I am building a wood fired pizza oven and that meant the old wood BBQ had to come down, it will be replaced but unfortunately I discovered rocket stoves before that could happen.
I read a few papers, saw a few designs, followed a few instructables, read a few flame wars as to why certain designs could or could not be called rocket stoves etc. And got hooked.
When I first googled 'rocket stove BBQ' nothing came up, now there are a decent number of hits so I am guessing this is a big area of interest.
Google sketch up can make the most ridiculous ideas look professional and I have convinced myself that my design will work first time. I was about to make it but it is raining so I figured I would go on-line first and see what everyone else is up to.
I had a lot of things that I was just going to wing it and see how they worked out but then I thought that a lot of the experimentation had probably already been done.
Then I thought I would join a few forums and ask a few questions but most people seem to like you to read the forums first before asking questions that have already been answered a hundred times so I will lurk a bit more!
That's about all, is there an area which introduces the subject, FAQs or stickies that will bring me up to speed before I dive straight into the physics?
Welcome Jislizard.. Board topics aren't always laid out in the most sensible way.. It's pretty organic 'round here so you gotta dig sometimes. It's mostly assumed that you've read the Rocket Mass Heaters book, which lays out the basics. If you haven't, you probably aughtta get it over at rocketstoves.com. Wev'e got pretty friendly crew here. so make yourself at home.
The book has been on-again-off-again in my Amazon wishlist.
It seems to have a lot of cob in it and my wife is pretty strict on me bringing dirt in on my shoes, I think if I tried to bring mud into the house on purpose it would end in divorce.
I did read a couple of papers by Dr. Larry Winiarski, some on justa stoves, hit wikipaedia and followed all the links as well as the usual YouTube etc. I have seen hundreds of diagrams of the principals (some animated) and plenty of how-to guides and progress photographs of actual builds.
I was not that interested in heating, I live in Queensland, and definately not interested in mud in the house so I pretty much judged the book by the cover which is why it never made it into the cart.
If it has lots of information on perlite/vermiculite concrete, or proportions for designing that are nowhere else on the internet I will have another look at getting it.
Thanks for your speedy reply, it looks exactly like what I need. The photo is great and I can not understand why the board has so few photographs and/or sketches.
Judging by the photo I assume that you have used a 100mm diameter plastic sewer pipe to create the stove body, the pipes being pulled out after the clay/cement has dried and before firing. I would like to have your suggested dimensions especially the thickness of the clay and the height of the heat pipe. I can estimate these from the photo but why not ask the experts! Intuitively I feel that the higher the heat pipe the more of a 'rocket' effect will be achieved. The ratio of 2 to 3 times the combustion chamber diameter has always appeared very low to me. I do not understand the two holes in the fuel/air feed area. What are the functions of these two holes.
You say add a bit of cement to the clay to speed up drying. Our hardware stores sell a product called Fire Mortar, I am going to try this. I bought some clay at a potters shop at seven dollars a kilo, outrageous price for clay! Assuming the clay has a water content of 40 % what ratio, by weight or volume, do you suggest (as opposed to a bit).
Any more photos or details will be appreciated.
DONKEY has been asking for suggestions to improve the board. As a totally novice new member I have to be careful not to overstep my welcome but the position I am in helps to identify where the board can be improved. Novices have lots of questions. I have already mentioned that more photographs/sketches will help to clarify concepts that require a lot of text to understand. Nothing succeedes like success and I would love to see what others have built or even failed at building. This is to me the area where the best advances can be made. Things have progressed a lot since the rules were laid down many years ago. We need a lot more of 'this is what I made and why and how I made it'. Some myths die hard and need to be cleared up (like galvanised iron is extremely toxic, water can kill one as readily if not respected.)
I look forward to hearing from you again and hopefully from others also. Maybe DONKEY would like to comment on a novices comments.
I would like to have your suggested dimensions especially the thickness of the clay and the height of the heat pipe. I can estimate these from the photo but why not ask the experts! Intuitively I feel that the higher the heat pipe the more of a 'rocket' effect will be achieved. The ratio of 2 to 3 times the combustion chamber diameter has always appeared very low to me.
The dimensions are always Trade-Offs between different goals. Thicker walls, longer burn tunnel and higher raiser will give more mass and surface. Mass will capture and surface spread heat, which may not longer be available for the main goal. One can use insulation to limit unwanted effects, but insulation adds mass and surface too. It depends also on the time the fire will burn. A cooking stove for home needs to heat up fast and does not need the amount of insultion desirable for a cooking stove used in a business. For home it needs just enough mass for not to to easily be tilt over inadvertently. About one inch wall is enough for home cooking in a hot country.
I do not understand the two holes in the fuel/air feed area. What are the functions of these two holes.
The horizontal hole is just for removing the tube and should be closed with a closure of clay, removeable or permanent. A downfeed downdraft stove is safer and burns hot and clean without a grate.
You say add a bit of cement to the clay to speed up drying. Our hardware stores sell a product called Fire Mortar,
Portland cement is sufficient. The small amount of cement does not need to resist the heat, it can be destroyed by the fire without weakening the strength significantly.
I recoment a dry mass ratio of: fat clay 4 parts (clay of high plasticity) sand 3 parts cement 1 part
fibers 10% to 15% of the dry mixture.
For clay of low plasticity or clay soil the amount of sand needs to be reduced. One will have to test what is possible.
Thanks again Karl. I am going to try your suggestions as soon as I can find the sewer pipe. Input from others would also be most welcome. Donkey is trying to revitalise the board so why not surprise him, post something that has worked for you (or even something that still fails to work for you).
Donkey's workshop schedule is deeply over his head.. Donkey will be mostly unavailable till August, with infrequent check-ins from time to time.. Welcome to the boards, make yourselves at home.. PLEASE!! Feel free to post ANY images, drawings, plans, videos or whatever you wish, as long as it's ON topic and in the appropriate area. Be kind to the bandwidth challenged (like myself, I'm STILL on dialup) and keep your images small.. Under 100 Kb (or so) is good. You can link out to as large an image (or file) as you wish, just warn us properly... Thanks.
Hi Karl When you add cement (to speed things up and waterproof) do you still have to fire your creation or does the cement give the required strength. If it must be fired does it have to go into a kiln at 1000 C or can I build a big wood fire around it.