Insulation for the heat riser?

Hi everybody.

Well, in my first rocket, i have used two tubes with vermiculite in between and i have closed the ends.

The next one gonna be far bigger. I mean, i can access 12" tube pretty easily.

I'm not a pure permie, and i'd rather avoid cob. Due to the lack of clay over here.

What would you think would be best for insulating the 12" heat riser?

I can access vermiculite pretty easily, rockwool too. I should say i'm not too keen on rockwool either.

Is slate powder refractory?

Thanks.

Max.

Back up.

Just to say that i am dumb.

And ask the same question in a different way.

Well, On another forum Peterberg says 5cm insulation around the heat riser. But, what insulation?

I can't easily access clay. Vermiculite, rockwool easy. Perlite i don't know. I can get "ciment fondu" (refractory cement) I have few 30gal bags of ash chips, from the last stairs i built. Most of this is about 1/4 x 1/4 x 1/32 or 3/32 thick.

What do i have to do? Heat riser for the next build gonna be à chimney top tube. about 87cm long x 6.88". I might lenghten it a bit. Bottom will be made out of half bricks.

What insulation do i use around heat risers? Liquid "slip" of some kind or just a tube around a nother tube and the walls filled in between? Do i make a "slip" with ciment fondu and ash chips? Would that be suficient?

Thanks a lot and best regards.

Max. Who admits it's hard to understand proper insulation

I can't answer all your points, but the ash chips are too big to give effective insulation. You need sawdust, and the finer the better. Calcium silicate board is one of the best insulators around just because the cells are so small that air molecules would not expect to meet another one very often, and so be unable to pass on its heat. When the cavities get bigger, the molecules can be bashing into each other and the heat can travel easily.

Vermiculite's a pretty good alternative to perlite. Both are foam-like minerals, 'nearly natural.'
Perlite is not chemically altered, just heated-up volcanic glass with natural gas inclusions, puffed like rock popcorn. It's the white nubbles in potting soil.
Not sure what the process is for vermiculite, but it works fine as insulation.

Are you interested in trying your local natural materials?
If so, where is "over here?" What are your resources locally? They've gotten some 'clay-' like effects in Ontario with soils I would call glacial silt or loam.

I would hesitate to try the slate chips - whole slate chunks can shatter or explode under heat due to trapped steam, I would not be surprised if slate chips act like shrapnel popcorn.
In any case, chunky dense material isn't a great insulator.

If not interested in natural, just functional...
- refractory cement comes in grades rated for temperature, for rocket heat risers (esp. the bottom third or so) you want the highest-temp you can get. 2800 F or higher.
It will not be insulative unless you mix it with something, like the vermiculite, that has a fine foamy structure. Sawdust can work.

If you have to use a coarser material, go much thicker, as the insulative value will be less per inch.

On 6" or 8" diameter systems, steel can be used as a liner with insulation around it, but on larger systems you need materials that will tolerate higher heats.
- you can make the heat riser of firebrick (splits works well) or ceramic chimney liner, then insulate with a convenient material.
- or you can make a cardboard foam and try pouring a refractory or ceramic liner around it.

-Erica

Thanks a lot Erica, for taking the time to reply.

As for where i live

http://en.wikipedia.org/wiki/Le_Mon%C3%AAtier-les-Bains

In the alps, Slate and source made limestone on one side. Old volcanic on the other side. With ferous stones, quartzite, which by the way is suposedely refractory, some old coal mines. But clay, haven't ever heard of it.

Talking about refractory cement, or ciment fondu, it's just the cement, no charge in it. I can buy that easily here. Vermiculite too. In flakes which look like burnt cork. So this will be the stuff i'll make the next one out of. most certainly.

Would this mixture be insulative enough; would you think; in 2 inch thickness around the heat riser and burn tunel?

Thanks a lot again.

Max.

Oops! I read the ash chips as being chainsaw chips (or similar) from an ash tree. Language can cause problems in different countries I guess.

Roy Clarke wrote:Oops! I read the ash chips as being chainsaw chips (or similar) from an ash tree. Language can cause problems in different countries I guess.

Nope, chips came out of this.



But the chips i'm talking about are in the same size range as chainsaw ones.

Satamax in your area there are high alpine lakes thats where you will find clay but its going to be a trek. the vermiculite and cement will work and you will need about 3 inches around the heat riser. you will want 2 inches around the burntunnel, Dont insulate the feed. every thing back from the first bridge brick should get insulated to the top of the heat riser. the manifold does not need insulation.

Thanks a lot Ernie for replying.

Well, heat riser gonna be made out of a clay chimney top, that i have.

Bit like the center one here



http://www.mitre-terre-cuite.com/images/mitre-en-terre-cuite3.jpg

Tube is 6.9" inside, bout 9 ish outside, something like 33" long. 3 inch around it, too much for what i had accounted for. Would i get away with only two of pure vermiculite? Burn tunel, i think i have sorted pretty much. 1 inch firebricks and vermiculite refractory cement mix around. I'll make a metal mould around, which might stay there, so it can crack, it will still hold. The insulation of the heat riser is the point that i'm uncertain of.

Thanks again.

Max.

thats going to be a 6 inch system you can go bigger but i think its going to be a problem since ducting tends to be 6 inch around the world of HVAC. you will need 3 inches to give you as much of a temperature difference as you can get. I believe you said you could get 1 inch Rockwool and for this application i would do so. to secure the rock wool to the heat riser take some contractors cloth (wire mesh) and wrap around it. you dont have to do anything else. the rock wool is a really really good insulator.

let me know please how the clay heat riser is working for you; it should work as well as or better than brick in my mind. I know that in the burn tunnel it doesn't last very long due to thermal shocking but in the heat riser this may be far different.

Hi Ernie. I will tell you when i have finished.

Talking about clay and refractory etc.

I've bumped onto this site, http://www.svk.be/fr/autres/boisseaux_refractaires_gamme

Refractory chimney tubing.

Asked them for a quote, but they're hard to deal with. I have to call the guy again someday.

Thanks again.

Max.

no I dont imagine they would be. I do remember france and trying to get anything out of the suppliers if i didnt have the paperwork they thought i should.
OK skip the rock wool they sell cause i think that is just the brand name, you want refractory stuff like is used in furnace applications.

Ahh international business; I have to remember things i had long and joyfully forgotten.