Fluxer R&D News:
14mm vs 16mm Work Coil Diameters
One of the nice things about diving into a goal-oriented project like this is that you don't know exactly where it's going to lead. You know in general terms what you want to do ("I want to build a small, portable induction heater," say), but you don't really know the path you are going to follow to get there.
When I began researching induction heaters back in June, I read widely on the subject, because I didn't know a lot about it coming in and wanted to understand the field better as a whole, beyond the simple mini IH devices we were using. I read pretty widely, including an interesting article on customized commercial induction heating applications (can't find the link, sorry) and as one might expect, there is a considerable amount of engineering involved in customizing and refining commercial induction heating applications to make them effective and efficient. One of the areas that receives a considerable amount of engineering time in these custom applications is the work coil, and it isn't a one-size-fits-all item.
These are some of the variables in play for choosing an ideal work coil:
- Diameter of the work coil
- Number of turns in the work coil
- Size (gage) of the wire used to form the work coil
- Composition of the wire used to form the work coil
- Size and composition of the object being worked
- Power being applied to the heater
- Etc., etc.! - there are many more, too
Specific work requirements cause engineers to alter their work coil formulations to suit the needs of each situation. Which, you know, only makes sense.
The Mini-ZVS heaters that are commonly used for Dynavap heating come with a work coil that is pretty good for our needs, and its size can be altered for an even closer fit.
The standard inner diameter for the work coil most commonly used for Dynavap-specific induction heaters is 16mm. This is the outside diameter of
the Cloupor M3 Vaporizer tank, which has become the glass insert of choice for these Dynavap IH projects since
@Pipes pioneered these devices. It's a bit smaller in diameter than the Mini-ZVS work coil, but the stock coil can be wound a bit tighter so that it works with this insert. Indeed, the resulting 16mm ID coil works pretty well, as we all know.
I always wondered, though,
is 16mm ID coil the best size, or just a very convenient size? Well, I finally have some answers.
I ordered a couple of 14mm OD tanks with which to experiment, and they arrived with my last order of Cloudpor M3 tanks.
I finally poked at this problem over the weekend and built out a heater with a 14mm ID work coil, and I can say that I learned a few things:
14mm ID work coil vs 16mm ID work coil
The 14mm ID work coil heats differently than the 16mm ID coil. Neither size is necessarily better, but they do have different heating characteristics.
- The 14mm coil heats more quickly, and the heat penetrates the Dynavap's chamber more efficiently and more thoroughly.
- The 14mm coil also provides less margin for error - respect the click and react to it quickly, as it is more likely to combust than the slower-to-react 16mm coil.
- The Deluxe with the 16mm coil is well suited to a number of relaxed, dip-and-sip hits
- The Deluxe with the 14mm coil is suited to clearing your Dynavap in about 3 big hits
To those who asked about how to get a hotter hit with their Flux Deluxe: Use a 14mm ID coil.
A car analogy: In terms of responsiveness, using the 16mm coil is more like driving a sedan, while using the 14mm coil is more like driving a sports car. And as some of you know, not everyone likes driving a sports car
So what does this mean for you, the potential Fluxer Heater customer? It means that in the future you will have a choice of heating coil diameters. They'll be the same price, so this will be a matter of personal preference.
What does this mean for you if you are a Flux Deluxe Batch #2 customer? It means that you have the option of the smaller coil if you want it, but I won't be able to complete your heater until the smaller diameter inserts arrive.
What does this mean for you if you are a Flux Deluxe Batch #1 customer and want a smaller coil? PM me. It isn't hard for me to make this switch, but you'll need to send me your heater, and if you are outside the US the shipping is pricey, as we both know.
Now, I'm sure just by reading my description, some of you have already decided you want to try this, and some of you have already decided you DON'T want to try this, lol. If you aren't sure, stick with the standard 16mm option, as it is more forgiving and available immediately.
I ordered 50+ of these 14mm inserts over the weekend, and they will probably be here in 10 days or so. Once they get here I can build out some heaters with smaller coils, and at that time I'd love to get them to a few of you existing FD owners for evaluation and feedback. Probably stick to people in the US to get some quick evaluations (and domestic shipping is a lot quicker and cheaper), but I'd really like to get some more people trying the smaller coil size ASAP, so people who might want it can have some unbiased opinions of its merits and/or detractions.
I think it is something of a game changer, at least for my device, as the better penetration of the smaller diameter coil may be a better complement for the smaller diameter wire I use in the Deluxe.
Finally, I want to acknowledge
a mistake I made in an earlier post. I had posted about some qualitative heating differences I had observed between using glass inserts with thick 2.5mm walls and glass inserts with much thinner 1.2mm walls. At the time I asserted that the heating differences were due to the thickness of the glass and/or its presumed impurities. This was likely wrong, as I now think it was the proximity of the coil to the work piece that made the difference. Anyway,
@analytika questioned my assertion, and I see on further review that he was right to do that, and I was wrong about the possible cause. Oops - sorry.
So...that's concludes part 1 of my R&D for the weekend.
Part 2 of my R&D post will cover some improvements I'm making to increase the range of the temp control circuit, thanks to the extra protection offered by the new pyrex switch covers! I still need to write that post, though, so that post may not happen until tomorrow.