This swing was made from a few pieces of pallet wood and some old nylon rope.
The white rope was painted brown and grey to make it look older and stand out less.
The motor and plastic gear are from a garage door opener.
The motor arm was made from 25mm x 3mm flat aluminium.
Two holes were drilled into the plastic gear.
The gear has an odd number of teeth, so the holes are slightly offset.
Since the pull wire passes close by each rotation I used
countersunk screws to keep the bar surface clear.
I ended up using 2 pin DT series Deutsch connectors for the motor.
They should survive the weather better than the original QC terminals.
Motor mechanism with original short arm:
Operation with longer arm:
Night shot with longer arm and LED lighting in place: