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All Metal RMH....?  RSS feed

 
Aj French
Posts: 19
Location: Mahanoy City, PA
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Hello everyone. Instead of Introducing my entire situation yet, for your experienced scrutiny, I'd have one primary question.

Can I build a permanent, entire house heating, RMH completely out of metal?

I work for a mining company and in looking and asking about materials everywhere, my employers were nicely willing to let me have any metal pieces I could haul away. So, I can, for free, have 1/4 - 1/2 - 1 - 1 1/2... inch thick metal ranging from steel, cast iron, armor cast, stainless steel..ect I can cut them to whatever pieces I need from larger sheets and I have been looking at taking the spec's from Ianto's book and Ernie and Erica's available "blueprints" to have some heavy, pre-cut "legos" to piece together with help from a professional welder friend.

As I see it the problems are
1. Expanding, Contracting
2. Sizing metal thickness for proper insulation value (Some parts need to keep heat, some need to lose it)
3. Melting temperatures ( I read Erica stating temp's of 1500, 1800 and 2000ish degrees F)
4. Corrosion?
1-4 Basically would it last me the next 10-20 years?

I'm sure there's more problems. I am definitely going to build a RMH in my home, and I want it to last and be used all winter. I just hoped I could use these free materials to make my new best friend. Thank you for reading this and hopefully replying. Brand new to the forum but I have been reading, listening and watching for months. Thank you Paul, Ernie, Erica, Ianto (in no particular order! haha) and everyone at these forums!
 
Aj French
Posts: 19
Location: Mahanoy City, PA
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Oh I thought I'd just mention I would cover it in Cob. I don't actually want to look at a huge hunk of metal in my house. Also, it would be on a concrete floor, no weight issue. Finally....I really don't want to be the guy that wants to completely redesign a well tested great design, or to soil the invention of something so wonderfully spread for cultural improvement by making it out of waste metal from a evil mining company. Its just the only thing I can get for completely free. If it wont work, I will just simply wait longer and save. Sorry to say so much, forums make me nervous (LIKE ME) and I didn't want (be nice TO ME) to seem ignorant (THINK I'M FUNNY) subliminal messages work, don't they?
 
August Brooks
Posts: 14
Location: Rainier, WA
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Yes, it can be done. We pioneer'd that same idea. After A LOT of trial and error, we came up with a steel mass heater.
Just make sure to use at least 1/4" steel where it gets hottest.
For corrosion, paint the cylinder and trim with heat resistant primer, then paint.
Your welcome to see what we did here- www.zaugstoves.com
 
Aj French
Posts: 19
Location: Mahanoy City, PA
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Oh yes. Sorry I forgot, I looked a lot at your site. It looks very nice. I was wondering the difference between your stove and the, well, "traditional" dimensions. I know you kept the components but scaled down and compacted the unit. Very nice product in the end and easy to set up. Is there differences though in the tolerances for flow and exhaust? What sort of temperatures do you reach inside since everything is closer together? I guess it wouldn't matter as long as all the gases are combusted. Do you recommend the same amount of thermal mass? Sorry I'm just interested in seeing what the changes are as you separate or compact the usual components. Thank you for your quick reply, could you make a larger unit if ordered?
 
Adam Stjohn
Posts: 41
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Aj French wrote:Oh I thought I'd just mention I would cover it in Cob. I don't actually want to look at a huge hunk of metal in my house.


1) DONT COVER THE BARREL or whatever you're using to serve the function of the heat-exchange-barrel. It's called the heat-exchange-barrel for a reason: As the insulated heat-riser gets super hot, gases flow up it. Then they hit the barrel. This is where shit goes down! Literally! The hot gases are cooled as the heat-exchange-barrel acts as a radiator. This is what causes the downward draft that makes the whole system work. So yeah: find as many ways as you want to decorate the barrel, but do not cover it in cob -- or much of anything for that matter.

2) Do cover the exhaust in cob. Otherwise it wouldn't be a rocket-MASS-heater, but merely a rocket-stove (unless you're mass is made of metal too?) So long story short: Yes do cover it in a big cobby mass mess. Beyond just the usage of the mass, I thiiinnk maybe that such mass is also important for the thermo/aero-dynamics of the whole thang.
 
Aj French
Posts: 19
Location: Mahanoy City, PA
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Yes, I definitely agree. I only plan to paint the barrel and add a tea pot. If I understand what you mean by thermo areo-dynamics, I know the heat exchanger section should probably cool to facilitate the "push" from the barrel exhaust. If thats what you ment, then yes I should probably use some thin metal on that end so that it isnt insulated and thus doesnt keep the heat from the mass. Does that sound right? Maybe thicker metal for the first 4 feet then thinner from there out. Do you typically assume that over time the metal will disintegrate and leave a cob tunnel? I think I read Erica saying it's becomes more of a initial form for the cob. Does that mean rocks, sand, loose material would be bad to surround the exhaust with?
 
August Brooks
Posts: 14
Location: Rainier, WA
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AJ,

I'm not sure what you are asking here- "Is there differences though in the tolerances for flow and exhaust?"
Are you refering to our design, or traditional designs compared to ours? We've tried so many scenarios, and everytime we change something we get a different result. It's important to define what the stove is going to be used for, then you can build it with its' intentions in mind. For instance, if you are primarily going to be cooking on the stove, you'll want the top plate to heat up fast and hot. A thinner gauge, top-plate should be used and the distance of the plate adjusted a little lower above the heat riser. etc.. We balanced all these tests out and made 'clear exhaust' our priority. And that's what you get with ours. Really clear exhaust even at startup.

We've found that the stove cruises at about 500 degrees at the top plate. It seems to be the optimum temp for maximizing our refill time to heating power. The inside temps are close to 900 degrees at this speed.

As for thermal masses.... we are still in the process of testing different materials and lengths. More to come...

The larger unit... That's funny to me because the biggest concern we face is that people usually want a smaller unit. You're the first person to ask if we can make a bigger one. the answer is yes we can however, this unit puts out the heat. How big is the space that you are trying to heat?

 
Aj French
Posts: 19
Location: Mahanoy City, PA
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Thank you August for your info. I will contact you in the future when I decide what i'm going to end up doing for sure. I'm very interested in your mention of experimentation with materials and lengths used with your system. Also the question came up in some other threads, does your glass option present any heat loss or inefficiency?
 
Aj French
Posts: 19
Location: Mahanoy City, PA
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I'm getting very disenchanted with the idea of my RMH made entirely out of thick, lasting metal. It seems in many other threads, metal is the weak point of a good RMH build.
 
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