Chamberlain 1280 - 1/2 HP - Manual (Page 6)

ASSEMBLY STEP 1
Attach the T-Rail To the Opener
To fasten rail, use only those screws mounted
in the top of the opener. Any other screws will
cause serious damage to the opener.
6
• Remove the two washered screws mounted in top
of opener.
• Align T-rail and styrofoam over opener sprocket.
• Cut tape from T-rail, belt and styrofoam.
• REMOVE STYROFOAM.
• Insert both washered screws through the T-rail
into the opener. Tighten both screws securely .
USE ONLY THESE SCREWS! Any other screws
will cause serious damage to the opener.
Position belt over the opener sprocket.
Washered Screw
5/16"-18x1/2"
Styrofoam
Belt
T-Rail
Hole
The Chamberlain Group, Inc.
Attach Tee Rail To Opener Chassis
Liftmaster Synchro Drive GDO (Belt)
3/13/92 - 6/2/92 - 6/3/92
USE ONLY THIS
TYPE AND SIZE
SCREW
T-Rail
Hole
Opener
Sprocket
USE ONLY THIS
TYPE AND SIZE
SCREW
Belt
Washered Screw
5/16"-18x1/2"
T-Rail
Hole
ASSEMBLY STEP 2
Set the Belt Tension
• By hand, thread the spring trolley nut on the
threaded shaft until it is finger tight against the
trolley (Figure A).
Do not use any tools.
• Insert a screwdriver tip into one of the nut ring
slots and brace it firmly against the trolley
(Figure B).
• 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 C).
This extends the spring for optimum belt tension.
WARNING
CAUTION
WARNING
Assembly Section: Pages 6 - 7
The Chamberlain Group, Inc.
Liftmaster Synchro Drive
Spring Trolley Nut Assembly
3/5/92 - 5/16 /92 - 5/21/92 - 6/2/92
6/11/92
Trolley
Threaded
Shaft
Spring
Trolley Nut
Trolley
The Chamberlain Group, Inc.
Liftmaster Synchro Drive
Spring Trolley Nut Assembly
3/5/92 - 5/16 /92 - 5/21/92 - 6/2/92
6/11/92
Nut
Ring
Trolley
Threaded
Shaft
Nut Ring
Slots
Trolley
Square End Figure A
Figure B
The Chamberlain Group, Inc.
Spring Trolley Nut
1/25/96
Nut Ring Trolley Nut Ring Trolley
1" 1-1/4"
BEFORE AFTER RELEASE
Figure C