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rocket stoves

refractory & perlite cast core

thomas rubino

gardener

Posts: 2765

Location: latitude 47 N.W. montana zone 6A

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posted 5 years ago

Hi all; Planning on replacing my fireclay & perlite cast core this spring with a new core made with all high temp castable refractory with some perlite added for insulation. I believe that i read somewhere here at permies that i may need to have an expansion joint ? Does anybody have experience with using this material? Thinking of using EJ bartel ks4v . Matt, thank you for the info on my old core. Tom

Not all who wander are lost... J.R.R. Tolkien

Amos Burkey

Posts: 101

Location: Nebraska

posted 5 years ago

It is recommended that you cast it in halves (left & right). If you are casting a rocket, cast the feed, burn tunnel, and possibly a short section of the heat riser in a left and right half configuration. Assemble it with a ceramic paper gasket between the two pieces and it is all held together with stainless banding in a few spots. The riser can be poured in one piece or poured in short sections of tube and mortored together.

You can buy lightweight refractory mix that does not require perlite to be added. You can use the perlite around the cast core for insulation without modifying the mix. The place that I bought my castable mix from did not recommend adding anything to the mix.

Also in consideration, Dragon Heaters cast their rocket cores in a single piece.

I could not find any documentation about the ks4v so I will not comment on that.

Good luck with the build!

Cindy Mathieu

Posts: 244

Location: near Houston, TX; zone 8b

posted 5 years ago

Also in consideration, Dragon Heaters cast their rocket cores in a single piece.

Dragon Heaters casts cores in a left and right piece and ties them together with the paper gasket in between using stainless steel banding, as you recommended to Thomas Rubino.

In the image, you can see the stainless steel banding in 2 places on each size (4" 6" & 8"). The heat riser is made from vermiculite board and there is a paper gasket under it as the interface to the burn tunnel. There is also a paper gasket between the feed tube (which has a P-channel in it) and the burn tunnel.

The burn tunnel design is as Peter van den Berg discusses on page 111 of the 3rd edition of Rocket Mass Heaters. We have licensed his design for commercial production in the U.S.

All_3_sm.JPG

www.dragonheaters.com
http://blog.dragonheaters.com/

Amos Burkey

Posts: 101

Location: Nebraska

posted 5 years ago

Thanks for correcting me, Cindy. For some reason I thought that your cores were one piece. I apologize for the misinformation.

bob golding

Posts: 48

posted 5 years ago

Cindy Mathieu wrote:

Also in consideration, Dragon Heaters cast their rocket cores in a single piece.

Dragon Heaters casts cores in a left and right piece and ties them together with the paper gasket in between using stainless steel banding, as you recommended to Thomas Rubino.

In the image, you can see the stainless steel banding in 2 places on each size (4" 6" & 8"). The heat riser is made from vermiculite board and there is a paper gasket under it as the interface to the burn tunnel. There is also a paper gasket between the feed tube (which has a P-channel in it) and the burn tunnel.

The burn tunnel design is as Peter van den Berg discusses on page 111 of the 3rd edition of Rocket Mass Heaters. We have licensed his design for commercial production in the U.S.[/quote

cindy, on your video of assembling the vermiculite riser i noticed the inside seemed to be a different colour to the outside. do you use anything like iITC100 or satanite. on the inside of the riser? i am planning on making a riser from vermiculite after i finish experimenting on the outside test RMH. seems like together with the cast core it will save quite a bit of weight, not counting the thermal mass of course. the plan is experiment ion the bus before installing it in the yurt with the thermal mass.

Cindy Mathieu

Posts: 244

Location: near Houston, TX; zone 8b

posted 5 years ago

cindy, on your video of assembling the vermiculite riser i noticed the inside seemed to be a different colour to the outside. do you use anything like iITC100 or satanite. on the inside of the riser?

Good eye, Bob

I am not familiar with ITC 100 or satanite.

Yes, the inside has a heat reflective coating which is supposed to increase the temperature of the exhaust and extend the life of the material. It's very expensive and we never did the side by side tests it would take to confirm that it did any good in our application.

www.dragonheaters.com
http://blog.dragonheaters.com/

bob golding

Posts: 48

posted 5 years ago

Cindy Mathieu wrote:

cindy, on your video of assembling the vermiculite riser i noticed the inside seemed to be a different colour to the outside. do you use anything like iITC100 or satanite. on the inside of the riser?

Good eye, Bob

I am not familiar with ITC 100 or satanite.

Yes, the inside has a heat reflective coating which is supposed to increase the temperature of the exhaust and extend the life of the material. It's very expensive and we never did the side by side tests it would take to confirm that it did any good in our application.

i discovered both ITC100 and satanite after having a look at some blade and knife forging sites. it is very expensive, but for small forges it does seem to have a good reputation for extending the life of the refractory. given that it is the same price as replacing the riser using it just to extend the life of the riser may not be worth it. raising the temperature of the burn is another thing though. as i don't possess any test equipment apart from a IR laser thermometer i couldn't really tell if it made a significant different or not. a set of high temperature thermcouples is on the shopping list, but i have to built something worth testing first.

scott romack

Posts: 90

posted 3 years ago

+1 for 'satanite'

Tam Deal

Posts: 64

posted 3 years ago

I have used one of those reflectants, forget which one it was labeled as, in forges, and it didn't seem expensive to me. A 1/4 litre bottle was like 20 bucks but it only tool a tablespoon or so for the forge. It is like a heavy mud, and one applies it diluted like a paint. The small bottle is presumably sold like that on purpose, and the most likely purpose is to line a pottery kiln, which is more or less the size of a garbage can, a lot larger than RMHs or forges.

One thing to keep in mind is that they faithfully reflect UV, which is an issue in a forge where one is looking in the forge all the time to check the trans temp. Doubt most stove apps have that issue, but it is up to the user to judge. I suppose also that if you use it in a dirty stove it will not do anything useful for you.

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