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JAK
2007-01-03, 12:47
I am trying to come up with a lightweight insulative ceramic to use for the hottest part of a wood stove or wick stove in order to get higher combustion temperatures, and thus less smoke and perhaps a better draft. The lightweight isn't so much to save weight so much as to reduce the heat that it absorbs, and because light weight tends to go hand in hand with insulative properties. For strength it might be a composite of ceramic and metal or ceramic and wool. It could also be a thin layer of metal on the inside. I am not sure it aluminum would survive but it would be a great way to verify that high temperatures were achieved in a small stove it it did not.

Ideas so far:

1. Wool cloth packed with clay or a mix of clay and sawdust or clay and flour and sandwiched between two layers of muffler tape. Fired to 1000C the wool and sawdust and flour should burn or at least be reduced to carbon but should leave a porous clay carbon ceramic. Alternatively I could fire it at a lower temperature and leave the wool to burn later if the stove gets hot enough. If I get the density down to 0.50 a 2" inside diameter tube 4" high and 0.5" thick would weigh about 2 ounces. Perhaps 0.25" thick would be sufficient. I would be happy with 1 ounce.

2. Fiberglass or Kevlar cloth between two layers of muffler tape. Perhaps multiple layers.
Not sure sure yet how thick 1 ounce wound be for 2"D 4"H but this might be easiest to try first.

3. Perhaps a combination of 1 and 2.

4. Two glass lantern lenses with an air gap in between. This might be interchangeable with the above when in lantern mode.

This is for a relatively small stove, burning oil or wax or wood gas. The fuel would be no more than 1oz of oil/wax or perhaps 2oz of wood/char probably in a combustion chamber or a retort below the air inlets and the secondary combustion chamber above. Not sure yet of the design. Mostly interested in a good lightweight insulating ceramic or composite that can be homemade.

Any ideas/comments ?

Steinberger
2007-01-03, 13:33
I'm afraid packing in the clay would just cause it to explode.

Have you thought of using a high temerature air-cured cermaic based polymer foam?

Jim Henderson
2007-01-03, 14:50
Maybe fire brick or lava rock? The fire brick can be found that is very light. I think MAYBE it can be shapped with Dremel stones and the like. Some bricks I had were about 10x5x2 and weighed maybe 1/2 pound. Fairly pourous.

The lava rock weighs almost nothing and I bet thery are fire proof. But as far as shaping, could be tricky since they are so bubbly.

Good Luck,

Jim Henderson

Steinberger
2007-01-03, 15:37
If you want to spend a small fortune you could get some aerogel.

It is pretty much the best insulating material known to man. You can take a peice of chocolate and rest it on a half inch peice of aero gel and take an oxygen torch to the bottom of it and the chocolate won't even get soft.

It also is optically clear and weighs practically nothing.It's like 1/10th the mass to weight ratio of 800fill down.

Lanthar
2007-01-03, 17:34
Jak,

Ever since you're comments about your oil burner stoves, I've wonder if one of the smaller SP Double-Wall Stackable Cups (http://www.snowpeak.com/gears/tw-stackablecupspage.htm) (appropriately tooled) wouldn't make a nice burn chamber.

Of course, ti is more than I suspect you're looking to spend, but I wonder if someone else makes a similar product in SS.

Also, the firebrick idea might be really good.

JAK
2007-01-03, 18:49
Thanks for the link to those stackable cups. I wish they gave dimensions, although it is quite possible to estimate them.

I found a recipe for making firebrick which was basically 50/50 of sawdust and clay fired to 1000C. It ends up with a density of 30 pounds per cubic foot. I am not sure what would happen if you fire it to a lower temperature, like a self cleaning oven, and then later expose it to a higher temperature. 1000C could be achieved using a small pit kiln, basically a small bed of charcoal. This sort of think can be just as much fun as the stoves themselves.

Anyhow, I think for now I will try alternating layers of muffler tape and paper towel. I am not sure what sort of adhesive is on the muffler tape and what sort of crusty porous layer will be created when the paper towel and muffler tape glue is reduced at high temperatures, but I will heat it in the oven on self-clean and wind out if there is anything left in between the aluminum foil, or even if there is anything left of the aluminum foil. I think our self cleaning oven hits 500C, which is hot enough to reduce the paper. If the char ignites that might be hot enough to melt and burn the aluminum. Not sure. I think burning char can hit 1000C and aluminum melts at 660C, but burns at different temperatures depending on what it is reacting with and in the presence of. I am gussing there might be stuff in the adhesive that is intended for it not to burn too soon. I suspect it should hold together well enough. The question is whether or not it has much insulating properties after it gets fired. I'll try 5 layers of aluminum tape and 4 layers of paper towel and weigh it before and after firing and let you know how it turns out and how it might holds up and insulate after its done.

I might try to do something with clay and cloth also. I have fired the clay in the oven before. It doesn't explode as long as it is not too thick. I can't get too experimental when my wife is home however. I'll keep you posted.

CanoeBlue
2007-01-06, 23:10
For high temp, insulating ceramics check out a pottery supply house. I have built both pottery kilns and foundries with castable refractory cement and Kaowool blanket. Castable refractory works like a mortar - mix it up and mould it or shape it and it can take temperatures far higher than anything that you will subject it to with a stove.

For very light weight high heat insulation, get a piece of Kaowool blanket. Easy to work with, excellent insulation, high temp ...... I expect that you could make a pottery kiln that is good for a couple of thousand degrees with nothing more than a couple of burners, a cardboard box and a bunch of Kaowool.

TeeDee
2007-01-07, 15:29
Consider inswool also. You can get it in blanket form (1", 1.5" and 2" thick) like kaowool, or as a board (1" to 4" thick) or in moldable form (sold in 1.5 oz tube or 1 gal or 5 gal tubs). In the blanket or moldable form it is rated to 2300 deg and in board form to 2300 deg or 1900 deg. Prices are reasonable also.

Try this site for example:

http://www.hubglass.com/refractorycrucibles.html

JAK
2007-01-07, 22:12
Great stuff. Thanks guys.

stray1
2007-01-08, 00:04
Pyrogel 6250 by Aspen Aerogels. They make some of our emergency blankets and gear.

Lanthar
2007-01-08, 12:11
Consider inswool also. You can get it in blanket form (1", 1.5" and 2" thick) like kaowool, or as a board (1" to 4" thick) or in moldable form (sold in 1.5 oz tube or 1 gal or 5 gal tubs). In the blanket or moldable form it is rated to 2300 deg and in board form to 2300 deg or 1900 deg. Prices are reasonable also.

Try this site for example:

http://www.hubglass.com/refractorycrucibles.html

Ooh... nice... that moldable might be nice for some projects...

Take-a-knee
2007-01-08, 13:17
Papertowel and muffler tape ain't gonna work JAK, paper ignites at about 450 F, in a low oxygen environment it'll just char.

JAK
2007-01-08, 16:02
Yeah tried that. I was hooing the glue in the muffler tape would react with some of the char and form some sort of crusty layer between the two layers. Also, I figured out you can really only have one of the paper tower layers with tape glued from both sides, unless you introduced some other glue. I used the wrong kind of aluminum tape also. The stuff I used is thinner stuff and the glus is different I think. It is for taping that silly aluminim foil bubble wrap insulation, which ain't really good for anything, though it does look like it should be good for something.

Anyhow, I will look around for some of that inswool.
But I am a little concerned about the product information.
Wouldn't the sheep get they an aweful case of Alzheimers?

JAK
2007-01-08, 16:54
Here is an idea for what might be a better windscreen.

Muffler Tape
Ceramic Paper or perhaps a Fibreglass Surface Tissue
Muffler Tape

Ceramic Paper:
http://www.advancedthermalsupplies.com.au/products/thermal/#8
Thickness 1mm – 3.2mm , dependent on grade

Fiberglass Surface Tissue:
Weight: 25 g/m2 often used for gelcoat layer on fibreglass work
Weight: 5o g/m2 often used for roofing

Or:
Aluminum Tape with Glass
http://www.alibaba.com/catalog/11213683/Aluminum_Tape_With_Glass.html

Or you could just add your own strands of glass fiber to make it rip-stop.

High Temperature Aluminum and Fiberglass Tape:
http://www.heatersplus.com/tape.htm
Aluminum is only 200F rated ???
Fibreglass tape is only 500F rated ???

I found the Aluminum held up OK to self-cleaning oven temperatures.
I have notices it does not do well next to a steel at high temperature.
Being in direct contact with burning charcoal might do it in also.

For more insulation around high temperature combustion zones I will try the ceramic cloth up to 1" thick. I am guessing you could peel it down to 1/2" or even 1/4" also. I am not sure what would be the best tape or material for the inside surface however. I am not sure if aluminum tape would hold up. I think it would be best to have some sort of a smooth surface, if not shiny. Anyhow, I think it should improve performance, and perhaps reduce smoke in a wood or vegetable oil or wax type stove. Probably not neccessary for alcohol stove, though it might allow 99% isopropyl alcohol to be used.

What I have in mind is an outer wind screen, very thin, but strong enough for multiple use and not to get blown away. It might be worth insulating also and that might make it strong enough to hold up a pot and eliminate the need for an inner combustion chamber. I think an inner combustion chamber might still be useful however, like a rocket stove, to create a chimney to concentrate and mix the volatile gases and combustion air for complete combustion at high temperatures and to generate some draft before it goes around the pot and inside the upper wind screen. An under chimney does add height and weight and tippiness however. Perhaps a large diameter pot rather than a tall mug. The outer insulated wind screen could provide the stability. The inner combustion chamber would still need to be insulated and tall enough to generate draft, but the outer insulated wind screen would be more stable and the upper portion around the pot wouldn't need to be as tall. You would still need an insulated bottom and lid however.

Skidsteer
2007-01-08, 23:15
Ooh... nice... that moldable might be nice for some projects...

:hmmmm: Many, many possibilities....

Lanthar
2007-01-09, 12:54
JAK,

For the "inner surface" you could use SS Foil from McMaster Carr. Not nearly as expesive at Ti Foil, and you wouldn't be gluing it... but then again, I don't think you need to glue it... just make a tube with slit to interlock and wrap your preferred insulation around it...

JAK
2007-01-09, 15:37
Here is an illustration:
http://i130.photobucket.com/albums/p243/JAK_45/JAK_Stove/Stove.jpg

Outer Cylinder = Blue Foam with Alumimum Foil on Inside Surface (Blue)
Inner Outer Cylinder = Ceramic Wool Insulation (Light Grey)
Inner Combustion Tube = Steel Tube (Black)
Middle Disks (2) = Ceramic Wool Insulation (Dark Grey)
Bottom Disk = Ceramic Wool Insulation (Dark Grey)

Small tealight tin under Inner Comustion Tube to lift up stick fed in from side.

Lanthar
2007-01-09, 17:43
Jak, I'm assuming that is the drawing that you mentioned in this (http://hikinghq.net/forum/showpost.php?p=17006&postcount=43) post.

I see you point on your intended charring chamber, I assumed you're just going to allow gasses to escape the chamber simply due to the fabric to steel can not being air tight? (oh, and I just noticed your comments about the holes in the bottom, those will serve nicely)

The one point I'd make is that you definitely want to raise the burn chamber with some sort of a grate (some folded hardware / wire cloth inside your steel tube would do nicely) otherwise, I suspect you're going to have embers block your airpath pretty quickly and choke out the fire.

JAK
2007-01-10, 05:50
Thanks for the tips. The grate idea sounds great.

I will have to get some of this inswool and try all three possible configurations, also large stoves and smaller ones:
1. Simple but lighter and better insulated Hobbo Stove.
2. Retort on sides surrounding a 'Rocket' Combustion Chamber.
3. Retort under 'Hobbo' Combustion Chamber.
4. Combination of 2 and 3.

The 'Vesta' idea is still there somewhat in 2 and 4 since the area underneath the retort donut, and the retort itself, combine into a vesta like feature. There is a case when wood fuel being plentiful for keeping the hobbo stove simple but somewhat larger. The only real objective is less smoke, and a larger stove can burner hotter than a smaller one. In a top down burn with bottom hole slightly elevated it might be possible to get a less smokey fire sooner, and still have some char at the end. The nice thing about the design above is that all the parts seem to be there to be reconfigurable into type 1,2,3 and perhaps 4 also if I had a second bottom disk. The other variable is how large the stove should be relative to the pot, and of course how large the pot should be. I am not sure if I really need the blue foam Outer Cylinder. A larger reflector might be better, like my blue foam sleeping pad with aluminum tape on one side, and my three tent pegs (nails) to pin it down into a parabolic reflector. I sit on my pack when I stop for lunch.

I will have to get some of this inswool and have a go at it.

JAK
2007-01-10, 17:00
This stuff is a bit more solid, but better insulating for a given thickness.

Microsil:
http://www.zircarceramics.com/pages/microporusinsulation/microporous.htm

oops56
2007-01-10, 17:37
Did i miss something i thought you said to make it cheap and easy to use :albertein

JAK
2007-01-10, 21:40
$178 for 12 pounds. Ouch.

Anyhow, I'm going to look around some hardware stores and see what I can
get cheap. I just want to start with a lightweight but insulated hobo stove.