Minty Love - Dual Coil Installation On Dual Coil RTA

Installing a Dual Coil on a Dual Coil RTA

(under construction)

Intro

We previously described installation of a single coil in a dual coil RTA, but here we show an example installation using two coils.

Although we're demonstrating with an Arbiter 2 here, the procedure is effectively identical for the Dead Rabbit V3 and many other dual coil RTAs.

To eliminate the need for frequent cross-referencing, we'll include pastes from the single coil installation page,

Coil Choice

As mentioned on the single vs dual coil page, a dual deck opens many more options for wire types/gauges, numbers of turns etc. Here, we'll use dual 5 turn 26x2+36 clapton coils, with an inner Ø3 mm (strictly speaking it's actually ~3.2mm as here I've wound them around a 3.0mm rod tool)

👀Some RTAs which can accommodate dual coils have insufficent space to use duals unless a reduced coil diameter is used. For example, for the Fat Rabbit Solo V2, Hellvape suggest Ø3mm for single, and Ø2.5mm for duals. However the Arbiter 2, Dead Rabbit V3 & most other dual coil RTAs are fine with 3mm coils in both single or dual coil mode.

We'll use Ni80 or Kanthal A1 wire, which'll eliminate any concerns about whether our mod has the Stainless Steel Firmware Bug (described here - scroll down to "Stainless Steel Firmware Bug")

WireBuddy shows 5 turns fitfits the Arbiter 2 nicely. Also, it's suggesting a maximum Wattage of ~19W for each coil, so we should be OK for upto high 30s Watts max without risking pushing the coil into overload, provided we maintain optimum toke rate, which will be a somewhat harder pull than for single coil mode.

Consult wirebuddy for coil particulars

Coil Winding

I wound the coils around the 3mm part of a stepped diameter coil rod (see this page for details). This, (like many other coil winding tools) produces a slightly oversized inner Ø (by ~0.2mm), which for our purposes can be ignored.

In dual coil mode, we need to use inline terminals so it's helpful to bend the legs of the coil as shown in the pic, which generally be easier/neater than using offset legs & inserting the coils at an angle & then straightening after tightening

To cut the correct coil leg length, use a "coily" measuring tool (see this page for description), or micrometer (the manufacturers recommend 5mm for both Arbiter Solo & Dead Rabbit V3). However, be prepared to trim further to visually obtain the correct height. In short, ensure there's sufficient space beneath the coil for airflow, but don't mount so high as to risk contact with the main body when assembled.

Fitting The Coils

We'll mount the coil as shown, ensuring even & safe gaps between coils sidesides and top surfaces (when assembled)

After securing the terminal grub screws, perform a red heat burn & strum out any hotspots, ideally with ceramic tweezers but a small flat blade screwdriver will also suffice.

Also, (if space permits) space out the windings a little, just enough to see daylight between them, which'll reduce the risk of introducing inter-winding electrical contacts during the coil threading process.

How a 3mm i/d dual coilcoils might appear on the Arbiter 2. (use a similar height for the Dead Rabbit V3). Unlike our single coilcoil example, here no choice but to use inline coil terminals

Left: Initial red-heat dry burn showing unevenness & hotpots.

Mid: Heating evenly from inside to out following strumming and a gentle separation of the windings using ceramic tweezers.

Right: After cooling with windings separated just enough to see daylight between windings (not particularly visible on pic but there nonetheless). So now ready for wicking.

Ceramic tweezers cost pennies & make coil tasks much easier. Order a few pairs if you don't have any.

Wicking

Dual-coil decks normally have much larger juice well openings than their single-coil counterparts, as they're designed to accommodate cotton from two coils.
As we're using two coils here, insufficent cotton won't be a problem, and in fact it's far more likely we'll see fit to comb and thin out the tails, and perhaps even trim further before inserting

💡 If the cotton is packed in too tightly into the juice well openings, it may prevent backflow of pressure equalisation air bubbles and eventually cause overheating from juice starvation.

Insufficient cotton in the wells may result in flooding/leaking/gurgling but this isn't likely to be an issue when using 2 coils.

The Arbiter 2 juice well openings (left) are significantly larger than the Destiny's (right) because they're designed to take cotton from two wicks, not one.

The cotton is threaded through the coils using a slight twisting action under tension to compress its diameter. Don't rush, just take care not to distort the coil spacing or this may cause electrical contact between adjacent windings, causing hotspots.

Unlike when installing a single coil in a dual coil deck, it's likely that we'll need to comb/thin out the tails (for example using tweezers), before inserting into the juice well openings. We might even need even trim the shape of the cotton just the obtain the correct amount.
The cotton needs to form a juice barrier between the juice reservoir and the inner chamber), but still allow equalisation of pressure (i.e. the back-flow of air bubbles) in the reservoir.

So try feeding the tails into the juice well openings, ensure the cotton goes all the way through to the deck bottom (contrary to what some utube vape channels suggest) but without folding back on itself

Don't stuff it in too tight. Aim for an even spread of cotton, without visible gaps and with a gentle springiness against light pressure. If it starts feeling solid, take it back out for more thinning/combing before trying again.

Pics below show how a good coil might appear when newly wicked with dry cotton (i.e. before priming).

Actual length of tails depends on coil height, cotton thickness variance, plus juice well opening size themselves. This is how it might look for the Arbiter 2 and Dead Rabbit 3, but even this might well need further thinning out/trimming to avoid overpacking the juice well openings

Plentiful cotton under slight compression within the coil, showing upward "shoulders" as it emerges

Ensure even spread of cotton without gaps in the juice well openings.

Ensure cotton comes through from above, right down to the lower base as shown.

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