Chamberlain Merlin Whisper Drive MT3850 Installation And Operating Instructions Manual page 7

ASSEMBLY STEP 4
Assemble the Header Sleeve
• Install the carriage bolt through the header sleeve
bracket.
• Install the flat washer and spring assembly onto the
carriage bolt.
• Insert carriage bolt of header sleeve assembly into slot
cut into pulley bracket.
• Slide header sleeve assembly onto front (header end)
of rail.
ASSEMBLY STEP 5
Attach the Trolley to the Rail
Assembly
• Slide outer trolley into the back (opener end) of the
rail assembly. Be sure the end with the trolley release
arm is heading in direction of opener. Slide outer
trolley down rail until it engages with inner trolley.
• Move the engaged trolley assembly to the midpoint of
the rail, then turn the rail assembly or one-piece rail
over ready to fasten to opener.
ASSEMBLY STEP 6
Attach the Rail to the Opener
• Holding belt out of the way.
• Slide the rail assembly onto shim bracket until rail
assembly is securely fastened to the opener.
• Wrap the belt around the belt pulley ensuring the belt
engages the teeth of the belt pulley.
Spring
Header Sleeve
Assembly
Belt
6
Carriage Bolt
Header Sleeve
Assembly
Flat Washer
Carriage Bolt
Header End
Slot
Pulley Bracket
Rail Assembly
Release Arm
Trolley
Rail Assembly