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Post by wldhare24 on Dec 6, 2013 13:55:59 GMT -8
I am in the process of fabricating a rocket stove that incorporates using casting cement in a container similar to a 5 gallon bucket. I am having difficulties figuring out the best and least expensive type of material to use. I have learned that the cement I should use should be a casting refractory cement to deal with the high temp, but locally the only choice I have come across is a 50 lb sack going for around 50 bucks which is way more than I need and much to expensive. What I hope to learn is which is the best type to mix with vermiculite, which will stand up to the high temps, but the stove not end up weighing 50 lbs.
My first rocket stove was fabricated with a gallon paint can, perlite, and stove pipe fittings. The problem I encountered was it worked so well that the heat kept eating through the 90 degree elbow and rupturing the pipe after about 8 fires.
Phil in Maine.
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Post by matthewwalker on Dec 6, 2013 14:48:24 GMT -8
Phil, my experience is that it's difficult to do both durable and cheap. My favorite cheap option is local clay, perlite, maybe some sand, maybe some sodium silicate if you want it to get hard. It makes a decent core, but it will be fragile.
Next is a mix I describe in my "cast core" video, which is fire clay/perlite/furnace cement and maybe some glass fibers. Ratio is 14/14/1, and ends up fairly strong, but by the time you've bought all that stuff, you may as well buy the real casting refractory and be done with it.
I suggest if you want it to last to just buy the refractory. For continued experimenting, just dig up some clay and mix that with your vermiculite. That's my 2 cents, there's a lot of ways to do this.
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hpmer
Full Member
Posts: 240
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Post by hpmer on Dec 6, 2013 14:48:28 GMT -8
I've had good success with a mix of clay and wood ash. I've built a few of those can stoves you mention and used the metal elbow as a mold around which to pour my mixture. The metal burns out as you say, but the mix gets fired much like brick and continues to serve the purpose well.
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Post by wldhare24 on Dec 7, 2013 3:35:55 GMT -8
I guess this is what I was hoping for. If you type in casting refractory cement on Ebay, you will get a whole bunch of different types and makes that come in more appropriate sizes and costs. It seems that one of these would probably do the trick, I just don't know which one. If I could narrow it I would be on the right track.
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Post by satamax on Dec 7, 2013 4:10:04 GMT -8
Well, i've used Mapegrout "réfractaire" mixed with vermiculite, with good results. Tho, finding that outside of France and Italy, i'm not sure.
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Post by 2tranceform on Dec 11, 2013 13:28:57 GMT -8
You are looking for a mix that has a working temp of at least 2300F. The insulating (light weight) refractory concrete will help to keep the heat in the burn tunnel. This mix is not as durable as the dense refractory concrete, which will conduct some of the heat away from the burn tunnel.
I plan to use a mix from Plibrico. It was the only refractory supplier that was within 150 miles of me. The mix I selected is $33 per bag. With the light weight mix, one bag is about .6 ft^3.
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