Chamberlain Power Drive PD428D Owner's Manual page 9

Assemble the Rail (Continued)
4. Beginning with the sprocket end, straighten the
two rail sections so that the screw rod is in a
straight line at the joint. (Avoid handling the joint,
which may have sharp edges.) Connect the
extension rail at the front (header) end of the rail.
5. Carefully slide the pins at the top edge of the rail
into the openings on the adjacent rail. It is
essential that the rail assembly be on a level
surface to achieve proper alignment and to
avoid damage to the pins.
6. Insert two 1/4"-20x1-3/4" bolts through the center
holes of a brace, and place its open length against
the rail at the joint, aligning the holes as shown.
Position another brace on the opposite side of the
rail over the bolts, add 1/4"-20 lock nuts, and hand
tighten. Insert two additional bolts and hand
tighten.
7. Keeping the rail straight and on a level surface,
grasp the screw rods on each side of the
remaining joint and pivot into a straight line.
Repeat steps 5 and 6 for the extension rail
assembly.
8. With a 7/16" wrench, tighten bolts until snug,
beginning with the center holes. Do not
overtighten.
Rail
Support
Brace
Lock
Nuts
Rail Pin
Alignment
Hole
Extension
Extension
Rail
Rail
Rail
Support
Brace
Lock
Alignment
Nuts
Hole
Door End
(Front)
Slide end rail
toward center rail
Bolts
1/4"-20x1-3/4"
Alignment
Hole
End
Rail
Rail Pin
HARDWARE SHOWN ACTUAL SIZE
Bolt
1/4"-20x1-3/4" (12)
Rail
Support
Brace
Lock
Nuts
Rail Pin
Rail Pin
Center Rail
Bolts
1/4"-20x1-3/4"
9
Lock Nut
1/4"-20 (12)
Alignment
Hole
Slide end rail
toward center rail
Bolts
1/4"-20x1-3/4"
End
Alignment
Rail
Hole
Rail Pin
Center
Rail
Sprocket End
(Back)