Chairlift Hanger Arm

This is a hanger arm for a travelling rope system, like a model chairlift. I used this to move Halloween decorations around under the eaves of the house, such as this skeleton bat: https://youtu.be/ikYbX-nNsps

You could also use a simple bent wire for the hanger arm, but with multiple items, it is an advantage to have each hanger exactly the same size when they must pass through support and guide structures that keep items vertical, prevent the ropes from coming off the pulleys with bounce from wind, etc. You can play with dimensions in the openSCAD file but make sure to leave enough space to the side of the pulley to prevent a collision if the rope is not fully in the center of the pulley wheel, as inevitably may happen.

I attached the hanger arm on the cord with a fold of gaffer tape assisted with a dab of hot glue. The tape alone doesn't have enough grip on the thin nylon cord.

The vertical support pulley I used is "pa66 nylon 1.57inches 8x40x20mm U type groove pulley" from http://www.amazon.com/gp/product/B01M9G96S6 and the cord is "Atwood Rope MFG 1.18mm x 125' Micro Cord" http://www.amazon.com/gp/product/B00YSR9NWM/

The larger horizontal drive and idler pulleys at each end were made from plywood. They weren't large enough to prevent two bats from hitting their wings together and getting tangled when passing on opposite sides, so I had to add two more pulleys to spread the loop farther apart, making the plan view of the rope loop more of a trapezoid shape than a simple U-type oval track.

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