Scott Weinberg

kees ijpelaar wrote:

The book roacket mass heaters do state that the tunnel is the smallest part, also with square or round rizers.

C is the burntunnel in the book see attachment need smaller then the rest.

I go just test all, if nabure is quite but I have trouble with her who is heavy anti woodfires.

I think I would toss what ever book your referring to, and use the well published and PROVEN numbers on this site.  The J-tube with the right numbers simply works well if your able to keep feeding it. Pretty hard to get around that fact, if you want something that works on the first go,  it would seem relavent to go with proven numbers.

kees ijpelaar wrote:HI James andBenjamin.


I have pick a piece of tekst here from a book rocket mass heaters II

C is the cross-sectional area of the horizontal
 The size of the cross-sectional areas of
all parts of the stove’s internal ducts should never
decrease below that of C. In other words, the crosssectional areas of F, G, H, J, and k should all be
greater than that of C.


Wel I do now now why it does not work well, the cros sectional space in tunnel is 225 cm3  and the rizer
is 176 cm3.

I went back thrugh your post, and did not find anywhere that you explained what these crossectional areas of F, G, H, J and K are So I am thinking your leaving a lot to us for our imagination.  This is hard to suggest anything, not knowing the details.

And you list cross sectional  space as  cm3,  Where you actually in your calculations needing a description of cm2  Where yours would be listing volume, and other area of opening.  Again, I am just trying to guess what your trying to tell us.  if everyone else has it figured out, great.  

Best of success.

[quote=Peter van den Berg

Glenn Littman wrote:Once the system is fully dry it will be interesting to know the firing cycles to get it up to temperature and maintain it considering the enormous mass. It will also be interesting to see how it retains the heat over the 35-40 hours that the store is closed and the external temperature when they reopen on Monday.

At the moment, they use the clever thermostat of the gas heater as temperature gauge. It is able to show the temperature over each 24-hour period, hour by hour. So they'll know what temperature decline is going on during closed hours.

The beauty of recording devices today, depending on what you want to spend, is that everything can be recorded and saved. As the stoves don't get really get sofisticated, the how to's and why for's really get interesting.   In my case, going into the third year, we are comparing heating up the mass 25 degrees warmer than in the past, having it cool down about the same % as always, but then with next day firing, get to the warmer level with about the same amount of wood,  while I don't have solid numbers yet, it would appear that we are "feeling more heat" with the same amount of wood, after day 2.  Part of the equation if you love the math, is that the exit flue temp went up 14 degrees on average vs the mass increase of 25 degrees..  Fun working the numbers.

Please read-  This is only my experince, I am not suggesting or implying your results will be the same.  But without gages, recording, and study, it would only be a great working warm stove.  now it is a on going experiment daily.  

Matt Todd wrote:

Fox James wrote:Sounds good apart from putting super wool in your oven, that is not a good idea due to the risk of microscopic fibres being ingested!

Super wool is the mineral based safe alternative to Kaowool and Ceramic wool. I would still probably rigidize it though! Or perhaps use vermiculite board.  

Mineral wool or not, I will agree with Fox James 100% about Microscopic fibers, I have used all kinds of Super wool, and if you still don't believe, just have some strips by the heating area ( and when they have turned a slight tan/brown in looks, hold in the sunshine and very gently rub them slightly together) And that should cure you of any thoughts of using it as a seal in any food bearing areas.

As we get older, we unfortually get to learn what cronic things  micro fibers can  provide for you.  Think of it as a persistent present for the rest of your life.

I relate that to a lable that reads 1 part per million is safe, and 20 parts per millon is not safe,   Says WHO?

Glenn Littman wrote:  

The other piece that you haven't mentioned that fits in nicely here is the time commitment. This is not a minor undertaking. My build took me roughly 3 months but being a compulsive perfectionist with my projects and having the luxury of being retired I took my good old time. Tom Rubino can comment on expected time frames to build since he has built so many over the years, both by himself and with the help of Gerry Parent (that's an advertisement for you Gerry in case you want to hire out as a professional batch rocket scientist). So, the builder needs to plan their time accordingly and have the available time to commit.

I will jump in with what I consider some time saving but in no means lowering the quality of your build.  

1) scrounging  for material-  with the avenue presented to us, are all kinds of companies looking to get rid of waste ( bricks ) almost any brick yard has toppled over pallets, some have been there for years or months.  you may end up with 3 different colors, but if your doing a double skin bell it don't matter, as no one will see the inner bell.  I was patient, and ended up with enough bricks for 4  7" sized bells ( big ) for $0.10 each,   Yes that is 10 cents. And they were brand new and still on a pallet.   It can happen.

2) A trick)-- There is so much info out there and what I would call  "new tricks" that simply should not be ignored.  The double corner laser lines are one of them letting you do two directions and know they are square in two directions at the same time.  

   b trick)== knowing that if your two corners, back left to front right and back right to front left have exactly the same measurement the the likely hood of your bell is square is high. Always good.

   c trick)-- Preplanning your bell size so you have NO cut bricks per side, lets you build one tier at a time very quickly.  And having all the bricks for this one tier ready to place, you can then plan for the time involved per level.   Suddenly you can say, " this tier takes 1 hour, and I have 1 and 1/2 hour, might as well do it"

  d trick)-- if you build a tension frame for the burn unit,  the same squareness rules apply, just makes everything else work so much easier  Measure twice, tack once. check and weld.

  e trick)--  if you know your 4 corners are square, you can actually set those 4 bricks in place,  and place the balance between these 4 corners. A big time saver again.  Remember  Brick length + joint thickness equals total length per unit. You can fudge a bit as needed between the 4 corners.

   f trick)--  spring loaded string lines between the set corners, really can speed things up.  A lot of the best brick layers in the world use the guide strings for good reason.

Hope some of these will apply to your build, a person doesn't have to use all or even any, but most will help.   Even the best, can't often just build on the fly without checks on his or her progress.

Best of success.
   

Jackson Bradley wrote:I get somewhat confused on the longevity of the different parts for the different types.

I can't quite wrap my head around what I'll need to replace/clean, about how often it will need replaced. That seems to depend on the type of RMH. I have read through your masonry build in the large building, the Wisner's materials, Thomas Rubino's projects, etc. I have seen where some of the metal components need to be replaced and some of the bricks crack and need replaced, etc.

I understand a factor of that would be climate dependent due to the amount it would be used (wood burned). The larger masonry heaters seem like what I would work up to in my residence but practice building one on in my accessory building.

Longevity?  Lets flip this a bit, and look at the numbers,  so we have a outdoor stove that cost 10 times more and burns 10 times more wood (ok, lets cut that to 5 times more wood)  and still needs repairs after a few years, at the mercy of electricity and dealership cost.  vs rocket mass stoves that probably and possibly need some general maintained cost of a few dollars per year

Tom has clearly shown what hard burning, looks like and how he handled it.

I am on my third year of burning, and while I think I can detect some future repairs, they appear to be minor. and while I am trying to get a better video, I can honestly say, no hotter fire has burned in a standard wood stove.  I can heat a 1/2 round rod, to deep red in less than 3 minutes and cherry red in 7 minutes so hot it is.   I have been a proponent of building a stove where the entire core burn unit could be replaced without touching the bell. This was not hard but has not been needed. But I probably will do this again. Just takes a bit of planning.

Excellent post Glenn,

I would like to add to this a bit.

1) any in the Midwest with basements, you have great potential room, if you have a chimney that goes with the house.   Heat rises nicely. and yes it might not be a center piece, I think many will enjoy this especially if you have a window on your door ( easily done )

2) insurance- I bet I have heard 100 times from home owners that they feel they could not get insurance if they have this built by themselves or a contractor, So I ask why?  other than hearing  " because that is what I heard "  I have yet to have someone tell me, this is a non-insurable unit, causing the house to be uninsurable.   Better yet, show me.  So I have to presently believe this is a classic case of  Somebody said that somebody said, that somebody said, it can't be done.  Which generally plays out that it was never a fact, I don't mind to be proven wrong, but simply have not seen this yet.

  To back this up further, for every reason that a classic wood stove with smoldering fires that might be producing a potential chimney fire, I can show you why that is simply not true with a rocket mass stove.

3) Time, everyone seems to be short on time, but, for every hour spent gathering wood, for a Rocket Stove, you can get 2-5 times more usable heat, plus if you add in all the easy to gather woods ( throw away boxes at nearly every lumber yard, construction sites, storm damaged areas,  that are in fact FREE )

This of course is just food for thoughts, but the 1st step of any job, is starting, whether that is in the planning, cleaning, or constructing. But, if you don't have time to do it right, when are you going to have time to do it over?   Might as well, start with a great plan and follow through.  Tom of Dragon Tech just showed what got done with a great mission and determination.

Best of success!

Glenn Herbert wrote:I agree that a ducted mass would continuously lose heat with any amount of residual draft. I think a stratification chamber would be more dependent on details of the configuration. If the combustion core exit (riser top or secondary chamber exit port) is near the top of the stratification chamber, then it will be introducing cooler air and diluting all the stratified hot air remaining. If the core exit is low in the stratification chamber, it can move more directly to the chimney exit and leave the hot upper part of the chamber undisturbed. This is assuming that draft is restricted from full burn-time flow and does not "jet" at all.

As many may know, I have tremendous draft, even when the stove is not lit.  and this is nearly all the time.  Yes, even in summer.  Thus it can be concluded, that if something ( air ) goes in it has to come out, and of course if it comes out and makes it through the bell or any other part of the mass, it is just the law of physics, that X degree cooler air, will gain temp if allowed to travel through, X degree of warmer environment.  The speed of such can be expressed as CFM (cubic feet per minute)   Thus the tiniest level of inlet, left unchecked but having a clear shot of air travel, can loose just as much  heat as loosely sealed but large area of air inlet. such as a door.

Perhaps one of the easiest ways of knowing, is simply when you shut down your stove, before the wood is completely coaled out, and it is nothing but ash in the morning.  Something allowed this to burn. i.e  air entering your stove burn chamber.  Basically if you have a great drafting stove, you will also have a stove that wants to just keep the cycle alive, ( heat going up )  And of course, this can be simply tested, if your exit pipe is very warm 3 foot from your stove, it is getting that way from flowing heated air.   I have come to believe that some will simply migrate up the flue, but stiving for the lowest CFM will save a great deal of heat.

When burning let it roar, when not, shoot for the lowest snore.  A true sleeping dragon so to speak.

Best of success.  
Note- if any of the areas that need to be sealed up, never gets over 500 degrees F, some silicon sheets come in handy for air stoppage. And can last for years. Just like the stoves themselves, a little ingenuity can go a long ways.

3rd year for the stove, where does the time go.

Thought I would do a quick share/update  I fired up the stove, 10/26/25 for the first time this fall.  Had it all cleaned up internally from this past spring, so no dampish ash or other things to deal with (damp basement application)

Almost scary how quickly, things sprang to life with the mighty roar,  used by pass until I felt it was HOT, then closed off after 2 minutes.after than a success was determined. I design my cast-less top a little differently now adays, but this one is working just fine.  Video, might not be so good, a winter project to figure out how to do better.

Cheers all, and stay warm.  Also completed my 50th harvest season yesterday! Pretty good feeling with record corn yields for me on most fields.