Ramzez Imaginative

I decided to take a step back.

I am now going to build a cast core based on broaudio two videos.

Thomas: Can you show a photo of what it looks like without the wood or fire?

And I don't see why you did that when you can simply cover the feed tube and get same effect.
Or partially... adjust as needed.
Your plate is permanent
E&E do that.

Here are some numbers I learned from E&E on the DVD with paul wheaton.
Don't rent from Vimeo... had a lot of problems viewing the videos on line, get the DVD's.

8" system is 50 square inches meaning 7" x 7" or 6" x 8", etc..
6" sytem is 30 square inches meaning 5.5" x 5.5 " or 4" x 7.5", etc...
(I am sure there is a limit, 1/4" by 200" for example)

burn tunnel length no more than half of heat riser
(that is from the front of the feed tube to the back of the heat riser)
(from the bottom of the burn tunnel to the top of the heat riser and not the barrel that covers it)

heat riser at least 3 times longer than the feed tube

the space between the heat riser and the barrel should be 1/4 of your system size.
ie: 8" system should be 2" and 6" system should be 1.5"

the feed tube, the burn tunnel and the heat riser should have the same cross sectional area
(meaning they should all have the same square inch area)

6" system can't have more than 40 feet of linear duct
8" system can't have more than 50 feet of linear duct
(from the barrel to the exit of the house)
And every elbow you lose in potential length because of drag (5' or 10' per elbow...I forget)

proportions suggested by E&E 1 : 1.5 : 3 (feed tube : burn tunnel : heat riser)
I was given another proportion by a permies user of 1:2:4 but if you compare them the only difference is the feed tube is a little longer if the heat riser is the same length

Hope this is helpful

I didn't catch that. In an 8" system the feed tube, burn tunnel and heat riser should be 7" x 7".
This is Erika and Ernie's recommendation
Thats what I did except the heat riser (inner steel liner 5/8 thick) is 8" in diameter.

For 6" system you need 5" x 5" (double check that figure).

Hey there

I am on my first build so please take that into consideration when reading my comments.
When I fired up mine for the first time I kind of cheated. I read that when the RMH is cold it can be hard to get a good draft.
I started a fire at the bottom of the heat riser to get things started.
I found that once the "heat riser" fire died, the feed tube fire was good and the heat riser was warmed up the draft was fine.
Obviously you can't do that in normal operations but it will at least show that your set up is good.

screenshot from video
I suspect it is for visualisation and not really for heating permanently

I am noob here
What is the temperature coming out of the flue or just out of the thermal mass?

I don't think fire brick is good for thermal mass (maybe I am wrong) but doesn't it have the property to refract the heat?
Like if it was insulating the heat on one side from getting to the other side.

Before cementing/cobing all this up you should have tested it.
I postulate you may need to take out the fire bricks.

The drying process maybe stealing a lot of the heat and part of the problem.
But I suspect the fire bricks are the problem.

Go see any farmer and ask if you can load up your car with rocks that he took out of his field.
They have tons of rocks that they discard along the fields.
I would get as many bowling ball size rocks as you can or smaller that can fit in your car (without damaging the suspension).
Then it is a matter of how many trips will it take to fill the bench.

Please take care to verify what I share as I am a newbie
Hopefully a more experienced RMH builder will confirm or correct me.
I humbly apologize for any errors in my comments.
In any case we will both learn something out of this.

Good Luck

I got the core to work!!!

I understand how proportions work. Since my inner riser tube is kind of fix, if I wanna keep my proportions correct I can't very much play with the other two.
Unless I rise the heatriser with bricks.

Inner heat riser tube is 5/8 steel. I don't have a torch to cut myself.

I assume that no comment to other stuff means I didn't write anything overtly incorrect.

Thanks Glenn with your patience with my noob questions.

"What are you using as "1" in the ratios?"
Is this what you mean?
Feed tube : tunnel length : heat riser
I am using what E&E suggested in the DVD unless I calculated it wrong.

And yes its an 8" RMH system.

"...it could probably be between 0.7 and 1.3 times nominal system diameter."
Sorry noob here. Not sure what you mean.

The whole J tube is 7" x 7"
My heat riser is 32" + 11" depth of heat riser tube
Starting from this I calculated the rest

1:2:4 gives me 10.75 : 21.5 : 43
1:1.5:3 gives me 14 : 21.5 : 43
This is basically what I have now.

Since my heatriser exterior is 15" (barrel is 23)
I am left with 8". I guess I can put 5" on one side and 3" on the feed tube side.