I am putting together ideas for a 5" system and want to cast the entire thing, but am unsure on the refractory. Can you just use high temp castable refractory? Does it need a steel liner on the burn side of the tunnel and riser, or will exposed refractory be OK?
I found this "recipe" for a crucible furnace, does it sound ok, or any other suggestions?
Here is the recipe: The refractory mix is composed of Portland cement (1.5 parts), silica sand (2 parts), perlite (1.5 parts) and fireclay (2 parts). The first three components are mixed together thoroughly.
Or, should I just use refractory cement mixed with perlite to lighten/insulate it?
Another question, if this system is entirely cast, is there a minimum thickness? I planned to use 5 gallon steel pails like paint thinner or something comes in for the riser. This would be about 2.5" wall thickness with a 5" round riser. For the tunnel, I planned to make it 5" wide x a little under 4" high rectangle. This is close to the 19 cu/in to match the 5" round riser.
Also, it sounds like this cement is gooey and won't pour, so I will have to plan my assembly of this to fill the outside steel form?
Seems to me that if it's good enough for a metal casting furnace, it's good enough for a wood stove. Either of your ideas might work just fine. I would be looking for a more insulative mix, even though it will be fragile around the wood box area. Perhaps you could cast the wood feed out of the heavier, heartier stuff and the burn tunnel and heat riser using the insulative mix.
I don't really know about minimum thickness in your castings. peterberg's opinion would be valuable here.
I've found that the intuition can get it roughly right more often than not. If you don't get a decent answer from someone, just make your best guess and go for it.
Minimum thickness would be 1 1/4 ", this will heat up very quickly.
My opinion about Portland cement in refractory: it won't hold. Normal cement and sand contains silicium. This is changing christal structure at about 1000 F and expands at the same time. I've been using proper refractory castable which contains aluminum cement and ground porcelain. Specification: 2190 Fahrenheit and it's still intact. Instead of elephant grey it's color has been changed to vaguely pink. Tapping it, it do sound fragile.
Post by carllittle on Nov 19, 2009 13:02:52 GMT -8
It appears great minds.... Yesterday I cast a burn tunnel and the beginning of a heat riser using the refractory mix Dave mentions. My idea was to have one piece that would serve as the burn tunnel and the base that would hold a stainless 8" heat riser. My plan is to build Peterburg's initial rocket/bell heater. I have a section of double walled stainless stove pipe left over from when I built my house that seems perfect to build a heat riser. Here is a link to a couple of pictures. picasaweb.google.com/Carl.Little.law/Desktop?feat=directlink I'm not sure of this cast will work, especially after Peterburg's warning about Portland in refractory. ( I wish I would have seen it before i did this.) If I were to do it again, I wouldn't. I think the few extra bucks for firebrick would be worth it. This thing weighs probably 200 lbs and I greatly underestimated the amount of fireclay that I would need. Therefore, the top of the firewall is just at 1 1/4 inches, but I imagine it will need more insulation. The reason that it is the shape and size it is, is to fit just inside the brick tower that will act as the bell. It will also sit on concrete fireplace foundation, so I wanted plenty of refractory between the bottom and the concrete.
Wow carlittle that is huge looking! Perhaps you can shell out the money for some proper refractory cement and plaster your burn tunnel with and inch or so to take the high temp shock (or precast some that slide in)? Might even need an expansion joint or two? I don't know, just ideas.
Well after researching the weight and cost (incl shipping) of refractory cement, I'm wondering if it is worth it considering I want this to be somewhat moveable, plus the expense.
If I used heavier walled steel tubing for the burn tunnel and riser, with an outer sheet steel shell, could I just fill it up with perlite? I understand that it greatly expands when heated above a certain temp, but does it stay in that form? Perhaps build the thing, fill it with perlite with open tops, fire it, then cover the tops with steel again?
I am greatly interested in hearing how this works out. I've seen refractory recipes, but they all seem to require a high temperature kiln firing. Sculpting the entire innards of the stove seems like a good thing, but all the mud stoves I've seen are fragile and vulnerable to water and cracking. (the banana stem form and such) Could something like a two-part cast work: the inner lining out of more durable cement mix, but not thick. Surround that with the mostly perlite insulative mix. And then finish with a coating of cement to make the outside durable.
I'll go off and do a lot more reading on such things.
briank: Hi guys, been lurking, registered a while back, just stopped in to make a first post. Good to see some familiar faces here from the wider world of firewood hoarders.
Dec 31, 2015 23:04:12 GMT -8
satamax: Lapinou year to everybody!
Jan 1, 2016 12:58:58 GMT -8
keithturtle: Working overtime on the holiday to support the habit (lemme see, how many firebricks can I buy next week?) <grin>
Jan 1, 2016 16:01:16 GMT -8
Daryl: Hey Bri! Nice to see you!
Jan 1, 2016 17:37:46 GMT -8
ericvw: Nice to see ya over here BrianK
Jan 1, 2016 23:58:54 GMT -8
briank: Thanks Daryl and Eric. The rocket bug has been in the back of my mind a lot lately. Thought I'd do some catching up here on the latest and greatest developments. I'm really liking the half barrel bell idea Matt came up with a couple years ago.
Jan 2, 2016 8:11:08 GMT -8
ericvw: Staying warm, Daryl?
Jan 12, 2016 15:09:15 GMT -8
Daryl: I remembered why I hate winter. Oil is at an all time low so I am good.
Jan 14, 2016 13:04:21 GMT -8
keithturtle: How long will it stay low?
Jan 14, 2016 19:10:34 GMT -8
wolf1004: Oil will stay low for a while, the bigger question is how long will we have jobs so we have the money to buy it? Low or not?
Jan 16, 2016 6:56:31 GMT -8
Daryl: Keith, prices are supposed to continue to go down. Wolf, I could lose my job today. No biggie. I'm taking life as it comes.
Jan 18, 2016 9:14:23 GMT -8
Daryl: Hey, Eric. What is up!!! How does it go down there in VA? Got a dusting of snow last night. Too cold to go hiking but we did catch some football this weekend.
Jan 18, 2016 9:15:46 GMT -8
Daryl: Oh, and one more thing, Eric...about a year with the guitar! I am happy that I reached that anniversary.
Jan 18, 2016 9:22:41 GMT -8
keithturtle: Daryl, one door closing leads to another one opening. Walk thru wisely
Jan 19, 2016 15:56:07 GMT -8
Daryl: I meant that I can handle what comes my way. I don't care. Lol. I will survive. I may have my job for the rest of my life or lose it tomorrow. You never know. But I am cool with it.
Jan 19, 2016 17:31:03 GMT -8
Daryl: By the way, HOWDY MAXIE!!!!!
Jan 19, 2016 17:31:41 GMT -8
janmetal: Fireproof stones.. Can they be made DIY or do I have to buy? - Simple Nepalese design wanted.
Jan 20, 2016 22:40:03 GMT -8
ericvw: Looks like you've had some time to reflect, Daryl. We got about 14" snow this past weekend. It is melting away nice and quick.
Jan 27, 2016 20:46:59 GMT -8
Daryl: No more snow, Eric! Keep it! Supposed to be close to 50 the next couple of days.
Jan 30, 2016 13:47:09 GMT -8