The RMH Builders guide build-pic heavy

I thought I read every post in this thread, but didn't see info on what you used for the vertical heat riser in the barrel.  Was it firebrick?  I have read somewhere on permies that brick is better than steel, even heavy steel, as it will degrade over time.  I read that a few years AFTER I built my rmh with a steel riser.  I've done my best to align mirror and lights to see what is happening inside my sealed barrel, and it all looks okay.  I have fired it up again for this season and it runs well.  The only issue I have had is the corrosion that happened in my pipe as it exits the cob wall of my house.  I had a gentle downward slope, as I had been directed, but neglected to add a tiny drain hole.  Moisture that collected at this low point as the pipe takes the vertical turn eventually rusted through and affected draw.  There just wasn't enough heat in the pipe by this point to keep it dry, and I suppose moisture made it in even in summer.  Anyway, I was able to just replace one section of pipe and all is well again this year. a tiny drainage hole doesn't seem to affect draw. I'm guessing that the insulated stainless pipe you chose for the exit pipe will hold up better.  I have 4 clean-outs and use them at least twice a year.  I get quite a bit of ash in the horizontal bench areas and some creosote, especially in the cooler exterior pipe.  Luckily I have a clean-out at the bottom of the exterior vertical, so I can clean it from the ground.
Laura

The heat riser was built of half bricks and then wrapped with the fire blanket stuff (which was then wired and wrapped in chicken wire).  You can see it in his first post - dry stacked.  The pictures of building it with clay slip mortar are about halfway down the first page, on my desktop.

Did you insulate your heat riser?  What did you use?   (It's possible the original metal is gone but your "insulation" has hard-fired to the point it has structural strength on its own, if you used something like perlite in clay for the insulation.)

Eric Hammond wrote:Ok I understand the channel. What do you mean by a trip wire?

Here's a video of Donkey making a trip wire.

Julia Winter wrote:
Did you insulate your heat riser?  What did you use?   (It's possible the original metal is gone but your "insulation" has hard-fired to the point it has structural strength on its own, if you used something like perlite in clay for the insulation.)

I insulated, but just with loose perlite most of the way up, and then a perlite/cob mixture to cap it off  It is held in place with a stainless sheet wrapped and tied with wire.  When the steel goes, it'll go catastrophically.  But as I say, it still looks smooth and grey.  It was quite thick, which may give me a few years yet.  About 5/16".

Eric Hammond wrote:

Mark Tudor wrote:One tip I recently read was to make sure the surface is actually comfortable to sit on, which is rarely a flat surface that meets the wall at 90 degrees. Instead they suggest that there be a slight slope down as you go back, about 5 degrees, so your butt is a little lower, and then have the angle from seat to back rest be greater than 90 degrees, more around 100-110 degrees. If you aim for 17" high, test that with a chair to be sure your feet can sit flat on the floor and your legs don't have a gap under them. You also want the bottom of the bench to be several inches further in (closer to the wall) than at the top, so you can scoot your heels in to aid in standing up.

I've really enjoyed watching your progress, mentally building my own vicariously through you!

This is a good idea.  I'll sit in as many chairs as possible and figure out the best slope.  The width of the bench I got from measuring half a queen size bed, because I fully intend to take as many naps as possible on it.....a little slope might keep me from rolling off as well

Hi- this was great information.  I am having to re-think my own bench which is in progress.
Eric,  how are you backing your benches?  Are you going with cob all of the way up?  
I would like to widen mine...though they are nearly at complete height (15").  Do you think that adding 3-4 inches to the outside face would compromise integrity?
Thank you!

Staci Kopcha wrote:

Eric Hammond wrote:

Mark Tudor wrote:One tip I recently read was to make sure the surface is actually comfortable to sit on, which is rarely a flat surface that meets the wall at 90 degrees. Instead they suggest that there be a slight slope down as you go back, about 5 degrees, so your butt is a little lower, and then have the angle from seat to back rest be greater than 90 degrees, more around 100-110 degrees. If you aim for 17" high, test that with a chair to be sure your feet can sit flat on the floor and your legs don't have a gap under them. You also want the bottom of the bench to be several inches further in (closer to the wall) than at the top, so you can scoot your heels in to aid in standing up.

I've really enjoyed watching your progress, mentally building my own vicariously through you!

This is a good idea.  I'll sit in as many chairs as possible and figure out the best slope.  The width of the bench I got from measuring half a queen size bed, because I fully intend to take as many naps as possible on it.....a little slope might keep me from rolling off as well

Hi- this was great information.  I am having to re-think my own bench which is in progress.
Eric,  how are you backing your benches?  Are you going with cob all of the way up?  
I would like to widen mine...though they are nearly at complete height (15").  Do you think that adding 3-4 inches to the outside face would compromise integrity?
Thank you!

Staci, I hate to confess this and I hope my wife doesn't read this post.......honestly I have no plan currently at this point as to how I am going to do the backs.  I simply keep telling my wife how great it's going to look, while deep inside I'm sort of panicking and trying to figure it out while trying to believe my own words.......pretty much like any given Monday of every week.

My ideas were either to continue cob for the backs...or make some sort of wooden structure that could be removed when I want to take a nap.  I'm going to keep progressing and see where it takes me.

I'm no expert in cob by any means, but I think building another 4 inches to widen will be no big deal as long as you have good surface adhesion to the existing cob.  I've tried to poke finger and thumb holes in every layer for the next to adhere to like this



If you have sufficient holes in the front, I see no reason why you couldn't keep adding to it's width indefinitely. Just try not to build more then 4-6 inches high at a time.  If you need more adhesion to the original layer you could get creative driving nails into it and building your cob onto the nails.

LOL-  I am having the same panicky feeling about the bench. Thank you for sharing.  I have a window right there, and now I am finding that my raised bench will put that window ledge just at the uncomfortable shoulder blade poking level. I am keeping the faith that "all will work out in the end".  Will let you know if I come across any super stellar bench back ideas.
 Will also proceed with widening it a bit- thanks for the info.
Staci

Laura Kelly wrote:I thought I read every post in this thread, but didn't see info on what you used for the vertical heat riser in the barrel.  Was it firebrick?  I have read somewhere on permies that brick is better than steel, even heavy steel, as it will degrade over time.  I read that a few years AFTER I built my rmh with a steel riser.  I've done my best to align mirror and lights to see what is happening inside my sealed barrel, and it all looks okay.  I have fired it up again for this season and it runs well.  The only issue I have had is the corrosion that happened in my pipe as it exits the cob wall of my house.  I had a gentle downward slope, as I had been directed, but neglected to add a tiny drain hole.  Moisture that collected at this low point as the pipe takes the vertical turn eventually rusted through and affected draw.  There just wasn't enough heat in the pipe by this point to keep it dry, and I suppose moisture made it in even in summer.  Anyway, I was able to just replace one section of pipe and all is well again this year. a tiny drainage hole doesn't seem to affect draw. I'm guessing that the insulated stainless pipe you chose for the exit pipe will hold up better.  I have 4 clean-outs and use them at least twice a year.  I get quite a bit of ash in the horizontal bench areas and some creosote, especially in the cooler exterior pipe.  Luckily I have a clean-out at the bottom of the exterior vertical, so I can clean it from the ground.
Laura

Julia has it correct, I utilized firebrick for the riser.  Only time will tell for your heat riser made of metal.  There's enough research at this point that no one should go down that route.   My neighbor builds his rocket cook stoves out of 4 inch square tubing insulated with perlite.  He uses them between 2-3 times a day and leaves them out in the weather.....surprisingly they last about 3 years and the part that fails is the burn tunnel and not the heat riser.  It rusts through on each side.  If I were to build my heat riser again, I would do as Thomas has suggested in this thread and put ceramic fire blanket inside of a 10 inch hvac tube for an 8 inch build.

That condensate you speak of is extremely acidic and will eat through most things, be careful with the stuff.  I always wondered if it might be good to pour condensate next to blueberries, strawberries or azaleas

Nicole Alderman wrote:Some days I'm really glad I have infinite apples. Today is one of those days! Thank you so much, Eric, for this awesome, detailed, helpful and informative thread!

Thanks for the kind words.  We are all in this together!  Return of surplus in Permaculture can be as simple as knowledge.  I appreciate you taking the time to share this in the dailyish email.  Estimated completion of this project is Thanksgiving weekend (although I grossly underestimate every project.)

A little update.  The brick situation in the feed tube is in pretty poor shape.  I'm sure with cob surrounding it, the structural integrity would be awesome, but me jamming wood in on a daily basis has been detrimental to the orientation of the bricks.  They are starting to get loose all around the top.  A part of me hurts inside.  Here's what it looks like:



Its no longer attached!  The front brick is that way also.  As a note, ever since I started putting tons of wet cob on....it's been a pain to start, wanting to burn up the feed chamber and fill the house with smoke.  One piece of newspaper at the bottom of the chimney cleanout has completely resolved the smokeback on start up currently, but I felt it was important to mention so others do not worry in their builds.  I'm sure once the mass is dry, this will no longer be an issue.

Because of the bricks mortar failing on the front, I decided to pop the lid on the barrel(awesome addition Thomas, they should all be built with lids)  everything is immaculate inside!  The mortar failing in the feed tube is only because of rough handling of fire wood.

Eric, when you say the part that fails is the burn tunnel and not the heat riser I have more hope.  I built my burn tunnel out of firebrick.  I'm on the fifth year of use now.  Curious about the acidity of the condensate.  I do farm blueberries. . . .

Two updates I wanted to share.  The first update.  I've made more progress on the cob side of things.  Battling record cold temps and snow, so it's hard to get outside and do any cob mixing.  Got three more "loads" attached.







The amount of rocks I'm putting in is borderline rediculous now.  As much as I can fit in a single row without overlap

The one other thing I wanted to mention....reading through this topic and through Staci's build, both Satamax and Staci have mentioned that they find feeding the beast finicky/requires a lot of attention.

I have not found this to be the case with me at all.  In fact right before it was mentioned in Staci's post I had loaded the stove up and went to take a hot bath, while thinking in the tub I was wondering "Why did Satamax say these things required constant attention?"  I basically filled mine up and walked away.  I wonder if its a difference between 6" and 8"?

Here is how it's going for me.

First I'm using terrible wood.  Every attempt I have made to keep it dry has failed.  The majority of wood is osage orange/hedge that was cut in late september early october of THIS year.  Super green.  It's been rained on a couple times, and now has snow on a large portion of it.   There is some well seasoned oak mixed in, but I'm afraid it's been rained on once or twice as well.  I HAVE to start the fire with the oak as it's the only thing that will sort of burn to start a fire.



I will admit, starting it is a bit finicky....I do not have smoke back issues what so ever, but the wood is hard to get lit.  I use quite a bit of cardboard and the smallest pieces of wood I can find.  It  usually takes about 15 minutes to get the fire large enough to stoke the firebox with fuel.

I then fill it will whatever wood I have completely full, paying special attention to put the largest ends down in the fire first so that it will feed the best.



I timed it one hour and came back and it now looks like this



I then insert more wood and it will instantly light




I stoke the firebox again and I'm good to go for another hour.  I literally have to do NOTHING for that hour other then let gravity do it's job and the fire to burn the wood.  It self feeds.  I do not find this RMH finicky at all.  

I did have the baby fall asleep on my lap one day and he took a really long nap.  I could not get up to tend the fire for 2 hours, the fire had burned out but lots of coals and relit easily.

I ask you.....is this what some consider finicky or are others experiences different from this?  I did make the location of my stove perfect to where we constantly have to walk by it doing any household chores, but to me, a one hour burn interval is awesome and not burdensome at all....I love this stove!

Eric;  I couldn't agree more!  
My 8" performs the same way, 45 -60 minutes easy. If it's out ,it relight's easy easy !   Stacie's 6" is still wet and it will get better. Max prefers batch box's. They have hotter temps and use larger wood but only burn 1 hour....
  They all work well,  its not much different than what brand of beer you prefer...

Eric Hammond wrote:

"Why did Satamax say these things required constant attention?"  I basically filled mine up and walked away.  I wonder if its a difference between 6" and 8"?

The amount of rocks I'm putting in is borderline rediculous now.  As much as I can fit in a single row without overlap

Well, may be because i race the J tubes, and i have never used bigger than 6.  My batch burns for more than one hour. But it's big. Firebox is approximately 74 liters.  IIRC, i can feed it 16 kilos of logs at once. But this may be more.

I love the architecture of the J, top load i really like. And i like top vertical load. I have been working on a batch for this. But with mixed results so far. If only i wasn't soo much of a tosser.

http://donkey32.proboards.com/thread/1803/peter-vertical-batch?page=7

And as for the stones, i prefer big ones! ;D

Ha Max;  I think that living in the Alps you have a great selection of large stone to choose from.  I prefer the large stones as well.

Thanks for the updates Eric.  I'm well into the build of my RMH now and noticed a detail in your photos that didn't come to my attention before.  Am I seeing correctly that you used a pipe to initially angle your duct work DOWN after exiting the manifold?  My understanding was that it should have a slight upward rise until going straight up and out the chimney?  I'm asking because it sure would be convenient for me to be able to do such a shift down before starting a slight upward rise in order to better fit into my mass bench.  (I'm doing a pebble style.)  I suppose since the hot gasses have been dropping down into the manifold there's no real reason why they can't drop a bit further just outside it too.

David Huang wrote:Thanks for the updates Eric.  I'm well into the build of my RMH now and noticed a detail in your photos that didn't come to my attention before.  Am I seeing correctly that you used a pipe to initially angle your duct work DOWN after exiting the manifold?  My understanding was that it should have a slight upward rise until going straight up and out the chimney?  I'm asking because it sure would be convenient for me to be able to do such a shift down before starting a slight upward rise in order to better fit into my mass bench.  (I'm doing a pebble style.)  I suppose since the hot gasses have been dropping down into the manifold there's no real reason why they can't drop a bit further just outside it too.

Hey David.  You are correct, it does go down.  If you look closely, coming out of the manifold I have two adjustable 90's, The first 90 is used to shift the pipe back towards the wall, otherwise the pipe would be too close to the face of the bench, and the second 90 lowers the pipe down, otherwise it was going to be too close to the top surface.  The pipe is then pretty much spot on horizontal for the first 3 sections.  The last jog of pipe where it connects to the chimney actually drops about and inch, so in no way does my pipe constantly "rise" towards the chimney.

I did place all of the seams of my pipes at the top so any condensation formed in the pipes could not leak out, and I sealed every joint so I have experienced no condensation issues.  My bench pipe length is actually about 7 feet longer then it should be by the book if you figure in all the 90's and such, but it seems to work fine, and I attribute that to a well sealed system.

I would see no issue why you couldn't go down as well.

Awesome!  Thanks so much for the quick reply.  Doing the duct work is my prime job for today!  Due to a lack of space my bench is actually shorter than it could be so I figure I do have a bit of leeway to slow things down a bit too.  I had planned on placing my seems toward the top of the pipes too.