Chamberlain WHISPER DRIVE 248754 - Manual (Page 9)

9
ASSEMBLY STEP 2
Fasten the Rail to the Motor Unit
• Insert a 1/4"-20x1-3/4" bolt into the cover protection
bolt hole on the back end of the rail as shown. Tighten
securely with a 1/4"-20 lock nut. DO NOT overtighten.
• Remove the two bolts from the top of the motor unit.
• Place the “U” bracket, fl at side down, on the motor unit
and align the bracket holes with the bolt holes. Fasten
with the previously removed bolts.
• Align the rail assembly with the top of the motor unit.
Slide the rail end onto the “U” bracket, all the way to
the stops that protrude on the top and sides of the
bracket.
ASSEMBLY STEP 3
Install the Idler Pulley
• Lay the belt beside the rail, as shown. Grasp the
end with the hooked trolley connector and pass
approximately 12" (30 cm) of belt through the window.
Keep the ribbed side toward the rail, and allow it to
hang until Assembly Step 5.
• Remove the tape from the idler pulley. The inside
center should be pre-greased. If dry, regrease to
ensure proper operation.
• Place the idler pulley into the window as shown.
• Insert the idler bolt from the top through the rail
and pulley. Tighten with a 3/8" lock washer and
nut underneath the rail until the lock washer is
compressed.
• Rotate the pulley to be sure it spins freely.
• Insert a 1/4"-20x1-3/4" bolt into the trolley stop hole in
the front of the rail as shown. Tighten securely with a
1/4"-20 lock nut.
To avoid SERIOUS damage to garage door opener,
use ONLY those bolts/fasteners mounted in the top of
the opener.
Bolt 1/4"-20x1-3/4"
Lock Nut
1/4"-20
“U” Bracket
SLIDE RAIL TO
STOPS ON TOP
AND SIDES
OF BRACKET
Cover
Protection
Bolt Hole
Lock Nut
Motor Unit
Belt Pulley
Bolt
Bolts
Lock
Nut
Screwdriver
Bolt
Bolt
Idler
Bolt
Idler
Pulley
Idler
Pulley
Pulley
Lock
Washer
3/8"
Washer
Grease
Inside
Pulley
Nut
3/8"
Nut
Trolley
Stop
Hole
Trolley
Connector
Rail
HARDWARE SHOWN ACTUAL SIZE
HARDWARE SHOWN ACTUAL SIZE
Bolt 1/4"-20x1-3/4"
Lock Nut 1/4"-20 Lock Washer 3/8" Nut 3/8"
Idler Bolt