RDA Hot legs?

[CactusSam]

I've been having an issue lately where it seems like my coil builds are working great, for a while, and things suddenly go sour. I'm using a kangertech tank with a rebuildable atomizer, using 30ga kanthal, and Japanese cotton. Sometimes things work great for weeks, and there are times within a day, suddenly out of nowhere, I start to get this weird harsh burnt taste, just like what you get from a hot leg. Every once in awhile I'll open it up to take a look at things, and sometimes some of the cotton is burnt, but other times I can't see anything at all.

Last night I put some new cotton in after a little bit of it had burned, but kept getting the same harsh burnt taste, so this morning I built a new coil and put new cotton in. Almost like magic, everything was great again. Good flavor, nice clouds, no harshness whatsoever. Now, a few hours later, that harshness is starting to come back. Any ideas what could be causing this?

What causes a hot leg? Is there anything that can be done to fix them or prevent them?

I always do a dry burn of the coil without cotton inside, take time to properly prime the cotton, and wait a while to let it soak in the tank before taking any pulls. At this point I'm just at a loss for what could be going wrong :-/

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[93gc40]

Sounds like you are running the wick and coil, dry..... Getting dry hits. Either due to too much or too little cotton in the coil. Wicking is the hardest part of building, takes practice, and is different for almost every build. Some tanks are sensitive to high VG (thick) juice.

Take some COLD pulls to prime you clearomizer. A few hard pulls WITHOUT firing will draw juice into the wick faster than absorption alone.

 

[CactusSam]

After I pulled this one apart, I noticed that part of the coil was was getting hot near the cotton, causing it to burn. One small section of coil getting red hot while the rest didn't was what was causing the issue. Turns out it was my coil all along, I just need to be more diligent about making my coil turns tight and keeping everything as symmetrical as possible.

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[edyle]

After I pulled this one apart, I noticed that part of the coil was was getting hot near the cotton, causing it to burn. One small section of coil getting red hot while the rest didn't was what was causing the issue. Turns out it was my coil all along, I just need to be more diligent about making my coil turns tight and keeping everything as symmetrical as possible.

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That would be a hotspot.

One common problem is a hot leg, often it's on the positive leg, because the negative leg is usually more of a heat sink, being part of the main body of the item.
What I do is on the positive, I wrap the leg all the way around the screw, and let the extra stick out and come back onto the leg, like effectively making a thicker leg.


Another thing is if I am just too lazy to dryburn/rewick, gunk builds up on the coil and at some point if the coil gets a bit too dry, some part of that gunk goes hot charcoal and burns, and continues to burn.


When I read the original post, I was thinking you were probably running the wattage too high.

 

[CactusSam]

Yeah, I think it's definitely been hot spots. I'll just have to be more meticulous, and I'll try that trick of wrapping around the post screw too

Thanks!

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[CactusSam]

Aaaaah, it feels good to be vaping on a proper coil again. Even turned it down about 1/2 a watt and it is workin mighty purdy right now.

* happy vaper *

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[DaveP]

If you think about the technical aspects of a coil and wick, it's the wick that acts as a heat sink for the heat produced by the coil. If there's an air gap between the coil and the wick at some point, then the coil can produce a hot spot.

When you wind a compressed coil, heat it and squeeze it with tweezers as soon as you release the fire button to ensure that coil windings are in contact. Whether it's a spaced coil or a compressed coil that you are using, the wick is going to be the problem. It's too thin.

A new wick shouldn't be really loose inside the coil. When you insert it you should feel light drag as you pull it through. You might see even the coil legs
bend very slightly as you pull the wick back and forth. Find the point in the wick where it's not too tight or too loose and the wicking on each side is a little higher than the coil.

Yes, the wick will swell when it's wetted, but light drag ensures that there's no gaps in the contact. There should be just a little blossoming of the wick on each side of the coil. If not, then it's probably too thin.

 

[battouter]

First time I've seen my wick somewhat shrink and isn't in full contact with the coil. Is it normal for it to shrink? It was in full contact even after priming. I vaped a few mils and just checked how it was doing then i noticed it wasn't in full contact anymore.

black = coil , blue = wick

 

[CactusSam]

First time I've seen my wick somewhat shrink and isn't in full contact with the coil. Is it normal for it to shrink? It was in full contact even after priming. I vaped a few mils and just checked how it was doing then i noticed it wasn't in full contact anymore.

black = coil , blue = wick

What material is your wick? Cotton or something else?

It's generally unusual, in my experience, to have the wick shrink, unless it's getting dry, since the e-liquids cause the fibers to swell. If you aren't getting enough moisture to the coil, though, it seems possible that it's drying out and shrinking, or that you just didn't start with a thick enough piece of wick to begin with.

My $0.02, FWIW.

 

[ZeroOhms]

if your coil isn't burning inside out, try sliding the rod you used to coil few times.
slide it in and out few times, take it out, fire it and check. repeat until you see a nice red glow in the middle of coil.

avoid having a sharp bends at the leg.

if you think that it might be a wicking issue, try putting extra layer of cotton on TOP of the coil (used to be called flavoring wick).