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rocket mass heaters

Phase 1 Completed

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Well, I need one more brick layer, I believe, in the feed tube, and some cob on top of the heat riser, and then we're close.

Any thoughts?

Thanks to Big Al for all the helpful tips!

Cheers,

Adam

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Christopher D Brown

Posts: 4

posted 10 years ago

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Hi Adam looks really good!

I am looking forward to being to this phase hopefully this weekend! Building my first so take that into consideration with my comments...

The first thought that came to mind was your combustion unit looks like my first design...

I've recently purchased Erica & Ernie's DRAFT RMH Builder's Guide (http://www.scubbly.com/item/93600/) and I'm seriously considering changing my design. I just finished a mock up tonight using some of the parameters set forth in that publication: 16" deep feed tube, 24" burn chamber (8 x 6-1/8"), 50" riser! I like it! Burned really well from the start. However after firing for while and upon putting some larger and possibly wet pieces of bark in - it began to smoke on the feed side and flamed up fairly close to the edge. I'm thinking I'll lower the feed tube to 10-12" and see how it performs.

What are the dimensions of the brick your using?

What are the dimensions of your combustion unit; feed tube depth? burn chamber height, width, length and riser height?

Have you figured out your manifold/transition to duct?

Looking good! Enjoy!

Happy Participating!

Christopher

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Christopher,

Thanks for sharing your pictures, thoughts and questions! I guess you and I will be in the same "graduating class"!

The size of the heat riser is just right for my 55 gal. drum. That kind of inhibits a change of size.

The dimensions of the brick I'm using are 9-4-2.125.

The dimensions of my combustion unit:

Feed tube depth, 14";

Burn chamber height, 6"; width, 7"; length, 27" (end to end, including feed and base of heat riser); and riser height, 38" (from the very bottom).

Not sure I've figured out my manifold/transition to duct just yet.

For mortar I used clay slip.

Cheers,

Adam

Glenn Herbert

Rocket Scientist

Posts: 4566

Location: Upstate NY, zone 5

590

posted 10 years ago

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"length, 27" (end to end, including feed and base of heat riser); and riser height, 38" (from the very bottom). "

This does not sound like enough riser height to draft for that burn tunnel length. Recommended proportions are 1:2:4 (feed - burn tunnel - riser)and you have more like 1:2:2.7. You need to either shorten the burn tunnel (generally no need to have it that long anyway) or lengthen the riser, or both. 14:24:48 would be reasonable and likely to work well.

With a 7" high burn tunnel plus 3" or 4 1/2" of tunnel roof, you could easily get a 55-gallon barrel (generally 35" tall) to have 45-46" of inside clearance even without adding a ring of brick to raise the barrel. This allows a total riser height of 42-44" depending on other factors.

Glenn Herbert

Rocket Scientist

Posts: 4566

Location: Upstate NY, zone 5

590

posted 10 years ago

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If measured by the "centerline" method (there are no official standards for the measuring points), you would currently have 10.5" x 20" x 34.5", which is only a bit on the short side for the riser. Lengthening the riser to 43.5" from the floor would give a textbook 1:2:4 proportion.

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Thanks Glen!

The barrel I have is not that large, and I have ceiling constraints for putting the barrel on.

I'm going to shorten the burn tunnel by 9", shorten the feed tube by 4", and add 4" to the heat riser. That would give me 10"-20"-38".

Does that sound like a reasonable approach?

Thanks for the suggestion!

Adam

Adam Jonathan

Posts: 55

Location: Shenandoah Valley

posted 10 years ago

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Updated measurements are 10"-18"-38". I will likely add 4" to the heat riser, if I have room.

This design looks a little odd to me, and strikes me as unworkable with the barrel, etc. any thoughts?

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Peter van den Berg

gardener

Posts: 1063

Location: +52° 1' 47.40", +4° 22' 57.80"

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posted 10 years ago

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Adam Jonathan wrote:Updated measurements are 10"-18"-38". I will likely add 4" to the heat riser, if I have room.
This design looks a little odd to me, and strikes me as unworkable with the barrel, etc. any thoughts?

You are right, this wont work at all with the barrel. That 1:2:4 ratio should be measured in the heart of the core. The tunnel will measured from heart of feed to heart of riser using this method.

regards, Peter

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