Simplest "rocket stove" ever

[zxcvbob]

https://www.youtube.com/watch?v=kmDYUrVHPWc

I've never seen those 'H' blocks before, OTOH I haven't really looked.

[geronimotwo]

simple design.     i'm surprised that the cement blocks hold up so well to heat.

[zxcvbob]

Maybe most of the heat goes *up*, and the draft keeps the blocks cool enough.

[RevDisk]

Make sure the concrete or cinder block is very dry. It's porous, and can crack/explode if enough steam vapor builds up.

[AJ Dual]

Doesn't fire or high heat eventually degrade concrete, driving of the hydrates in the matrix or somesuch thing?

Or maybe not, since just about every fireplace on the planet is held together with it... (shrug)

[230RN]

Shoot, I don't know.  With all the junk they put in concrete to stabilize it, fast-cure it, de-grongilize it, fordilnok it, etc., I'd hate to think of what might be vaporizing in the heat and flames and ending up in my  chow.

I could be wrong, though.  Been wrong before.  Or so they say.

Terry, 230RN

ETA:  Dammit, AJ DUal beat me to it with a similar comment, but about its degradation under heat. 

[RevDisk]

Doesn't fire or high heat eventually degrade concrete, driving of the hydrates in the matrix or somesuch thing?

Or maybe not, since just about every fireplace on the planet is held together with it... (shrug)

Yes, no.

Refractory cement is NOT portland cement. Portland cement is used in general construction, and is not fire proof. It is fire resistant. Refractory cement uses different materials.

[vaskidmark]

So where can I get cinder blocks (generic term) made from refractory cement?  As in "where can I swipe them from a construction site?" because nobody that I know has ever bought cinder blocks unless they were themselves doing some sort of construction.  (At which time I may or may not have swiped a block or so.)

stay safe.

[K Frame]

I had a fire pit made out of concrete blocks at the house where I grew up.

It's where I cast bullets (when I did that), we used it to boil BIG pots of water when we blanched and froze corn and other vegetables, we cooked over it.

It was used a LOT over the 10 or so years it was there, including more than a few very large and very hot fires.

The blocks were still in good condition when my parents moved from that house in 1999.

I don't think you're going to really need to worry about those block degrading quickly.

[Triphammer]

 Cocrete, plaster & the like degrade quicky @ 14- 1600 F. slowly at lower temps. Fire clay bricks plus an air space protect the red clay brick or cement block of a fireplce.

[zxcvbob]

If they do degrade, you'll just have to pay 98 cents each for new ones    ...or use clay chimney liner next time.  Probably only one or two blocks will really be exposed to high heat, and it won't be *that* high a temperature.

As far as the funky double-H block goes, instead I think I'll just cut one end off a regular cinder block using my little angle grinder w/ a diamond cutoff blade.

[Triphammer]

The "H" blocks btw are for the coloumns in block fences or where you have a rebar & don't wan't/ can't lift the block over the end.

[K Frame]

I don't know whether it's really the case anymore, but there used to be a very definite difference between a concrete block and a cinderblock. A cinderblock was more a a lightweight, light duty block made from concrete mixed with coal cinders obtained from industrial power plants and the like.

I think the same concept is still available, just using different lightweight aggregates.

Concrete blocks were a LOT stronger, a lot denser, and a lot heavier.

You'd often see cinderblocks used for above grade construction like garages, while the denser, stronger (and more expensive) concrete blocks were used in house foundations.

I don't think a cinderblock would stand up to rocket stove use nearly as well as a concrete block.

[Triphammer]

They haven't made "cinder" (coal plant residue) blocks since the 60's.

[zxcvbob]

Do y'all think this would work okay for smelting lead?  Next weekend I go clean the local bullet trap, and I haven't quite finished melting-down all the lead from last year's haul.  I need something bigger than the hotplate-and-Revereware pot setup I'm using now.  (it works great, just too slow)  I have a Freon tank to cut in half for the crucible.

Yeah, I know about turkey fryers, but what's the fun in that?  Propane is expensive and hard to find this year; sticks and trash are not.

I probably shouldn't set it up on the wooden deck, JIC the block break under the heat and weight...

[cassandra and sara's daddy]

Roofing torch from harbor freight

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[eyebrows]

Regarding cinder blocks, I made a 8' diameter ring with them last year. Then proceeded to spend the summer burning a old barn piece by piece in that cinder block ring. We had flamees 12' tall at times. Plenty of times you could not get within 10' of the fire its self it was so hot. We just kept chucking barn parts in there.
By time the barn was gone those cinder blocks were, every one, cracked in many pieces. More than half of them had started crumbling to dust.

I wouldn't use them for a long term stove.

[Scout26]

Do y'all think this would work okay for smelting lead?  Next weekend I go clean the local bullet trap, and I haven't quite finished melting-down all the lead from last year's haul.  I need something bigger than the hotplate-and-Revereware pot setup I'm using now.  (it works great, just too slow)  I have a Freon tank to cut in half for the crucible.

Yeah, I know about turkey fryers, but what's the fun in that?  Propane is expensive and hard to find this year; sticks and trash are not.

I probably shouldn't set it up on the wooden deck, JIC the block break under the heat and weight...

Setup out in the dirt it should be fine to melt lead.  The only problem you may have is temp control.

[birdman]

Regarding cinder blocks, I made a 8' diameter ring with them last year. Then proceeded to spend the summer burning a old barn piece by piece in that cinder block ring. We had flamees 12' tall at times. Plenty of times you could not get within 10' of the fire its self it was so hot. We just kept chucking barn parts in there.
By time the barn was gone those cinder blocks were, every one, cracked in many pieces. More than half of them had started crumbling to dust.

I wouldn't use them for a long term stove.

We had a fire pit like that back home.
Best thing we burned was a VW transmission case. 
Ever wonder what 20lbs of magnesium looks like when it burns?
Well, first it melts, and its little rivers of molten silver running out, which is pretty so you look at it with your dark adapted eyes.
Then it ignites.
The result you can probably see by the retinal burns in my eyes and the shadows we probably left permanently on buildings 100m away.
"The light of god" we called it...of course, I later figured it was roughly 150-200 KILOWATTS of light.

[cassandra and sara's daddy]

And the fire dept can't put it out with water. Or so I hear

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[Boomhauer]

And the fire dept can't put it out with water. Or so I hear

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When you use water on a magnesium fire this is what happens

https://www.youtube.com/watch?v=VUgFzCjsRzE

You can put it out with water, but it's not easy.

http://www.firehouse.com/forums/t117478/

[Brad Johnson]

Doesn't fire or high heat eventually degrade concrete, driving of the hydrates in the matrix or somesuch thing?

Only if it's Neo fire. Every other fire which has gone against the hydrates has died.

Brad

[French G.]

We had a fire pit like that back home.
Best thing we burned was a VW transmission case. 
Ever wonder what 20lbs of magnesium looks like when it burns?
Well, first it melts, and its little rivers of molten silver running out, which is pretty so you look at it with your dark adapted eyes.
Then it ignites.
The result you can probably see by the retinal burns in my eyes and the shadows we probably left permanently on buildings 100m away.
"The light of god" we called it...of course, I later figured it was roughly 150-200 KILOWATTS of light.

I can probably put my hands on a few hundred pounds of scrap Mg castings. Wonder if a little campfire can be coordinated with an ISS flyover. I live in a normally pretty dark spot of the map.

[birdman]

I can probably put my hands on a few hundred pounds of scrap Mg castings. Wonder if a little campfire can be coordinated with an ISS flyover. I live in a normally pretty dark spot of the map.

Hahaha, awesome.