Ideas for higher heat candle "stove"

[Jon Fong / Flat Cat Gear]

I see this evolving into a rock sauna

[Ken M]

Waiting to see who wins the prize on this one.  In the meantime a couple of questions about the catalytic heater idea.  First,  someone must have tried this but would multiple old style Zippo naptha (lighter fluid) hand warmers give off enough heat to warm a tent?  Second,  If you got some wax melted to the point of gassing off would some sort of catalytic process be possible if you could re-cycle some heat to keep the wax gassified.  Maybe that’s an impossible cycle?  Any chemical engineers here?  -Ken

[Franco Darioli]

http://zenstoves.net/G-Micro.htm

https://mollybernarding.myportfolio.com/camp-stove

BTW, Raymond Gatt , the inventor of that stove, is still around.

https://www.gattenergy.com/

 

[DAN-Y]

Franco, tell a little about the stove and why it’s not in production, what were the disadvantages of the stove?

@kenmoz, yes, the large Jon-e is capable of giving off enough heat.

[Jon Fong / Flat Cat Gear]

http://zenstoves.net/G-Micro.htm

 

[DAN-Y]

Yon, give us your expert wax opinion of why the stove failed and is no longer being sold.

[Anonymous]

Ok, refined some ideas related to said stove. This is not based on any stove I’ve seen, but based on some basic principles after reading about different kinds of wax stoves and candles.  The below is not what I was talking about earlier about minimizing soot, CO, and wax build up–funny that David should mention a flue shortly after my earlier post, because that design involves a unique flue/pipe system.

But first, let’s get the stove and tent made!

Anyways, here is a quick rough draft draw up of the more refined version of stove (getting some brazing rods and punch tool set tomorrow, but wonder if I could use silicone adhesive?).  Feedback and criticism welcome.   

 

[David Thomas]

“but would multiple old style Zippo naptha (lighter fluid) hand warmers give off enough heat to warm a tent?”

At the scale of a hand warmer, it could do a lot of good inside your sleeping bag (which raise a few safety concerns). but not really do anything for your tent.  In an igloo or sod house, with almost no draft and body heat, then a few candle flames can eventually make a significant contribution.

“Any chemical engineers here?”

Yup.  U.C. Berkeley.  Now working as an environmental engineer, cleaning up after my former classmates.

“If you got some wax melted to the point of gassing off would some sort of catalytic process be possible if you could re-cycle some heat to keep the wax gassified”

Not in the way chemists use the term “catalytic” but as a feedback loop?  Yeah, the brass stem of a SVEA 123 or a copper Moulder Strip on a butane canister stove are examples of how you can take some of the heat of the flame and use it to keep a fuel vaporizing.  Wax has to be kept hotter, so you’d want a pipe heat conduit and/or a shorter length and/or a more insulated fuel reservoir.

[Anonymous]

The tea tin I currently have, has about a 3″ diameter and is about 2.25″ tall so it will hold a pretty good amount of wax.

I’m wondering about the lid covering that goes on top.  Should I just keep that as an extinguisher, or should I make a hole in the lid for the straw/carbon felt wick, place it over that and the tin, and see what it does to the gas vapor/air mixture (maybe with a tiny puncture towards the outer, upper part of the tin body)?

[Anonymous]

Couple more questions for the stove experts.  Would it be good to insulate the body of the tin (and/or lid) or no?   If yes, for insulation, I would use 1/8″ EVA foam plus wool liner for the body, and wool (treated with some borax) and/or kevlar for the lid.

[Anonymous]

Realized the first pic was probably hard to see/read. Here’s a better one:

As it is, I’ll have to carry some soy wax chips with me and add some once in a while to keep the level up.

[Roger Caffin]

I would not use Kevlar at elevated temperatures. Try Nomex instead.

Cheers

[Anonymous]

Yes, Nomex would be more ideal.  Just don’t have any of that currently.   Might just use carbon felt (which I have plenty of) on the bottom part touching the tin and then kevlar layer above that.

(provided it’s even a good idea to try to insulate this to begin with??)

[Jon Fong / Flat Cat Gear]

The drawing make no sense to me.  Please describe the basic fundamentals of operation.  Thanks

[Anonymous]

Hi Jon,

There’s nothing fancy going on–it’s just a glorified wick, albeit it larger surface area and more air rich. The stainless steel straw/tube, will be punched through the bottom of the tin, and at the top of straw will have some holes drilled in it. The idea is for a bit of a chimney/flue effect–once warmed up, it should updraft air from the bottom more efficiently (if it’s too much air, I can always put a piece of foil on the bottom with a small hole)?   The copper wire wrapped around the carbon felt which is around the SS straw/tube is mostly to secure the felt to same.

But I know that chimney’s/flue’s work best when they are heated.  I figured the carbon felt wick would tend to insulate the SS tube some at the mid to lower parts.  I thought the copper wire wrapped about same might help counter balance that some and help the SS tube to get a bit hotter, a bit quicker.

Again, I have never built a stove of any kind before (except for the Ti one, but I never used/tried that because of safety concerns), have a high school level education, and have no job engineering experience, so I don’t really know what I’m doing.  I do know that ideally with a wax stove, you want pressurized and controlled gasification of wax vapors, but I don’t know how to achieve that.

Unless you, Dan, or somebody who knows what they’re doing is willing to sell me a proper wax stove, I’ll probably have to settle for what is basically a glorified wick design.  I’m not necessarily looking to cook with this, so awesome efficiency while it would be nice, is not absolutely essential. I’m going to have a way to deal with soot, CO, and smell some.

Before I try the above, I’m also going to try modifying an alcohol stove I have and see how that works. It would be simpler and easier to do.

[Ken M]

From my box of failed dreams…   (And it’s a big box!)  This looks similar to what you are trying.

As I recall the burner (with a central air supply) on the stand was just one big (sooty) candle.  The soup can with an orifice above the flame and an air gap at the bottom was an attempt at getting a secondary burn with the gasified wax.  I can’t say that having a central air supply did much.  I did not hit the magic blend of air as evidenced by the soot.    It can be done as witnessed on some Youtube videos but it’s definitely a balancing act without a formula.  Trail and error.  Wishing you some serendipity.

Wax smokes a long time when extinguished but if you can move it outside of a tent that may not be a problem.  -Ken

[Anonymous]

Seems to be similar Ken.  Thank you for sharing and for the well wishes.

The good news:  I’m not married to the idea of using it for cooking and I’ll have a way of dealing with a lot of the soot, smoke, and CO while minimizing heat loss (it’s fairly simple but somewhat ingenious, provided it works like I think it will).

What I need to do is get off the I-net and finish making the tent.

[Jon Fong / Flat Cat Gear]

I am so confused.  In my mind a good stove is +50 efficient, part of that is because you are trying to heat something like a pot.  If you are heating up a tent, I suspect that the rules are somewhat different.  It seems like you want to capture as much energy as possible to spread throughout the tent.  Below is a sketch of what I thought might work.  Create a flue and fill it half way with rocks and heat the rocks.  Conductive heat transfer will be dependent on the delta temperatures.  Since the rocks have a high thermal mass, they should absorb a lot of heat and since the mass is so high, it will help to maximize the heat transfer rate.  Chimney flues work because of the difference in pressure between the flue and the outside which is driven by the gas density (basically temperature difference).  With the sketch below, you should be able to achieve a much higher efficiency than 50%.  I may be wrong.

[Franco Darioli]

Get the wrong rocks and they will explode. Something I personally would avoid inside a tent.

[Anonymous]

“I am so confused.”

I’m glad I’m not the only one : )    Most of the literature on lightweight, backpacking candle stoves are in relation to cooking/heating water and seeking higher efficiency with that.  I also reckon there are probably some differences between heating a tent vs cooking in relation to these.

Thermal mass sounds like a good idea, but best way to do that, dunno.

I suspect this will be a long time work in progress with some definite error after trial…

[Anonymous]

No, doesn’t sound fun at all.  Many of the rocks around here are granite, but probably still a bad idea to pull them out of the creek if they can absorb water into them?  (I don’t know, never have thought about it before).

Sounds like simple dirt in a steel can would be most safe, but when the ground is frozen solid–mighty hard to get dirt out of same then.

So back to square one with thermal mass, unless someone has a better idea?

Maybe there is some over thinking going on here in any case. My main objective is raise the temp inside a bit on particularly cold days (near 0*F and below) and to dry things out some. I’m not expecting nor trying for a truly hot tent situation, like I can accomplish with my large Ti box stove from Seek Outside and my large 9×9 pyramid tent from Oware.  When that thing is going well, it’s actually too hot for me, and due to lack of insulation it doesn’t retain the heat worth a dang.  It’s good for some situations, but not the average casual weekend trip or the like.

I’m not looking to re-create that by any means.

[David Thomas]

Sure, rocks can “explode” and maybe spray some chunks around, but it’s not like a rifle shot.  Since the rocks would be contained within the metal flue pipe, I wouldn’t fret about some of them cracking or shattering.

A simple pot on a stove is about 30% efficient.  An ideally sized simple pot/burner might approach 40%.  You need HX fins or other tricks to get to 50%.

Jon, “hot-rocks” HXs like that can be extraordinarily efficient.  Long such beds, switched over at the right time, can exceed 95% efficiency.  To get those highest efficiencies, you need to heat in one direction and remove the heat with reverse-flow air.  Which, in a BPing setting, could be done simply by turning the chimney of rocks upside down.  Then one end stays near ambient and extracts the last bits of heat from the exhaust gases.

[DAN-Y]

Try the larger, hotter handwarmer, tis better than a candle ;-)

Your wax project is admirable but wax stinks, smokes, flame lift-offs are as bad as isopropyl stoves.

[Anonymous]

“flame lift-offs are as bad as isopropyl stoves.”

Found that out last night–there was both flame lift offs and a few pops of hot wax out.

I’m going to have a flue/chimney system of sorts for it, so that will cut down on some of the undesirable stuff you mentioned just previous.

I’m open to trying various different things and approaches as long as they are a combo of relatively lightweight, relatively safe, and relatively inexpensive.

What about chemical reaction/oxidizing warming in a Ti pot with a lid that has a couple vent holes?   Not talking thermite here (!), but something a lot more mild.  Any ideas anyone?

 

[Gary Dunckel]

How about 2 or 3 ten-hour body warmers inside a ti pot? They don’t need  lot of ventilation, but at least some air (oxygen) has to get to them to keep the chemical process happening. It might be worth trying.

[Author]

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