first build- constructive criticisms( or otherwise) needed

Hi all--

Well, First off, I'll preemptively strike by apologizing for yet another newbie question.

I've been interested in the rocket heater concept for some time now; I'd posted a question several years ago when I was hoping to build one with scrap materials I'd managed to locate.

I ended up going to Korea for a few years. Semi attempted to locate materials to build one there as well, but I could never find the materials or motivation, besides the $500 heating bill every month, to build it. So, was lazy.

Fast forward to 2015. I came home in the beginning of January, to take a breather and get my head on. Decided to try and build this thing.

SO-- I've gotten the heater core built. Read Ianto's book, read it again; kept referencing it. Tried my best to pour over this forum. Easy to blow several valuable hours learning. It's been a great resource.

I'll try to be concise with my questions- see if I can get some constructive or deconstructive criticism.

Here's my dimensions: I had some clay flue, which is around 6 7/8th. So building on that,

Heat riser- width: 6 3/4-7/8 wide square
vertical length: 40 inches tall

Burn tunnel:
dimension: 6.5x6. 6 inches tall ( 1-brick laid on side, 1 brick laid flat), by 6.5 wide
length: 19 inches long (if I am right in my measurements, in that going from the last brick on top of the burn tunnel, to the one butting against the feed tube)

feed tube: 6.5 square
height: 10 inches tall.

heat riser insulation: around 19 inches diameter. It's not exactly uniform, but It seems to mostly stay within this range. filled with some sort of vermiculite my father had stored away.



I don't have the barrel put on yet. I've been burning it, just to make sure it was working properly.
So- question #1- should the flame actually be reaching the top of the heat riser? I've yet to see any sort of action with this setup. I know there's lots of variables...is that burning at all times, or just when the thing is red hot? If you've got the barrel on...how do you know it's burning to the top?

question 2.: I was reading a post that someone had asked that was very similar to a problem I experienced, in that when I put the barrel on top, loosely without a cobbed base mind you, The drawing effect was dampened significantly. I'm figuring it was either 1. top of heat riser didn't have enough gap,1.b. top of heat riser insulation was somehow disturbing airflow 2. side walls, "H" in the book, were too slender and bottlenecked the flow,b or 3. As someone mentioned in that other post, you must have a vertical chimney on it.

right now I'm mainly concerned with the fire extending throughout the burn tunnel and up the heat riser. Not sure if I should shorten the burn tunnel, and how that will affect the dynamics of the heater.

of course the barrel going on and smoking is also a concern...but i'll work with that when I get to it. And hopefully not shoot myself in the face out of aggravation in the process.

Well- i will go ahead and update my post before I actually post it. I put the barrel on, and as suggested by a poster in a previous post, I raised it much higher than need be- 3 bricks flat high. Fire seemed sort kinda dampened; although I need to do it again when I have someone here to actually watch the stupid thing. right when i'm putting it on.


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Fire without barrel:


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fire with barrel: ( video sucks....fire doesn't. enough. get it...bada...walk away slowly)



shit- looking at those pics, I just now realized how lopsided that insulation is.

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Q1) 2/3rds to 3/4

Q2) #3

Q3 Sealed at the base AND #3

I am kinda expecting that one or more of your Clay Tile Flues will not be able to take being made freaky hot as fast as we normally do with out failing !

Other people have split the Tiles into two pieces each and then clamped them back together with Stainless steel banding !

''The Book ''describes the use of 100 year old dead soft House brick, you have taken a few liberties with interpreting what that means, When we say dead
soft 100 year old house brick we mean a brick that when rubbed on Blacktop or a Concrete Sidewalk leaves a red mark behind very similar to the mark
left behind by sidewalk chalk - The harder brick you appear to be using will also have longevity issues !

So seal the barrel at its base and add a final vertical chimney, you should actually have done this step outside, but winter is a pain in the . . . and we all
do understand !

Come back soon and we will move on from there ! we all started from where you are now ! For the Good of the Craft ! Big AL

To expand on Allen's comments: clay flue tiles are made to stand high heat, but not fast temperature changes. Their inner faces will get hot and expand while their outer faces are still cold, and they will crack. Then when the fire is out the inner face will cool and shrink while the outer face is still hot. Cutting the tiles in half vertically will let the parts warp a tiny bit when heating and cooling, lessening the stress on them.

Modern (cored) bricks have the same rigid, brittle quality, and it is likely that eventually the bricks in the highest-heat areas will crack and maybe even disintegrate.

Your riser insulation is 19" diameter, while a standard 55 gallon drum is about 22" inside diameter, leaving only an average of 1 1/2" space all around. This is considered the bare minimum, and you might benefit from reducing the insulation jacket diameter by a couple of inches. You would still have plenty of insulation. Vermiculite is said to settle with time and probably heating, so you should check it periodically. Perlite is a more stable insulator, if you need to buy more.

Glenn ; Thanks! I had to hurry to answer a ''second alarm'' for our local Rescue Squad, If I had had another 1/2 an hour i could not have explained me better

Kinda scary-huh ? Big AL

i appreciate the help , guys! I wasn't sure about the clay flue- I figured it would do well enough , but of all the comments I'd read about the high heat mania going on inside the pipe, I wasn't sure. For some reason I have a feeling that this heater won't be the last I build...we'll see.

in the meantime I'll go about trying to do something with the clay flue- cutting it/ accidentally dropping it, something. I have more brick, not sure how it would hold up to the heat in the heat riser ,compared to the clay flue...but whatever.

As for the brick- I wasn't completely sure the quality of it. He'd told me that it came from a building they'd knocked down over in Fort Payne, but I never knew the actual source. Clay in between bricks came from a local churt pit,sand was from a pile at my cousin's house where they'd been mixing cement.

And of course, deal with that heat riser insulation- I just poured it in loose fill, after trying to mix some of the vermiculite with slurry to make it adhesive. The vermiculite on hand was some sort of water resistant sort and it did not take to mixing all that well. I did mix a bit and packed it in the bottom, to try and seal up the gaps between heat riser insulation ..container, and the rest of it.
I don't think I mentioned in my earlier post that I I'd laid the thing on a bed of vermiculite- the cored bricks in the pics were just the border for that.

Anyways- I'll work on it and maybe post something later trying to get another explanation why I failed miserably. Regardless, thanks again guys-- I'll keep going!!!

I built my l feed out of the same terra cotta flu liner material anticipating cracking as their is minimal vertical lode atop
Sure enough first burn cracked it. The riser gets hotter that sand may crumble in. A cheap insulator I've used is wood ash I will be casting a high quality core next winter probably a Peter style batch box