The RMH Builders guide build-pic heavy

thomas rubino wrote:Hi Diane;
Welcome to the world of rocket science! I have a few questions about your build.
Do you have a copy of the RMH builders guide ?
Is this rmh going to be in a basement?
Is your uneven concrete slab insulated ? If not or your not sure then the best start might be to put down a level insulated base to build your rmh on.
Are you planning an 8" J tube ?  with horizontal mass ? What did you have in mind as your chimney?

I started another thread with my pictures.
https://permies.com/t/93476/RMH-exhaust

Very nice rocket mass heater and splendid presentation.

I have also a plan for building one, it has to be 15 x 15 cm tunnel, and put on a 11 cm chimney, this is not good because the shimney is smaller, and this is not allowed.

To tackle that, I go use a chimney ventilator I am busy to tigg one together, building a fan is much cheaper then buy one, the electronic around I do myself because I am
a electronics man. With a fan I get a virtual bigger chimney, and the starting of the rocket gets much better.

the idea of the rocket you can see on pic. I go build that because here the woodstove smoke of the steel one do disturb mine nabure who do not like the smell, I hope a
rocket will do be smokeless and odorless. In holland we have much people living close together and as such wood burning is a issue here, maybe a roc ket will help the
fine particles from such a stove are also low, and maybe I go build also a electrostat for catching these particles, that can be done very easely in a part of the chimney
where the  flow of gasses are low.

regards

kees

Just a quick update.  My deadline for finishing around thanksgiving has been postponed to thanksgiving 2019.  I'm still plugging away.  Honestly, I absolutely hate making cob at this point.  I will finish, but I despise it currently

I used a ton of cob around the firebricks that was structural with straw in it.  I used this structural cob for the front as well.  I cut the straw with the chop saw in about 2 inch pieces for the most part.  I would grab a handful and cut pretty quickly, throwing it against the closed shop door so I could collect it.




The recipe I found for the best structural cob, 1 bucket hand dug clay with small rocks, 1 bucket sand, mix it up with tons of water to make a soupy mess.  Add 1/4 bucket straw well packed, chopped to 2-4 inches.  Mix thoroughly.  Add in sand a few shovel fulls at a time to thicken the mixture and then apply.  I have never "soaked" any hand dug material and It has all worked great, no cracking, plenty strong.







Here's where I am at today

Eric,
 Looking great!!! Your cob is beautiful- I wish I could have some of that lovely home grown clay.
I feel your pain on the chore of "making cob".  It became SUCH A CHORE, at least for me. (I am so put off, I am wondering if my plaster will ever get done...)
Hang in there. The end is nigh!

This is a great thread ! Thank you so much for your careful documenting & sharing of the build. Would LOVE to see a video of your rocket in full burn - wanna heat that dragon roar ! And what a great score on all those cut-off oak pieces.

If you can believe this, this thread remains unfinished because I simply quit working on the RMH.  I got it into a usable state and that's where its remained to this day. I have just come back to this project. I started mixing cob today and put another layer on bahahaha.  In the winter of 19/20 I heated my house entirely with this stove from October to May, no supplemental heat and used about 1.25 cords.  Last year it wasn't my primary heat but I used it quite a bit. That big cold snap on presidents day that froze all the gas wells and took out the power grid, I was able to share most of my wood pile with neighbors and keep my house over 80 degrees all week without much effort.  This thing is nice and deserves to finished.  I'll take some pictures of progress like before and share some of my observations of using it the past 3 years.

Hi Eric!
 Fun to hear an update.  I know how quick time seems to pass. My final "update/review" is still pending
Can't wait to see pics and hear how things are going!
Staci

Well if it makes you feel any better Eric I started mine around the same time as you and just finished mine this year!  I too got mine to a usable state and then just sort of got used to it in that state.  I appreciate all the help I got from you and Staci by following along with your threads while I did mine.  Here's a pic of my finished RMH.  It is a pebble style so the look is different than yours.  

Please hold while I remember how to post photos...

I don't even know where to start.....its been so long.  Maybe I'll just make a post and see where it heads from there.

Lets talk about Rocket Mass Heaters.   I never wanted to build one.  3 years in is it worth the effort?  Absolutely!  Hands down, single most efficient way to heat a home, period.  I haven't even finished mine, so I have not experienced the glorious pleasures of laying on it and taking a nap with it's warmth and all the blood sweat and tears were completely worth it.

Lets talk about wood.

When you own a regular wood stove, you throw your wood outside in a pile and cover it with a tarp and have some damp wood that doesn't burn but it sorta seems ok because that's what everyone else is doing.  With a rocket mass heater, it takes a significantly less amount of wood and needs to be bone dry.  I keep mine in a greenhouse.  This lame 5 foot by about 12 foot stack is more then enough wood to keep me warm all winter.



I have decided the absolute best size for this rocket mass heater is a length of 12 inches.  This length lets you build up quite a bit of ash in the bottom and you don't have to clean it out for several days or even a week.  The tops don't poke out so you don't ever have to worry about smoke  working its way up through pieces and into your house, and at any point of the day if you need to run out and not attend the fire,  you can close off the wood feed almost all the way with firebricks without having to wait for wood to burn down below flush.

I prefer 2-3 inch diameter wood, with zero knots, and 12 inches long.  I'm very particular about this.



I cut all the knots off and throw them in a 55 gallon barrel.  I love burning the knots.



The kind of wood I burn is irrelevant.  Whatever I have, I burn.  I just cut a standing dead sassafras, so that's what I'm using.  I used to get on craigslist and source free wood, but my priorities were all wrong.  I was basically cleaning up other peoples property for free wood, when I have my own property to clean up and my own free wood lol.  I have about 10 acres here and I think I could heat my house every year with just the branches that fall off trees.  I'd say even 2 acres of heavy wooded land would be sufficient to collect and not actually remove any trees.

I have a couple must have tools for the rocket mass heater:

The kindling cracker:

I make sure there are no knots so that each piece can be split easily if I need kindling.  If you don't have a kindling cracker, this is a must have tool for the rocket mass heater.  Combine with a 3 or 4 pound sledge and you are on your way to heating self sufficiently.



The torch:   Makes lighting your RMH a breeze, must have.  1 Propane tank lasts a whole winter.  If your mass is cold, you can just lock the trigger on, place it in the burn tunnel for about a minute and then light your wood.  It's really cheating and awesome.



A couple tools that make life easier but not a must have....

This is the greatest chainsaw ever invented.  It's the lightest gasoline powered saw in the united states.  Echo 2511T.  Super expensive.  I switch out the bar to a 1/4 inch picco, I have about 550 dollars in this saw.....but let me tell you, Its the rocket mass heaters friend.



I bought one of these sawzalls, and it works ok, but not as good as I thought it would be.

It looks like your pictures aren't sharing properly Eric, I've uploaded copies if that's ok:

Thanks for having my back! It took me a bit to remember how to do it!

Let me know if these pictures work.

Back to making cob.....



If you let your sand sit for 3 years, it grows enough plants to make a useful amount of roots to bind your clay together and you don't need added straw...bonus!



Adding Mass

Burning some wood to try to dry the new mass...... its clearly not burning as well as it used to.  Fire is creeping up the wood.  I think all that cold wet clay against the pipe is affecting it.



I had designed my house to have a rocket mass heater from the beginning an the design works quite well.  The house is basically a big rectangle, 20x40 and 2 stories.  In the corner where the rocket mass heater is, there is a big opening to the second story and a ceiling fan.





On the opposite side of the house I have the opening for the staircase with a mini split heater/air conditioning above it.  So basically I can turn the fan on above the rocket mass heater and just the fan with no heat on the mini split and circulate the warm air through the whole house.

Eric Hammond wrote:Let me know if these pictures work.

Photos are working now!  Thanks for continuing your documentation of this project.

I think part of the problem with me taking so long was the fact that I over think everything.  The edge of the bench was getting almost rounded and I was afraid that I would need some sort of metal mesh or rebar to keep stacking higher......that was completely unnecessary.

 I also couldn't wrap my mind around how to frame out a little arch for the clean out duct.  Finally I just used some bent license plates.  At some point you have to quit thinking and just starting working.





I am so tired of making cob.......I can make about 4 batches a day, but I'm pretty tuckered out when it's over.  Its been a hard 4 days



I can't say I tried my best, but I gave a fair effort to try to wet down the 3 year dried cob to accept new cob



and then I built up all the edges  probably in about a 6 to 8 inch deep layer, much deeper then I thought I could get away with.  I kinda spread the layers out a few hours between and it worked out good.





Then I went to town making lasagna and got down to the corner.  I'm making progress!

RMH heater failure and maintenance.  Since there really is no moving parts, its hard for things to break.  However during use I had a fire brick crack.  The book warns about this first brick cracking and that you should design your stove for easy replacement.  Honestly it's been cracked for a couple years now and I dreaded replacing it, and its been working fine, but if you touch it, its for sure a loose brick.  No better time then now to replace it.



I took a small screwdriver and chiseled out a bit of the cob



I worked the top brick out with a screw driver.



Cracked brick out



I chiseled out a bit more cob to slide the next brick in.  I used no mortar, I just cleaned everything up with a shop vac and set the brick in place and started cobbing it in place





Top brick in





Fixed







Best part of a RMH, roaring fire inside and nothing outside....




It's probably best I went ahead and replaced it.  The brick actually had 3 cracks.

I ran out of sand today!!! I'm going to have to get more. If you remember I bought 2 tons!  I've been mixing roughly equal parts sand, clay and rock.  I know it's rough math but if I used 4000 lbs of sand and that was only a third of the mix, so I reckon the bench is roughly 12,000 lbs now!

The bench is getting super close!!! I have a lot of it up to the finished surface!

I had put a faint blue chalk line on the wall years ago to build the surface up to.



Can't have too many rocks....



Look at this beauty!

Thank you for sharing your work! It's great seeing RMHs getting put into use, and seeing what designs people come up with for their situation.

Wonderful documentation, Eric! Thank you so much, this is a huge help for anyone in the planning stages.

You'll be lying on a wonderful warm bench, soon!