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Slip Rings

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solomar

New Member
So am I just missing something? Could you technically make a through-bore slip ring by soldering some wires to the inside and outside rings? I checked the resistance between the inside and outside and there was no resistance. Can I do this or would this simply not work?
If not I am finding it really hard to find any manufacturers for slip rings, the only ones I can find are for industrial use...and are really expensive :(
 

Sceadwian

Banned
Slip rings are not complex. Simple bushing works well as slip rings, you just need to isolate each ring for more than one connection. You need two isolated connections for V+ and V- The isolation is the main problem as most bushings are on conductive shafts which makes them hard to isolate.
 

tcmtech

Banned
Most Helpful Member
Just use copper pipe fittings pushed onto or glued over PVC pipe.
The copper pipe is thick enough and heavy enough to take a high current without problem. Then use a spring loaded copper strap or two for the comutator. Or just stop by the local auto parts store and get the actual brushes for starter rebuilds if your really getting into the high amps!
 

solomar

New Member
Slip rings are not complex. Simple bushing works well as slip rings, you just need to isolate each ring for more than one connection. You need two isolated connections for V+ and V- The isolation is the main problem as most bushings are on conductive shafts which makes them hard to isolate.
So if I had a simple radial ball bearing on a steel shaft, I could just use electric tape to isolate the bearing and it would work? If this isn't what you mean could you explain a little more? I wiki'd a few things and I still don't see how I could use bushing instead of slip rings.

Just use copper pipe fittings pushed onto or glued over PVC pipe.
The copper pipe is thick enough and heavy enough to take a high current without problem. Then use a spring loaded copper strap or two for the comutator. Or just stop by the local auto parts store and get the actual brushes for starter rebuilds if your really getting into the high amps!
Thanks tcm, you gave me a few ideas, I wouldn't need a commutator at all but I think I'm gonna go lurk around my auto store =]
 

Thunderchild

New Member
i'd be inclided to use something more hardy than tape, what voltages are you operating at ? you need to take into consideration the isolating spec of the material you use, if the tape is damaged whilst putting the bearing on you've lost the isolation
 

Sceadwian

Banned
Thunderchild, it's called electrical tape for a reason =) Vinyl is an extremely good insulator, unless he's dealing with more than 1000 volts (I hardly find this likley) there's nothing to worry about.
And yes solomar, you could just use electrical tape to isolate it, the only problem being I don't think a bearing would make a good electrical conductor, they're covered it grease which will likley insulates it somehwat, if you're transfering more than a trivial amount of power you'll end up heating the bearing up, and you'll have a whole messload of electrical noise, but it might work. Check the bearing on a meter and try testing it with your load current on the bench before you decide.
I like Mike's copper tube and spring loaded brush idea, I think I'd trust it a little more than using the bearing as a conductor, but if the bearing works it's mechanially simpler. You could investigate the possibilities of conductive grease for the bearings as well, then it's a win win situation.
 

Thunderchild

New Member
if bearing heats grease will melt, with no grease the bearing will cease up, at least thats the theory you could test it out and see though I'd be interested in the results.
 

Sceadwian

Banned
It really depends on how much current is going through it, and it's bulk resistance.
 

tcmtech

Banned
Most Helpful Member
Sorry guys Ive tried the bearing consept on my wind genrators many times.
It does not matter what you do if your moving any usable amount of power across a bearing it eventualy kills it. The steel they use is a high carbon type and that by nature is not a good electrical conductor. Plus the actual clearances in a bearing are just big enough to cause miniscule arcing as the rollers turn. This starts pitting them and then they get rough and the pitting gets worse and around it goes! They always end up welding themselves together and seizing up!
Conductive grease does some good for lubrication but still it does not overcome that inherant design flaw.
A simple spring loaded copper strap sliding against a copper bushing will last many times longer!
 

Sceadwian

Banned
The mighty tcmtech has spoken! =)
Bearings are out.
Bushing might work but it depends on the scale, bearings don't much like load. If you're already using bearings then keep em and do the tubing/brush setup that TCM suggested.
 

tcmtech

Banned
Most Helpful Member
I may sound wise, but really all I got going for me is a good memory and loads of failed experiments! :D
 

solomar

New Member
The mighty tcmtech has spoken! =)
Bearings are out.
Bushing might work but it depends on the scale, bearings don't much like load. If you're already using bearings then keep em and do the tubing/brush setup that TCM suggested.
Thanks everyone for all the responses =]

So it looks like everyone has decided that the tubing/brush setup would be good

So TCM could you explain a little more about this assembly?
The reason why I needed some sort of slip ring assembly in the first place is because I'm making a bike powered radial generator (using magnets and coils). There will be 36 coils on two plates and in the center will be another plate with magnets. I'm going to make the magnets spin one way and the coils another way, and the problem is when the coils spin the wires will get all tangled up so I needed to have a slip ring in there. The most power it will be generating is ~1KV @ 1A
 

solomar

New Member
It's 3 phase AC with 1 Tesla Magnets (6 of them) the amount of power varies with the number of coils you use, the cross sectional area, and the time (frequency)
I've done quite a bit to make it generate more power...its a school project and the winner gets a scholarship =]
 

Sceadwian

Banned
Mind what Nigel said there solomar, no matter what your intent, you're not going to get more than about 100 watts of power out of it, maybe 150 watts peak if the biker is in good shape, and that's asuming your generator can produce that much. Sounds like a good project though, what'cha gonna do with the power?
 

tcmtech

Banned
Most Helpful Member
What I have found to work rather well is to go to your local home supply center and check out what you can put together with the materials you find there.
Find a short pice of PVC pipe(gray or white plastic water line) then just look for some copper pipe or copper pipe fittings that will fit over it.
Due to the large amount of pipe wall thicknesses a little trial and error test fitting is needed. Once you have a good combination just use a PVC glue or a two part epoxy resin glue. Use some sand paper to scuff up the PVC and the inside of the copper and then cover every thing in glue and press fit it together. When the glue is dried just drill through the copper and PVC and then thread the wire into the hole and solder it into place.
 

solomar

New Member
Well this is a project in school, the point is to simply design the generator :p
The group that gets the most power gets a scholarship, and the reason I say that it can output 1000 Watts is because thats what the team last year did and theres only had one plate that was rotating...and our group has two if we can get this slip ring problem out of the way.


and TCM thanks that makes sense...and is absolutely perfect thank you again =]
 
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duffy

Well-Known Member
It does not matter what you do if your moving any usable amount of power across a bearing it eventualy kills it.
This sounds reasonable. Passing current through a roller-bearing would be a little like an EDM machine. Galvanic action alone could eat away the bearings.
 
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