|
|
Post by Norman Silva on Feb 5, 2008 13:28:27 GMT -8
Thanks in advance for the advice.
I recently installed a my first rocket stove and am a bit reluctant to build the remainder of the bench after firing up the stove for a test run and filling my house with smoke. I just want to see if it is user error or if I need to redesign the unit (it is designed after the 8" flue system in Ianto Evans 2006 rocket stove edition).
I used k28 insulating bricks surrounded by one inch insulating fiber cloth (i'm a potter so i had a bunch of extra kiln materials around) to build the heat riser. My worry is that the insulating bricks don't absorb and radiate enough heat to really warm up the heat riser and create the drawl needed to make the rocket work. Could this be the case? In case you need to know--the weather outside was warmer than inside and the mass bench has not been build around the 38' of ductwork.
My second and last question is how much rubble should i use to build the bench out of (in comparison to clay)? It is going to take a hell of a lot of clay if i don't use rubble but I am concerned about creating air pockets that will hinder the flow of heat through the bench.
Thanks again, Norman Silva
|
|
|
|
Post by Donkey on Feb 6, 2008 9:39:52 GMT -8
In my experience, the less absorption of heat in the heat riser, the quicker it will take to get up to heat. I have used steel pipe with pearlite insulation, which so far has been by far the fastest to get running well... Less thermal mass THERE (heat riser) seems better. I think that your choice here should be fine The conditions you stated (warmer outside than in) may be enough to smoke you out. Wet - newly laid brick can hurt as well, moisture will steal heat from the system. Have you installed a chimney primer? I don't remember how well it was covered in the book but it's a helpful feature. A small door below your chimney (where it leaves the house or goes vertical for any distance) can be used as a primer. Just toss a piece of burning paper into it to get things going in the right direction when conditions are difficult. I always advise people to position the chimney close to the wood feed, that way the primer box is likely to be used.. I can't tell you how many times I've sat blowing over an obstinate stove because the primer is on the other side of the room, or outside.  So if yours ain't that way... I advise that you make it so before you close up if at all possible.. To your second question. As much as you can get away with. More mass in the bench equals more storage. You want enough to get MOST of the heat, though it is good to leave just enough heat in the exhaust gasses to keep water vapor from condensing inside your bench (unless you provide an exit). Here, I would say to add mass WHILE the stove is running and watch your exhaust. At first (no mass added and burning clean) you will see heat waves coming out of the pipe. Add mass along your pipe till you just see steam then stop. Now, it's how fast the pipe is loosing heat to your mass that you are measuring, so what is counting here is how much (direct) contact the pipe has with the mass, NOT how much mass you add on top of it all.. Or restated more simply, it's an indication of how long your pipe run can be. I like using sand rather than rubble for the reason you've stated.. Fewer voids. You could mix sand with your rubble to fill up the spaces.. |
|
|
|
Post by Norman Silva on Feb 6, 2008 19:54:54 GMT -8
to you,
Thank you for your quick reply. Just another thought, have you heard of anyone wrapping the 55gal drum with copper pipe and cerculating water through it in order to heat a radiant floor or domestic water? The same kind of system used in solar water heaters but using the stove in lue of a solar how water pannel? If so how hot would the water in the copper pipe get just around the stove? Would I have to worry about it volitalizing in the pipe?
Norman
|
|
|
|
Post by Donkey on Feb 7, 2008 8:12:41 GMT -8
Yes I have.. Ernie has done that to great effect. It is my understanding that he created a very dangerous water heater that had the tendency to flash to steam.. Perhaps the pipe he was using was too small.. ?? Dunno..
But anyway, yes you can do that. It's still a bit experimental (as is everything rocket stove) but with a little fiddling I'm sure a coil system could be put to good use.
|
|
|
|
Post by ilovecob on Feb 15, 2008 19:27:41 GMT -8
Hey Donkey,
What type of steel pipe do you use?
I'm building a 8" system. I'm in the process of scrounging the heater riser's internal tubing. I have a old water heater tank for the exterior of the chimney that contains the insulation. The price of new steel is a bit pricey so I'm still looking around for options. I'm thinking of a 8" metal tube about 40" tall. Thicker stuff - 1/4".
Would a 8" regular stove pipe be to wimpy for the heat?
My other option is fire brick, but I like the idea of steel better.
I used ceramic chimney tile in the last one, but I hear tell of ceramic exploding and breaking apart under the heat. Though there was no noticeable shards of ceramic while cleaning it ~ yet.
Mic
|
|
|
|
Post by Donkey on Feb 16, 2008 23:24:01 GMT -8
I use whatever I can find.. One of my favorite hunks of steel was 1/4" thick, 8" diameter and quite long.. I bought it for a buck a pound in an obscure Oregon scrap yard. Standard, black stove pipe does indeed burn out fairly quickly, perhaps stainless steel could be tried.?? The heat riser in my home rocket is cast-able refractory.. I cut cardboard gaskets to hold apart 2 sonotubes, one inside the other. Inside tube was 8" and the outside 12". I then filled the gap with cast-able refractory material. Let set, then peeled off the form. Works great.  |
|
|
|
Post by canyon on Feb 17, 2008 17:14:03 GMT -8
Hey, Has anyone heard of anyone using stainless triple wall? It is mentioned in the book with good potential. Donkey, what is the castable refractory recipe you've been using. Forgive me if you've already posted this! Thanks, Canyon |
|
|
|
Post by ilovecob on Feb 19, 2008 19:17:11 GMT -8
I like the idea of a cast-able heat riser. Isn't the cement a bit pricey?
Today I'm leaning toward the firebrick heat riser, because I have enough brick to do it!
Wouldn't the cast-able cement and firebrick perform about the same?
Mic
|
|
|
|
Post by Donkey on Feb 19, 2008 20:06:47 GMT -8
Canyon, I just bought a bag of something clever... Dunno how it compares with firebrick...
My feeling is that it would do somewhat better as there are fewer rough spots in a cast surface to create turbulence and slow things down.
|
|
|
|
Post by canyon on Feb 20, 2008 21:18:51 GMT -8
Donkey, Do tell what is in your clever bag of tricks? Grogg?  |
|
ElfN
New Member
Posts: 9
|
Post by ElfN on Aug 21, 2008 16:44:00 GMT -8
I've been researching refractory cement . . . I've seen a lot of pricey ($1/lb) commercial preps, and found a couple home brew recipes. The recipe I'd like to try (will be testing next week) is portland, silica sand, perlite and fire clay. (http://www.backyardmetalcasting.com/refractories.html)
I'm still hunting for a riser. There's a scrap yard in Rochester. I'm going to try there next. I've visited our local recycle 6 times so far with no joy. If I don't come up with something pretty quick I'm going to have to jump in another direction.
ElfNori
|
|
|
|
Post by larsmith on Sept 11, 2008 5:56:30 GMT -8
|
|
|
|
Post by chronictom on Sept 12, 2008 17:02:55 GMT -8
Has anyone tried using commercial insulated stove pipe for the riser? www.doityourself.com/invt/7542400like that stuff... Besides being expensive, and not something a lot of people have just laying around, it does fit all the properties needed no? |
|
|
|
Post by canyon on Sept 12, 2008 22:13:08 GMT -8
I used a similar product called excel. Metalbestos is insulated with some kind of industrial slag waste that settles over time so I don't want it around. Excel is insulated with a high temp fiber blanket insulation. I contemplated using a 2' section alone for my heat riser in my "test rocket" but I ended up slipping it over a 2' section of schedule 40 pipe as I was concerned about how long the thin stainless liner would last because I wouldn't be able to rebuild it easy(its all welded together gas tight). I think they have potential for some relatively narrow barrel style heat exchangers and definitely are quick to use. You can find sections used for cheap in my area once in a while. |
|
|
|
Post by chronictom on Sept 13, 2008 2:04:52 GMT -8
I wish I could say the same about finding them cheap, I actually need about 5 lengths to get the normal woodstove hooked back up, sometime before we bought the place someone stole what was there. The only reason they didn't steal the stove is that it weighs too much for less then 3 or 4 really tough people...
I've been trying to find replacements for it, but the only thing I have found is new stuff at like 110$ a length....
|
|
