Chamberlain WHISPER DRIVE WD912K - Manual (Page 10)

10
ASSEMBLY STEP 4
Install the Belt and Set the Tension
INSTALLING THE BELT
1. Drop the notched side of the trolley clip into the
retaining slot on top of the trolley (Figure 1).
2. Grasp the clip connector at the end
of the belt and slip it through the belt
pulley bracket from behind, around
the pulley and toward the trolley.
3. Fasten the belt clip connector to the
trolley clip with a master link:
• Push pins of master link bar
through holes in trolley clip and belt
clip connector.
• Push master link cap over pins and
past pin notches.
• Slide clip-on spring over cap and onto
pin notches until both pins are securely
locked in place.
4. With the trolley against the screwdriver,
dispense the belt along the rail and around
the motor unit sprocket. The sprocket teeth
must engage the belt (Figure 2).
5. Use the second master link to connect the belt
to the flat end of the trolley threaded shaft
(Figure 1). Check to make sure the belt is not
twisted.
6. Remove the screwdriver.
SETTING THE TENSION
1. Insert the trolley threaded shaft through the hole in
the trolley.
2. Hold the belt at the trolley shaft to avoid twisting as
you thread the spring/trolley nut by hand on the
shaft until finger tight against the trolley (Figure 3).
Do not use any tools.
3. Insert a screwdriver tip into one of the nut ring
slots and brace it firmly against the trolley.
(Figure 4).
4. Place a 7/16" open end wrench on the square end.
Rotate about 1/4 turn until the spring releases and
snaps the nut ring against the trolley (Figure 5).
This extends the spring for optimum belt tension.
Nut
Ring
Trolley
Threaded
Shaft
Nut Ring
Slots
Square
End
Motor unit
Sprocket
Belt
Pulley
Slip Belt Clip
Connector around
Pulley Bracket
from this direction
and attach to trolley clip
Trolley
Clip
Master Link
Clip-On Spring Master
Link Cap
Trolley
Threaded Shaft
Master
Link Bar
Master
Link Bar
Pin Notch
Pin Notch
Belt
Clip Connector
Figure 2
Figure 4
Belt Clip
Connector
Trolley
Threaded
Shaft
Spring/Trolley Nut
Nut Ring Trolley Nut Ring Trolley
1" 1-1/4"
BEFORE AFTER RELEASE
Figure 5
Figure 3
To avoid possible SERIOUS INJURY to fingers from
moving garage door opener:
• ALWAYS keep hand clear of sprocket while operating
opener.
• Securely attach sprocket cover BEFORE operating.
WARNING
CAUTION WARNING
WARNING
Figure 1