Why don't they short out?

[kland]

Hi, noob here, so apologies in advance.
I've been watching demos/tutorials on how to do your own coil builds. One thing continues to puzzle me: every one of these guides I've read or watched has you squeezing the coils against one another using some type of heat-proof tweezers. Since the coils are metal, I assume they are conductive on their surface...so if you're squeezing the coils together such that they are touching one another, why does that not cause a short circuit, which would cause the whole thing to act like a simple (short) piece of solid wire? To put it another way: if I didn't create a coil at all but rather simply installed a straight piece of wire across the terminal posts, I would guess the resistance would be very close to 0 ohms (much closer than 0.5 ohms), and the mod would detect a short circuit (right?). Why doesn't a conductive coil with no insulation between its windings, and the windings touching each other, yield the same result? Instead the current seems to flow through the coils instead of going straight across the terminal posts. Are the coils not REALLY touching each other? Thanks.

 

[Eskie]

The coils are really, really close to each other in "contact" coils but current will flow along the wire as its resistance to conduction is far lower than arcing between the wires. You'll note that even with careful compression with a pair of non-conductive ceramic tweezers, the metal is never "welded" together to make one continuous cylinder, so conduction across wraps is not seen.

As to straight vs. coiled wire, assuming you used the same length of wire in a coil or a straight run, the resistance would be the same. Running the wire strictly post to post would certainly give you a very low resistance, but to compare apples to apples it's the total length of wire that matters, whether it is in tight coil, or unwound and flopped across the side of the deck.

 

[whiteowl84]

The wire is resistant. We aren't using a substantial length of wire to get resistance so we rely on the resistance of the alloy.
Kanthal conducts pretty poorly across the surface and it's very resistant anyway so the electricity has and easier time going through the coil than to jump across the wraps.
Nichrome conducts better across the surface but it really doesn't matter. You'll find out what I mean if you ever start building.

Most people are using regulated mods these days and if the resistance is too low or a dead short it'll just cut out.

The only short you're likely to experience is when a leg or wrap touches the atty somehow.

Sent from my E5306 using Tapatalk

 

[kland]

Thanks guys - so it sounds like even though the turns of the coils are "really, really close" to each other, they're not in fact touching, so the current flows through each turn rather than traveling directly terminal-to-terminal through what would essentially be a short-circuit, if the wraps were in fact touching. Did I get it???

Interesting what you said about Kanthal being less conductive at its surface...don't think I've ever heard of that before other than in discussions involving high frequencies ("skin effect"). Thanks again.

(BTW I have built a few decks...even tried hand-winding a Clapton...wasn't pretty but it works.)

 

[Eskie]

When you dry burn Kanthal you develop an alumina coating on it from the oxidation. That acts as an electrical insulator surrounding the wire as well.

 

[kland]

Aha. That explains it. Thanks very much.

 

[Flavored]

When you dry burn Kanthal you develop an alumina coating on it from the oxidation. That acts as an electrical insulator surrounding the wire as well.

What he said. The wires are indeed touching, but the first heating forms the insulating layer.