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Multi-strand twisted wire builds offer some great benefits

Discussion in 'Coil Builds' started by jersey_emt, Sep 21, 2017.

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  1. jersey_emt

    jersey_emt Super Member Verified Member ECF Veteran

    Aug 26, 2009
    New Jersey, USA
    Over the few years I've been building coils, my "typical" or "go-to" build has changed many times. Sometimes it was basic single strand dual coils, other times it was twisted single or dual coils, or single or dual Clapton coils, or single or dual fused / twisted core Clapton coils. While I have (and still do) experiment with more exotic coils, they have never become an everyday thing, just something to try every now and then.

    Lately I've been experimenting with twisted coils using more than two strands of wire, and the results have been rather remarkable.

    Let's examine the numbers. I take long drags and thus prefer a fairly cool vape, so these numbers are for a low heat flux of 150 mW/mm². But since heat flux scales linearly, the comparison is still valid, even if you like a much hotter vape.

    Building for equal resistance and similar wraps:

    2-strand 24 gauge twisted dual coil, 3 mm @ 0.25 ohms (7/6 wrap)
    Heat capacity per coil: 188.82 mJ/K
    150 mW/mm² heat flux: 136 watts

    4-strand 28 gauge twisted dual coil, 3 mm @ 0.25 ohms (8/7 wrap)
    Heat capacity per coil: 118.15 mJ/K
    150 mW/mm² heat flux: 135 watts

    Both have the same resistance, same heat flux, and similar total wire length (just +1 wrap on the 4-strand 28 gauge twisted coils). Yet the 4-strand twisted coil's heat capacity is dramatically lower, almost 40%.

    Building for equal heat capacity and equal wraps:

    2-strand 24 gauge twisted dual coil, 3 mm @ 0.20 ohms (6/5 wrap)
    Heat capacity per coil: 151.05 mJ/K
    150 mW/mm² heat flux: 109 watts

    4-strand 26 gauge twisted dual coil, 3 mm @ 0.13 ohms (6/5 wrap)
    Heat capacity per coil: 155.34 mJ/K
    150 mW/mm² heat flux: 141 watts

    Both have the same heat capacity and the same total wire length. Yet the 4-strand twisted coil can handle a 30% higher wattage with the same heat flux.

    So what does all this mean?

    Building coils is a balancing act. In order to support higher wattage without getting too hot, you need to minimize heat flux. But this usually requires more wire mass with a higher heat capacity, causing a longer ramp-up time, often even with the higher wattage being taken into consideration.

    A higher strand count twisted coil seems to somehow get around this particular issue. For the same heat capacity, they have a lower heat flux, allowing a higher wattage without being a hotter vape. And for the same heat flux, they have a lower heat capacity, allowing a quicker ramp-up at the same wattage, also without being a hotter vape.

    And the coils have more nooks and crannies compared to a standard 2-strand twisted coil, which helps with wicking. In fact, if instead of twisting all four strands at once, and you build a chain coil by twisting 2 strands normally, then twisting that wire in the opposite direction, you end up with a complex twist which looks like interlocking links in a long chain (hence the name "chain coil"). It wicks juice so well that it can even be used as a wickless coil – it will hold several drops of juice by itself without needing any cotton, enough for a couple of pulls before drying out. While not at all convenient for normal use (since you would have to re-drip every two or three hits), this is incredibly useful for rapidly testing juices if you mix your own. A quick dry burn and you can try a new flavor without any of the old flavor lingering.

    Of course nothing in this world is perfect, so there are drawbacks to these types of builds. The obvious one is the quantity of wire required. Depending on how tightly you twist it, you will need about 5–7 times the length of wire than for an untwisted build, and more than twice as much than for a standard 2-strand twisted build. But if you're an experienced builder, you are already buying wire in 100+ foot spools for cheap, so you'll be just fine. And if you're still buying wire in overpriced short lengths, then stop! 100-foot spools can be purchased for not much more than what a lot of places charge for 3–5 foot lengths.

    But the other major drawback is springiness. A 4-strand twisted build is quite a bit more springy than a 2-strand build of similar final diameter. And while you can get even more of the benefits (lower heat flux or heat capacity) by twisting more than four strands of a thinner-gauge wire, a 6-strand coil, and especially an 8-strand coil, is excessively springy and difficult to work with. Torching the twisted wire before coiling it does help, but a 4-strand twisted build is about the practical limit. Maybe a 6-strand twisted build will work for you (for this, I would recommend the chain coil technique, with three strands twisted in one direction, then twisted itself in the opposite direction), but four strands is what I will be sticking with for my builds.

    There is still a lot of things that can be done with "just" four strands though. You can make a staged-heating version, twisting together two lengths of twisted wire of different gauges. Or take a 3-strand twisted wire and twist that with a single strand of a thicker wire. Varying how tightly you twist each section of wire can change the final twist "pattern" quite a bit. And that's just round wire – throw in some ribbon wire and that opens up even more possibilities.

    I actually prefer the performance of a 4-strand chain coil over Clapton coils, and they are quicker and easier to build, especially if you haven't quite been able to master the finesse required for making Clapton wire. They can handle surprisingly high wattages without getting too hot, and their self-wicking ability is at least as good as Claptons, if not even better.

    For someone who wants to move beyond basic twisted or parallel builds, multi-strand twisted coils are an excellent option with lots of potential. The only drawbacks are the lengths of wire required, and the springiness, but torching the twisted wire before you coil it will definitely help. But it's not really that bad at all if you stick to four strands, even without pre-torching.
     
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  2. jersey_emt

    jersey_emt Super Member Verified Member ECF Veteran

    Aug 26, 2009
    New Jersey, USA
    After a few weeks experimenting with multi-strand twisted builds, I've settled on using three strands for thicker wire (24 - 27 gauge), and four strands for thinner wire (28 - 34 gauge). 34 gauge seems to be the limit; going any thinner makes the finished wire too springy.

    It really is pretty impressive how much power these builds can handle, while still keeping a relatively low heat capacity for quick ramp-up and cool-down.

    Right now on my 24 mm Goon, I have a dual coil twisted build with four strands of 32 gauge wire, 9 wraps @ 3 mm, and a resistance of 0.67 ohms. It has a low heat capacity of 47 mJ/K per coil, yet can easily handle 100 - 120 watts without getting hot at all (114 watts at the "standard" heat flux of 200 mW/mm²). I'm running it at 100 watts since I prefer a fairly cool vape, but those who like things a bit hotter could probably push 140 watts through this build. That much power through a relatively simple build using just 32 gauge wire seems impossible, but somehow it works.

    And it heats up damn near instantaneously. I've always needed to use a fairly strong preheat (125 - 150%) to get my two-strand twisted builds up to temperature quickly. But with a four-strand build I find myself not needing any preheat at all.
     
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  3. poolman

    poolman Full Member

    Jan 8, 2017
    great knowledge. I have been thinking about doing a twisted build to run a higher resistance dual coil, with using SS. I don't know what flux and those other numbers mean but I am interested in finding out now.

    With using SS to make a multi-strand wire with a target high resistance of dual coil .35 to .5 and good ramp up and down. What numbers should I be looking at? Flux? Heat Capacity? Larger surface area?

    Thank you in advance I knew there had to be more science than just resistance and pretty looking builds
     
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  4. stols001

    stols001 Mistress of the Dark Nicotinic Arts Verified Member ECF Veteran

    Supporting member
    May 30, 2017
    Tucson, AZ
    Very informative, thank you! :) I'm not too worried about exotic coil builds, but it's fascinating to learn more about the differences between builds.

    Anna
     
  5. Skreech

    Skreech Senior Member

    Oct 16, 2017
    Ipswich
    I use 2 strand twisted titanium wire on my TC builds just to increase surface area. Trouble is they don't cool down quick enough between puffs, so although I'm getting more vapour, my mod is always flashing 'Temperature Protection' at me. It is bit of a balancing act between pre-heat, max wattage, and temperature limit to get it right because I take long draws. If I was Quick Draw McGraw then it would probably be easier.......lol
     
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  6. Skreech

    Skreech Senior Member

    Oct 16, 2017
    Ipswich
    Yesterday I built a new dual deck with 3 strand twisted 28g kanthal wire with as tight a pitch as I dare. I made 2 coils with 8 wraps on a 3.5mm former. It comes in at 0.45ohm. It crackles and pops really loudly even after two tanks. (And boy does it go through tanks). It's like a mini firefight going on in my atty all the time.

    Reading up on this, it says twisted coils can trap juice and cause crackling, popping and spitting. The way around it is to increase wattage.

    Well I started off at 60 watts, and increased it to 70 watts and then to 80 watts. At 80 watts it is really too hot but still crackles and pops. I've settled back at 70 watts and am considering whether twisted coils were such a good idea. I wouldn't have thought it was over wicking. I'm crap at wicking......lol
     
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  7. Jim_ MDP

    Jim_ MDP Ultra Member ECF Veteran

    Sep 24, 2015
    Nice topic, I've heard for a while now that triple twisteds have great performance.
    I'll have to check out the specs when I get a chance.



    Point of order...

    In TC mode, the "temp protect" message means the mod is at the set temp and holding there... however long you keep firing (helps to draw as well or it won't really produce).

    If you never or rarely see that displayed... you're taking short draws (hasn't ramped up yet) or your temp is set too high for the build or wattage.

    Don't fear the temp protect... it's your friend. :D
     
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  8. Skreech

    Skreech Senior Member

    Oct 16, 2017
    Ipswich
    I totally agree. And I apologise for not explaining my point better.

    My concern was with the twisted coil not cooling down quickly enough, probably due to it's mass.

    When I start vaping from cold, then the mod is giving me the full max wattage I've set for the whole draw which is satisfying. After about 10 draws I get the 'temp protect' warning. The next draw will have the mod giving max wattage for about half a second and then scaling down the power to maintain temperature, which isn't so satisfying. From cold the coil has to heat from 20C to 250C. 10 draws later, the coil has to heat from say 150C to 250C so max wattage is only needed for a very short period and then it's pushing out 4 watts to maintain temp through the draw and the hit is no longer there. Bit like riding my bike with a restrictor fitted. No fun.

    Maybe I'm doing it all wrong, I don't know, but I just changed the max temp to 280C and I get a much more satisfying vape without hitting 'temp protect'. I'm just not happy at setting 280C with a titanium coil.
     
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  9. Jim_ MDP

    Jim_ MDP Ultra Member ECF Veteran

    Sep 24, 2015
    Ok... Ti for some damned reason often needs a substantially higher set temp (yours is a tad much, but... Ti's wonky that way), however, your setup isn't dialed in.

    Start a new thread so the folk can get you put right.
    You should always be seeing the temp protect message, during every full draw (it'll flicker), if things are dialed in.
     
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  10. Zakillah

    Zakillah Super Member ECF Veteran

    Jan 24, 2015
    Vienna
    Heat flux is not about mass, its about surface area; basicly "how big is your coil".
    Wire diameter doesn't really matter here. Well, actually it does matter a lot when it comes to how hot/cool your vape will be, but for heat flux calculations not so much as heat flux is generally calculated by the total surface area and not the coil to wick contact area. That's why heat flux alone doesn't tell you the whole truth.

    All the positives you mentioned about twisted builds are true for parallel builds with thinner wire as well. You minimize mass by using thinner wire. And nothing is stopping anybody building larger coils with it; you just need more wraps.
    A 10 wrap 0,5mm (~24G) has double the mass (therefore also double the heat capacity) compared to 0,25mm (~30G) 20 wrap (or better, 10 parallel wraps), but both builds will have the same total surface area and therefore the same heat flux. However, the 30G build will still run cooler.

    I have heard lots of positive opinions about twisted wire and tried it a couple of times, but I cant get over how springy this stuff is.
     
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  11. chanelvaps

    chanelvaps Vaping Master Verified Member ECF Veteran

    Oct 3, 2013
    Burbank CAlifornia
    Help please
    I love my Aromamizers. Have always had them built by others. Usually claptons. I have now moved far away from the guy that built them for me.
    I took them all apart and cleaned them, removed old coils.
    I cannot build a coil to go in here to save my life.
    I wanted .3 ohms but not twisted or claptons. I want dual.
    Yes I consulted Steam Engine but it is confusing me.
    Can anybody just tell me what to use.
    I have 24 gauge, 26, 27, 28 and 30
    When I put the spec in SE it says only two wraps of 26 gauge using 2.5 diameter. TWO wraps??/ That cannot be. I need more wraps.
    Someone please help me.
    PS I know how to build simple things like a Taifun.
     
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  12. Caterpiller

    Caterpiller Super Member Verified Member ECF Veteran

    Apr 3, 2015
    Malaysia
    Dual Coil, Kanthal, 26g, 2mm ID, 6wraps, 0.32 Ohms

    Dual Coil, Kanthal, 24g, 3mm ID, 6wraps, 0.3 Ohms
     
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  13. chanelvaps

    chanelvaps Vaping Master Verified Member ECF Veteran

    Oct 3, 2013
    Burbank CAlifornia
    When you say dual coil you do mean two wires wrapped at once right?
     
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  14. chanelvaps

    chanelvaps Vaping Master Verified Member ECF Veteran

    Oct 3, 2013
    Burbank CAlifornia
    I have a 2.5 jig. How many wraps would that be with 24 gauge
     
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  15. Caterpiller

    Caterpiller Super Member Verified Member ECF Veteran

    Apr 3, 2015
    Malaysia
    yes, two coils.
     
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  16. Caterpiller

    Caterpiller Super Member Verified Member ECF Veteran

    Apr 3, 2015
    Malaysia
    Dual Coil, Kanthal, 24g, 2.5mm ID, 7wraps, 0.28 Ohms
     
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  17. Wraith504

    Wraith504 Ultra Member Verified Member ECF Veteran

    Aug 25, 2014
    New Orleans, LA
    2 wires wrapped at once is parallel. 2 individual wires wrapped into individual coils so you have 2 coils that are exactly the same would be "dual"
     
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  18. MidwestGuy

    MidwestGuy Super Member Verified Member ECF Veteran

    Aug 17, 2014
    Iowa
    Same experience here. I've always had this issue with twisted coils ... I've not done too much experimenting with them and it's been a couple of years since I've tried, but no matter what I did, how I built them, how much power I put through them and attempting different wicking methods, there were always what seemed to be low yield nuclear explosions going on in my chambers ... some so significant that I thought the atomizer was going to explode. Now, don't get me wrong ... I do like a little light crackling, but this was BAD. :)
     
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  19. IDJoel

    IDJoel Ultra Member Verified Member ECF Veteran

    Feb 20, 2015
    Boise, ID
    First off, I think you are mixing up your terms. A dual coil simply refers to using two identical coils (vs. using just one coil). A basic single-wire dual coil looks like this:
    upload_2017-11-23_20-48-11.png
    (image #1)

    A parallel coil uses two wires wrapped at the same time, side-by-side, around the jig and will look like this:
    upload_2017-11-23_20-58-34.png
    (image #2)
    Note that each lead has two wires instead of just one; that is what makes it "parallel" (that; and the fact that the two wires are not twisted around one another).

    If I use two parallel coils on one build deck; then I would have a dual parallel build. Like this:
    upload_2017-11-23_21-3-9.png
    (image #3)

    So, with that clarification; what are you wanting to build? Single wire dual coils (image #1), single parallel coil (image #2), or dual parallel coils (image #3)?
    I understand Steam Engine (SE) can be a bit overwhelming to the unfamiliar. I will use your example of a target resistance of 0.30 ohms; 26ga kanthol; and an inside diameter (your jig size) of 2.5mm to show crucial fields and results for the three coil types I mentioned in the first part of this post.

    (single wire) Dual Coil
    upload_2017-11-23_21-29-34.png

    (click on image for larger view)
    Referring to the green-circled numbers; this is what you are looking at:
    1. Wire type/material. You want to make sure this matches the type of wire you want to use; such as kanthol, stainless steel, titanium, nichrome, etc.
    2. for a single wire wrapped coil; leave this as round (default).
    3. Set to gauge of wire you wish to use (26ga in the case of our example).
    4. Set to "Dual" for the dual (single wire) coils we want to use.
    5. This is the desired, or "target" resistance for the total/overall build (what your regulated mod will display for resistance).
    6. This is the size (inside diameter) of the coil(s) that are going to be wrapped.
    7. This right-hand box displays the "result" of the data that was put into #1-6. This particular line (#7) shows the exact number of wraps (and partial wraps) that would need to be wound, to hit all our targets. Because this is not usually practical (I couldn't eyeball precisely 4.64 wraps) so lines #8 and #9 give us the next closest whole and half wraps (easier to estimate).
    8. This is the closest number of whole wraps (5 wraps in this instance). Note that this line also displays the adjusted resistance for this number of full wraps; in this instance it is 0.64Ω per coil. Because we are using two coils; that would give us a total of 0.32Ω, or 0.02Ω over the target of 3.0Ω.
      NOTE: a coil made with "whole" wraps (based on 360 degrees; or one full turn), can be identified by having the lead going away from each other like this:
      upload_2017-11-23_22-15-24.png
      Also note that both leads are coming off the bottom (though top would be fine too). Wherever, on the coil, I chose to count the number of wraps they will be the same.
    9. This is the closest number of half wraps (6/5 wraps in this instance; though 5½ wraps might be a better way to phrase it). Note that this line also displays the adjusted resistance for this number of half wraps; in this instance it is 0.70Ω per coil. Because we are using two coils; that would give us a total of 0.35Ω, or 0.05Ω over the target of 3.0Ω... still fairly close.
      NOTE: This type of coil will have both leads pointing in the same direction (where the whole wraps pointed away from each other), and look like this"
      upload_2017-11-23_22-42-49.png
    10. This is the resistance per coil of the intended build. In this example; each coil would measure 0.60Ω. Two coils are to be used, so that halves the resistance, and hits our target of 3.0Ω.
    Okay... sorry that was a long one. But, now that you should have a reasonable basic understanding of the SE fields, the rest should go more quickly. I will only highlight, and note, what I change for the other two coil types.

    (one) Parallel Coil (using two wires as in image #2 above)
    upload_2017-11-23_23-2-59.png
    (click on image to expand)
    Note that I only really made two changes: #1, and #4.
    1. Using the drop-down arrow; this has been changed from the default "round," to "round, twisted/parallel."
    2. New field. This defaults to zero; and as the instructions immediately below, has been left at "0," because a parallel (not twisted) wind is desired.
    3. New field. Defaults to two. The parallel build desired is using two wires so it is fine.
    4. Because this is for one parallel coil only (not two/dual); this has been changed from "Dual Coil" to "Single Coil." (The second/extra wire has been accounted for by using the "twisted/parallel" status in line #1.)
    Note that the Results box values haven't really changed; that is because we are still using the same amount of wire (and the same size); but instead of using two single wires (in parallel), we now have one parallel coil (though it did double the heat capacity).

    If you are still reading, don't give up, you're almost done!;) Here's the final example (again, I will only note the changes):

    (two) Dual Parallel Coils (using four wires as in image #3 above)
    upload_2017-11-23_23-31-28.png

    (click on image to expand)
    1. The only change required (going from one parallel coil; to dual (two) parallel coils was to change this field to "Dual Coil." Everything else remained the same (as far as the fields that can be changed).
    2. The results box is where we start seeing noticeable differences. Wraps have gone up from 4.6+, to almost 10! And power (wattage) required to fire the coil(s) has gone from 27W, to 108W!! Other results remain the same/similar to previous results (these are highlighted blue).
    I hope this helps give you a better understanding on how to use SE. To see how your different wire sizes affect the results; just plug the appropriate gauge into the Diameter/AWG box (the mm box will auto-adjust).
    :toast:
    PS: If you scroll down on the SE page; you can find further explanations, and how-to videos, for further understanding.

    PPS To @jersey_emt: Sorry for running away on the off-topic question; I know this was not the topic you intended for this thread. This is at least the second place @chanelvaps has tried asking about this (the first was in a DIY E-liquids thread), so I hoped to help her along. Again; I apologize.:blush:
     
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  20. chanelvaps

    chanelvaps Vaping Master Verified Member ECF Veteran

    Oct 3, 2013
    Burbank CAlifornia
    Joel! Thank you for your in depth help! I know SE and have been using it for years. I feel so stupid to tell you that I was entering it all in but not changing setup from "single" to 'dual'
    Hence I was getting something like 2.5 wraps and I knew this atty in question used to have coils that were wrapped at least 6 times.
    Forgive me, I am 58 and sometimes forget my dogs name! LOL.
    I so appreciate you going to these lengths to help me and YEs folks please forgive us hijacking the thread!
     
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