Yeah.. Actually you're right, air channels all the way under the stove are better. Heat can get through the insulation and concentrate!! I was totally wrong back then. You can insulate under, but you need air space that can vent away under that! So now the recommendation is to use the same trick, bricks on edge with bridge bricks or something similar to create air channels under the combustion unit and perhaps also some of the bench/bell, depending.
Wood provides 6000 BTUs of heat per pound (yes, theoretically it's 7000 BTU per pound, but realistically I just use 6000) One BTU is enough heat energy to raise the temperature of one pound of water, one degree Fahrenheit.
How big is your pool?
Let's say I want to heat a large hot tub, which holds about 800 gallons of water. (it's capacity is really bigger than that but the heat exchanger and the people will displace some of the volume, etc.) Water is 8.35 pounds per gallon, so an 800 gallon tub holds 6680 pounds of water. Let's say the initial temperature is 68 degrees F. and I want to heat the water to 108 degrees F. (a change of 40 deg. F.) It looks like we can safely round off here (just call it inefficiencies in the tub and other bits) and make a local rule that one pound of wood can raise the temperature of our tub about a degree F. That gives us as a thumbnail estimate of around 35 or 40 pounds of wood for a sweet evening under the stars. Colder nights and colder water will require more wood. How many gallons of water are in an average pool??
apollokit, That will certainly work, though you cannot turn a wood fire off so easily as a gas flame (unless you use wood-gas), as a result wood fired systems can become a bomb more readily. Be very aware of safety equipment for hot water systems and provide backups/redundancy.
gretchen, That's exactly what I've been thinking. (or something like that) What if it was a metal bell chamber just under the water level, with insulated input (from the stove) and chimney on. Then the J-tube (or Batchrocket) can be outside the hot-tub/pool, easy to feed. fully insulated, etc. It would have to be bolted to the side pretty well, it's going to want to float out with some oompf.
Do you have a chimney or are the gasses just exiting under the window at the end? (looks like some smoke on the wall hence the guess)
There's no chimney. Exhaust goes out the first uncovered hot-spot. If all the hot-spots are covered, it goes out by the wall.
How are you forming the channels in the cooktop? Is it all "solid" perlite-clay except where the pots are and the connecting channels? Are you bridging with adobes?
The sides of the channels are formed with adobes, but the top is sculpted with cob, freehand. A thin plaster of perlite/clay is used to insulate the channels somewhat, though it's not on the ceiling of the channels, so it's likely ineffective but that's OK. The stove still works like a champ.
It seems like you are not minding the potential energy and efficiency loss of using perlite-clay for the riser compared to IFB. Do you notice a significant improvement with IFB for the riser? Does the perlite-clay last?
I don't know what IFB is, sorry. I use perlite/clay because it's easy and inexpensive. I don't mind a slight loss of efficiency if I gain in utility and ease. My measure of a stove (or a building or anything else for that matter is "arse value"... The 80/20 rule is my greatest master.
I'm going to be starting my outdoor Rocket cooker build next week so your post was perfectly timed inspiration. Thanks again!
Good luck with it and don't forget to post your builds here!!
This stove is all earthen mixes of one sort of another. The body is mostly adobe bricks with cob. It is insulated with a perlite/clay mix.
First, we laid out the hot-spots. It was decided to stagger the hot-spots so that reaching to the back pot won't burn you.
2 Rocket J-tubes built side-by-side, the closest to the camera is an 8 inch stove, the one in the back, 6 inch.
The only fired brick we used was for the top opening of the feed. It is my experience that if the top edges are adobe (cob), they will be wrecked over time by the wood. Bricks at the top edge of the feed will keep the firebox in good order.
We added in wood storage underneath. This arch passes through to the other side.
To make the heat risers, we placed stovepipe inside of adobe enclosures, packed between with a perlite/clay mix and then pulled the stovepipe out (metal is doomed!) Here, you can see that the risers are angled, so that the fires will be offset.
We had some nice stone pieces that served well for keystones in our adobe arches.
Test, a LOT. After the base was built, we ran the stove pretty much the entire time of building the rest.
We insulated in and around the pot holders/hot-spots as much as possible with perlite/clay.
Hot-spots are built to fit a particular pot like a glove. We built the channels like a Lorena stove; pots fit down inside the stove so that heat will flow all around the sides as well as the bottom.
ALWAYS RUN IT WHILE YOU BUILD IT! This has been my philosophy since the very beginning of my adventures with stovery. It's treated me VERY well. Yes, you risk burns and smoke inhalation, but if you're paying attention, you can build superior stoves. Use your hands, ears and nose! They are your best guide.
Though the potholes are shaped around a specific pot, reducers can be used to adapt to other pots and pans.
This is as far as we've gotten with this stove. Not documented here yeat is that there will be another, much smaller rocket stove as well; a tiny, 4 inch twig stove will be build into the side. This way, if you just want to boil water for tea, you don't have to start and run the big-guns. There will also be 2 holders for a variety of beer-can alcohol burning stove that I like so much..
Hello everyone, I am very happy to announce, (and excited to attend) the 2017 Rocket Mass Heaters Workshop Jamboree. The event will feature MANY workshops and some raw experiment time, with some long time innovators in Rocket Stoves; including our good friends Peter van den Berg (peterberg), Lasse Holmes (canyon), Myself (Kirk Mobert), Ernie and Erica Wisner, Tim Barker, and Chris McClellan (Uncle Mud). The event is in Montana, at Paul Wheaton's (of Permies.com) permaculture farm. There will be 17 workshops, in 3 parts, from October 6th through to October 17th; take any combination of one, or all parts!
Sign up early (now!!) and get the Earlybird price!
Yeah.. Make small batches, a little wetter than you might think. The stuff goes off quickly, I've seen it set in the pot, while working. You will have to work fast to get the material on and smoothed to your preference before it sets. Drywall mud is essentially gypsum, though there is a lot in there that is NOT gyp. Karl could probably shed light on what all is in there, I don't know the details. Anyway, the drywall mud is FAR easier to use than traditional gypsum and if you don't mind the compromise in favor of ease of use....
I recommend that you experiment a bit before committing. Try it out on the same surface material (cob, brick, etc), you don't want ugly surprises on the final build!
Yes. Glass angle has a LARGE effect. For solar gain, you want panes as perpendicular as possible to incoming light. There's always a small percentage of reflectance based on the thickness of glass as well, something about quantum spin.. Feinman talks about it in his "6 Easy Pieces" book.
A trick: In deep walls, like bale or cob; glass can be angled (tilted out at the top, in at the bottom) to exclude solar gain on a west wall while providing that view you just had to have..
On the practical side, angled glass can be a pain in the ass to deal with. The extra hassle can make it less attractive for some uses.
Depending on the thickness of the glass, and the color of the light, a certain small percentage is reflected off. Light that passes through the glass does so fairly well unaltered, then strikes objects behind the glass. When light strikes a surface like cob or something, some is reflected and some is absorbed. Light that is reflected can pass back through the glass, making objects inside visible to the eye. When light is absorbed into an object, it becomes heat energy, some of which is re-radiated back as infra-red. Glass is reflective to IR, which is trapped inside the space and is known as the Greenhouse Effect.
panos: Some fireclay products say thy exhibit resistance up to 1000 celsius.Would that be fine for a 150 mm Batch box rocket?Would it be better to search for reistance up to 1200 celsius?
Jul 1, 2017 16:38:34 GMT -8
idahodave: I'm getting ready to build my first RMH, and have some specific challenges. First one is that the site has a high water table, which in February got as high as 8 inches above the projected base of the heater. Any suggestions?
Jul 15, 2017 13:49:58 GMT -8
panos: Can someone make a sketchup file for the support base of a batch box rocket as per Peter's van De Berg following reply:
Aug 13, 2017 11:06:09 GMT -8
panos: those pumice cinder blocks are better suited to a base support. On top of the blocks a ring of bricks, an infill of perlite/clay and the firebox and maybe even a bell on top of that. If possible, arrange the blocks in such a way that there are channels
Aug 13, 2017 11:06:27 GMT -8
panos: under the whole of the heater so heat won't accumulate under there but can be vemtilated away by air currents.''
Aug 13, 2017 11:06:57 GMT -8
SilverFire: Yes, our designs have moved from the experiment design to production, as with the other stove models that were listed on this thread. Hopefully this will inspire others to continue to improve stove designs as we have done.
Sept 15, 2017 7:24:54 GMT -8
SilverFire: Regards and good cooking.
Sept 15, 2017 7:25:18 GMT -8
permaculturebob: citrus paint removers --"citra solve" is one and Walmart distributes another--non toxic fumes, softens tough barrel paint--sometimes it takes a couple applications and some scraping, but I prefer it over sanding and burning
Oct 13, 2017 17:08:53 GMT -8
martinm: Hi there ! I need chart / comparisson on : RSMH vs mass produced wood burning stoves. I need to write a proposal to local govt. to convince them on choosing Rocket stoves for supplying families in poor neighborhoods. Thank you Will look through the threads
Nov 8, 2017 14:25:57 GMT -8
burnclean: You guys all rock !
Nov 14, 2017 15:28:03 GMT -8