LuAnne Welch

I misspoke.  Is not dura-board under the bricks but high temp insulation fiber board rated at 2300 degree.  (its 1 inch thick)

I'd be using that to wrap the riser and the fire box.  

Thanks,

Jim

small correction

The first row on the base of the fire-tube is 2.5 inches thick - sorry fat finger syndrome kicked in there

Jim

All,

I have taken all the advise I have received and now provide you with the following design and ask for your comments before I begin this last build.

For the foundation I have:

Marble 1.25 Inches thick
Firebrick 2.5 inches thick
Dura-board 1 inch thick rated at 2300 degrees.

For the base of the firetube i have:

Firebrick at 1.25 inches
the first layer on top of that is 2.8 inches thick

the fire tube dimensions are:

Length 24 inches
width  7.5 inches
height is 7 inches

The width and height dimensions are also those for the feed tube and the riser
except the feed tube length will be 16 inches
and the riser will end up at 47.5 inches in height

The gap between the riser and the top of the barrel is 3 inches.

The exit pipe from the drum is set at 8 inches and begins 2 inches from the bottom of the barrel
The gap from the first row of the firetube and the drum exit is 3.6 inches

I had to move the drum 1 inch to the rear of he RMH to accommodate the feed tube

If you see an error in this design, please let me know.  I appreciate all of your comments to this point.  

Thanks again for your time.

Jim

Glenn,

Roger that on the core proportioning.   The fire tube is as follows:  
Length 24 inches
Width 7.5
Height 7inches.

Measuring from the bottom of the burn tunnel the rise will be 47.5 inches.

Jim

Fox,

Going forward on the 8 inch build.
Yes, I had intended to build the burn tunnel on the top of the dense brick.  I added the non-essential bricks only to protect the dura-board underneath. (the white layer in the drawing)   If I eliminate the non-essential bricks I'm back to the minimum the RMH guide calls for. Taking into account what you mentioned, if I make those bricks 1.25 inches thick instead of the 2.5 I'd normally get, those bricks would come up to temperature faster and I'd be left with the 2300 degree rated dura-board and the marble base to insulate the floor.

Then insulate the riser and the fire box with dura-board inside of the drum and I should be good to go. Do I have the thinking correct at this point?

Jim

It would appear I have confused some of you with the drawings of the new design of version 3 (8 inch system) vs the current 6 inch system I'm running.

On the 6 inch platform, the base of the fire-tube is 1 inch of #2 firebrick.  (this stuff is supposed to be much more heat resistant than normal firebrick).  The brick below that RMH (the same as in the drawing) is simply for insulation (along with the lower levels of dura-board and marble) so I don't toast the carpet underneath.

In the future system (8 inch per the drawing) the layer of firebrick will now become the base of the fire-tube (see new drawing).  Again the goal is not to heat the bricks but contain the heat of the fire-tube.  I posted the pictures because the RMH guide is just a bit off, because when I added the drum, it appears there will be a conflict between the drum and the feed tube using the specs in the guide.

I've modified the new design to measure the riser from the bottom of the burn tunnel, and that seems to be good advice.  

The only remaining question I have now is, I received counsel that I should have the exit from the drum about 4 inches from the bottom of the barrel, I did that on this latest build (5 inch) but that seems pretty high and will cause a lot of excess mass to fill in the box and since heat rises I wonder if I should lower the exit somewhat?   Any thoughts?   My issue is I'll have to fill in about 6 inches of mass (pebbles in this case) just to reach the bottom of the exit tube.  It just seems like a lot, that's all.

Jim

James: the firebox is constructed out of 1" #2 firebrick. That rests on top of the full size firebrick.   I'll check my new design with a 42" riser and see what that looks like.

Satamaz: - sorry - I didn't get your first but am grateful for the second.

Hit a snag on the new design.  I'm using the Wisner RMH guide and using their specs the drum really doesn't sit well.  Odd.  I'll double check.  

Jim

One more thing, I've noticed the Wisner RMH guide calls for a 2" gap but assumes a 25 inch circumference on the barrel. Standard 55 gal barrel has a 22.5 inside diameter.  My presumption now is I'll need to increase to 3" to accommodate te difference. Correct?

Jim  

The goal is to heat a 20 by 48 foot space as efficiently as possible.  There is no insulation along the walls.  (this is a temp tent situation)
So I'm looking to extract as much heat from the barrel as I can - the hotter the barrel the better.  The riser is insulated, but I could remove a layer of brick without too much effort.  The wood I'm burning is as dry as your granddaddy's scalp, so that is not a concern.  

I think I mentioned earlier that I measured the riser from the top of the burn box level of brick and went 48 inches up from there.   If I've over done it, that would present a situation where I'd have to adjust (possible) the height of the manifold barrel to get the right height of the barrel assemble correct, given any changes to the height of the riser and the gap between the rise and the top of the barrel correct.

Jim

I have run the RMH continuously for 18 hours (still attempting to figure out how to keep it going during sleeping hours lol)  and the average temp hangs around 530 once it gets going.  

Quick question.  Is the riser measurement from the bottom of the burn tunnel to the top of the riser, because I started from the top of the burn tunnel to the top of the riser.   Maybe I don't need to so much riser then.

I am using a combination of anywhere between 1x1, 1x2 and 2x2 lumber and usually I can get between 5-6 pieces going at any one time.

If you're correct and the extra riser height is robbing the heat .... I do know the Chimney is not that hot.  I can always place my hand on that and its warm but never hot.

Jim