Strech McAnnally

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!!!

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.

Ernie Wisner wrote:I try to make sure the burn tunnel is as short as possible. if i could get it on all the systems the burn tunnel would not be more than a third of the heat riser height. if you have no problem with a barrel column in the house. by all means make the heat riser a but taller I think ours at the moment is 44 inches. burns like a champ. the other thing i would suggest is that instead of pipe you use brick for the heat riser. steel pipe will burn out and while thats not a bad thing if you have your perlite and clay mix right it is annoying to clean out flakes of burned steel. Sides i found out you can get 1/2 fire bricks and they work a treat.

Great!! Thank you so much for the information--I will take it and run with it!
Again, thanks so much!

Ernie Wisner wrote:nope wont melt the barrel. the book was written several years ago its about 17 years on the barrel now and still no problem. taller means more pull however; it also means your flame path will not in most cases reach the top of the heat riser. the perfect combo is for the flame path to be two thirds to three quarters the heat riser height.

so you're saying that the burn tunnel, the horizontal section, should actually be above the 1/2 length prescribed in the book? I just want to make sure i'm clear on that- I was wanting to start putting this thing into place today...

Roger Merry wrote:What do you want the heat for ? The barrel will have to be way too high to boil a kettle !!

I really don't have any plans on using the rmh to boil water or roast chickens or help power my plans to take over the world- it's primary purpose would just to be to heat the house. As for right now, that's it.

I've got a heat riser that is several feet long- once it's all in place, the top of the heat riser goes up to about 6'4". I have acquired two barrels from the sorghum factory over the road, so I was considering using my brother's welding talents and experiment with the length of the heat riser, as in the heat riser being more than 2x than the burn tunnel.

My main question is does anyone have any comments or thoughts on this- I know that Mr. Evans gave the draft formula in the book, so I was figuring that this would really PULL- not that it's needed since the rocket heater already pulls sufficiently enough if built correctly.
I know that also Mr. Evans said he hadn't used the same barrel for 12 years...so I was thinking, if I BUILD this to this length---will it melt the barrel and or spontaneously combust or create a small thermo-nuclear explosion? Can't have that happening.

If anyone has any comments or suggestions or questions, i'd be happy to hear them.

Len Ovens wrote:What you are looking for is constant CSA (cross sectional area) through the system. Generally the squarer the better. If one part will be smaller than others, it should be the riser, but not by much. So size the riser first. 6inch seems to be the minimum size that works well. That is 6inch diameter for a round riser at 28sqin CSA. I do not know if 5.3 inchs square would be fine in a square configuration or if it should still be 6*6. Generally all of us have built a massless setup to test what we have outside before installing it inside. So figure out the CSA of your riser first then go through all of your runs and calculate them to make sure they are the same or slightly larger. Then look at each transition from one run to the next and make sure they are ok. From what I have seen, most people who have problems have had a bad transition (barrel to mass pipe mostly because it has to be hand formed of cob and is therefore hard to judge the CSA. In that case oversize is better. My core is steel and so was easier to make sure of.

That- THe csa-- was something I wasn't , well wasn't sure what the book meant by it. I know it said that CSA had to be greater than the burn tunnel, but I was confused because it didn't include the heat riser in that calculation.

Yea, I've been fooling with this for a few days in my off time, building a dry run of the combustion unit. I built it up once , put some hardly burning cardboard in the unit that i'm sure had no proper dimensions, and was dismayed by the fact that it didn't start producing near fusion quantities of energy.
I appreciate the help! If I actually get this thing going I'll post pics with myself standing over my creation triumphant.

Hi all,
I have a dimensions question concerning the Rocket Mass heater.

I've went through the book, and I'm concerned about MY dimensions , compared to what the book says.

the first dimension i'm concerned with is the burn tunnel, "C" in the book. it says that it should be 6x8 or 7" squared- but if i don't get it to that am I screwed? I have only 3 9"firebricks, and the rest are only 8" old building brick. I'm not sure what the length of it should be exactly; the book just gives dimensions in proportionality as far as I understand it. Don't let this this and this be less than "C." So...I guess to put in down, does the dimensions of burn tunnel have to be exact? if mine is 6 high by 7.5 inches wide, will it blow up and kill everyone within a 3 mile radius ( or just not work?)

My second questions is concerning the feed tube and heat riser. I had planned on building both out of brick ( although I'm looking for a metal tube for the heat riser.) If you put bricks together so that they interlock and form what reminds me of a swastika in it's own way, the tunnel is about 6"- less than the 7" called for in the book. Will this kill the draw?

these are the main problems I've had with building this thing so far. I don't want to put it all together, and then realize that i'm gonna have to smash it down because I didn't put the dimensions to the correct proportion/ and or size.

Any help will be rewarded with delicious cake.