That's right folks, Lars is just now putting on the finishing touches to some new features in the coil program. The most useful will be a "Suggested Wattage" cell that will offer a wattage recommendation based on wire gauge and coils in parallel.
What this means is that, for people who don't grasp the concept of wire gauge and coil count in parallel having an effect on heat flux and heat capacity... the program math will sort it out for you, with a range of wattage (or voltage) recommendations.
You still need to understand what HF & HC are (see SE user guide parts one and two)... but these folks will no longer be using too thick or thin a gauge, or too little or many coils... ending up with a far too hot or too cool vape, or one that seemingly takes an eternity to reach operating temperature.
These new features will be beneficial for both unregulated and regulated mod users.
I'll be updating this article and others as the SE changes take effect.
Low resistance is a byproduct of a (mostly) unrecognized benefit... not the goal.
"It's that damn SoF again... talkin' 'bout that damn heat flux. Get him! - burn him at the stake!".
Don't light the match just yet...
More surface area means more juice is vaporized for a given duration of adequate, applied current.
In the simplest of terms... more surface area equals thicker clouds, more flavor.
Our 'functional goal' is made of two parts. Coil surface area, and a wattage sufficient (or more) to support that surface area with enough radiant heat (heat flux) to vaporize e-liquid.
That low resistance 'number' is the result of increased surface area... and a simpler way to provide a recognizable value than using an actual surface area value. Resistance is the value we all learn up front when we get into vaping. It's engrained... just like wire gauge is an easier way to say 'more' than surface area.
But that's not a completely true statement.
"Damn it SoF... here we go again with these 'maybe' answers".
Surface area doesn't know anything about wire gauge... you can have a thinner wire, and have more surface area than a thicker one. It just takes more length of wire - along with the higher resistance value hitching a ride - to obtain that surface area.
"Hold on now... what the hell did he just say? This is starting to make... not a lot of sense".
That's right... you can have the same surface area (83 mm²) with 30 gauge wire at 1.5Ω as you can with 26 gauge wire at 0.38Ω... again, 83 mm². And these comparisons can occur over and over with other gauges/resistances ... until we actually exceed an atomizers physical space to contain wire.
Lets apply a bit of wattage and see what we get. it takes 34 watts to obtain a HF of 200 mW/mm² +/-... for both builds.
Yep... the same power produces the same temperature for the same wattage... and yet, the wire gauge is different. As I said up front... it's surface area first. Maybe.
"'Maybe... MAYBE'? I vote we burn him now, before he says anything else. OK, I'll bite... Is one better than the other?"
Glad you asked. Yes... the 30 gauge build is a little more efficient than the 26 gauge build, because even though the surface area is the same, the thicker wire has greater mass and density, making it a bit slower to reach functional temperature.
"Time to temperature is 17.5 mJ/K for the 30 gauge vs. 28.4 mJ/K for the 26 gauge... where the lower value is "faster" than the higher one.
"So, why is everyone going to thick wire, if it's less efficient than thin wire?"
This is where surface area and resistance start to share desired characteristics. We could use that 30 gauge wire to make a 0.38 coil, but at a dramatic loss of surface area... and we all know that surface area is a high priority.
To get our surface area back, at the resistance we desire, we need thicker wire.
"But wait... screw desired resistance. Why don't we just run "normal" resistances with thin wire to get the same surface area?"
Again... we run into issues with physical space. For example, lets try and double the above 83 mm² surface area to a nice fat 166mm² +/-. We'll do it with the same wire gauges.
OK... to get 166 mm² of surface area, we need lengths of 133mm for 26 gauge wire and 211mm of 30 gauge wire.
Using a 2.4mm mandrel, the 26 gauge will make a single 13 wrap coil, while the 30 gauge will produce a 23 wrap coil.
For all practical purposes, we need either a bigger atty, a much larger mandrel (and some magic wicking to go with it), splitting the single coil into parallel duals (or more)... and/or thicker wire.
Of those most practical and likely to occur... whata' ya' think? I'm leaning towards the multiple parallel coils and thicker wire... with the byproduct of lower resistance. Did I mention that we need higher wattage power supplies to support all this? No... oh well.
And what direction has vaping taken in the past few years? Oh yeah... right.
Still want to burn me at the stake?
"Maybe... tomorrow good for you?"
After I responded to an interesting thread found here... I started thinking about the (highly unlikely) chances of truly identical multi-coil builds - considering how atomizers are made and the individual components that go to make up the whole - where heating lag time from coil to coil is... should be, for all intents and purposes, identical.
What elements of an RDA - or any multi-coil atomizer for that matter - and "build methodology", will lead to improving the chances of identical individual coils in a parallel build?
To "test" an atomizer, or individual coils for that matter - will be not only impractical, but fairly difficult and even costly - due to the nature of how atomizers are designed, and how we fit coils.
Some of the methods I'll mention will be wildly impractical and unlikely to be followed by anyone - including myself, an OCD geezer with time on his hands - so this is more an exercise in fanaticism. ;-)
Atomizers with "monobloc construction" - negative terminals machined as part of the atomizer base will have reduced variation in resistance vs. atomizers with pressed or screwed in terminals. This first one is entirely reasonable, and quite common, even with cheap clones.
Atomizers with monobloc positive individual post holes (machined from a single piece of metal, with multiple fixing holes/screws), or single "common point wire attachment" terminals will have reduced resistance variation vs. positive terminals with multi-element construction. Another, not uncommon practice.
Individual coils, made in such a fashion that the tension applied can be measured, so that the stretch rate of the wire will be identical, one coil to the next. This isn't too unreasonable when you realize that the Jon Kuro's "KuroKoiler" and super_x_drifter's coil manufacturing methodology provides some level of repeatable, wire tension consistency.
Moving on to the (far) less likely...
Screw (female) threads and (male) threaded terminals... manufactured with a goal of high precision - identical engagement - rather than mass produced at a scale intended to meet practical economic requirements.
Torque values of individual wire fastening points. Yes, you read that right... torque values, as in identical inch-pound values of torque applied at each terminal. Chance of this happening - considering the investment in a low value, precision torque screwdriver - near zero, unless you own this tool already.
Individual testing by the manufacturer, for milliohm variations - within limited acceptable parameters - of each and every wire fastening point. Not holding my breath on this one.
Measurements of coil tails, from coil main body to terminal attachment point - with a goal of length consistency - to the one hundredths of a millimeter place. Another highly unlikely event, even if one owns a quality digital caliper.
Thinking of other ways to do this quickly and easily... one could develop a "length spacer" - made from a material I've not come up with a good answer for - that pre-sets the leg (or tail) length of each coil... then dissolves when heat is applied, with no toxic residue.
Another method might be a plastic or metal "standard" that one could hold next to a coil leg, insuring that each leg is near identical in installed length.
That's about all I can think of... if you want to play this game, think of other materials and methods, and include the chances of your ideas actually being used.
This article has been pulled... as it's being rewritten.
Also, so the excel files won't disappear every other week.
The practical applications of heat flux, wire gauge, parallel wire count & net resistance as they relate to... the simplicity of a mech mod vs. the independent wattage control of regulated mod.
In simpler terms... the Ohm's law limitations of mechs vs. the ability to "force" wattage with an APV... as it effects user vaping performance / satisfaction.
I'll keep this relatively short. If you've read the Steam Engine User Guides - parts 1 and 2... then you (probably) have a good handle on the fine tuning aspects of your builds. If not... then much of this may be beyond your current knowledge level. We're dealing with potentially high wattages and current values, so be smart and play it safe... until you really have a good understanding of the variables.
This is directed at both mech mod diehards - who, much like guns, won't surrender them until they're pulled from your cold, dead hands - to more rational folks, who may be on the fence about mechs and APVs in general... or those considering a first time purchase of a high wattage APV.
If you're a complete noob, with little to no understanding of Ohm's law, wire selection and so on, start with the "Advanced Education" article, and proceed in what ever direction suits you. A good bit of reading, but your brain will be bigger for it. _______________________________________________________________________
Trust me when I tell you, although I'm a true lover of mech mods... in actual fact, if you don't give a crap about the Ohm's law knowledge prerequisite, "battery holder" simplicity (and "style"?) that mechs provide... the high-output, regulated APV is the way to go... if you want more build freedom than Ohm's law will allow.
(But you should still know your OL formulas... m-kay?)
Without independent regulation, a battery will discharge wattage/amperage at a rate determined by net resistance and voltage.
For wattage ("Power") the formula is V² ÷ Ω = P.
For amperage ("Current") the formula is V ÷ Ω = C.
The calculated wattage doesn't care about your wire gauge or coils in parallel count... just the net resistance and battery voltage.
Heat flux is the coil(s) radiant heat, expressed in milliwatts per millimeter of coil surface area... squared. For our purposes... it's simply how warm you perceive your vape to be.
Heat flux and capacity do care about the wire gauge (AKA wire surface area & mass), coils in parallel count and net resistance, and is directly affected by them, both together and independently.
With that out of the way, lets move on to examples. All values are arrived at using the Steam Engine vapist's calculator.
With a mech mod... if you want to run at 0.5Ω with a heat flux of approximately 300 mW/mm² +/- .
Ohm's law formula calculates this to be a discharge of 35 watts @ 4.2v (and less as the battery voltage diminishes) ...
Disregarding wrap count and surface area for now, for a single coil, you must use 24 gauge (or thinner) wire... for dual coils you must use 28 gauge (or thinner) wire. That comes out to 309 & 311 mW/mm² respectively.
With a regulated wattage mod (for consistency, we'll call this a 250 watt output APV) you can use what ever wire and build you want... or at least a broader spread of possibilities.
A 300 mW/mm², 26 gauge dual parallel build at 0.7Ω? No problem. 95 watts will provide 300 mW/mm2 even. With a mech, you simply can't do it (at least, not with 26 gauge - try 30 ga.)... Ohm's law dictates that you will discharge only 25 watts, for a stone cold 39 mW/mm² with 26 gauge wire.
Another example... lets go deep sub-ohm, say 0.2Ω, with a quad parallel 24 gauge build. From a mech mod, Ohm's law dictates 88 watts @ 4.2v.
Run those numbers through Steam Engine, and we get a very cool 121 mW/mm². With a regulated mod, all we need to do is run at 218 watts to obtain our HF of 301 mW/mm².
Can we get 300 mW/mm² from a 0.2Ω, quad parallel 24 gauge build with a mech? Yes, we can. but it can only be done with 27 gauge wire, for a slightly hotter than desired, 345 mW/mm².
This last example is through the eye of maximum net coil surface area, with the lowest acceptable heat flux.
Our resistance limit is 0.20Ω on a dual parallel coil build. We'll use the resultant 88 watts from an OL calculation at 4.2v. 23 gauge wire provides a HF of 343 mW/mm², and a net coil surface area of 177.59 mm² per coil.
How low a coil temperature can we accept? 200 mW/mm²? 150mW/mm²? Lets split the difference and see where we end up. By accepting a 171 mW/mm² using 21 gauge wire, we increase our net coil surface area to a whopping 253 mm² per coil!
The point to that last example is that if you have enough wattage, you can increase net coil surface area, without trading off a loss of heat flux._______________________________________________________________________
The most important values to the vapist are heat flux, parallel coil count net coil surface area, wire gauge and net resistance.
My personal preferences are, in order - coil surface area, heat flux and resistance. What ever wire gauge will provide those values will be what I use.
Mech mods pretty much require that order... and I'm sorry for you, if all you have is 24 gauge and want a dual parallel, mid sub-ohm net resistance build.
Secondary values are heat capacity ("lag time" to desired temperature) and leg power loss... which is the percentage of power wasted heating the legs. This last value is based on wire mass/density... the greater the mass, the more energy wasted to the coil legs.
I'd not get too spun up if something is a bit high, but keep an eye out for extremes. Steam Engine will actually change color in the value box if something is extraordinarily off the mark.
In either case, we want low secondary value numbers... and to obtain those low numbers (and good primary values), we need to perhaps use thinner wire than we'd prefer... or possibly a higher net resistance, or a single coil build, when we'd prefer a dual parallel build.
With a regulated mod, you don't have total freedom in the sense that you can do stupid stuff, but... the range of possibilities opens up greatly when you can force wattage above that of the unregulated Ohm's law discharge.
Again, I'm a mech fan. Don't even own a hi-watt regulated mod... Yet. ;-)
That's it. Ciao for now!
A few days ago, this post popped up... with my answer to follow.
Although you provide no detail regarding your net resistance and wire gauge used... everything you need to be successful at higher wattages can be found in Ohm's law formulas, the Steam Engine coil modeling program... and an understanding of "heat flux". Heat flux is a number representative of coil radiant heat, expressed in milliwatts per millimeter squared.
I'll offer one example, which will apply to all comparisons, regardless of the variables, save for the constant of heat flux.
If you have a 32 gauge single coil at 1.8Ω, 8 watts is plenty for producing a "nicely warm" heat flux of 317 mW/mm².
To reduce that temperature, all one needs to do is lower the wattage, and/or increase the resistance value.
Why the hell is sub-ohm so damn popular?
To put it bluntly, sub-ohm or "high-performance vaping" is so damn popular because of increased coil surface area and higher heat values.
The net coil surface area of the above build/wattage is 23.95 mm². Flavor and vapor concentration, for a given heat flux, are commensurate with surface area.
With sub-ohm, it's not so much the amount of heat you can produce (although in some instances, it's advantageous), but rather the increase in net coil surface area, along with the amount of wick exposed to that surface area.
If our net surface area is twice that (or more) of the previous 32 gauge build... it would stand to reason that for the same heat flux, you'll produce twice the flavor concentration and vapor volume and/or density.
Is it a true 2:1 or more ratio? Not exactly. There are assorted losses, but depending on the juice PG/VG ratios used, along with a few other physical and electrical variables... empirical observations indicate that it's not too far off.
To obtain an 317 mW/mm²+/- heat flux from say, 40 watts, one of many optional possibilities would be... a 27 gauge, dual parallel coil build of 0.4Ω net resistance - producing a 313 mW/mm² heat flux.
In this example, the juice vaporization potential more than doubles from our previous 1.8Ω build - with a net surface area of 61.55 mm² - an additional 37.6 mm² of net coil surface area.
Use Steam Engine to run any set of comparable high & low resistance numbers you wish. To obtain a valid surface area comparison, adjust wire gauge, parallel coil count, net resistance and wattage, with the goal of obtaining relatively constant HF values... try to stay in a 10 mW/mm² plus/minus window.
That's All Folks!
(If you have any questions, please PM me. If the question and response merit sharing with others, they will be added to this article. Thanks)
First... you need a digital multi-meter (DMM). How much you choose to spend is entirely at your budgetary discretion.
A word of caution before we begin. Make sure that your meter is set correctly before any test. If you forget to switch from resistance to voltage and apply live voltage, you will pop the fuse in the meter... and unless a spare came with the meter, I doubt you'll have a back-up.
The terms conductivity and continuity I tend to use interchangeably, as they tend to be two sides of the same coin when it comes to resistance, but... in electrical terms, continuity is defined as an unbroken circuit, while conductivity is the ability of something to conduct electricity.
In other words... a copper mech mod conducts electricity better than one made of iron, but neither will conduct electricity if the conductive pathway has poor continuity.
Moving right along...
With the meter set to it's lowest Ω resistance range, touch the probes together and hold them. The lowest test reading you get should be zero to maybe 0.4Ω (at worst)... this is the baseline resistance in your meter and test leads. You will subtract it from any future resistance readings.
1. Measure the resistance from the RDA body to any bolt-on, screwed or press fit post (negative posts that are machined from the base are immune from conductivity issues)... it should be the same as your test baseline.
Measure from the positive post to the 510 positive pin... again, should be the same as the meter test number.
Some positive post/510 pins are made from once piece... and some are made of two components.
If you have measurements greater than the resistance baseline, you have an internal resistance problem with the RDA. This would be pretty rare, but you needed to eliminate as a source of resistance.
2. Again, on your lowest resistance setting... you can test the entire mech, or individual sub-assemblies for continuity. For example, with one probe on the mech top cap and the other on the button itself... press the button. This tests the entire ground conductive pathway from the button to the top cap, all at once. The resistance should be the same as your original meter baseline test... in other words, no additional resistance. If there is, then somewhere between the two probes, you have poor conductivity causing excessive resistance.
3. Next is a "no load" conductivity test. With the meter set to the lower voltage position (usually 10 or 20 volts DC), measure the voltage of a freshly charged, "known good" battery. Install it into the mod - carefully place the positive probe on the 510 positive pin and the negative on the mech case - fire the mod. You should have voltage identical to the bare battery. If you had less than battery voltage with no load... that's an indication you have terrible conductivity through the mod.
4. Next is an applied load voltage test, or "voltage drop" test. Because the meter, load, atomizer and battery are unique to you and not a universal constant, this test is not for comparison purposes to anything you see or read on the interweb... especially the testing conducted by Jon Kuro (see below).
This test is to allow you to "see" the conductivity loss or resistance in your kit, with a load applied. Got it? Good.
In a perfect world, there would be no resistance in our kit that would create a loss of voltage delivered to our atomizers... then reality sets in, and very few mods in day to day use have zero voltage drop.
5. Build a coil on your RDA at approximately 1.0Ω. With the meter set to the lower voltage position, again measure the voltage of a freshly charged battery. Install the battery in the mech and the RDA to the mech, with the cap off. This next part you may want help from a second set of hands.
Holding the positive probe firmly to the center or positive RDA pin, hold the negative firmly to either of the negative posts. Now fire the mod until the volt reading is relatively stable... preferably no more than 5 seconds.
The alternative, and far more convenient method of VD testing, is to obtain a 510 threaded, "in-line" volt meter. These too can have internal resistance to consider, but seldom in excess of 0.005v.
Referring to the Kuro Concepts (Jon Kuro) spreadsheet, a genuine BCV XXIX, under objective, repeatable testing - with a controlled 1.0Ω load has a VD of 0.00v. The absolute worst VD measurement I've ever seen or personally taken, with any mod, has been no more than 0.70v.
The difference between the battery only reading and the reading at the RDA is your voltage drop. Considering the circumstances, if you have a difference greater than 0.3 volts, you have conductivity issues with, in order of likelihood... your button, your contacts, your tube/cap threading and your atomizer.
More often than not, if you mod is of good quality, the most frequent cause of voltage drop is contamination (dirt, hand sweat) and/or tarnish & corrosion of conductive pathway parts.
Mild tarnish is easily removed with a pencil or ink pen eraser. Corrosion may require a bit more aggressive abrasive... like scotchbrite pads or 1000 or finer grit wet/dry sandpaper.
Finish up with a good cleaning with IPA (isopropyl alcohol - great for copper and brass) or just plain old hot, soapy water...
That's it... take it as it is, do with it what you will. ;-)
Notice! With the change in forum software, we're not limited to 10,000 characters per article... so this article is now part of the original part one article.
Steam Engine: Basic & advanced features: Pts. One & Two | E-Cigarette Forum
Thanks for taking a look... cheers!
This is going long... so get comfortable, and I'll try and make it as painless as possible.
Update: On 5/24/15 I discovered that the new forum software allows far more than the old vBulletin limit of 10,000 characters per posting, so I've combined what was originally a two part series into a single article.
More so than any other element of the Steam Engine modeling program, the variable of "heat flux", is the most difficult to understand. Along with questions about wire gauge, surface area, net resistance/parallel coil count (or why anyone in their right mind would want a 300 plus watt APV)... that I wonder just how many folks there are out there who may be avoiding 'SE' completely... perhaps because they feel a bit technically overwhelmed by the multitude of input options.
(Note: Things advance and improve rapidly in the vaping world. 200+ watt mods are now common place, as is temperature control - making some of the more critical tuning options, er... less critical. If you run a modern device, it still doesn't hurt to build an efficient atomizer, and if you run an unregulated (mech) mod, this article is still highly applicable)
In the next few several paragraphs, I will endeavor to explain how to use specific elements of SE... to the users best advantage.
First, lets give credit where it is definitely due. Steam Engine was created (and is continuously upgraded since it's introduction) by ECF member - and an extremely clever and generous fellow - by the name of "Dampmaskin" (AKA, Lars Simonsen). I'm honored that Lars has read both parts of this article, and approves them for content and accuracy.
The word 'Dampmaskin', as it turns out, is Norwegian for 'steam engine'... and Lars lives in Norway. Now it all makes sense, yes?
And for even more reading (as if this isn't enough already), here's Dampmaskin's blog and his FB page, on the subject of Steam Engine.
To begin, lets visit the often overlooked variables... variables in which you, the vapist must enter appropriate values. Viewing from top left, our first variable is "metric units/imperial/USCS units"
(top left hand corner). Use which ever method of measurement you're more comfortable with. I prefer metric, and/or decimal inch.
Certain aspects of the program, like "Inner diameter of coil" (top right hand) has a default of 1.3mm. If you use metric units, and click on the x/y" (top far right, lower corner of Inner diameter of coil)... a drop down will list values in fraction, and the display will indicate a metric conversion - i.e. 1/16" will show as 1.59mm.
If you chose "imperial units", the drop down will still be fractional, but will convert to decimal - i.e. 1/16" will be displayed as 0.0625".
Coil inner diameter (ID) is based on the outer diameter (OD) of the mandrel you use - be it a toothpick, a drill bit, the shaft of a micro screwdriver - all are considered, for our purposes, a mandrel.
If you use unmarked mandrels, a good investment will be a digital or dial type caliper, which will allow you to accurately measure your mandrel OD.
Our next variable will be "Advanced and Reset" (upper mid left hand). 'Advanced' will show more detail of your build model, and 'Reset' is just that... erasing all user loaded data, and returning you to a program baseline.
Want to play with braided or twisted coils? In the box for "Material and profile" the default profile is "Round"... as in round wire. If you click on the drop down menu on the right of that box, you'll see "Round, twisted/parallel".
Clicking on that, two new windows will open... "Twist pitch" and "Number of strands". You can use up to 4 separate strands of wire... and pay particular attention to the twist pitch value where you measure the distance between wire ridges... and insert that value into the twist pitch box.
Here is a re-print what Dampmaskin has written regarding twist pitch:
"The distance between each "ridge" on the twisted wire. Use 0 (mm) for non-twisted wire (parallel strands). For improved accuracy: Count 10 ridges, measure their total width, and divide by 10."
A bit of critical info for multi-strand users... if you have two strands per coil, even though they alone technically qualify as dual parallel coils, the program considers it a single coil, when you click the "round, twisted/parallel option. It's not a dual parallel build.
If you have four strands making up two coils... then it's considered a dual parallel build.
A thread from 6/18/15, where a more extensive explanation of the variables in twist pitch can be found here.
Next is perhaps the most valuable reference you can click on... "How it Works" (bottom lower left)... which extends the page (don't forget to scroll down a bit) and provides an overview of the program details, and how to interpret those details.
Quick note - The only thing that determines resistance is the wire length and thickness. Example: A 72.6mm length of 28 gauge Kanthal A1 wire (call it as you wish, terminal to terminal - post to post or positive to negative) will always have a resistance of 2.6Ω.
The wrap count, coil ID, leg lengths... any and all physical changes you make to the wire (aside from stretching it with high tension, or cutting it to a shorter length), have no effect on resistance.
Let's look next at "Setup". Setup is a drop-down option of the physical elements, for the determination of net resistance ('net' being the combined resistance value), of your build.
Individual lengths of wire have a singular resistance value - adding additional lengths of wire will alter the net resistance - dividing the value of one wires resistance by the total number of wires used. This is called a "Parallel" build.
Example: If you have 2 individual coils (dual parallel), the net resistance will be the resistance of one coil, divided by 2. Five coils... divide the resistance of one wire by 5, and so on. An example of this would be a penta (5) parallel build, where it would require five 3.5Ω coils to produce a 0.7Ω net resistance.
The "Serial" build option is when coils are end to end... like one piece of wire used to make two or more coils. Basically, regardless of the number of individual coils made in a length of wire, you are using the resistance value of that length of wire for the total resistance value.
So... four coils made using one length of wire (and ending in one pair of +/- terminals) has the same resistance as one coil, made from the same length of wire... and a whole lot of leg length.
Jumping ahead to some additional less than obvious elements of SE...
"Leg length"... is the approximate length of the wire "leads" at the ends of your coil. Call them legs, tails or pains in the backside... this is something that can be measured accurately, but typically only after the coil has been installed in the atty. Long legs waste available energy... keep 'em as short, within the limits of RBA physical properties and placement relative to air flow.
I tend to use 5mm (or 10mm for 2 parallel coils) as a general purpose length (2.5mm length X 2 legs per coil)... because it takes a substantial change in leg length - unless you're on the ragged edge of a "Number of wraps" - to have any effect on the finished wrap count.
There... that didn't hurt too bad, did it? Good... the next bit might.
Heat Flux... and you.
Lets look at perhaps the most ignored, misused and/or misunderstood option in SE... and the reason I wrote all this in the first place. "Heat Flux" (HF).
Heat flux (HF) is a measurement of radiant heat our resistance wire coil generates, measured in milliwatts per millimeter squared, or mW/mm2.
Dampmaskin has provided, along with actual numeric values, a color code range that runs from a cold blue to a flaming hot, deep red... so you can, by calculating your current build and PV power output, create a baseline reference, or optimal HF to suit your personal preference.
The easiest way to view heat flux is as the radiant heat potential of an atomizer - not a specific, Fahrenheit or Celsius value. Even with an infrared, laser aimed thermometer, the variables that effect
temperature are too many and too inconsistent to be remotely relatable.
The way heat flux works... you can approach it from more than one direction.
You can use it to determine the optimal wattage value for a given build, or the optimal build for a given wattage. With the latter, a single change to one element, will affect all other elements.
In practical (and overly simplistic) terms, the lower the peak wattage output of your device, the thinner the wire must be... and of course the higher the current output, the thicker the wire gauge you can adequately support.
Let me offer an example. You are a mech user, and are - like most RDA fans - of the opinion that thicker wire is always a good thing. You build a dual coil RDA with a 28 gauge, dual parallel build at 1.0Ω. You're using an 18350 mech with an Efest "Purple" 10.5a rated battery.
So... why the hell is my vape so darn cold, or why does my wick and coil "gunk up" so quickly, you ask? Heat, or rather... a lack of it.
You may think that because your battery is rated for 10.5 amps continuous discharge, that you're getting a full 42 watts of power and your heat flux is around 186 mW/mm2, right?
Recalling Ohm's law... your resistance dictates how much current is being discharged, which in the case of a 1.0Ω net resistance and a 4.2v battery... that's only about 17 watts. Your HF is a chilly 75 mW/mm2.
To "push" your unregulated 18350 battery mod to it's maximum continuous discharge, you'd need to run at least 30 gauge wire for a 1.0Ω net resistance, dual parallel build, and preferably 31 or 32 gauge, to obtain a warmer heat flux.
Other options are a lower resistance, or build a single coil with your 28 gauge... any of these, or a combination will increase your HF temperature.
Watch the HF values change - sometimes dramatically - as you change just one variable.
If you're a unregulated mod user (mech), you can't "force" wattage as you would with a regulated APV. You'll need to use Ohm's law formula to calculate wattage discharge for your resistance and battery. Same goes for APVs that are voltage controllable only... to obtain a wattage value SE will accept.
Another example, is with a 100 watt VW APV. Because you can, you want to run the full hundred watts, to see what it's like... right? What can you build that won't turn your mod into a Tiki torch?
First, set your wattage value at 100 (or what ever you want to start with), then on to your "Setup".
For setup, we're using a dual parallel coil RTA, like an Orchid. Next set your target or desired resistance... lets try a net resistance of 0.6Ω.
OK... based on past experience, we don't want our heat flux higher than 375.
Now... start to adjust the size of your wire, while you watch the HF values.
Click, clickity... click. 28 gauge is too hot and 24 gauge is a bit too cool... but 26 gauge, with a HF of 369 is (well, if you're into pretty darn warm) just right.
Let's run a popular low powered example... for an MVP2, at it's limit of 11 watts, 1.3Ω+/- and 3 amps. You may have already guessed that we might need thin wire for this one... but as a single coil build, we can do better than you might expect.
Using 28 gauge wire at 8 wraps (on a 2mm mandrel), we get a "green zone" HF of 163 mW/mm2, and if we go with a 30 gauge wire at 5 wraps... a very nicely warm HF of 326 mW/mm2.
The only down side here is the coil surface area... but as all we have is 11 watts to work with, not to mention that 1.2Ω limit, it's the best we can do.
If we had a lower resistance limit, say enough current output for 0.8Ω... we could get a warm 244 mW/mm2 with a 28 gauge 5 wrap build.
So, is there an "optimal heat flux"? Good question.
Although one might consider something in the green to yellow as an optimal value, I continue to run into individuals who prefer a heat flux in the blue / green range... and some into the deeper red zone. It's a highly subjective value, and one that drawing comparisons of - unlike wire gauge, juice blend or net resistance - offers only limited value to the individual.
What you like, is... what you like. If you like a warm 356 mW/mm2 in December, and a cooler 189 mW/mm2 (or less) in August... that makes all the sense in the world, don't it?
Perhaps the easiest way to determine your best heat flux is to run the numbers of what you are currently happy with. If you're somewhere in the 150 to 400 mW/mm2 range... it's a wide range, but surprisingly, fairly normal.
The more experienced RDA users tend to run the hottest, then, due to their limited coil chamber space - RTAs, with clearos glassos and cartos usually running a bit cooler. The latter vapists are frequently beginners - and having read all the scary ECF warnings - are a bit paranoid about things exploding, or being rendered unconscious from the massive vapor hit.
The text book optimal or perfect build would have a user preferred HF... along with the more universally desirable low HC for a rapid heating time, a low leg power loss, so you're not wasting energy to heat legs... while we're at it, and if that's not enough, a terrific surface area - more area - so more juice gets vaporized.
Does that exist? Absolutely, but only within certain parameters - a parameter target you can hit squarely... or miss by a mile.
Based on what I read in the vape forums on a near daily basis... there are far more builds that miss the target by varying degrees, than are direct bullseyes. Seriously.
Don't believe me? Run someone else's numbers. You might be surprised (as in builds that are far too hot or cold, with terrible temperature lag, and/or high heat capacity values)... at what you discover.
Speaking of heat capacity...
Another ignored and misunderstood reference value (even more so than HF) is heat capacity (HC). It's important... but not as user critical as heat flux.
This is a representation of time-to-temperature efficiency... or how fast a coil will heat up - to the heat flux value. Time is directly relatable to the coil(s) mass.
The value - mJ K-1 - is measured in millijoules (time) to Kelvin (temperature per mass). The higher the mJ/K value, the longer it takes for the coil(s) in question to reach peak temperature (HC).
(After spending a good bit of time researching reference material, converting Kelvin to C° and F°, converting millijoules to BTUs and watt-seconds, making pages of notes, discussing it with Lars and "readeuler", (both of whom did meaningful research - and the vast majority of "hardcore" mathematics) about alternate references - until further notice, it shall remain as stated... or simplified to just mJ/K.)
In atomizer heating elements, a clear example would be... a pair of thinner gauge parallel coils are more efficient than a single thicker gauge coil - at the same resistance and wattage input - due to the greater net mass of the single coil.
The net mass value can be found by clicking on the "Advanced" button (upper mid left hand) and scrolling to those coil physical dimension values.
Examples: (where a lower HC value is preferred)
30 gauge dual parallel build at 1.0Ω/24 watts. HF is 214, HC is 12, net coil mass is 25 mg.
28 gauge dual parallel build at 1.0Ω/24 watts. HF is 107, HC is 30, net coil mass is 64 mg.
24 gauge single build at 1.0Ω/24 watts.......... HF is 106, HC is 94, coil mass is 205 mg.
22 gauge single build at 1.0Ω/24 watts.......... HF is 53, HC is 239, coil mass is 519 mg.
Example 1. Is our baseline... the most efficient, with the highest peak temperature.
Example 2. Efficiency decreases 2.5 times that of example 1. Peak temperature decreases to 1/2 of example 1.
Example 3. Efficiency decreases 3 times that of example 2, and nearly 8 times that of example 1. peak temperature remains constant from sample 2.
Example 4. Efficiency decreases 2.5 times that of example 3 and 20 times that of example 1. Peak temperature rises to 1/2 of example 3 and 1/4th that of example 1.
What you can take from this is that - for a desired resistance (wire gauge and length to produce a specific resistance) along with coil count and wattage - coil mass can have a substantive effect on the efficiency of your build.
There will be an optimal value for a given set of elements, where you can have the desired high HF, with a fairly low HC.
The way I see it... coil net surface area comes first (or not... because many will limit surface area because of power or lower resistance limits,) desired HF, then the lowest HC I can produce for that desired resistance and surface area. I'm willing to tolerate a few extra seconds of time to get the HF and surface area I want.
5-23-2015 Addendum: Having read this through a few times, I've decided to re-write it in it's entirety... with a more "step-by-step" process suitable for brandy new Steam Engine users.
I'll save this old version when I post the re-edited, "new and improved" version... for those that have it linked as a reference source.
10-18-2015 Addendum: I am a lazy ........ I will write something soon. This year... promise. No, really. Honest.
For a long time now, we've seen threads -
"What size are the o-rings on a fill in the blank atomizer?" or,
"What size are the magnets on a fill in the blank mod?"... or the broadest of inquiries,
"I need to measure anything you can think of that might need accurate measuring... how can I do that?"
More often than not, if these inquiries even get a response... it's from a member who owns both the device in question, and a dial or digital caliper... and is willing put forth time and effort to take some measurements. (that or some douche spouting useless blather, just looking for a post count bump)
Time was, only engineers and machinists owned and used vernier... and later dial, and now digital calipers. The initial costs of quality measuring tools, at one time kept them out of the hands of hobby class users. That has changed.
These days for as little as $12, you can get a dial caliper with 0.002" (0.04mm) resolution. 0.001" resolution is common place for around $100, and - in the hands of an experienced user - down to 0.0005" or less resolution, for a digital caliper costing no more than $250.
My point? If you are a RBA, RTA, RDA, mech mod... or otherwise "advanced aficionado" of vaping products, this is a tool - much like a DMM, ceramic tweezers, thread gauge, butane torch or o-ring fabrication kits - that belongs in your bag O' tricks. Without dial or digital calipers - like being electrically "blind" without a DMM - you are dimensionally blind.
So, rather than resort to asking the most base of questions... in the hopes that someone - with both device, calipers and enough empathy for your sad plight - will take the time to measure... drop $25 and get your own.
P.S.... Do you build your own coils? You do! Great! Ever wonder why your builds will often come out different from the calculated values generated by a Steam Engine build model?
Ready for it? Did you obtain a decent caliper or micrometer? Measure your coil wire. Now compare that measurement to the default value for the gauge, as indicated in Steam Engine. Not the same is it... there's the reason your builds always seem a little off.
So many questions, so much misinformation - and all it will take to clear up at least 80% of both... is a bit of knowledge.
If you can do basic math... the most useful Ohm's law formulas are:
For wattage ("Power") the formula is V² ÷ Ω = P.
For amperage ("Current") the formula is V ÷ Ω = C.
This isn't going to be a class in all things Ohm's Law, so much as a few things you need to know about resistance and power... so that both your vape and your safety is well considered. First... lets open up a very easy to use, uncluttered with BS, on-line Ohm's Law calculator, or 'OLC'. Got it? Good.
Most common misconceptions I run into are:
"What wattage do I need for X resistance?"
If we are using a regulated APV, then we need a few of it's specifications. The maximum wattage and amperage maximum or limit.
Lets say you want to run up against the "edge of sub-ohm"... but you have a 15 watt limit. Can we go sub-ohm with just 15 watts? Yes... yes you can.
Lets put 0.9Ω into the appropriate box of our OLC.
Insert the 15 watt value, the 0.9Ω value... and hit the button. We get 3.7v and 4 amps filling out the other boxes.
Can we use this? Yes we can... because the specs of our APV indicate an amp limit of 5 amps - and we're under than value.
If we were over that value, you could still run your wattage, but at the selected resistance, there would be no additional benefit.
Most VW APVs have lower resistance limiters as well... for example, the Innokin MVP2 has a 1.3Ω/3 amp/11 watt limit. If you insert any two of those numbers into our calculator, you'll see that they line up fairly well with Ohm's Law.
If you try to use a resistance less than Ohm's Law indicates the maximum power of your APV is capable of supporting... there is no benefit.
The above doesn't take into account a value called "heat flux"... which is the coil radiant heat temperature. Heat flux is one of our most desirable tunable elements... second only to net coil surface area for value. You'll learn a lot more about heat flux when you read the two part series on using the Steam Engine coil modeling program.
"What's the smallest battery I can run with X resistance?"
This is the kind of question a new mech mod user will ask, because they don't really know anything about battery ratings or how Ohm's Law applies. Because unregulated mechs are used mostly with low resistance, lets use 0.5Ω as our reference value.
The batteries we have on hand are AW IMR 18350 (6a), 490 (16.5a) and 650 (24a/1600mAh version).
Now... we need to know how much amperage we need for 0.5Ω. Because an 18XXX series battery has the same base voltage regardless of size, we can use that as a constant. I use 3.9v as it's not a full charge, but still above base voltage. Insert 3.9v and 0.5Ω into the OLC. Our required amperage draw is 7.8a.
Because our mech mod is unregulated, we need a margin of safety. I use 10% of the rated battery maximum continuous amperage drain value... so, a battery rated at 15 amps, I would subtract from that, 1.5 amps.
I would seriously suggest that new mech users use 10%~15% margin of safety... until you have a good understanding of what you're doing.
If we look at our battery amp drain ratings, we see that the "smallest" battery we can use is the AW IMR 18490, rated at 16.5 amps... leaving us a substantial margin of safety.
This begs the secondary question... "So, how much lower can I go with that 18490 battery?" Insert your base voltage, and our AW IMR 18490, with a 10% margin of safety subtracted from it's max. amp drain rating. 14.8 amps is the number we're "pushing up" against. Run the numbers, and we can go as low as 0.26Ω.
"How low a resistance can I run with X battery?"
This is a variation of our last question. Lots of folks want to run an 18350 battery to keep their mechs compact. Nothing wrong with that, but there is a resistance limit you can't ignore.
Using our AW IMR 18350 6 amp limit... we can easily calculate our lower resistance limit. With our safety margin, we have 5.4 amps to work with... so, lets insert amps and volts. What did you get? I came up with 0.7Ω.
If we had one if those new Efest "purple" 18350s with a mfg. rating of 10.5 amps... run the numbers again and we come up with 0.4Ω.
"How can I use Ohm's Law to figure out the right voltage for my mechanical mod?"
This question is coming from a place of confusion. Can you control the voltage of a typical unregulated mech mod? Nope... battery voltage is what it is. Even with a Kick, you only control wattage.
I run 0.3Ω dual coils... which Kick should I buy?"
Ahh... the kind of question that makes you go To begin, how is it that someone "runs 0.3Ω dual coils", yet apparently has no concept of what a Kick is, or how Ohm's Law works? What are they currently running "0.3Ω dual coils" in - on what APV and why the hell do they think they want a Kick?
Kicks were designed to allow mech mod users the look, feel, style and "simplicity" of a mech... with the safety advantage of a wattage regulated, amperage limited APV. Kinda like turning your $200 Nemesis into a Vamo.
All Kicks, from the genuine Evolv Kicks 1 & 2, to the various clones, have lower resistance and maximum amperage limiters... just like any other VW APV.
Toss on your atomizer, crank it up and go. If you didn't do your OL math, installed a atty with too low a resistance... it will either not work, or run your battery down pretty quickly.
What wire is best for X resistance? (Sorry... not everything is about Ohm's Law)
A good question this one... and one encountered often. There are a few ways to go about it. You can read posts, look at YouTube videos, see what others are doing and experiment with those examples.
You can refer to Super_X_Drifter's coil building thread with examples of differing resistance values for a common coil build... or you can figure out the perfect, optimal build yourself using "Steam Engine"... a multifunction vaping calculator that may be the most valuable vaping tool you ever use.
Heat flux (HF) and heat capacity (HC). These are two values available found in Steam Engine... that are far more important than you might first imagine.
You can use HF to determine the optimal wattage value for a given build, or the optimal build for a given wattage.
Although not as useful as HF, pay attention to the HC... if you selected the wrong wire, your HC value will go up, and you'll wonder why it takes so long for your build to heat up and cool down.
More information on these two values... can be found in the Steam Engine Advanced User guide. Yes... yes I have promoted the user guide twice in one article. Steam Engine will be that valuable to your vaping happiness.
What is the momentary or "pulse" rating of a battery?
Batteries may have two ratings. A Maximum Continuous Current Discharge (MCCD) rate... and a pulse rate. Pulse can be anywhere from 1.5 to 3 times that of continuous, and is base on the amperage potential within a short time frame... from as little as one second to as long as 30 seconds.
Pulse rating can be used for an unregulated mech mod to calculate resistance. For example, if a 10a battery has a 20a pulse rate for 10 seconds... then you can calculate resistance for 20a... for 10 seconds. After that, amperage drops rapidly to the continuous rate.
Not all batteries have an advertized pulse rate, and although you might feel comfortable extrapolating your own, based on the continuous rate... you are only guessing.
In the end, I do not recommend using pulse rate values to beginners. Stick with continuous ratings until you have confidence in your knowledge and abilities. Don't go supersonic, until you first learn to fly.
Addendum 5-1202015: These fairly recent, unusually high (35, 38 & 40A) 18650 ratings are not in fact MCCD ratings, but rather pulse or "momentary" ratings.
Granted, they are relatively modest pulse ratings within a time limit likely exceeding even a deep draw vapists usual application... but they are still a lie, and not the true Maximum Continuous Current Discharge.
The same applies to the the smaller popular vaping batteries, where the listed amperage is above the norm.
That's it for now. If anyone who reads this has a specific question... feel free to ask and if it's a good one, I'll include it in the above. Same for errors... see any? Let me know.
As always, take it for what it is, do with it what you will.
RBA, RDA, RTA... oh my! For those folks that are new (and semi-new) to RBAs, what are they and how do they work?
I could delve into the history of the RBA, but I imagine that most of my "gentle readers" don't really care about history - rather a bit of definition for what is available now. I'll also toss in a few bits of editorial commentary for the reader to ponder.
I apologize if I don't mention "your" atomizer. In the scope of this short article, I can't cover every atomizer design made, so I'm focusing on what the blue collar "Joe Vapist" is buying now.
If this annoys you, write your own elitist POS article.
First, lets define what an RBA is. An RBA is any atomizer, designed so that the wick and coil elements are, to a large degree... at your discretion.
Beginning around the fall of 2014, you can buy RTAs with your choice of ready to go coil/heads, or the option of a DIY RBA head. You can start off with know RBA experience and just use the supplied coil/head assemblies... and at your discretion, learn how to produce your own builds.The Kanger Subtank and Subtank mini are good examples of this relatively new genre of "user optional" atomizers.
Beats the hell out of trying to rebuild a clearo/glasso that was never intended to be rebuilt... don't it?
Some will require, due to their design, a specific shape or even specific coil and/or wicking material, but for the most part... it's builders choice, hence the name "rebuildable atomizer".
They can be a rebuildable dripping atomizer, like the ubiquitous and still hugely popular JPGE Nimbus... or a genesis type atomizer - the Smoktech RSST being a popular entry level example, or a tank type atomizer or "RTA" - as represented by perhaps the most popular RTA ever made - the SvoeMesto Kayfun.
In the last few paragraphs, I'll include a few RBAs that fall into a, mostly undefined category - the "top-filler-to-wick" atomizer.
In basic design, a dripping atomizer or RDA, is the simplest form of atomizer. They do not have a built-in, semi-sealed or sealed juice container or tank. You build your coil(s) and wick(s), drip juice from your bottle onto the wick... and vape away. When the draws start to taste a bit dry and less flavorful, it's time to drip in more juice.
The upside of RDAs are that they allow practically any coil - shape, quantity and resistance values are limited only by the number of terminal posts and the size of the build deck. The wicking materials used are unlimited as well - from "roll-yer'-own" cotton ball to ceramic rod or rope... it's your call.
The downside to RDAs is that they don't have a juice container - with even the deepest juice wells holding no more than 30 or so drops of juice. RDAs can leak, and will require that you have a separate juice bottle at your disposal.
"Drivin' and drippin' can be a dangerous habit to develop - particularly with a manual trans, or motorcycle.
Still hugely popular, but... as drippers become larger, more refined and complicated, what will they turn into - something else entirely?
The Genesis RBA
A genesis atomizer is a device made from necessity - and a "Eureka moment". We look at the dripping atomizers greatest negative, a lack of juice container - and think, "how do I get around carrying a juice bottle and dripping?" - with the answer being... "lets just attach a juice tank to the bottom of an RDA, and run the wick down into it!!!!" And that's how the "genesis" was born.
OK... maybe it wasn't quite that simple.
Genesis atomizers have some limitations and requirements. Because the liquid tank is not sealed, if you tip it over or upside-down, juice may leak... or even pour out the wick hole or tank vent port.
Because they essentially feed from the bottom up, you may need to "tip" the atomizer to get juice up to the portion of wick that is wrapped by the coil. Wick materials and design become more important in that capillary action is a critical consideration.
Stainless steel mesh and rope, as well as ceramic rods are popular wick materials, as they can provide a balance of adequate, but not excessive, capillary action.
There are new and interesting variations of genesis atomizers introduced every day. Some that are guaranteed not to leak and some with tanks on top.
"Genny's" have lost a lot of love in the past year or so... mostly due to the next RBA on our list.
The RTA - "tank" atomizer
All of the popular tank type atomizers can be defined using another term... they all operate on the principal of "pressure differential". The hyperlink is to an article on how pressure differential or "PD" tanks work.
For those that don't want to read the entire PD article, in short and sweet terms... positive pressure (in the air venting system) and negative pressure (in the liquid tank) are held separate - yet balance... serving to feed juice, in appropriate quantities, to the wick. The wick itself may aid in this function, acting as a seal between the two pressures.
Added 7-1-14: (Sorry... I'm about 2 months behind in adding this)
If you've not heard of it, don't feel too bad... because the Highwinds Ruzgar, and it's recently introduced clone (first one... anticipate better quality ones) have been a bit under the radar. Think of it as a top fill, glass tanked evolution of the KFL. It doesn't have AFC, but the genuine one I tried had air flow on par with a stock Kebo R91%.
The previously mentioned Kayfun is one of the 'true' pressure differential atomizers, in that the design does not use the wick as a seal, but rather only the "boundary layer", established by juice channel orifice size, to keep the pressure, and juice, separate.
Other popular PD tank atomizers, like the Stattqualm sQuape and Taifun GT use orifice size restriction as well, but in concert with the wick, which, not unlike a glassomizer coil/head assembly, serves to define that restriction.
"Filler" type RBAs.
OK... I'll be honest here, I'm not sure what to call them. Gravity tanks, top-filler-to-wick tanks, capillary tanks - are any accurate enough to stick?
This category is populated with atomizers like the VapourArt GP Spheroid, early version GP Heron and Gus Aiolos... which can be considered closer to genesis atomizers than RTAs, because they do not use pressure differential or a true liquid tank, but rather a filler material, usually "cerawool", to both hold juice, and feed the wick.
Interestingly enough, the latest version GP Heron, with the addition of a spacer/separator, or as VapourArt calls it - "a topper that works as a reducer and cotton feeder at the same time" - this after-the-fact part, aside from the stated design intent, creates the potential for a seal between liquid storage and vaporization chamber.
This seal, depending on the build, may be sufficient to create and hold a negative pressure, effectively turning the atomizer into a semi-PD type tank... but one where the pressure variance is not used to feed juice. There is a Heron clone available now from FT.
There's a relatively new atty on the market made by GUS in Greece, called the Estia.
It is a PD atty, and is designed around 3 coils with 6 wick tips "in the juice"... with the highest air flow of any RTA to date. It's currently the very best RTA I've ever used... and as close to a good RDA as one can buy.
Not much else I need to say, because qorax has done a very well photographed, slightly gushy and subjective, but never the less informative review here.
If you get a chance, take a look at the Inverno Erlkönigin review too. I don't know qorax, but I know he does two things very well... buys the latest cool attys, and produces some very well photographed reviews.
The Fogger V4 came out a month or so ago. This is a dual coil atty... and I mention it in the same breath as the Estia, because it's, well... quite a flavorful vape for such a low cost atty.
It doesn't have the air flow, features or quality of fit and finish of a genuine RTA, but it's 1/5th the price... and easily one of the best performing clones you can get. Only the single coil, genuine Taifun GT is on par.
Due to it's low price, there are many threads in the RBA forums on this atty... so find one, and read.
I return and update as things change... stay tuned.
As always, take it for what it is, do with it what you will. Cheers!
It is not voodoo, or related to internal combustion engines - it's the way the wire is designed - and this "feature" of Kanthal ('A' series, including A-1 and AE) has been well known since before you or I were born... and just one of the qualities that make it so common and useful. ;-)
When heated, Kanthal wire (iron-chromium-aluminum) builds up an aluminum oxide insulative coating on it's outside surface that protects the individual coils from shorting, one to another. This is called alumina (Al2O3).
This is most clearly noticed when you test fire a new compressed coil... the coil initially shorts and heats unevenly. The more you fire it (and shape it to final perfection) however, the more evenly it will heat - from the hot center out to the cooler ends.
This is the alumina layer developing and insulating the coils surface. Although the coils are "touching", the electrically conductive component of the coils are insulated by the alumina coating.
That is it. No magic... unless a self-generating, protective oxide layer is considered magic. Maybe it is magic - Kanthal wire is both thermally conductive and electrically resistive. Pretty convenient for us, and several billion other handy applications for heating coils.
Consider as well... for a given length and thickness of wire, the resistance does not change whether it's a 7 wrap conventional coil or a 7 wrap compressed coil.
Again... resistance for a given length does not change any appreciable amount.
What does change is the amount of heat the "compressed coil" is capable of generating. Reduced to a short, concentrated segment or element, the heat generated for a given resistance/area can be greater than the sum of parts.
Why you ask? The simplest of answers.
As stated, we have concentrated the heat generated by the individual coils into that smaller, more cohesive heat generating "element".
If you're still on the fence, consider this analogy. Ten matches, lit and separated by 1 inch per match, generate the heat of... 1 match or individual heat source per inch.
Now, ten lit matches, all within one square inch... 10 times the heat concentration / compressed down to one square inch.
Last, although "micro" is used to define a small diameter (1.5mm or 1/16" - or less), compressed coil heating element, you can compress a larger diameter vaporizer coil and have the same result of greater heat concentration for a given dimension of resistance/area occupied.
That's it. Share if you want, or keep the "magic" to yourself and continue to be entertained by the voodoo explanations. It is fun, ain't it?
You might be thinking, "boy SOF, you are one smart SOB".
Well, maybe... but I didn't invent Kanthal, and I'm not the first on ECF to comment about the wonders of the Kanthal wire design (for which there is a vast supply of interesting history and applications... if you like reading about such things that is).
After writing this, I was both generally curious - and because terms tend to be specific with this subject, didn't want to publish if there might be an impression that I was plagiarizing. I don't have much... but I do have a annoyingly huge sense of integrity.
So... I typed in "aluminum oxide layer electronic cigarette forum" (among other combinations) into Google (it parses down better than the ECF search engine) and the first to pop up (of perhaps more?) was a post by LucentShadow.
So you see, not only not magic, but not a secret either.
Addendum for 12-17-2015: Something you will likely run into is that, when comparing your actual net resistance to the default resistance found for a given gauge of Kanthal wire... your actual doesn't match the default.
This is likely not any mistake you've made, but more likely to be a manufacturing variance in gauge thickness. Every single gauge of genuine, Temco sourced, Sandvik Kanthal A-1 wire I have on hand is not as thick as the default given in Steam Engine.
For example: Item number RW0249, 24 gauge Sandvik Kanthal A-1 has a listed "average" thickness of .0201/.511mm... which is what Steam Engine uses as a default.
The 4 rolls I have - which were obtained over the course of several months and not likely to be from the same production date - measure from a low of .018"/.465mm to a high of .019"/.494mm, but none match the average dimension.
So... always measure your wire with a caliper or mic, and if not the same or very close... substitute that value for the default. In Steam Engine, the gauge number box will change to "N/A", but with the right or "corrected" value, your measured resistance will be far closer to calculated.
Addendum 3-3-2015: A thread on Kanthal metallic taste and coil degradation
Addendum 6-18-2015: A terrific thread with electron microscope photos and X-ray metallurgic content analysis of Kanthal wire - posted by ECF member @Alien Traveler
This is about all copper China mech mod clones. Not necessarily about copper and SS or copper and brass - but all solid copper tubes & top/bottom caps as well.
As it erks me to see uninformed people pissing away money on trendy crap - then complain because there $20 mech isn't as well made as a $200 mech... if you have the time and energy, read on...
Copper tubes and even end caps/buttons are the current - and not done yet - rage with mech mods. Copper however, in many of it's forms, is relatively soft... and I imagine some, but certainly not all, are aware of this.
Yes, there are the high end, C101 oxygen free and various alloyed copper (and bronze) variations, that if used, stand up nicely as the building material of a mech... but even at rock bottom discounts, these are still at a price likely 4 times that of typical clone prices.
As you can imagine... with clones, it's a different story. Going in, we can be safe in assuming, unless otherwise noted, that the copper used in a China clone mech mod will probably be rather soft - and that is what I'd like potential copper mech buyers to consider.
Because copper can have some unique attributes in machining - like heat expansion for example - that the Chinese, in a rush to mass-produce, may ignore... we may find that a good number of copper mechs will describe much like the one below.
This link is to a ongoing continuity test thread at Calivapers. I've linked this before, for a number of reasons, but mostly because I believe the tester, jkuro, is about as unbiased and well versed as one could possibly hope for in a experimenter, and has provided, without compensation, hours and hours of, accurate, repeatable test data and ancillary information about our beloved mech mods.
Where I'm going specifically, is to post #405 - made by jkuro regarding his findings of a copper Nemesis clone. I think, before you lay down cash on a copper mech mod, even the relatively small sums associated with clones, you might want to read, and consider.
There is a reason why genuine mod makers are treading carefully into the copper mod arena. And why those like Bay City Vapor, who make the SurfRider and XXIX mechs, use premium C101 copper.
Separate names with a comma.