New Atomizer Prototype

[Bubo]

:-)
I was messing around this evening with glass (artsy fartsy stuff) and the instructor couldn't come up with any reason for this not to work... Of course, she didn't understand the full aspect of what we are doing - but she didn't see any issues with sticking metal in glass - she says that she does it all the time.

There is a kiln there that I should have access to, so I just need some nichrome coils - I know people have done this before - so what gauge, length, coil size, and how many coils do I need to make... I should be able to get a few made up with just normal glass - I'll see how that goes before moving to the boron stuff...

I personally would like to keep it under 10 mm in width and don't know how long to make it.... But if the coil is in the bottom of a cylinder of glass, I can always make it shorter...

[roadkilldeluxe]

There is a kiln there that I should have access to, so I just need some nichrome coils - I know people have done this before - so what gauge, length, coil size, and how many coils do I need to make... I should be able to get a few made up with just normal glass - I'll see how that goes before moving to the boron stuff...

I'm not 100% sure on the gage. But the resistance you want (I think most attys are in the 2-3ohm range) will determine the length. My coils are about as big as they can be to still fit in the glass. The 510 is about 10mm, my bulbs are around 5mm in diameter.

What size wire and resistance should we aim for?

Bulb w/ coil


Length.. about 20mm


Width, 5mm


I heated the tip of a poorly cut bulb with a butane lighter. It smoothed out and the opening constricted, leaving a much smaller hole. I liked the result.

[jacko]

The bulb looks great. have you applied a voltage to the leads yet to see if it will glow?
The resistance should be in the 3-4 ohm range, I believe. It seems that what I have been able to find out should put the current at around one amp.... which is 3.7 ohms for a 3.7 volt unit. The wire that has been used before has been 36 gage. one to one and a half inches should get in the right resistance range.
When I can get some nichrome I'll try to help too.

[roadkilldeluxe]

The bulb looks great. have you applied a voltage to the leads yet to see if it will glow?
The resistance should be in the 3-4 ohm range, I believe. It seems that what I have been able to find out should put the current at around one amp.... which is 3.7 ohms for a 3.7 volt unit. The wire that has been used before has been 36 gage. one to one and a half inches should get in the right resistance range.
When I can get some nichrome I'll try to help too.

Excellent... this sounds good to me. Now what's the best way to solder the Nichrome to the copper? All I have is regular rosin-core solder.

Also, if this was used as a cartomizer, would the two leads have to be insulated, since they will be surrounded by liquid? Or does it not really matter if they are both bare?

Edit: I will try to edit my OP every once in a while as we gather more knowledge. I've updated/reorganized it and added two great links related to working with glass: 1 2. This should help anyone attempting anything similar...

[roadkilldeluxe]

Experiment #1: I did a quick stress test and it didn't turn out well for the bulb.

Volts: 5.00v from a computer power supply
Coil: 3.5" of 32ga NiCr (3.2ohms, theoretically)
=1.56 Amps
=7.8 W (theoretically)

Observations
-Running at 7.8W dry, in free air, then dripping onto the bulb directly caused it to crack all over. Carlos49 mentioned the possibility of this happening.
-The cracked bulb maintains its shape but will separate into pieces with minor force.
-My "PG/VG 80/20" mix vaporized violently upon contact with the glass directly above the coil
-When juice is dropped onto the very tip of the bulb, it hangs there, slowly vaporizing. This tells me that only the glass immediately next to the coil will get very hot.

Hopefully this establishes the worst-case scenario as I doubt anyone will be vaping with 32ga and a computer power supply directly onto a bulb in free air.

Before


After

[moktarino]

Excellent photos!

I'll continue to follow this thread with great interest, but I've got to be honest with you.. I'm not personally sure I understand what you're trying to accomplish.

Let's say that you are ultimately successful with getting some nichrome put inside of a glass bulb or coating. And that you are able to figure out how to get the time constant down so that it heats up quickly enough. Then what?

You still need to devise a delivery mechanism for the e-liquid.

Well, you know what they say about eating elephants - use an enormous blender and a big straw!

Seriously though, yes the feed mechanism needs to be designed as part of the overall form factor of the device. The atomizer, battery (if any), reservoir, and electronics must be integrated into a cohesive whole for a successful device, like pieces of a puzzle that complement each other.

The goal of the glass-encased heating element is to solve the oxidation and maintenance issues related to the "disposable" atomizers. I'm not interested in a disposable device. I can deal with replacing a wick, but I'd rather not replace the heating element.

In my head, at least, the form factor consists of a pipe. I've never enjoyed cigarettes or thin cigars (bidis, perhaps), and the extra space provided by that form factor will allow for significant "wiggle room" to accomodate less-than-precise engineering.

I think that to accommodate the "instant-on" feature, the glass barrier between the nichrome and the glycerin will need to be exceedingly thin.

I'm trying to acquire some of the pipettes I mentioned in an earlier post, I think I can stretch them out to make them thinner with the judicious use of a blowtorch.

[Applejackson]

Not to be a killjoy here, but has anyone considered the fact that PV's tend to get jostled and bumped around pretty regularly, and the glass could easily be broken without you knowing. Also, unless it's Pyrex, the heating/cooling is going to break the glass eventually. Last thing I need is an unexpected mouthful/throatful/lungful of broken glass. I just don't see any way this could be accomplished safely. Glass is just not a material I want in a PV mechanism. Definitely an interesting idea though.

[moktarino]

Experiment #1: I did a quick stress test and it didn't turn out well for the bulb.

Volts: 5.00v from a computer power supply
Coil: 3.5" of 32ga NiCr (3.2ohms, theoretically)
=1.56 Amps
=7.8 W (theoretically)

Observations
-Running at 7.8W dry, in free air, then dripping onto the bulb directly caused it to crack all over. Carlos49 mentioned the possibility of this happening.
-The cracked bulb maintains its shape but will separate into pieces with minor force.
-My "PG/VG 80/20" mix vaporized violently upon contact with the glass directly above the coil
-When juice is dropped onto the very tip of the bulb, it hangs there, slowly vaporizing. This tells me that only the glass immediately next to the coil will get very hot.

Hopefully this establishes the worst-case scenario as I doubt anyone will be vaping with 32ga and a computer power supply directly onto a bulb in free air.

Yep, that's the reason most laboratory glassware is borosilicate. If you melt some borosilicate glass and stretch it out into a long fiber, it will be quite flexible. If you stretch out flint glass it will be very fragile and break easily. It's that stretch that keeps pyrex from cracking during heating, especially after many cycles.

Good! you've proven that it will work in concept, now we need to refine further

I found a good supplier of nichrome wire on ebay and used the ohms/ft values given to make a small table of the lengths the various gauges would require to achieve 3ohms:

38 21.12mm 0.83in
37 24.79mm 0.98in
36 30.05mm 1.18in
34 44.82mm 1.76in
32 71.44mm 2.81in


I just had an interesting thought... perhaps the tube could be bent 180deg to form a loop with an axial coil running through it... The open ends could be secured with epoxy into a holder of some kind or crimped around the edges of the nichrome...

I wonder if you could use that with a compression-based socket, allowing for easy removal.

[roadkilldeluxe]

I think that to accommodate the "instant-on" feature, the glass barrier between the nichrome and the glycerin will need to be exceedingly thin.

I'm trying to acquire some of the pipettes I mentioned in an earlier post, I think I can stretch them out to make them thinner with the judicious use of a blowtorch.

I completely agree. I'm sure we could even find the perfect size glass rod online, then just cut it to size and seal both ends... I really wish I had the tools to play with glass.

I need more butane and hopefully I can make use of it somehow. It cleaned up the ends of that one bulb pretty easily, though. They were pretty ragged/sharp, which is why I wasn't scared to test it in a super hot flame in the first place.

Not to be a killjoy here, but has anyone considered the fact that PV's tend to get jostled and bumped around pretty regularly, and the glass could easily be broken without you knowing. Also, unless it's Pyrex, the heating/cooling is going to break the glass eventually. Last thing I need is an unexpected mouthful/throatful/lungful of broken glass. I just don't see any way this could be accomplished safely. Glass is just not a material I want in a PV mechanism. Definitely an interesting idea though.

The glass is pretty sturdy, plus it will most likely be in the center of a metal atty housing surrounded by padding (i.e., wick/filler/etc). Pyrex would be very nice in the long run if this is successful. In my opinion, glass is the way to go because it's so.. clean. It's like cooking on top of a gross metal grill vs in a glass pot on top of the stove.

It seems like the biggest dangers most people are concerned with are the vapors from Nichrome, the wick, and the solder joint. This design will place all three elements within a protective barrier.

I found a good supplier of nichrome wire on ebay and used the ohms/ft values given to make a small table of the lengths the various gauges would require to achieve 3ohms:

I ordered from Jacobs'. Real cheap, $2-$2.50 for 10' sections, and free shipping on 26-40ga wire orders.

Is 3ohms the ideal? With a 3.7V source, we get 1.23A and 4.55W. Does this sound about right?

I just had an interesting thought... perhaps the tube could be bent 180deg to form a loop with an axial coil running through it... The open ends could be secured with epoxy into a holder of some kind or crimped around the edges of the nichrome...

I wonder if you could use that with a compression-based socket, allowing for easy removal.

You mean something like this?

That would be cool...

Any ideas on how to connect Nichrome to the circuit? I figured copper would have to be soldered directly to the Nichrome within the bulb. I read that since Nichrome oxidizes, the best approach is to tin the tips of the Nichrome and then solder it to another metal. Otherwise, the connection will slowly get weaker. However, my alligator clips seem to be working fine so far, the oxidation only gets heavy right after the contact points.

[punkman]

Been thinking about this a little and if I where to try to make one this is what I would
do.

Go to the store and grab a fiberglass wick for a oil lamp. Separate out one of the bundles from the wick. Wrap the nichrome wire around it in a vertical position just as you have done here with the bulb. The fiberglass wick should hold up to the heat and work nicely to pull the fluid to the coil. Cartomizers are constructed this way and is about the simplest design I have seen so far to reproduce.