RDA Tri coil build

[frjaldomr]

My first attempt at a tri coil build, and it's on an Onslaught clone.
I don't have a lot of experience with building.
I have one coil in it now, at 1.7, and it's working well.
My question is, does the resistance of all three coils have to be exactly the same?
Will it work if they're a few .1s different? If so, how much of a difference will work?
I'm testing the coils with a multimeter. I've got three ready.
I was going for three coils at 1.5, hoping I would end up with a .5 build with all three coils in place.
I ended up with
1.7
1.5
1.3
My guess is, that it won't work.
Any and all thoughts welcomed and appreciated.
Many thanks in advance.

 

[State O' Flux]

Guessing on your wire gauge at 28, and running some numbers through Steam Engine... you'd have to be off by a good bit from your median 1.5Ω coil.

Assuming I did the math correctly... ;-)

In wire gross length, that would be 11.2mm less for the 1.3Ω and 11.1mm more for the 1.7Ω. As each wrap is 9.56mm+/- long... your variance is greater than the length of one entire wrap.

 

[frjaldomr]

Well that's weird...I'm using 30 gauge, I did four wraps on all of them, and I wrapped them all on the same drill bit.
They all look pretty much identical. Maybe my readings are off. I put each coil into an old RDA I have, and used the multimeter to read that.
So, if it were you, and you had these three almost identical coils, would you build the onslaught and see if they fired?
Am I running any risk, other than, that some coils don't fire?
I just don't want to risk safety.

 

[supertrunker]

My opinion is you want them as equal as you can build them and the reason is otherwise one will glow brighter, clog faster etc. It's no different from dual or any other number of coils in that respect.

As far as your battery is concerned, it sees a total resistance is all and it doesn't care if it's one or 200 coils. As long as you are not asking for more current (Amps) than the battery is able to deliver, all well and good.

Would i try it? Depends on your mod and battery.

T

 

[State O' Flux]

1. So, if it were you, and you had these three almost identical coils, would you build the onslaught and see if they fired?
2. Am I running any risk, other than, that some coils don't fire?
3. I just don't want to risk safety.
4. I put each coil into an old RDA I have, and used the multimeter to read that.

1. Sure... it's 20 cents worth of wire. If they fire fairly evenly, you're good to go.

2. Not really.

3. Not a major safety concern, unless... as supertrunker mentions, you don't have the amperage to support the net resistance.

4. A DMM can be a bit sketchy with RDA measurements... included resistance from the DMM and each individual ground post can add to inaccuracies.

 

[frjaldomr]

Efest purple 35A flat top from RTD
Vanilla mod clone from 101

 

[supertrunker]

Yep - i'd fire that!

T

 

[frjaldomr]

A DMM can be a bit sketchy with RDA measurements... included resistance from the DMM and each individual ground post can add to inaccuracies.

So what, then, is a more accurate method of measuring resistance?
Analog multimeter?

 

[State O' Flux]

So what, then, is a more accurate method of measuring resistance?
Analog multimeter?

This is long... but I'm sharing the who & why as much as the what.

I'm very particular about accuracy... doesn't matter if it's a less critical 1.5Ω, or a near-dead-short serious 0.10Ω. I want repeatable, reliable accuracy.

My thinking was probably much like yours is now. As a one time technical instructor for DC electro-mechanical devices, I've owned and/or used a variety premium DMMs and specialty meters. My thinking was that a $20 ~ $50 build box couldn't possibly be be better than - or at least as good as - a Fluke 88 with a Tech-Thing "Half-Ohm" milliohm adapter, or an Extech 380580 4-wire milliohm meter.

My "new logic" is... with probe type leads (and even the excellent Fluke AC220 clips), test methodology tends to vary as much as the attys themselves - and point to point tests frequently aren't as consistent and repeatable.
With a good quality 510 screw-in, dedicated build box/ohm meter - no doubt due to the solid contact a 510 connection provides - I find measurements to be far more consistent & repeatable.

After a good bit of research, I finally broke down, and now prefer to use a USA Ohm Meter / build box. I like the quality so much I gave them to friends that vape as gifts last Christmas... and are the only build boxes (so far) that I will recommend, without reservation.

When I build coils (with my desired values) using the Steam Engine modeling program... the results seldom exceed 0.03Ω of the calculated value, and frequently are so dead-on when compared with the above, alternate meters... it still sometimes causes me to

 

[frjaldomr]

Definitely not too long...all the info is much appreciated.
I actually have a female 510 wired into the DMM, and I was screwing the two post RDA into that.
Even so, I still have to hold the wires just right to get the thing to stop jumping around, and give me a 'solid' reading...
With the USA Ohm Meter, which one did you get, and do you just trust that company...would recommend any of them?

 

[alicewonderland]

the hard part i find when building dual coils or more, is getting them precisely the same ohm so they all heat up the same. The trick is using the same tool you use to wrap all the coils, then making sure the legs are all the same length. if that doesnt help try putting them on individually and scrunching them up. when i try to use more than 1 coil, I just go on a coilmaking frenzy and build a handful of coils then just pair ones that match, save the other ones for some other builds.

like someone else said though, you dont run much risk if the coils arent the same resistance, they will just heat up unevenly, if u find that happening you could just try to push the leads into the holes further and snip off some extra leg off the one thats heating up slower.

 

[State O' Flux]

With the USA Ohm Meter, which one did you get, and do you just trust that company...would recommend any of them?

At the time, I bought several, for myself and for gifts... all they had was the $23 one. The newer ones - the "Ultimate" and "3D" weren't available at the time.

A friend recently bought the 3D... it's very nicely made and although I didn't subject it to any testing against the DMM/Half-Ohm or 4-wire, as I recall, it nearly matched my "econo" model within a few thousandths. The SS 510 is nice... more durable, and more "ham-fisted proof", I'd imagine. You can get that in both the Ultimate and 3D.

I'd probably get the $27 Ultimate, were I buying another, just to get the spring-loaded SS 510... and I can live without the fancy box and nicer switch. ;-)

"Trust"? One of the original meters I bought had a switch a bit rougher than the rest. I called, just to ask about a replacement switch... and before I could explain in detail, the guy on the phone apologized and offered to send a whole new meter, postage paid - so yeah, good CS.

 

[frjaldomr]

Thanks so much for all the replies. I got the thing built...it reads .5 on the DMM and .4 on my xgun.
One of the coils does heat up a bit faster, but I can live with that for now. I'm just happy it's working.
Quick battery questions: as I said, I'm using the purple Efest 35A.
This is one of the best batts on the market now, yes?
Is it true that the sony vtc line is discontinued and the authentics can't be found any longer?
Is there a button top of the same caliber?

 

[alicewonderland]

Thanks so much for all the replies. I got the thing built...it reads .5 on the DMM and .4 on my xgun.
One of the coils does heat up a bit faster, but I can live with that for now. I'm just happy it's working.
Quick battery questions: as I said, I'm using the purple Efest 35A.
This is one of the best batts on the market now, yes?
Is it true that the sony vtc line is discontinued and the authentics can't be found any longer?
Is there a button top of the same caliber?

I know vapordna sells sony VTC4's. Dont know if they are authentic or not as I haven't ordered any yet but I see vapordna as a reputable vendor. I've also been told that the purple Efests arent 35A continious, they are 20A continuous.

 

[frjaldomr]

I've heard that about the purple Efests, as well...but I guess if you stay at .3 or above, that's plenty.