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Permsteading.com • View topic - Rocket Mass Heater Cast Core Plans

Rocket Mass Heater Cast Core Plans

Rocket Mass Heaters, Rocket Ovens, Cold boxes, Solar collectors, etc..
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Moderator: matt walker

Re: Rocket Mass Heater Cast Core Plans

Postby matt walker » Thu Feb 28, 2013 2:26 am

No problem Manny. 6" flue has a cross sectional area of just over 28". If you reduce the mold pieces such that the finished openings and tunnel in section form squares with sides that are roughly 5 3/8" instead of the 7 1/4", you'll have the same CSA throughout. Hope that makes sense.
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Re: Rocket Mass Heater Cast Core Plans

Postby mannytheseacow » Thu Feb 28, 2013 4:00 am

Thanks! That's kinda what I was guessing. Would that also reduce the feed tube depth, barrel height, and size of earthen mass it can heat? I have a 55 gallon drum laying around but it seems too big to be a rational design integration for such a small firing chamber, but I'm just basing this on looks, not engineering. I need to study the engineering of these things much more and keep searching this forum. There's a lot of great info on here! Thanks everyone for sharing!
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Re: Rocket Mass Heater Cast Core Plans

Postby matt walker » Thu Feb 28, 2013 4:10 am

Depth and height should be fine as is, and I'd stick with the 55 gallon drum. Smaller drums can be harder to come by and the large size just plain works. It will mean shorter mass runs, but not necessarily less mass. You will have less fuel in the stove at any one time, so lower btu's, so longer to heat a similar mass. Donkey's forum "Rocket stoves, experimenter's corner" is a great place to do research as well.
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Re: Rocket Mass Heater Cast Core Plans

Postby matt walker » Fri Mar 01, 2013 4:38 am

Sorry it took so long, here's part II. The Heat Riser.

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Re: Rocket Mass Heater Cast Core Plans

Postby georgesr » Fri Mar 01, 2013 11:43 am

Thanks for the detailed information, I apprecieate it
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Re: Rocket Mass Heater Cast Core Plans

Postby Nutcase » Fri Mar 01, 2013 2:13 pm

How much does the finished assembly weigh? About 65 lbs. dry, I suppose, if you are using a whole bag of fireclay, plus the drum. Obviously a lot more than what I am currently using. Do you have any thoughts on the functional consequences of the heat riser having more thermal mass? I am sure that your riser is very well insulated and sealed, which are plusses. Is the mass a plus or a minus of any consequence?
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Re: Rocket Mass Heater Cast Core Plans

Postby pa_friendly_guy » Fri Mar 01, 2013 3:17 pm

I seem to be having a problem Matt. When I try to watch the videos, any video here on the site, I can't see them. I can hear the sound but the screen is white, no pictures at all. If I put my mouse arrow on the line of streaming videos it will show me the picture that should be on the screen but isn't. So if I sort of move the arrow along as the sound is going I can sort of get an idea of what the video is about. I do not have this trouble watching videos on you tube. Is any one else having this problem here on the site? Or am I the only Dummy here? I do not know what kind of setting I could have changed to have caused this problem, I am at a loss.
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Re: Rocket Mass Heater Cast Core Plans

Postby matt walker » Fri Mar 01, 2013 4:56 pm

Guy, I can view them on site with both of my computers. Perhaps a security setting in your browser? What browser do you use?

George, good to hear from you. I was thinking of you when I was trying to get this done. Keep us posted on how your project progresses please. I'm really curious.

Nutcase, we could go on for a long time on the pros and cons. Flywheel versus concentrating the heat on the gasses, combusting and moving things along. Honestly though, until you came along I thought this was a super insulated low mass riser! I think you are about right on the weight.
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Re: Rocket Mass Heater Cast Core Plans

Postby Nutcase » Fri Mar 01, 2013 5:24 pm

The heat riser mass may be of very little consequence to burn dynamics and therefore to home heating as a practical matter. However, it may have some sort of impact on starting or stopping. Do your systems start easily after, say, an hour break? Is there some point in the burn-down when they stop drawing? It's something I will be looking at eventually, I suppose.Of course, connecting to a post-barrel thermal mass will have an effect too, quite likely large enough to make the heat riser mass inconsequential in the overall system.
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Re: Rocket Mass Heater Cast Core Plans

Postby matt walker » Fri Mar 01, 2013 7:01 pm

You've got a pretty good handle on things Nutcase. My stove draws like a champ for 12 hours or so after a burn due to the fact that I am coupled, after the mass, to a large existing masonry chimney. After 24 hours or so of being out, I need to cover the feed for the first 20 minutes of start up as a precaution if I'm away from the stove. A bit of mass in the burn works does the same job as the chimney, giving a little flywheel effect. To add to that discussion, my core is pretty well insulated. Due to this, if I let the stove lose it's flame, there's only a couple minutes of coal time to get it back up before it's all the way out. It just doesn't coast, at all. The upside is it is hot right from start up. Trade offs abound, and there are a lot of ways to go.
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