Lasse Holmes

CO2 released from fermentation can be used wonderfully for plant/algae but I don't think that exhaust from a rocket will be clean enough. Can algae handle CO not to mention the plethora of other compounds that will be present in the exhaust at different times/stages/conditions? Perhaps some small scale experimentation is in order before too much investment in plannning and construction. I appreciate the approach of not wanting "waste" so don't let my doubt get in the way of your mission. Please share your results for us fellow "gleaners". Canyon

Hi Jonathan,
I am a beer brewing rocketeer (just did a batch on tuesday) and can relate to your quest. I made a 1/2 barrel keg rocket wood stove conversion that works well as a hot liquor tank or brew kettle. But for real hot h20 making you need more surface area than just the bottom of a keg "barrel". So I built a tube shell heat exchanger but it is a bit of work,$, and more complicated. I added copper pipes in my mass bench so that I can extract hot h20 low tech for brewing or otherwise , or add hot h20 from my solar flat plate collectors to add heat to the mass. I think the pipes in a bench are a good low tech heat exchanger for lower temp heat (preheat) of brewing liquor. Rocket kettles are tall so must be built sturdy and stable even more so if you are going for a full three tier gravity system. Are you a welder? I think a bell with large enough copper pipes embedded in the top would be a sweet way to go for hot h20. Anyway, lots of ways to do it, just depends on your particular needs and $ and skills and time! My best advice, get rid of the plastic mash tun right away!
Canyon

It looks like you are wanting to exhaust into your occupied space? not recommended-CO kills. Perhaps that isn't what you mean. Have you studied the book?

I assume you are talking about a barrel of an insulated heat riser? If so, it gets plenty hot, like a barrel stove. I have measured 900 F at the exit point! Of course the top(cooking spot) gets red hot.

KT,
Cleanouts are key for long term maintenance. Any flue run needs to have an opening where you can stick a flue brush/shop vac hose into to clean even if it isn't that often. I only need to open mine up and clean every other year unless I burn less than ideal wood (I only had to do that once to learn that lesson). I thought one of my runs would be accessible from one end (it has some twists and turns) and when it came time to clean I found out that I really need another cleanout so now I have to add one after the fact which is a pain. So, if you have any u-bends to do, make them H's with two tees and you have cleanouts or figure out what it takes. Breakup is kind of starting I guess (it is melting a bit in the latter part of the day these days but we still have feets of snow!). Yes, what an awesome winter!
Lasse
(Canyon)

Kia Tikaboo wrote:I am currently building a rocket mass stove to heat the perimeter of my greenhouse.

I am using 6" single wall stove pipe to channel the exhaust, and was wondering what the maximum length should be.

I consulted Ianto's book and he indicates a range of 32 to 40 ft.

My run will be 40 ft with 4 90 degree turns.

Does that seem reasonable?

Thanks,

kt

There are many variables but as a general statement 40' can work for an average rocket. Use tees instead of 90's so that you have cleanout access.

James McFall wrote:I am thinking of building a rocket mass heater and was wondering if the 55 gallon drum has to be food grade or not.

Thank you.

No problem, just make sure you pre-burn it outside to get rid of paint/resisdues. canyon

Andrew Parker wrote:Jason,
The internal heat riser in the RMH is not what makes it a rocket stove.

A rocket stove is, IIRC, an insulated (though not always insulated) duct or flue of relatively constant internal cross-sectional area, in the shape of an L or J (though not restricted to those shapes). The constant cross-sectional area keeps the gases moving. The insulation helps to keep the flue gases from cooling before combustion is complete and maintains draft. (Those are the rockety parts)

In an RMH, the internal heat riser, made by putting a barrel over a J-shaped rocket stove, is used to help passively pump hot flue gas through the labyrinth of ductwork.

Hi Andrew,
I am not sure if you really want to have a nomenclature discussion (I am frequently challenged discerning when people are serious or sarcastic) but I am interested in clarification of these terms as I teach people this stuff and would like to be accurate. I have been teaching that the main defining feature of a rocket is the insulated "heat riser" or "internal chimney". The internal heat riser is made by insulating the internal VERTICAL chimney (which the L or J shapes inherently have), not by putting a barrel over it as that is just one option for heat exchange or flue gas path. I like your effort to simplify the rocket stove definition but I would say that it could be simplified further by dropping the words "chamber of constant cross-sectional area" and adding the word vertical. So the description of a rocket stove could be simplified to an elongated, insulated combustion chamber with a vertical leg. An evolved design without that vertical insulated heat riser would indeed be at the point of difference to warrant its own label and NOT be considered a rocket. Feedback?
Canyon

Jason Munzke wrote:I have the same type question. Is there more about converting woodstoves into Rocket Heaters. I want the efficiency (or near the efficiency) of the RMH with the quick radiation heat of my cast iron stove, to be used as a sauna.

You can build a RMH without the mass ( a rocket air heater) by adding lots of surface area for heat exchange after the heat riser (like extra barrels). I have converted woodstoves to rockets by adding insulated heat risers and have this problem of looking at every woodstove I see and imagining how I'd rocketfy it. There have been alot of fun ideas but I much prefer to build rockets from firebrick as it is generally much less work and lasts longer and I believe more efficient. Canyon

Somewhat similar to Matt Walker, we have been building rocket combustion systems that double as masonry ovens up here in Alaska. Our heating needs are pretty great so we have been building more batch style rockets with a horizontal loading front door instead of the downdraft. We have developed a simple plan using firebrick with a masonry arch that creates a nice oven for use after the fire is out and it equalizes similar to a traditional black oven. This way it is not something extra, just a side benefit to the design for more approachable batch load burning. Now after a full season of use with several of these we are refining the design, doing some flue analyzing and we're looking forward to leaning on some of the more experienced rocketeers in the PNW for more testing/input/refinement next month while on tour. We have a goal to make this "kit" or plans available as an affordable option for the do it yourselfers after we are ready in a few months, so stay tuned. I have also played around with the idea of a cob oven downstream from the heatriser and still hold this to be a viable option. In fact, our ash fall out areas right after the barrel have essentially been cob "bell" ovens (we have even bisqued some clay sculptures in them) but they lack the larger door to load with bread etc. Adding an oven door and shaping/adding more mass with the intention of baking would be another great way to go. There are a lot of approaches possible in this oven quest! I look forward to others sharing their experience! Canyon