rocket heater-longer than usual heat riser experiment?

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.

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

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.

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.

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...

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.

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!

I've been thinking along these lines as well. Having a very tall riser for more pull.
One thing I wonder is if this would allow a venturi to be built in the burner tube for stronger velocity air flow right where the wood is. When I blow on burning with a very narrow stream of air, it seems to burn very strong. The conclusion I hope to make in that scenario is that it's the air velocity more than the total air volume that increases the temperature of the burn. I also wonder if with a taller riser, inducing a vortex would also make things work better. Does watching youtube count as research? If so, I've researched fire tornadoes and flame vortexes a bit. The most dramatic ones are where a very short unfocused flame is drawn into a tall narrow flame many feet tall. One example showed a sterno flame (usually 1 inch tall) being drawn up to 3 feet tall when placed within a rotating mesh screen.

Please let us know your results once this is built.

If you do some thermal radiation calculations you might find that one barrel will already put out many times more btu's than a traditional wood stove. With two barrels you will likely be standing outside since your house may be closer to the temperature of the sun...

Paul talks with Ernie and Erica about rocket mass heaters in this podcast: rocket mass heater podcast

They talk about the need for a tall, vertical heat riser.

Hi All!

I want to use a RMH as a masonry heater builtin in the north wall in my planned building. Sketch design is here:


Key points:
- Heat riser and "drum" will have spred from 0.3 m from ground to 0.5 m below ceiling
- Chimney will be 1 m from the wall and 0.3 m from the ground

The plan is: to use whole building as thermal battery.

I'm planing to try to build it, before actual house building, for an experiment in spring.
If somebody can foresee any issues with that design, please advise.

Have you ever built one to the plans and dimensions before? If not how do you know that one to dimension wont do what you want it to do? have you actually read the book? if not how do you want us to answer your questions that you cannot articulate?

Pardon me for being a bit forward but these questions are important.

Ernie Wisner wrote: Have you ever built one to the plans and dimensions before?

Not yet, I'm planing to build one small stove for coocking in spring.

Ernie Wisner wrote: If not how do you know that one to dimension wont do what you want it to do?

I knew that it will do what I need. "Russian" ovens is still prety common in my region, and RMH just have different combustion unit and more compact. My concerns is not releted to the: will or not will do? And more to: What problems will it cause while working?

Ernie Wisner wrote: have you actually read the book?

Plans for this stoves is available for free on the internet, or can be figured out from photos and videos.
As I'm understand key points is:
- Burn pipe (where wood is actualy burns) should have smaller diameter then heat riser, free space in barel and exhaust pipe
- Wood trey height should be as low as possible, and it should be as close as posible to the barrel
- Chimney should generate enought draft to not cause a "smoke back" problem, even if cold
- Ash pit should be as close to the barel as posible


Here litle list of my concerns:
- For enought starting draft it wil require high chimney to overcome air resistence of combbustion unit
- While operating it will consume room air rapidly, so it will require additional air intake to not cause wind draft in the living room.
- After burn stoped it will suck air from the room/intake because of hot chimney and will result in heat losses

OK you know it all so go build one in your back yard Well away from folks you value.

starting draft is no problem with the proper heat riser. if you can breath in the room so can the stove. put a couple bricks over the feed tube. Until you read the damn book this discussion is stalled.

Ernie Wisner wrote:Until you read the damn book this discussion is stalled.

No thanks.
If this community doesn't willing to help, than I will just stick to the "Kuznetsov’s Stoves" community.