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Thread: Dunnit. Dual core Kanger sub-ohm RBA

  1. #1
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    Lightbulb Dunnit. Dual core Kanger mini sub-ohm RBA

    I've heard talk of it but haven't messed with dual coils on the Kanger subtank mini. I didn't intend to build tonight - I am actually waiting for my coil winding tool and some 26g kanthal to come from Slowtech (it's in transit)

    The coil on my subtank RBA was starting to taste a bit ratty though and I haven't been completely happy with the 2.5mm coils done with 28g. I just don't seem to be able to run them at the watts I think this should handle, maybe 'cause they don't actually come out sub ohm... 3.0mm restricts the airflow too much, and I wasn't happy with the wicking in a single 2mm coil.

    I knew I should be able to do a dual core in this device even though the space is a bit tight but I hadn't really thought about the problem too hard. Then it hit me - I know you can poke the wire on either side of the terminal screw and the excellent system holds the wire just beautifuly no matter what - it's a really simple and easy build. If there's two sides that work fine with both screws, then you should be able to put two wires on each screw, and have them both work perfectly fine... and the parallel dual core Kanger sub-ohm RBA was born.




    Experience with larger coils taught me that if you fill up that small deck with coil then it restricts the airflow. For simplicity of build the coils were mounted one above the other, right over the airhole. The coils are in parallel, and this configuration always made more sense to me, for an atomiser. I've always found series coils a bit wishy-washy (different leg lengths and variable results), and this deck really does lend itself to a parallel build. Notice that bottom coil is raised slightly to give more air in front of the air hole. This is the maximum height you can do a complete build in the small RBA - 2mm coils, remember?

    Here's the top down view, and you can see how simple the build really is.



    Both coils are 6 spaced turns of 28g Kanthal wound on a 2mm bit. I wanted to maximise the airflow. I know from experience that these coils come out at around 1.1 ohms each. Yes, I know those wires need a little more clipping, they must be flush with the terminal block. if you wind both coils the same way, you mount the first one in the normal way (with the coil hanging down) and the second one with the coil higher than the legs. This allows them to fit neatly in the small space.

    I need to point out a potential trap with this build, which is having a leg of one coil touching the parallel coil and creating a short across two opposing legs. If this happens you will see a resistance closer to 0.2 ohms and the Kbox mini will not fire (minimum 0.3 to fire). Here's a picture that should make it much clearer.



    Notice that the legs must clear the opposite coils on both sides.

    On to the wicking:



    The wicking is a pretty simple affair. At least it is second time around when you realise that the top wick needs to be longer, to reach down to the juice holes in the side of the RBA.

    Nothing left but to check the ohms and throw it all back together!



    Make sure you check your ohms before you put the tank back together and fill it with liquid. Because of the height of the two coils There's potential to misjudge it and have the top coil to touch the top cap after you screw it on. If this happens just push both coils down a bit

    All things considered this was a successful build. It will run comfortably at 38 watts for direct lung inhale. Lots of vapour and flavour. The Kbox mini says 0.5ohms and 4.4V. Turning the power up gave a much hotter vape but it's not my thing. I just like a nice long comfortable draw. This one may make me re-think my nic level if I stay with it because it's possible to chain vape on this and it produces a *lot* of vapour and flavour.

    For the mouth to lungers, it's also a nice comfortable vape at about 29 watts with the air control on the middle hole. Heaps of flavour and throat hit. It's the best mouth to lung experience I've had from any vape. Your mileage may vary of course but if you like a warmish thick vape then this might suit. The Kbox said this one was at 3.9 volts. It seemed to be okay at higher power for MTL too, but you have to suck the air faster too since it was a bit too hot for me. I like a nice comfortable draw that makes the most of the minimal flavour quantity I use in my ADV.

    In both cases it was the temperature of the vapour and my own comfort level that limited the power I used. It never gave a dry hit even when I was chain vaping it. Oops, lower nic anyone? It vapes more like an RDA than an RBA.

    Sorry if this is old hat to some of you, but I wanted to share what I thought was a really simple and easy build that gives a great result.

    PS, found an alternate method for a parallel dual coil, video from Vapor Authority. I'm glad I didn't look at this first. He uses two micro coils side by side and one wick. Give it a go if you want, but I found that a single 2mm coil could only support a smaller wick and it couldn't wick fast enough for me. Also, he's got the resistance at 0.4 ohms. If you're using the Kanger Sub box (ie the kit with the Kbox mini) then it's a bit close to the minimum resistance that it will fire (0.3 ohms). This is because he's put two 28g 2mm micro coils side by side and only has 5 wraps in each. You'll also notice that this longer arrangement means that neither of the coils are centred over the air hole. I'll be sticking with my build but here's the video if you want to try it, or have trouble doing my build:

    Last edited by fabricator4; 05-02-17 at 11:32 AM. Reason: Added detail to show potential short
    Malikada, LimeB, wedgtail and 3 others like this.
    Chris: Tobacco free since 17:00 15th March 2013.

  2. #2
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    I put mine side by side as the top bottom approach has the coils heating unevenly (airflow)



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  3. #3
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    That looks Great! on that tiny deck it would be tricky.
    I put a vertical in mine for something different.... great flavour!


    http://tinyurl.com/zbl33e7
    Last edited by Mystico; 12-03-16 at 09:50 AM.

  4. #4
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    Quote Originally Posted by Mystico View Post
    That looks Great! on that tiny deck it would be tricky.
    I put a vertical in mine for something different.... great flavour!



    That looks great too. A vertical coil is also something I want to try.

    The dual coil is not too difficult. The hardest part is lining the two coils up but it's assisted greatly by the design of the post. The wires stay trapped even when you are moving the coils around to get them into position. I think I tightened the screws slightly to allow the wires to move a little, but firm enough that the coils stayed where I put them.
    Last edited by fabricator4; 12-03-16 at 10:49 AM.
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    Chris: Tobacco free since 17:00 15th March 2013.

  5. #5
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    Quote Originally Posted by MCYL View Post
    I put mine side by side as the top bottom approach has the coils heating unevenly (airflow)
    Nice one. Those are some tiny coils.

    The vertical arrangement of the coils in mine does not appear to have a problem with the coils heating unevenly. The two main advantages I think are that the leg lengths are all identical, and the smaller chamber gives a very efficient air flow. It seemed the correct thing to increase the space in front of the air hole by raising the coils up as much as practical. This puts the top coil right in the conical section of the chimney cap where the air is accelerating again.

    I've got a spare RBA and I'm going to do a second build the same way but with the coils set a little lower and compare it with this one. I don't appear to have an uneven heating problem because turning it up does not result in a burnt taste. The flavour just gets more intense, and the heat of the vape increases. It gives a much warmer vape compared to a single coil.
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    Chris: Tobacco free since 17:00 15th March 2013.

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    That's great to hear! I'd like to try myself later today.

    Those tiny coils were strange. I sandwiched the wick between the coils and found vapour were shooting out the ends of the coil. It didn't do what I wanted however. I wanted a cool dry vape with lots of flavour instead I built a hot spitting monster


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  7. #7
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    Quote Originally Posted by MCYL View Post
    That's great to hear! I'd like to try myself later today.

    Those tiny coils were strange. I sandwiched the wick between the coils and found vapour were shooting out the ends of the coil. It didn't do what I wanted however. I wanted a cool dry vape with lots of flavour instead I built a hot spitting monster
    Hahahah! That's the way it goes sometimes. I can see how that can happen. The coils are small enough that the capillary action might cause them to fill up with liquid, which then gets spat out again. You could try make the coils big enough to wick through the centre and wick it in the same way I did.
    Chris: Tobacco free since 17:00 15th March 2013.

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    I'll be trying what you've done there


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  9. #9
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    Quote Originally Posted by MCYL View Post
    I'll be trying what you've done there
    I just made the dual coil setup in my spare RBA, but didn't set it as high. There's still a bit of space between the air hole and the bottom coil so it doesn't block it, but it's not necessary to set it quite as high as my first one as I'm finding this vapes exactly the same. 38 watts is quite intense, you have to keep the air going otherwise it's too hot to vape (but not dry hitting, just very intense).

    A couple of other things I've found too.

    It seems to be worth spending the time pushing most of the wick through the juice hole. I used a very small allen key - 1mm and just spent a minute poking the wick through the holes. I then trimmed it off to about 2mm outside the hole for neatness. It doesn't seem to affect the already very good wicking and shouldn't do unless you've used a *real* lot of wick. I use just enough wick to go through the 2mm coils easily without being in any way loose. Mainly, it seems give it an advantage in how easily the air can be drawn through the RBA

    The previous coil wasn't touching the chimney cap after I screwed it on as I thought, the coil legs were probably touching. If you get a reading something closer to 0.2 ohms then this probably the reason. The Kbox mini won't fire it and you have to push the bottom coil down a fraction to get it read 0.54 ohms (or whatever your wire comes to). Once the coils are in operation the problem does not re-occur.

    Don't bother trying to position the coils as you put them in. Get the leads under the screws and turn them enough so the leads can't pop out again. Then get the coils roughly in position and tighten the screws so you *just* make contact but can move the coils a bit. You then position the coils to their final position and tighten the screws down properly.

    I never had the coils short together until the cap was on and the RBA was screwed firmly into the base. Don't fill the tank and reassemble it until you've done a low wattage test firing the RBA with a wet wick.

    I'm very happy with this build. Very intense flavour - I hope you get to see what I mean.

    I had a look at the RBA I've been vaping on for the last 24 hours. It's still very clean even though I've been giving it a hiding. The top coil has a little more colour than the bottom so it does run a little warmer as you thought it might, but there's no indication that it's burning or anything else that causes me any concern.
    MCYL likes this.
    Chris: Tobacco free since 17:00 15th March 2013.

  10. #10
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    This has been my challenge of the night


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    fabricator4 likes this.

 

 
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