accurately aligned to
run in the same plane and correct alignment must
be carefully checked by means of a straight edge.
The gearbox may be mounted in any
convenient attitude without risk of oil leakage. In
addition, the drive sprocket may face any
direction since steering sense can be corrected
when the installation is complete by reversing the
polarity of the drive motor connection (see section
3.3.1). Finally, the
should be tensioned until
it is
just tight and contributes negligible lost
motion to the drive system. Total lost motion
between the driven sprocket attached to the
steering system and the rudder stock should not
exceed 2% of total movement under any
circumstances. If lost motion exceeds this level it
must be corrected. otherwise steering
performance will be impaired.
(0.127”-0.1275”)
9.46-9.61 mm
(0.3725”-0.3785”)
GRUB SCREW
dia.
(0.5”)
(0.75”)
Fig.
19
