Nexdome has recently been supplying a new chain-based shutter automation system for it's Observatories. The system as provided has issues with the chain walking off of the sprockets, becoming jammed, and otherwise being sensitive to environmental conditions. This is a replacement for the sprockets that improves those shortcomings.

You'll also need

- 12 x 608zz bearings (1 per spindle).

- 6 x M8x40mm bolts and lock nuts for the bottom spindles. Top spindle and bracket secure to the existing bolts provided by Nexdome. Just remove the washers, spacers, gears, etc. Leave the lock nuts that hold the ones that don't go through the dome (you'll see them).

- #25 chain tool to remove resulting slack in the chain. I removed 12 from the left and 10 from the right. Adjust as needed.

Spindles and caps were printed with 3 walls, 15% infill.

Bracket were printed with 5 walls and 50% infill.

Use auto-orient in your slicing software.

All three components were designed to be printed without supports.

I used PLA for now, but will probably move to ASA depending on how they hold up this summer.