Nexdome has begun shipping a new shutter automation system that relies on power tracks embeded into the rotator track. The power transfer block that they ship is very rudimentary and unreliable. As we know, the observatory dome is not perfectly rounds so it potentially loses contact at certain rotations. This is an attempt to provide a better and more reliable mechanism for that power transfer.

It uses compression-spring floating arms and sealed bearings to maintain contact with the track through rotation. While it may not always maintain perfect contact during rotation (though mine seems to do so reliably), when rotation stops, the power contacts should be well placed to power the shutter.

Parts List -

4x 6800-2RS - https://a.co/d/aKmzSaS
4x M4x6x6 Threaded inserts - https://a.co/d/0pCVVgU
4x M4x50 Socket head bolts - https://www.mcmaster.com/92855A435/
4x 7mm x 25mm compression springs - https://a.co/d/bs9WtcK
1x Adafruit 2-to-6 Snap Action wiring block - https://www.adafruit.com/product/5615
1x 5.5x2.1mm DC Power Jack - https://a.co/d/dUMsh8I
21 or 22 AWG wiring - https://a.co/d/g8MKa72
Heat Shrink Tubing - https://a.co/d/eTlwemP
superglue
VHB tape (optional)

Soldering iron, heat gun, misc tools.

Print Settings -

Designed to be printed without supports. Use auto-orient and auto-arrange in your slicing software.
ASA filament recommended
4 walls
5 top/bottom layers
35% infill

Assembly Instructions -
1) Solder positive / negative wires to the inner surface of the bearings. 2 positive bearings, 2 negative bearings. You may need acid-based flux to make the solder stick. Make sure that the top of the wire doesn’t extend beyond the inner bearing surface. I made a small loop of the exposed wire for better soldering. Use 10-15mm of heat shrink wrap to protect the wire as it comes out of the bearing.

2) Heat press the threaded inserts into the bearing holders.

3) Mount the positive bearings into their holders. For the positive holder, the thinner part is ‘down’ and the wire should be oriented in that direction. Once positioned, you can use a small dab of superglue on the edge of the retainer that goes through the bearing and seats into the thicker part of the bearing holder.

4) Mount the negative bearing holders to the main body using the bottom holes. 1x m4x50 through the larger hole side, spring over it as it emerges through the front, then the bearing holder screwed onto that. Note the orientation of the negative bearing holder is that the thinner side is ‘up’; opposite of the positive bearing holder.

5) Place the negative wired bearings into their holders, wires oriented ‘down’. There are no retainers for this bearing. It will be held in place by the wire from the positive bearing.

6) Mount the positive bearings/holders into the top holes of the main body as you did for the negative bearings. Pass the wire for the positive bearing through the center of the negative bearing. You can use another 10-15mm of heat shrink tubing over both wires to give the combination some additional strength against flexure.

7) Insert the main power jack through the hole in the side. You’ll need to trim the wire to length. Insert positive / negative wires into the feed side of the wiring block.

8) Wire the positive / negative bearings into the wiring block. I’ve found that having the wires at about a 20-30 degree angle toward the main body as they come off the bearings reduces stress to the soldering points as they move in and out.

9) I suggest plugging the device into a 12v power adapter at this time and use a voltmeter to make sure that each side is receiving power.

10) If testing is successful, place the bottom cover on. A dab of superglue on each peg will make it permanent.

11) The device is designed to fit over the angle bracket provided by Nexdome in place of the power block that they distribute. I have included models for various shims to be placed under this main body in case there are inconsistencies in how that angle bracket is made.

Points for adjustment -

* You can use the M4 bolts for about 5mm of adjustment in or out.
* You can add M4 washers to the bolts if you need to bring the power contacts further away from the tracks.