Have just finished making all the parts for a rotary contactor, and now it's time for assembly. This is a stack of copper rings, which each have a deck with springy wire 'brushes' to make the connection. Insulation between the rings, or course, and the insulation is thick enough to create a groove for the brush decks to ride in.
The body of the thing is made from pvc pipe, as are the insulating spacers. The brush decks are made from laminate, with two layers of lam glued together for a decent thickness. A copper tab exits each deck, and will be where the outside connection is made.
The body will be solidly fixed to the ceiling, hanging vertically down towards my machine. A smaller diameter pvc tube will be in the center of it, and will be used for a vacuum system. The outer part where the outside connections are made will have an arm that is controlled by the gantry on the machine. As I rotate the gantry, the assembly with the brush decks will rotate with it. The fixed part hanging from the ceiling will have power coming to it, plus at least three other circuits coming to it from various power supplies.
Next step is to lube the copper rings so the brush decks will rotate smoothly around them. Four brushes will be in contact with each copper ring, so the likelyhood of contact sparking is very low. I don't think I have to worry about heat here, so my choices of lube are silicon wheel bearing grease, pure silicon grease, way oil, other light oils, contact lubes which are all fairly light, or dielectric grease and conductive grease.
From what I've read, conductive grease doesn't help much where the brush is sliding along a contact strip, and dielectric grease only offers an improvement where there could be arcing contacts or localized heat points. Because I have four separate brush wires in contact with the copper ring, the possibility of arcing is very low.
My choice would be the wheel bearing grease, as it has little smell and will stay put fairly well. It will also handle more heat than pretty much any alternative I have on hand. If I had a thinner grease I would use that. And this makes me wonder- could I get a decent mix with this silicon wheel bearing grease and silicon brake fluid- if so I could make up some thinned grease.
Wondering what thoughts y'all may have on this?
The body of the thing is made from pvc pipe, as are the insulating spacers. The brush decks are made from laminate, with two layers of lam glued together for a decent thickness. A copper tab exits each deck, and will be where the outside connection is made.
The body will be solidly fixed to the ceiling, hanging vertically down towards my machine. A smaller diameter pvc tube will be in the center of it, and will be used for a vacuum system. The outer part where the outside connections are made will have an arm that is controlled by the gantry on the machine. As I rotate the gantry, the assembly with the brush decks will rotate with it. The fixed part hanging from the ceiling will have power coming to it, plus at least three other circuits coming to it from various power supplies.
Next step is to lube the copper rings so the brush decks will rotate smoothly around them. Four brushes will be in contact with each copper ring, so the likelyhood of contact sparking is very low. I don't think I have to worry about heat here, so my choices of lube are silicon wheel bearing grease, pure silicon grease, way oil, other light oils, contact lubes which are all fairly light, or dielectric grease and conductive grease.
From what I've read, conductive grease doesn't help much where the brush is sliding along a contact strip, and dielectric grease only offers an improvement where there could be arcing contacts or localized heat points. Because I have four separate brush wires in contact with the copper ring, the possibility of arcing is very low.
My choice would be the wheel bearing grease, as it has little smell and will stay put fairly well. It will also handle more heat than pretty much any alternative I have on hand. If I had a thinner grease I would use that. And this makes me wonder- could I get a decent mix with this silicon wheel bearing grease and silicon brake fluid- if so I could make up some thinned grease.
Wondering what thoughts y'all may have on this?
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