Chamberlain LiftMaster Security + 3270 1/2 HP Manuel D'instructions page 21

INSTALLATION STEP 12
Connect Door Arm to Trolley
Follow instructions which apply to your door type as
illustrated below and on the following page.
SECTIONAL DOORS ONLY
Make sure garage door is fully closed. Pull the emergency
release handle to disconnect the outer trolley from the
inner trolley. Slide the outer trolley back (away from the
door) about 2" (5 cm) as shown in Figures 1, 2 and 3.
Figure 1:
• Fasten straight door arm section to outer trolley with
the 5/16"x1" clevis pin. Secure the connection with a
ring fastener.
• Fasten curved section to the door bracket in the same
way, using the 5/16"x1-1/4" clevis pin.
IMPORTANT: The groove on the straight door arm MUST
face away from the curved door arm (Figure 4).
Figure 2:
• Bring arm sections together. Find two pairs of holes
that line up and join sections. Select holes as far apart
as possible to increase door arm rigidity.
Figure 3, Hole alignment alternative:
• If holes in curved arm are above holes in straight arm,
disconnect straight arm. Cut about 6" (15 cm) from the
solid end. Reconnect to trolley with cut end down as
shown.
• Bring arm sections together.
• Find two pairs of holes that line up and join with bolts,
lock washers and nuts.
Pull the emergency release handle toward the opener at
a 45° angle so that the trolley release arm is horizontal.
Proceed to Adjustment Step 1, page 23. Trolley will re-
engage automatically when opener is operated.
HARDWARE SHOWN ACTUAL SIZE
Nut 5/16"-18 Ring Fastener
Clevis Pin 5/16"x1-1/4"
(Door Bracket)
Clevis Pin 5/16"x1"
(Trolley)
Lock Washer 5/16"
Hex Bolt
5/16"-18x7/8"
21
Outer Trolley
Ring
Fastener
Door
Bracket
Figure 1
Clevis Pin 5/16"x1-1/4"
Nuts
5/16"-18
Door Bracket
Figure 2
Nuts
5/16"-18
Figure 3
CORRECT
Straight
Door
Arm
Curved
(Groove
Door
facing out)
Arm
Figure 4
Inner Trolley
Straight
Door Arm
Curved Door Arm
Lock
Washers
5/16"
Bolts
5/16"-18x7/8"
Lock
Washers
5/16"
Bolts 5/16"-18x7/8"
Cut This End
INCORRECT
Straight
Door
Arm
Clevis Pin
5/16"x1"
Emergency
Release
Handle
Curved
Door
Arm