|
Post by mikemew on May 2, 2015 0:56:51 GMT -8
Dear All, When researching before buying a wood stove I came across the Rocket Stove concept which really interested me. I went ahead and bought a wood parlor stove by Vermont castings, on ebay (very nice price thanks). My thought was if I could use the stove as a fire box for a rocket stove so effectively place the domed vortex unit on the flue with additional air intake so that I would be using the vortex after burner for the exhaust gases. Two images are attached (I hope) that show dimensions and the stove in situ. There is a brick wall behind and I was thinking of core drilling a exhaust hole through the wall to the left of the stove. The room is a single story kitchen extension in south London (out side the smokeless zone). There is hole in the brickwork just above the level of the stove but I worry that this is too low for an exhaust/flue. I was thinking of; 1) using the shorter (as in image) length of flue pipe that is straight and would run directly into the rocket stove. 2) placing some insulating material within this section to maintain the temperature (any advice on what material and where to get it would be very nice) 3) welding a secondary air intake into the flue pipe, so that it entered just above the stove and ended at the top of the section where the fresh air would mix with the exhaust from the stove. 4) cast a concrete (cement for those in the US) shelf (with wall brackets onto the brick wall behind) at the level of the top of the flue pipe, on which the metal housing bell would sit. 5) continue the flue upwards using flue pipes, like fire bricks but circular and can be purchased in a range of sizes, until 1.5 to 2 inches below the metal bell housing. 6) Purchase and old bollard (those set in the ground that prevent cars from driving onto pavements ect) preferably in stainless steel with an exhust welded on one side slightly higher than the concrete shelf, which it would be bonded onto. 7) The final flue would then either exit directly through the wall at this level, run for a length before doing this (if this is advised by members of this site) possibly running up and then down, or pass down to the existing exit at a lower level (again only after advice). Your advice would be most welcome, Thank you in advance, Mike Attachments:
|
|
|
Post by patamos on May 5, 2015 9:02:53 GMT -8
Hi Mike, I'm not sure if i rightly picture what you are planning... But my first thought is that the metal body of the fire box may not be up to the higher temps and carbon-robbing tendency of these heaters. I too thought of converting a parlour stove a while back. Lasse Holmes (Canyon) did much of the early innovating of batch boxes using old metal body stoves as the box with a port and vertical heat riser at the back of it. I thought maybe a parlour stove could do the same, which would make it a side loading batch box with the port centred on the back wall. There have been numerous innovations of late with side loading doors and heat riser port placements in or near the corner. But so far as i know that variation has not been done. I checked in with Lasse and he had not tried that yet either. Still, it may be worth trying. I am just now finishing up a vortex firebox using 9"x4.5" and 13.5" x 4.5" bricks. Aside from casting the top and base it is pretty straight forward. I think one of the keys to its success is the way the air/gas flows in from the front low to the back, then up the back wall and forward up the sloping top into the throat. For this to work I think the firebox at least needs to be deeper than wider. Still, when innovating you never know til you try
|
|
|
Post by mikemew on May 5, 2015 23:12:44 GMT -8
Patamos
Thanks for the response, the trouble is as a newbie it is really quite difficult to understand the technical talk. I guess that it is worth giving it a try but previous experience is also worth its weight in gold. I will try to put down a technical drawing of the item. I was struggling a little while also holding 11 month old daughter who wanted to grab anything that I was using.
From the plethora of various designs that I've seen on youtube it does seem that rocket stoves are technically forgiving, I'm amazed that many work at all.
My thoughts were that as long as I kept the temperature up at the point where the exhaust from the fire box entered the "bell" housing (rocket vortex section) and was mixed with pre-heated air then it would create a vortex and get the thing going. This would could in theory combine the long burn times from a traditional parlour stove with the efficiency of a rocket stove. Certainly worth pursuing.
Two important question would be; 1) is it important for the exhaust (flue) to be higher than the intake for the rocket vortex section 2) I see people take the exhaust flue off some distance to heat a seat or something before returning to exit the building, Does this system have to rise at every point? Or can it drop and rise as long as one end is higher than the other?
Best wishes and thanks again for any and all the help and experience that anyone is able to give me.
Mike
|
|
|
Post by shilo on May 5, 2015 23:55:00 GMT -8
in my opinion, it's better to choose and not to mix.
|
|
morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
|
Post by morticcio on May 6, 2015 3:19:23 GMT -8
"You can't make a silk purse from a pig's ear". A hybrid incorporating a cheap eBay parlour stove it isn't going to perform like a rocket stove from a proven design! My advice would be to start from scratch and build a J tube with a bench or a batch box with a bell. There are plenty of examples to copy from on here and other forums. My thoughts were that as long as I kept the temperature up at the point where the exhaust from the fire box entered the "bell" housing (rocket vortex section) and was mixed with pre-heated air then it would create a vortex and get the thing going. This would could in theory combine the long burn times from a traditional parlour stove with the efficiency of a rocket stove. Certainly worth pursuing. Why do you want longer burn times? Long burn times from a traditional parlour stove mean two things - an inefficient dirty smouldering fire and/or increased fuel consumption. Like Pat said, your stove isn't designed to run at high temperatures - it will fail! Using a rocket core you can burn the stove hotter and cleaner then store the heat.
|
|
|
Post by mikemew on May 6, 2015 11:55:28 GMT -8
It was my impression that this was experimenters corner.
The parlour stove is an Intrepid from Vermont Casting in mint condition, not really a cheap stove and hardly a pigs ear, it is certainly designed to run at high temps. My thoughts were a couple of hours of burn time rather than 30min which should be entirely practical.
I've spent some time before making this post, looking on line and many rocket stoves and it should be theoretically possible to replace the fire box with a parlour stove. If any of you have tried this and failed then I would love to hear but please don't poor cold water on an idea if your've not tried your self, that is really not in the spirit of experimenters!
Many of the rocket stoves that I've seen seem to have very modest fires in them that I am sure I could easily match in the exhaust of the parlour stove,especially with a little insulation. It was my impression that what made the rocket stove work was the mixing of incompletely burnt gases from the fire box with pre-heated clean air at reasonably high temperatures at the entrance to the bell. Please correct me if I am wrong, this is why I am here. Happy to be gunned down but would rather that it was in a constructive way. I could always forget about the rocket idea and just put a conventional flue on and move on.
It was my idea to move the air quickly around the building with fans (which is really quite large and solidly brick built) rather than store it in any one place.
Mike
|
|
|
Post by shilo on May 6, 2015 12:32:32 GMT -8
"It was my impression that what made the rocket stove work was the mixing of incompletely burnt gases from the fire box with pre-heated clean air at reasonably high temperatures" at crazy high temperatures
|
|
morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
|
Post by morticcio on May 6, 2015 14:25:47 GMT -8
Dont take the saying literally as an insult against your wood stove. I admire your enthusiasm but I think you've got some of the theory muddled up.
All combustion should've taken place by the time the flue gases exit the riser and enter the bell. Mixing these gases with preheated air at this stage is counter productive - it will cool them down.
I've built a steel rocket. It was impressive watching the whole burn tunnel & riser glow bright red through the vermiculite insulation but it was short lived as the steel started to perish due to the high temperatures.
If you want to keep your stove then try capturing the heat from the flue gases in a bell. But please dont confuse this with a rocket stove.
|
|
|
Post by patamos on May 6, 2015 22:19:41 GMT -8
Mike, Firstly, I too appreciate your enthusiasm and creative visioning. Even if a new idea is flawed, it serves as an intermediate impossibility, catalysing new ways of imagining in my mind. You have expressed a new idea, and it has me wondering about all kinds of things in a new way. Thank you. At the same time, I don't think anyone you have heard from here will claim to have all the answers, and i am pretty sure we also welcome discoveries that blow our assumptions to bits. That is part of what makes this community so interesting… That said, for those of us who have endeavoured to study this forum and cross-reference as much as possible by sharing the results of our experiments. It reaches a point where certain orienting generalizations become apparent. The relationship between metal in a high-heat carbon-robbing atmosphere…is one of the clearer ones. And the shoot down you have received has been among the gentler ones - out of respect for the honesty of your inquiry, 11 month old daughter running the show to boot I think the crux of the matter is: how hot will your parlour batch box actually get? As a vortex firebox with forward and upward sloping ceiling leading into a throat parallel to the front door… it will get crazy hot. Granted, Trev (vortex) has found a way to shut down primary air and amplify a much slower secondary combustion. This is one of the beauties of his design. But this slow burn mode is only possible after the firebox has really heated up. The slow gassifying mode occur in the super hot firebox, and continues to because it remains super hot. Very likely a steady 1000c around the throat, and not much less elsewhere. The amount of re-engineering of the metal box would have to be extensive. You might find a way to build a port from out the upper back of the parlour stove. Check out 'a vortex variant' and the links to russian examples that dccbb (sp?) posted. ALso check out peter berg's rocket syphon experiments a few years back and all the 'adventures with a horizontal feed'. I think Kiko Denzer has a story about putting a big bell on to of a metal body stove in the latest edition of Ianto and LEslie's RMH book. And you will bump into other such hybrids here and there. But, i would urge you to consider how much time/energy you are able to put into this before you need the heat and need to get onto other things. Major experimentations and being in a hurry do not fare well together… And, a lesson that i wish i had learned faster: your partner is bound to appreciate all the downtime she can get via you hanging with your young'un. Have you had a look at Matt Walker's riser less core? That is very cutting edge and would benefit from experimenting with variables… For the time involved in cutting the parlour body, shaping refractory materials and insulation to fit inside of it… Matt's set up is the far simpler option. Much easier than the vortex i am building, which is already quite straightforward… Finally, i think building something with a bench to sit or lay on is worth its weight in gold. Profoundly relaxing to merge with the hearth in that way... my two bits worth pat
|
|