Assembly; Attach The T-Rail To The Motor Unit; Set The Belt Tension - Chamberlain 1280LMC-R 1/2 HP Owner's Manual

ASSEMBLY STEP 1

Attach the T-Rail to the Motor Unit

To avoid installation difficulties, do not run the
garage door opener until instructed to do so.
• Remove the two washered screws mounted in top
of motor unit.
• Align T-rail and styrofoam over sprocket. Cut tape
from T-rail, belt and styrofoam.
• REMOVE STYROFOAM.
• Insert both washered screws through the T-rail into
the motor unit. Tighten screws securely.
Use only these screws! Use of any other
screws will cause serious damage to door
opener.
• Position belt over the motor unit sprocket.
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 1). Do not use any tools.
• Insert a screwdriver tip into one of the nut ring
slots and brace it firmly against the trolley
(Figure 2).
• 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 3).
This extends the spring for optimum belt tension.
Trolley Nut Ring
BEFORE
1"
Figure 3
Trolley Nut Ring
AFTER RELEASE
1-1/4"
WARNING
CAUTION
To avoid serious damage to opener, ONLY use screws
mounted in top of motor unit.
Washered Screw
5/16"-18x1/2"
USE ONLY THIS
TYPE AND SIZE
SCREW
Washered Screw
5/16"-18x1/2"
T-Rail
Hole
T-Rail
Hole
Spring/Trolley Nut
Figure 1
Figure 2
6
Styrofoam
T-Rail
Hole
Belt
Motor unit
Sprocket
Trolley
Threaded
Shaft
Trolley
Threaded
Shaft
Nut
Ring
Square
End
Nut Ring
Slots