Ohms.... and their significance

[pipeman01]

I've been rebuilding a couple of months now and I've lost my way    maybe it's too much information or conflicting information or maybe I'm just thick.

I'm sort of hoping one of the experts (not naming names) will pick this up and produce a "sticky" as I can't find a single source of reference... 

I use Steam Engine and by playing around with numbers I can make a (for example) 1.5Ohm coil using an almost limitless combination of Kanthal / wraps / internal diameter

.28 9.5 wraps at 2mm
.28 8 wraps at 2.5mm
.26 14.5 wraps at 2mm
.26 12 wraps at 2.5mm

etc...

So the Ohms calculation is a correlation between length of wire and thickness (resistance) of wire.

My question is then, which is better (and why)... lots of wraps with a smaller internal diameter or less wraps with a larger one?

Bonus question 1 - What is the effect of spaced (non touching, as wound on a bolt thread) vs touching (heat / tweezer method to heat from inside out) ?
Bonus question 2 - Different wicking materials can be used (organic cotton, muji, bacon, silica etc)... apart from personal preference, what are the different characteristics?
Bonus question 3 - With the advent of TC - can we have similar responses to the questions using Nickel instead of Kanthal? (I accept you can't / shouldn't make a 1.5Ohm coil in Nickel but the comparison still stands)

I've started so I'll finish....

This is the noobie question (shows how confused I've got with this) - Given a choice of 1.5Ohm, 1.8Ohm and 2.0Ohm prebuilt coils for my Nautilus, what would I need to consider to decide which one to use? And, "if" I couldn't see the Ohms rating via the screen / on the coil, how would I be able to tell the difference (blind taste test scenario)?

I've deliberately left sub-ohming out of this as it's a different genre and I suspect those into sub-ohming know all the above already.

[VapingBad]

Unless you are using an unregulated mod ohms are not that important, but rather how the heat is spread over the surface area and how fast they heat up. Regulated mods have upper and lower limits on the resistance they will power that shouldn't be ignored, but as long as you are within these it is more about coil shape or geometry. Spaced coils mainly prevent shorting between loops especially with thinner wire. Thicker wire will last longer than thinner, but can be slow to heat up.

All this applies to nickel, but with the low resistances needed you are restricted to thinner wires, it shows up coils where you don't spread the heat well enough by hitting the temp limit early and ones where you spread it too much by not enough vapour.

So you may ask what shape/geometry should I go for? That depends on vaping style, atty, wick and airflow and ther is no one right answer.

[thatguy]

Wire thickness will determine how quickly a coil heats up and how warm the Cape is. Thicker wire means slower heating and a cooler vape.

the diameter if the coil is dependant onthe space available in your atty and the power you vape at. Too large a diameter and you risk shorting against the deck or other parts of the atty, and a large diameter will struggle to get up to temperature at low powers due to too much juice in the wick, but the larger diameter can help reduce dry hits.

Spaced coils allow you to cover more wick whilst keeping the resistance down, micro coils are more compact and heat faster due to the coils being closer together


On a regulated device, it's worth finding out what resistances work best for your mod. All mods have limits on voltage and current ranges, and can be limited in power output at certain resistances. Steam engine has a section covering this.

[letsavit]

Basically what vaping said unless on a mech I don't think ohms and look at the atty, its air inlet, where the juice will be heated and where the vapour needs to go, the chimney. Some waffle from me on another thread with regards to nickel

" for single cotton coil 10 wraps spaced is way too much, heat spreads and is also using the cotton itself as heat source, it heats it...also with spaced you have more channels for the vapor, not just the 2 like pinched, more air velocity because it's straight though the coil not around it. Temp control also seems to centre the heat to the middle of the coil anyway so why have 5 wraps of potential trouble, 5 wraps over the air hole, the rest is wasted. IMHO. Burnt cotton test on 6 wraps......most of the heat is applied to the center of the coil, if that was 10 wraps the cotton would be marked the same.




"Spaced, you can suck though the cotton so why not take the most direct route for flavour"

Was taking a Kayfun etc. why create turbulence in our atty's and have vapour we want flowing against the juice its pulling in a tube...ie pinched coil... Same can apply for kanthel, I'm experimenting...!

[giles]

I think the basic objective is to maximise the coil area without getting any of the coil too far away from the air hole or messing up the air flow in your chimney. Also a long coil may not get the juice to the middle so smoothly.

First question - it's a balance obviously. I think 14.5 wraps is too long - most of it won't be over the air hole. I'd go for the 8 or 9.5 wraps.

Bonus q1 - touching is better - you get more area near the air-hole, more heating area inside your rta. And personally I got more dry burns when I used open coil - possibly because the wick carries some of the heat itself, possibly because I'm better at it these days.

Bonus q2 - it's down to personal preference, and I haven't tried all of those. Cotton will wick better (carry more juice to the coil more quickly) than silica (and I think most people prefer the taste). You can dry-burn a coil with the silica wick still in it - you can't do that with a cotton wick. You can pull the old cotton wick out of a coil and insert a new one, which you can't do with a silica one (or at least you couldn't in builds we used in the old days - long time since I used it).

I don't have temp control, so I'll leave that to someone else.

Noobie question gets a noobie answer - do whatever works best for you. If you can't tell the difference it doesn't matter.

For a given watts setting they are likely to be very similar. Most people probably buy the lowest ohms that their device is happy with.

I don't have a nautilus, and I don't know how nautilus coils are made. For a given wattage: if they use the same size of coil and vary the wire thickness you may find that the lowest ohms burns a little hotter. If they vary the length you may find that the higher ohm produces a little less vapour (more of the heat further from the air holes).

[pipeman01]

Thanks guys, that sort of helps.

I suspect I have "not too fussy" taste buds as I've just done the exact test on 3 new coils in a Naulitus mini with the same juice and I can't tell which is better / worse

[chykensa]

pipeman01 - what did you test your Mini Nautilus on, and did you set it to the same watts each time? If you did, to my limited understanding, the mod will adjust the maths so that the coil gets the same amount of power, thus providing a broadly similar vape.
Of course, I may just be talking rubbish . . . Great thread though, I'm getting further and further into this subject, having failed my Physics 'O' Level (yes, I'm that old!) twice

[pipeman01]

chykensa, it was on an iStick 50w and set to 14.5 watts. Makes sense about auto adjust as I suspect the voltage changed whilst the wattage was constant, hence my inability to taste any difference.

I guess with VW regulated mods the Ohm value of the coil is less critical than it would be in a mech mod... which is nice as my only mech mod is an IN-AX dripper...

[Greg]

Jun 17, 2015 18:34:34 GMT pipeman01 said:

chykensa, it was on an iStick 50w and set to 14.5 watts. Makes sense about auto adjust as I suspect the voltage changed whilst the wattage was constant, hence my inability to taste any difference.

I guess with VW regulated mods the Ohm value of the coil is less critical than it would be in a mech mod... which is nice as my only mech mod is an IN-AX dripper...

Yep that's how VW works by auto adjusting voltage to achieve the watts you've set, you'll always get the same watts regardless of the coil resistance, within reason.

you can also get V/V mods (bit old hat these days) and with these you had to adjust the voltage manually to achieve the watts you want and therefore if you changed your atty to a coil with a different resistance then you had to adjust the colts to achieve the same watts.

[chykensa]

Phew, got that bit right then!! I'm glad some of this physics is sinking in