|
Post by flybyjohn on Jan 17, 2018 6:05:50 GMT -8
Hello all, I am new here and this is my first post. I have heard of rocket stoves in the past and did a little research about them at the time and it ended up being spring time before I got fired up to do anything at the time. The only downside was that my fireplace is to heat my detached 24’x30’ garage and I like to build a fire that I can walk away from and have it provide heat for the next 5-8 hours. I don’t have any space available for mass in my overcrowded garage to hold the heat created for long periods, so I continued to burn dirty fires that used a lot of wood. Fast forward to today and I just received my first violation of a dirty fire on a poor air quality day. This one was free but the next one is 100.00 and the following one 300.00 and then 500.00. I really need to do something. I researched rocket stoves and noticed that the Batch rocket stove has been being refined by some very fine folks more interested in helping others and burning clean wood stoves, than in making money off their research. So first of all, let me thank you for all your research you have selflessly done for the good of mankind. I am on quite a small budget, so pushing my pennies as far as they will go is my 1st priority. I have the ability to weld steel and my masonry skills only go as far as laying 3 rooms with tile if you can even call that masonry work. Time involved to the building process is the 2nd priority because I will be removing my steel wood burner to build this batch rocket stove. I have done quite a bit of research but there is so much information out there that I wanted to run my build plan by some of you and have it critiqued and get any comments or suggestions you may have on it.
WHAT I HAVE: I am starting with a large homemade steel box used to burn a lot of wood. It has a 6” chimney flue on it and does not have any kind of baffling or anything inside the box. It measures 24” x 24” x 36” long. I did inherit it with about 36 - 4.5” x 9” x 2.5” heavier fire brick. The door opening is about 15” wide by 13” high. The chimney consists of about 5 feet of single wall stove pipe in the garage transferring to insulated 6” pipe up threw the attic and out the roof. It is about 12 feet long. I have in my shed a 50-60 ish gallon hot water tank I was going to use for an oil burner but changed my mind. I also have a 55 gallon drum in good shape. I also have the Archie Bray clay foundation for the ceramic arts business about 6 miles away from my house. They have a large selection of fire clays in stock all the time. MY PLAN: I have enough room inside this steel box to build the entire batch rocket stove core with over 5” of space between the core and steel stove sides. I would cut a 19-23” Hole in the top of the stove for the riser to come up out of and then put the 55 gallon drum or the 50-60 gallon hot water tank on it for a bell. The 55 gal drum is 23” wide and 36” high and the water heater tank is 20” wide and 58” high. I would use the tank along with the void areas in the steel stove as the entire bell area and have the flue to the chimney in the lower rear of the steel wood stove box.
I will build the wood fire box and core base out of the fire brick that are inside the stove right now. I will have to purchase 4 bricks to span the top of the box but I have already sourced the bricks from the Archie bray foundation. They are 3” x 4.5” x 13.5” in dimension for $5.00 apiece. I will use the same door on the new configuration as I am using now. I will have to weld a air inlet through the door for the primary air and will weld two steel plates to fill in the extra space created by the narrower burn chamber. This should make the door air tight to the wood box burn chamber and separate the bell area from the burn chamber. I also plan to build the core in place through the top hole I cut out for the bell and the existing door. I plan to cast the heat riser from a mixture of perlite and fireclay powder in two parts. The lower part in one piece and the upper tube in another piece.
|
|
|
Post by flybyjohn on Jan 17, 2018 6:09:11 GMT -8
I had some jpeg drawings to place in the thread but I am having problems placing them here.
THE QUESTIONS: Here are the few things that I am concerned about. 1. The base layer of firebrick needs to be raised 1.5” off the floor of the steel stove bottom to have the existing door opening line up with the wood burn chamber. I was thinking of using concrete, sand or concrete paving stones. What would be the better product for this application or is there another alternative that would be better. 2. When grouting the base firebrick together, is it good to have it also grouted to the base concrete or patio block, if they are used for leveling the bottom of the steel stove or leave them free floating. 3. What is the best material to glue these fire brick together and also the best method for tying the riser to the wood burn box. There will be a 2.5” wall surface area that will be in contact with the riser face. If cemented together with refectory cement, will it break apart and cause leaks? 4. What is the maintenance required for these types of stoves? The bell will be removable by several bolts through a flange welded to the bottom of the tank so that I can get in to inspect things inside the steel box.
|
|
|
Post by flybyjohn on Jan 17, 2018 7:17:14 GMT -8
Trying pictures again.
didn't work.
While I was doing my research, I ran across a lot of risers made of perlite and fireclay. I am planning on making the throat and heat riser lower portion as one cast and then the upper riser as a second cast. I keep wondering if I will need anything to strengthen it like water glass or refractory cement. I am planning on placing it on top of my current wood stove after casting it and letting it dry really good before installing it in the stove for the first firing. I can place the water heater tank (has small holes in the top for vapor to escape) over the riser to help it hold more heat in and have it dry quicker. If it is bone dry before it gets its first firing then it might not crack quite as much.
|
|
|
Post by peterberg on Jan 17, 2018 8:09:05 GMT -8
Hi John, welcome to the boards. The maximum space for pictures and files on this forum has been filled up long ago. You need to upload it to another site or online picture database and link to the forum from there. I read your plans and I think it's doable as long as space is adequate for the gases to stream through. The space inside the steel wood burner seems to be large enough to use as the housing for a batch box and room to spare around it. I don't have experience with casting risers in fireclay/perlite, Matt Walker would be a better source for such knowledge I'd think. I hope you are aware of the fact that you can't walk away from a batch box rocket for 5 hours and expect it to keep going to provide heat. So in your case without any mass to speak of, you need to feed the thing every hour or so but it will heat the place, no problem. For a lot of information about batchrockets, please see batchrocket.eu/en/.
|
|
|
Post by matthewwalker on Jan 17, 2018 8:39:10 GMT -8
|
|
|
Post by flybyjohn on Jan 17, 2018 10:18:03 GMT -8
Thanks for the responses guys. Peter, I will have 5" on each side between the outside edge of the core and the inside edge of the steel firebox. there will be 3.4 inches over the top and 6.5 inches between the outside of the back of the riser and the rear inside of the steel firebox. I figure if this can heat the garage up to 75-80 degrees in an hour or two then it will hold the heat above 40 degrees in the next 8 hours. Then I can build another fire. I did toy with the idea of using masonry brick and building a mass bell box ahead of the steel drum that could heat up during the firing.
Matthew, thanks for the video link, I have watched that one a time or two before. I don't have access to the grease drum but was going to use a 12" sonotube for the outside and a 6" stove pipe for the inner. I would like to dry this core uniformly before using it just to eliminate any unnecessary cracking. I have a wood stove and can that I can use for somewhat of a drying oven right now so I might as well use it. Once the clay/perlite mix is dry, is it hard enough to gently move around without it breaking?
I was also wondering if I am working in the garage for several hours or even the whole day, can a batch heater be continually added to all day long with just a few pieces of wood every 20 - 30 minutes? or is it just burn one batch and then start again.
I have some perlite and fireclay right now so tonight I will mix up a small amount and make a mini riser and then let it dry for a couple days on top the stove and then get the fire running real hot and stick it in the firebox coals for a few hours and see what it does to the test sample.
|
|
|
Post by drooster on Jan 17, 2018 13:06:23 GMT -8
I'm sure you can fit a Batchbox in your metal box stove, but since you have all the equipment and your stove is there, how about fabricating a refractory (perlite/clay/etc on frame) baffle + secondary air to squeeze much cleaner burns and better heat from your existing wood? (Your existing stove has no baffle at all)
With no space for a "mass", surely a Batchbox is going to lose most heat straight up the chimney ...
|
|
|
Post by peterberg on Jan 17, 2018 13:29:57 GMT -8
I was also wondering if I am working in the garage for several hours or even the whole day, can a batch heater be continually added to all day long with just a few pieces of wood every 20 - 30 minutes? or is it just burn one batch and then start again. When the firebox is hot, you can add bigger logs every 45 minutes or so.
|
|
|
Post by peterberg on Jan 17, 2018 13:32:25 GMT -8
With no space for a "mass", surely a Batchbox is going to lose most heat straight up the chimney ... Not at all, John mentioned a 55 gallon barrel and the space between the batch box and the existing wood stove as a bell system.
|
|
|
Post by pianomark on Jan 17, 2018 14:58:52 GMT -8
If it doesn't already exceed the recommended internal surface area (ISA) for a steel bell, maybe you could strategically stack some bricks inside those spaces. Being very careful, of course, to not restrict the gas flow at any point.
But I would build it first, see if there is any excess heat (high stack temp) to be harvested, and then fine tune it by adding mass. Hopefully you will still have access to that space. For clean out purposes, too.
Good luck!
|
|
|
Post by flybyjohn on Jan 17, 2018 20:26:51 GMT -8
I have a thought this afternoon that I could weld some angle iron around the perimeter of the outside of the bottom of the stove. I then could place bricks along both sides and in the back of the stove and over the top of the existing stove that will not have the bell. That would give me at least 14 square feet of brick thickness of mass.
|
|
|
Post by flybyjohn on Jan 18, 2018 8:27:25 GMT -8
I did some searching but didn't come up with an answer. Something that I have easy access to and know how to work is concrete. Would concrete with large aggregate work well for thermal mass if I poured a 3-4" wall of concrete around the outside of the sides and back and over the top that does not have the Drum. At 4" thick this would add about 6 cubic feet (.22 cubic yards) of concrete mass to the outside of the stove with a total surface area of about 18 square feet. Concrete is something I could add for a minimal cost.
|
|
|
Post by DCish on Jan 19, 2018 17:56:53 GMT -8
I have a thought this afternoon that I could weld some angle iron around the perimeter of the outside of the bottom of the stove. I then could place bricks along both sides and in the back of the stove and over the top of the existing stove that will not have the bell. That would give me at least 14 square feet of brick thickness of mass. I heat with a soapstone stove followed by a bench. I have stacked brick flat from the floor up on the non-door sides of the stove at about 1" gap from the stove. I put some angle iron on top to create a gap and stack some slabs of soapstone there. Even though there is an air gap, the mass sucks up the radiant heat quite well, moderating the heat output much better than the stove alone. I don't have concrete experience, so I don't know what considerations would come into play when using that as mass, but I can vouch for common brick. Dry stacked with angle iron support I would think would work well, shouldn't be bothered much by the expansion and contraction of the metal. I would definitely recommend stacking not on narrow edge, but on wide edge to get more mass on. Thin mass cools much quicker than you would think.
|
|
|
Post by travis on Jan 19, 2018 19:33:57 GMT -8
In my opinion if your number 1 priority is your budget you could do some digging and find free clay rich soil and sandy soil to make cob and put that in the same space that you want to put the concrete. The only drawback I see is the time it might take, so I guess it will be balancing your priorities. Another possible drawback to concrete is that it does not handle high temperatures well. In any areas that will reach above 600 F cob is a better choice, plus you can get it damp and use it again if you want to make changes at all.
|
|
|
Post by flybyjohn on Jan 19, 2018 20:07:50 GMT -8
The place I grew up had clay about 1.5 feet below the topsoil. Where I live now, there is no topsoil, just rock down as deep as I have ever cared to dig. I drained a 3800 gallon pool in less than 1.5 hours and the the water drained through the ground as fast as it came out of the pool. The wet spot only went 20 feet from the pool. So I have lots of rocks but no clay.
The mass will come later after I see if I can make this work.
I need to get all the parts made so that when I go to convert to the batch stove, I can do it in one weekend. I am thinking of building the core on my leveling slab and then opening up enough of the top of the steel structure to crane it with engine hoist and straps from the top into the stove. Then I can reweld up the top of the stove.
|
|