I'd read the book on it and have been around only one it was used to heat a hot tub at Carole Crews' earth plastering seminar in Taos. I very much like the idea. Like many things about alternative living, you have to be present most of the time. It seems to me that if you just follow the example of the book I read.... I might have bee Yanto's book, he's the guy who helped author The Hand Sculpted House. The book on cob for my money, anyway, It showed burning what looked like old style rancher fence posts. It you have a steady supply of those and you are home enough to fire the thing it might be good system. And that's my question. To cut, dry and limb enough small diameter timber to feed one of those seems like a pretty daunting task. I haven't been around day to day use of one of these so my questions come from ignorance on the subject and not as objections to the idea. I like the idea of burning hot with little emissions just fine. And try to do that at our place. I have some questions on efficient wood use strategies just posted here. If anyone has some answers I enjoy the info and meeting some new like thinkers. They are a precious commodity in central N.M.
There are some forums here from people building "large-batch" rocket mass heaters ( I'm assuming that's what you mean, not a cooking stylerocket stove?). A fellow named Donkey has some videos up on YouTube as well. There is debate on whether some ofthese modified RMH's are indeed RMH's at all, since most rely on tightly restricted air flow (dampening down) and therefore they get an inefficient, albeit longer burn from the fuel. RMH are designed to have a quick efficient burn that transfers as much energy as possible to the mass (thermal battery some call it) so as not use large amount s of fuel.
And I'm sorry to repeat these things that I think you already know, BUT, that last statement answers a few of your concerns. Yes, you will have to chop up your fence posts to make a good efficient fast burn, BUT, once you get your mass up to temp, you will only burn one of those suckers per day, so it doesn't involve much work on your part. Most probably less work then pioneering a large batch style heater.
There's a great video that Ernie and Erica have posted on YouTube that shows the total amount of wood they burn per day to stay warm, and it is VERY little. I'm willing to bet that if you build a good RMH you will only have to quarter 10 of your posts per week to have an excess of fuel. Remember, long sticks will burn for a longer time-period and also have good surface area for a hot burn. The internal (cooler) temp of a large chunk of wood is enough to cool the whole combustion process and make you loose a bunch of your fuel as smoke and waste gas.
I hope this helps. I'll see if I can rustle up some of those vids for you.
oddly folks at first always seem to think that you need to make some sort of tiny fuel. for the 8 inch system you have a feed that is 71/2"X 71/2" nominal and thats a big space to fill with wood. our wood is split to normal firewood sizes and is 18 inches long just like folks use in a box stove. We use around thirty or so LBS of wood a day unless we are keeping the house way warmer for some reason. A cord of wood is around 1 long ton and we burn about a cord of wood a winter up here in the okanogin highlands. Tonasket washington 98855 for those who want to look up the heating day info. We get 20 and thirty below up here on the mountain and our wood usage doesn't change that much. A Little because you are battling the cold, but not much we might go through 50 lbs of wood on a horrible windy way below zero day. Depending on what we want for heating changes how much splitting we do, if we want fast high radiant heat we split the wood a bit smaller. but we usually just burn it the way it came. on this the back side of the heating season i have about 1/3 cord in the wood shed still. We will be warm and happy well into the spring/summer.
the RMH will burn small stuff as well as pretty large stuff it can if watched burn really long stuff. I should mention that we burn about 3 feed tube loads of wood a day and that takes around 6 hours to burn all the way out. you tend the stove about every hour and a bit depending on the fuel size. Smaller stuff you tend more often. good hard wood i remember tending about every two hours with pretty big wood. so i assume that if we had oak or something up here we might only burn 20 Lbs of wood for a total burn time of 4 hours.
I dont know we live in a place with lots of tamerak, pine and fir. this next year if i am lucky we will have a cord of apple wood to see how well a fruit wood does (hard wood).
Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info
Location: On top of a mesa in central New Mexico.
posted 6 years ago
Chirs and Ernie, thanks for the input. I not one of those who thinks the fuel has to be small. The fence posts I referred to were the size or better than the round stock you were holding in the vid. Except they were five or six feet long. Again I like the idea of burning less wood. I already live in a thermal mass paradise. But it not the size of a cottage. Who knew? Wish we'd gone that rout but it was a long time ago and we had lived in 420 sq. ft. Prior to moving to N.M. We just laid out lines on the ground with no idea of how big it would be.
I don't see much info on flue data other than the maximum length given in one of your vids I've seen little mention of clean out of a 25 foot flue or the extra burn chamber at the vertical rise that some have to use to get a draft going. Also I watched several of the vids, no one mentioned how large the space is that you are heating. It there data on size of burn chamber to cubic feet of space you need to heat? Why is triple wall pipe favored over heavily insulated..... I don't know, 6, 8 or ten inch well casing. Just a thought I had..... There is some of that kind of stuff around the county.I admit to zero practical experience. I just saw one in Taos and it may not have been properly constructed. It's did not draw very well on start up and they had the extra burn chamber where the flue went vertical. I'm pretty sure I have Yanto's book somewhere, are there updated ideas around that have merit? I read the book some years ago and didn't follow up on the idea. So any info you have time to provide would be a great help. I think it's a fine thing to spread the word on this kind of wood burning. Here in N.M. they think there is no end to the wood supply and the aquifer for that matter. They think nothing of irrigating all day in hot dry weather. Aquifers cycle on exponential math. Everyone here knows the rest.