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master steward
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I'm gonna be hanging out with ernie and erica in a couple of days. It might be fun to make a podcast. Anybody have any questions for them that I haven't covered in a previous podcast?
 
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What is the smallest and largest size that a rocket mass heater could feasibly be? I would like to make a tiny one for heating a small, outdoor workshop without taking up too much space. Thanks!
 
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Could a rocket mass heater be used to heat my 2 000 foots squared future two floor house including some hot water ?

What are the ways to eliminate smoke back in rocket mass heaters ?

What are the best way to keep the RMH clean with minimal maintenance ?

How long a life can a RMH have without replacing components ?

Did you ever used the "Peter channel" http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=355&page=1 ?
 
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Not sure if this has been covered, but how safe are they to use around babies and small children? Pets?
 
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I would like to know about converting an existing fireplace to a RMH. Is it feasible, and if not, why?
 
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Location: Near Beaver Valley, Ontario, Canada
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paul wheaton wrote:I'm gonna be hanging out with ernie and erica in a couple of days. It might be fun to make a podcast. Anybody have any questions for them that I haven't covered in a previous podcast?



I'd like a discussion on rocket cook stoves, particularily with construction details for one that will last for a long time. From what I've read about them, the rocket cook stoves made out of #10 tin cans don't last very long before they rust out. (Then again, they only take around 20 minutes to make, and are dirt cheap - literally, if you use sand/clay/dirt that you find nearby as the insulator.)
 
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Location: Willamette Valley
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Aside from cost and construction, how is a rocket heater better/different from a good, catalytic-converter-equipped, wood stove? Can a catalytic converters play any role in a rocket heater?
 
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Could you detail the best method if someone wanted to build one outside, test it, then disassemble it, and reassemble it somewhere else?
 
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I'm curious if anyone has ever modeled a rocket stove in a computer simulation. I'd also like to know if anyone has ever added cooling fins to the heat exchange barrel in order to keep the barrel cooler, possibly increasing the air speed inside the system. The same goes for a blower motor at the exhaust end to pull the air faster. Just curious if such testing has ever been done with these systems.
 
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Jo York wrote: Could you detail the best method if someone wanted to build one outside, test it, then disassemble it, and reassemble it somewhere else?



I agree with this, and it ties into my question, namely how do you get it past the inspectors/insurers? I have seen Erica and Ernie's draft building code they were kind enough to post on their website, but I am wondering if they can provide some real-world examples they have dealt with.

I'd also like to hear about any upcoming rocket-stove seminars they are aware of.
 
pollinator
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For heater starting, is a "pre-heating" or "priming" burn chamber a good idea, and where would it be located in the system? I don't want to use a propane torch for starting.

I live in a cold climate and in extreme weather there can be strong chimney downdrafts that make a conventional woodstove difficult to start. What can I do with my RMH design to minimize this effect?
 
gardener
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Ernie dosen't suffer fools well. On several occasions he has asked people to read the older threads, to watch the videos and when they're seriously ready to build, he encourages them to buy the book. He has built over 700 units and has answered many questions over and over again.

Many of the answers are available simply by searching his postings and on his website. Let's do him the courtesy of educating ourselves so that we don't waste his time on stuff that has already been covered to death.

My questions are all contained on a thread I created last week entitled Questions for Ernie and Erica----Large RMH in the new wood burning stoves section.
 
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I just got the book for Christmas. I added it to my wish list on Amazon and was delighted to get it.

I would love to hear discussion about how to could be set up in a non-permanant way in an existing house.

How much smoke can get back in the home?

Any plans to make a kickstarter project to pay for some kind of federal certification?

Please have a good long chat, we love hanging out with all of you, and it feels like we are part of the conversation.
 
Christian Burns
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Dale Hodgins wrote:Ernie dosen't suffer fools well. On several occasions he has asked people to read the older threads, to watch the videos and when they're seriously ready to build, he encourages them to buy the book. He has built over 700 units and has answered many questions over and over again.

Many of the answers are available simply by searching his postings and on his website. Let's do him the courtesy of educating ourselves so that we don't waste his time on stuff that has already been covered to death.



I wonder if a wiki compiled by others that would incorporate earlier threads would help?
 
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I'd like to know how long the exhaust tube could or should be when run through a thermal mass.

How much effect does exhaust tube diameter have on tube length?

Could the exhaust tube be lengthened if one were to taper the exhaust tube? Example: If the optimal exhaust through a thermal mass is a 20' length of 6" diameter tubing, could that 20' run be extended by tapering the tubing up or down after the 20' mark?

Perhaps a strategically placed venturi would help pull gasses down a longer exhaust path.

All this stuff is brand new to me and i am frantically educating myself through the use of web sites, blogs, pod casts and forums. I am also ordering books as often as finances allow. So, if these are stupid questions or topics that have already been discussed, please, accept my humble apology.

P.S. I also just finished reading your RMH article which really stoked my fire...
 
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Location: Snowmass, CO
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Any good designs for use in a large, year-round tipi with a canvas floor in a cold area? I've read the book, and know that when it was written tipis and other tent-like structures were not considered a good application, but since then we've heard success stories of RMH used in yurts. Did a quick search in the forums and have come up mostly empty.

Also, some feedback on the recent thread about using water as the thermal mass would be nice.
 
paul wheaton
master steward
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I would like to hear stories of rocket mass heaters used in scenarios that were utterly illegal and how they got away with it. And I want to hear about how insurance companies hate them - and people that then express their love for insurance companies by building one anyway.

 
paul wheaton
master steward
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I want ernie to talk about the lightbulbs with the replaceable filament.
 
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I do have a question for them. I am looking to build a rocket stove in the back yard this year to cook on and have a quantity of calcium silicate bricks I was thinking about using to line the heat riser. Have they tried or do they know of anyone who has tried this? From what I have been able to find they seem less susceptible to thermal shock and spalling than regular red clay brick and are far cheaper (e.g. free) than buying firebrick for the same purpose.
 
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I would love to see a detailed description of how to build the insulated riser inside the rocket portion of the rocket mass heater, the part which resides in the barrel, just after the firebox.
 
John McSmithie
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Dale Hodgins wrote:Ernie dosen't suffer fools well. On several occasions he has asked people to read the older threads, to watch the videos and when they're seriously ready to build, he encourages them to buy the book. He has built over 700 units and has answered many questions over and over again.

Many of the answers are available simply by searching his postings and on his website. Let's do him the courtesy of educating ourselves so that we don't waste his time on stuff that has already been covered to death.

My questions are all contained on a thread I created last week entitled Questions for Ernie and Erica----Large RMH in the new Wood Burning Stoves section.



How bout a link to the website for those of us who are not abundantly familiar?
 
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I would like to know the steps to take to when installing a RMH inside a woodframe slab house. Concerning insulation against the walls. I have a corner fireplace with a lot of rock that I would like to tear out and build a RMH. Also, what is the best way to keep a long exhaust tube in a shorter space, say 10 ft? I know tight turns should be avoided. Thank-you
Jesse M
 
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Would Ernie and Erica be interested in coming to Australia for a series of workshops around the South East part of the country. I would suggest 5 or 6 weekend workshops to make it worth the travel time. I could certainly plan that out. I have just been to geoff lawton's farm and had lots of fun playing with their, quite safe, rocket mass water heater (Non pressurized). Here is a link to the video http://youtu.be/YTnr8ua54Uw of it however the animation, which in principle is correct simplifies the design a lot. I have some more technical drawings of the structure that I can share once I get them on sketch-up. I already own the rocket mass heater book and have built several small units. Ready to step up to a biggie. Also I would like to ask for any tips on building on a suspended wooden floor.
Ernie and Erica are awesome. Thanks for all the inspiration and information you share.

Many Thanks
Daniel Hatfield
 
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Location: Vashon, WA
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Paul,

I would like to know how Ernie and Erica are doing with their permit process in Portland.

Thanks,

Ken
 
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Location: Ontario, Canada
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This is my second post...the first one I screwed up!

Anyway...I'm really glad I found this place and the RMH.

1. I would like to ask them about some of the different clay materials they've used over the years and how some clays measure up against others and what to look for in the materials used for making cob, fire cement etc? Are all clays created equal? I sure have lots of it here where I am.

2. Are there any refractory concrete mixes that they've used successfully? I've been thinking about pouring a small pad of refractory concrete, over perlite, to build the stove upon......or.....

3. Can an exisiting concrete floor serve as the floor of the burn tunnel? My intuiton tells me that it too would be subjected to too much thermal shock but I'll ask anyway...

4. Is there a better burn tunnel design? ie - Square or rectangular? I was planning a 6 x 6 burn tunnel in 7" system.

Thanks!
 
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We are looking at replacing our current wood stove with a rocket mass heater. The vent that goes from the top of the stove and through the roof is a good 10" exterior diameter. I haven't seen any this large in the videos and I'm wondering if we will need to replace this portion, use it as is, or pack some perlite in there with a smaller vent? Our house is a 1970's ranch style, should we look at cobbing one or more interior walls to get more benefit from the heater?

We are also placing one in our wood shop which is a garage door on one end rather than an actual wall. Should we take into consideration any special practices in this space to maximize effectiveness of the rocket mass heater in this space?

Thank you and hope I'm not too late on these questions.



 
gardener
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Hi everybody,
Thanks for writing in with so many good questions!

We just had a nice, loooong talk with Paul, and answered a big whack of these questions. But we had to let him go on to his next destination.

So most of you can eagerly await the podcast.

There were a few specifics that were in the later part of the questions, that we didn't address, and that I can't recall addressing in other forums.
(Sorry TK - - general questions about length, etc. are part of the basic design, and I think we've covered those well enough elsewhere. The text of the book is in the public domain, so you might see about getting a copy from someone else and buying the whole PDF or book later on. )

Dale, Christian, John M - thanks for looking at our other posts, and it looks like the Ernie fairy has already visited Dale's additional topic.
This is part of why we asked Paul for a woodstoves forum, so that it would be easier to find the large amounts of information already discussed on this subject. (And as many people are 'calling their crazy a rocket mass heater', and other people may quite legitimately prefer another appropriate solution for their particular needs, we brought the whole wood-burny-things along without prejudice.) I like how the forums work, but if you wanted to help us develop the existing info into another format, like a wiki or e-book, that would be fine. Especially if people are willing to pay a couple of bucks for the extra work involved to edit what is, essentially, a re-telling of an existing book, or its sequel.
The link to our website: http://www.ErnieAndErica.info. (The whole address navigates best).

Aaron and others - As far as tipis - it's possible to build an RMH in a tipi, the main issue is keeping it dry if the tipi is moved or leaks. A hot, wet mud floor is nobody's a weird idea of luxury. I guess it beats a cold, wet mud floor.
But if it's an established year-round dwelling that is keeping the rain out fine, and just happens to be conical, then putting in a mass heater would be reasonable. It would basically be the same steps as any other installation, you'd want the barrel inside and the exhaust to the outside, or straight up the middle, given the tipi's draft profile. I'd take the tipi down, dig drainage, and make a compacted gravel (or concrete) support pad. I would probably lay ducting in a thick cob pad to make a higher, entirely heated floor, with no contact with the tipi walls, to maintain maximum flexible space. You will probably have to shift your lifestyle to fit around the barrel and feed tube. I would be tempted to put the barrel near the middle, and make sure there's good air to the feed tube (open door or floor vent opening nearby, but not directly into, the wood-feed.) You could also try one of Paul's more portable mass-heater-in-a-box, with rocks or gravel added at each site for mass.

John C - sorry, never worked with calcium silicate, you'd have to look into its properties. Resistance to thermal shock sounds good, but it would also need to withstand the high temperatures that occasionally go well over 2000 degrees F; Ernie suspects as high as 3000 in some outlier dense-fuel-plus-draft situations.

Jess, Daniel, Michael: Building on a suspended wood floor involves two considerations: shoring up to support the weight (including water weight while building), and insulating to protect the wood from the heat especially in the burn area. We've done a raised stove on air channels that provide passive air circulation under the stove; this is a nice elegant touch but not absolutely necessary. About 2" of perlite should do it, and I believe we've gone into more detail elsewhere. We certainly have a plan for an 8" system on a wood floor among our offerings for sale.

Building on concrete: A concrete pad should not be the floor of the burn tunnel itself; it will cool (and dirty) the fire, and the fire will erode the lime out of the cement over time. But it is fine to use ordinary concrete pad for a footing, and insulate above it. Insulating below it also is ideal, but not practical with a pre-existing slab. I believe we've already talked about lengths in the other forums.

Clay questions are fun, but infinite variety makes it a hard topic to address in a public forum. In general, stickier is better, low-shrinkage is also good, and any old clay will work fine with the right proportions of sharp sand or other suitable aggregates. Silt, talc, and other 'softeners' are not as ideal.

We have no interest in working with refractory cement - it's an expensive and relatively low-temperature solution that is not re-usable like bricks or cob.
But we have been seduced into playing with refractory ceramic board and fiber-mat materials, and we are probably going to keep playing with those for certain applications. A 1" slab of duro-board or fibrefrax board, plus a half-firebrick to take the impact of firewood, would probably be a good substitute for the perlite and brick in the burn tunnel. Any masonry insulation will have the potential to make dangerous fine dust, so you want to avoid smashing it up into lots of little fibers at any stage while coexisting with it.

Lori, Jesse, and TK:
Yes, Lori, stick to the stove dimensions for the exhaust.
And yes, technically, you can drop the diameter about 1" for better flow in the last part of the system, but for Pete's sake don't enlarge it, it will slow down too much as it cools.

Tight turns are not a problem if they are 90 degree elbows paired into 180 degree turns, we usually use one elbow and one Tee to make a cleanout at each sharp turn. HVAC guys will tell you this slows the flow down like an extra 5 to 10 feet of pipe, and they may be right. All the systems we've built include at least one sharp turn and work fine; this is an expected feature and factored into the general design.

For the work space: think about how often you use it. Heat penetrates cob at about 1" per hour, so if you are only in your shop a few hours a week, you may not get much heat from your mass. A non-cobbed ducting heater is not a good idea for smoke leakage and chimney-fire problems. So, either make a very small mass, or consider a more quick-heat system. Ernie's dad was tickled with a pocket rocket that burned 'stickers' (scrap wood) as a substitute for his old propane shop-heater. Obviously, vent to outside like a normal high-temp chimney.

Regarding upcoming workshops:
Thanks for your interest, everyone. Here are some upcoming dates, in various regions:

Will confirm within the next 2 weeks: Looks like a March quick intro, and a June full build, near Reno, Nevada.
An April introduction (1-2 days instead of a 3-day weekend) here in the Okanogan, and possibly another full workshop later in the year.
July and August will most likely be boat-related and private workshops, unless the owners decide to open these installations to a public workshop.

September we are in New England - in Vermont for Yestermorrow workshop the weekend of Sept. 15th (Friday-Sunday), heading up to Maine the next week or two with an installation at NewForest Institute the last weekend in September.

We know others are interested on the East Coast, and in the Great Lakes region. The question is, how interested?

We could use about 4 people who want to do the groundwork to organize and/or host additional events.
This could be committing to host a full workshop or pay us to supervise your work-party on an installation project. Or it could be a few phone calls and emails to introduce us as guest presenters for a local venue. We can do a slide show in your local library, or a fire science night in someone's backyard firepit; or a Do-It-Herself demo on emergency heaters. Obviously, a larger site with shovels and bricks and kindling lying around, will get you a much more hands-on learning opportunity. Might be worth drumming around your local forums or bulletin boards to see if there's enough interest that you could make a buck by selling tickets to see us in your town.

In my ideal world, we'd come across and do a workshop in the Great Lakes area the very first weekend in September. (Host needed)
We'd continue east, with a couple of private site visits or speaking events on the way, do a bang-up job at Yestermorrow mid-month (confirmed), and smaller events as available the following week. (Hosts for smaller events?)
The third weekend in September we'd visit the Common Ground Faire; install a working model in Maine the following weekend; and then we might need a week off before we hit 2 other destinations on our return.
We could easily make a detour southward in early October, if the North Carolina and Virginia folks could get together to coordinate a good strong location that can host overnight visitors from the whole region.
I'd love to stop off in Montana on the way there or back, too. Again, hosts needed to set up a site or event forum for these extra stops.
We prefer homestay hospitality over hotels, both to meet nice folks and to reduce travel costs.

Then we hightail it for Australia in whatever part of our winter is their almost-wet season. And stop by New Zealand to see some great friends of mine.

If our itinerary does not include your area, we are also happy to do phone consultation or email plans back and forth. We generally ask about $300 for either a site visit or a detailed long-distance planning session. This can double as your workshop deposit to reserve a later date for installation help. Long-distance planning sessions include scale drawings; on-site visits can include whatever you want us to look at for a couple of hours, rockety or otherwise. Note that our 45-minute podcasts often become 2 or more hours, so our 2-hour site visits can stretch to include lunch, dinner, supper, or occasionally all three.

and I've completely ignored Paul's questions.

paul wheaton wrote:I would like to hear stories of rocket mass heaters used in scenarios that were utterly illegal and how they got away with it. And I want to hear about how insurance companies hate them - and people that then express their love for insurance companies by building one anyway.


I prefer to cultivate a reputation for discretion where other people's fifth-amendment rights may be involved.
I will tell my own stories, as I did on the podcast, and I will tell other instructors' stories that I've heard them tell in public.
A good one is Ianto's surprise visit by a local inspector, who sat on his rocket bench for half an hour drinking coffee and chatting before he asked about this thing he was supposed to look at. Ianto pointed out he'd been sitting on it for the past hour. He looked it over and decided that as it wasn't this, one rule didn't apply, and as it wasn't the other, it must not need to meet that code either, and went away perfectly happy to do nothing at all.
(We've mostly forgotten the details, but it went something like this: it's not a woodstove, and the wall wasn't combustible, so you don't need the woodstove clearances or permit. It wasn't a fireplace or open fire, so the chimney and foundation codes didn't apply either.)

Technically anything over 900 kilos (1860 lbs) has been exempt from EPA regulation by weight alone; they may change this ruling to specifically describe masonry heaters, but you could build a rocket mass heater to meet the ASTM code for masonry heaters, it's just more expensive and slightly less efficient that way.
I suspect the building code offices would have to know something about rocket mass heaters before they can make them illegal. They fall tangentially under guidelines for heavy objects, or hot ones, but nobody seems to know for sure. Most of the people we've worked with, it's either in an outbuilding, or is the sole heat source for a non-flammable building, which is yet another reason for exemption from most applicable rulings. So I can't swear to it that ANY owner has done ANYTHING illegal in installing one.

The story I want to hear one day (hasn't happened yet that I know of): someone building a house on a hillside with a traditional Chinese or Navajo or Roman hypocaust (a slowly rising masonry channel under the house to heat the floors, lit from the outside) and having the conversation with their insurance company about how it is not a violation of the policy to light a fire under their house. What can they do if you keep lighting it, yet it never burns down? Stop letting you pay the premiums?

Owner-builders can get away with a lot more as they scrabble together their first home, than could a renter, mortgage-debtor, or a landlord of rental units. In a sense, if you are paying a mortgage, you are essentially renting from the bank without them assuming any of the landlord's legal responsibilities.

Ernie will do some digging to see if the replaceable-filament light bulbs still exist. I've seen scrappy kid-science projects to build one, and I suspect it could be re-created that way using a mason jar as the bulb, and installing a filament-holder and vacuum-valve in an ordinary seal-able lid.

And that's all.

G'night, and thanks for stopping by!

-Erica W
 
Michael Brant
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Location: Ontario, Canada
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Thank you for that, Erica!

Michael
 
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Location: Dallas TX
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(Hosts for smaller events?)

I would be very interested in hosting an event in Dallas if you are ever in the Texas/Oklahomas area.

Thank you for all the information you have communicated to those of us who didn't know what a rocket mass heater was (or for that matter what hugelkultur was) two or three months ago.

Susan
 
Jesse Matlock
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Thank you so much for your reply!!
 
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Re shippable core: how much would it weigh?
 
If you are using a rototiller, you are doing it wrong. Even on this tiny ad:
It's like binging on 7 seasons of your favorite netflix permaculture show
http://permaculture-design-course.com/
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