Insulated copper

On Mon, 06 Jul 2015 14:27:39 +0100, Tim Watts Gave us:

Bare copper was not used in motors or coils. Think about it. It HAD/HAS to be insulated in some way. EVERY TURN from each other.

So it WAS ubiquitous for a very long time, and has been for a very long time.

On Mon, 06 Jul 2015 14:29:24 +0100, Tim Watts Gave us:

Think about what you just said.

Yes - and the half arsed method I described showed that could be done.

I think trying to use bare wire is daft, but it IS possible - you simply have to provide the inter-turn and inter-layer insulation some other way.

I did - have you?

On Mon, 06 Jul 2015 17:48:11 +0100, Tim Watts Gave us:

At which point, it is NO LONGER BARE.

On Mon, 06 Jul 2015 17:48:28 +0100, Tim Watts Gave us:

Two things. You really mean inter-turn insulation. Long before you would bridge and short to another winding, you would bridge and short to other turns in the same winding.

Second, "insulating" them MEANS that it is no longer bare copper, by definition!

So yeah... I spotted the glaring errors immediately. :-) Hehehe

It started bare, which was the premise...

Yep. Don't know why you are arguing about this...

It MUST use mag wire or it will fail, and that is regardless of what you varnish it up with. (but you knew that too)."

Which is not correct. You can use bare wire. You have to provide the insulation as you go.

Listen mate, it's quite clear we are arguing about wording and nothing else.

And no, I am not advocating skimping on enamelled wire is a good idea (it's not, it is a crap idea save special cases). I am just saying if all you had was bare copper, it could be done.

But why bother...

Two suggestions:

2: When (not if) that fails, sell what you have for scrap, and buy some decent enameled wire on eBay. You'll lose a bit in the transaction, but you won't spend a bunch of time screwing around to make a bunch of substandard enameled wire.

Not necessarily. You can build workable coils from bare wire. You just need to use sufficient spatial separation ("air") as the insulator.

Heck, this works for capacitors as well. When I first got interested in electronics most of the radio tuning capacitors used air as an insulator (and dielectric).

Frank McKenney

On Mon, 06 Jul 2015 13:50:05 -0500, Frnak McKenney Gave us:

Sure. Little s*it, small turns count. Nothing real though.

Also, making that first layer is fine. Subsequent layers, however, tend to give trouble with spacing as underlying layers influence placement, even with tap or paper separation. And don't even think about making an HV transformer this way.

You wound a few. I have wound hundreds. NOBODY (in their right mind or who wants to stay in business) uses bare wire for transformers or motors or chokes, etc., etc., etc., yada, yada, yada ad infinitum.

Enameled mag wire has been around for over a century and there is a reason that it IS what gets used. Even cloth wrapped Litz wire is fully covered.

Yes; brings back memories..

On Mon, 06 Jul 2015 21:14:18 -0700, Robert Baer Gave us:

Funny, since I rebuilt a B supply transformer in a Chrysler radio from well before then (1944), and had to fully disassemble it (the transformer) to do so. It used enameled mag wire then, and I used enameled mag wire to replace it with. The owner of the restored vehicle was very happy that he was able to retain the original radio.

"Pretty sure" doesn't cut it. Magnet wire in its current form has been around for a VERY long time. The only advancements made have been in the dielectric insulative strength of the coating. Spools of the (old) wire can still be found in old radio shops and military surplus shops.

the a photo on the internet of a dude who built a welder with the windings insulated with paper. it appears to be working.

I imsulated some salvaged copper wire with cheap enamel paint twisted it into a rope and wound a tranformer that sort of worked, I picked the wrong toroid for the core so it also mostly sucked. but I didn't measure any shorts, (it was about 10 turns of 10 core "rope" on a 30(?)mm toroid. none of the conductors showed coductance to any other.

big oil filled transformers use bare copper spaced apart to let the oil flow between them.

tesla coils often use bare copper in the primary and the turns on the secondary can be bare too as they don't touch.

On 7 Jul 2015 11:06:33 GMT, Jasen Betts Gave us:

Umm... NO. They are enameled. It is called "single strength". The oil *still* does a fine job of cooling (and insulating)

Not true. The primary is typically separated coils because of the construction design, and folks have used copper tubing to allow them to arrive at that design construction. They should *still* cover them.

The secondary is definitely enameled as the arcs would short down the tube in a New York millisecond! And no, they are not spaced windings. they are a single vertical layer and are place one turn right next to the next turn so the volts per turn keep the shorting from happening, but the volts at the top of the "stack" would instantly short "down the stack" instead of to ground, were they not insulated. Folks typically varnish their finished secondary tubes as well.

I think you "often make s*it up".

On Tuesday, July 7, 2015 at 5:24:29 AM UTC-7, DecadentLinuxUserNumeroUno wr ote:

(snip)

I'd have said "as *long as* they don't touch".

That's a tautology. Primary turns are typically separated to prevent arci ng between turns and to allow space for a movable tap point for fine tuning . The tap requires good electrical contact.

Primaries can be made of solid wire, tubing, or thick ribbon. I've seen s ome miniature coils with flat spiral primaries etched on PCBs.

There's no real point in insulating higher-powered Tesla primaries given how often you get strikes from the topload that will pinhole pretty much an y insulation available. Many people use a grounded strike rail around and a bove the primary but the primary will take occasional hits anyway. Such str ikes can cause catastrophic mayhem in the primary circuit but can be manage d e. g. by having extra separation between primary turns and overdesigning the primary cap.

Spacing secondary windings in very high-volts-out coils helps reduce the likelihood of strikes to the primary too, simply by lowering volts/meter be tween topload and primary.

Yep. Prevents interturn arcing due to voltages exceeding the rating of th e stock coating on the wire.

There was a long discussion on the Tesla Coil Mailing List a few years ba ck about the finish coating on multiple-half-wave-long secondaries taking a semi-permanent DC charge in spots.

Several mechanisms were proposed (the topload preferentially emitting pos itive ions that followed field lines to high negative potential spots on th e coil, and the coating's propensity to become an electret, weird stuff lik e that) but as I recall no consensus was reached other than that it tended to depend on the finish used, and that certain brands of marine spar varnis h didn't show the effect. I don't recall which.

Mark L. Fergerson

I was starting to think that I was the only one here old enough to know what scc, dcc, ssc, and dsc mean (meant?).

I don't recommend it.

Mark L. Fergerson

I expect most of us know those. I've still got bits of scc & dcc in service. Probably no silk though.

NT