Help needed for a 6" rocket stove conversion to a cyclone batch style stove

Hi All RMH builders and testers;

I really like what was done in this post
Kirk Mobert cyclone style in the red cabin

I want to convert my 6" RMH to function similar to the stove  in the above post.

My firebricks in the picture below are 4.5"x9"x2" (this will give you the dimensions from the below picture).



Imagine that I create a lower and upper "box" where the current hook of the J tube is.

Now it seems I have a few options now that my imaginary two tier boxes are setting on top of each other:
Option 1 (safest):
-connect the two boxes together with a portion of the vertical J tube;
-create exit passages from the upper box to the bench pipe.

Option 2 (may not burn wood gases just the wood instead; or stove might not burn at all):
-connect the two boxes with a square hole going from the ceiling of the lower box directly into the floor of the lower box (this hole would be in the rear near the bench);
-create exit passages from the upper box to the bench pipe.


Questions:
Will Option 2 work as do a secondary burn which burns the hydrogen gases etc and leave me with nice steam smelling exhaust?

Has  anyone put the p channel  under the  box instead of on top?  (seems to me the air intake would be inline with the flow of flame and gas instead of being forced downwards which disrupts the horizontal flow....yes, I know I would have to blow/clean the p channel out if it was placed on the bottom) ?

In Option 1, how long does my 6" riser have to be?  Kirk Mobert's doesn't seem to be as tall as described by the spreadsheets or formula for these types of stoves.  The answer seems to be 43" for a 6".... can it be 32 to 36" and work correctly?

If you have viable answers to these questions, please take the time to answer!!!   And by all means, make the suggestions you want to also.

Hi Orin;  Welcome to Permies!
Yes, Kirk's tiny house batch build is very nice!  
Converting yours to a batch like his ... well basically you disassemble yours , collect , locate , buy  a big pile of clay bricks to go with your firebricks.  Then you build one from scratch.  


About your J tube build. Is that metal I see at the top of your riser ?
Is that a complete system ?

thomas rubino wrote:Hi Orin;  Welcome to Permies!
About your J tube build. Is that metal I see at the top of your riser ?
Is that a complete system ?

yes, I used a 6' stove pipe and surrounded it with firebrick. I believed the metal would heat up quickly and achieve a higher temp than the firebrick.

complete? well, I used it this winter to keep warm :)   The cob needs a finish layer. Here is a link to the complete build: the build of the 6" system

I definitely will get more bricks. But i intend to keep as much as I can....sort lazy that way. if I can make it work with less work, I'll do it!

Orin Raichart wrote:Has  anyone put the p channel  under the  box instead of on top?  (seems to me the air intake would be inline with the flow of flame and gas instead of being forced downwards which disrupts the horizontal flow....yes, I know I would have to blow/clean the p channel out if it was placed on the bottom) ?

A p-channel on the bottom of the firebox is called a floor channel, its workings are different and it's a bit more complicated to make. As such it's similar to the secondary air channel developed by Matt Walker.

Orin Raichart wrote:In Option 1, how long does my 6" riser have to be?  Kirk Mobert's doesn't seem to be as tall as described by the spreadsheets or formula for these types of stoves.  The answer seems to be 43" for a 6".... can it be 32 to 36" and work correctly?

Donkey's cyclone batch rocket is a smaller system, it's a 5" system if I remember correctly. So the riser is shorter as compared to a 6" system.

I second Thomas, take down your J-tube and use the materials to create from scratch. Trying to adapt your existing heater will inevitably lead to cramped compromises.

Peter van den Berg wrote:I second Thomas, take down your J-tube and use the materials to create from scratch. Trying to adapt your existing heater will inevitably lead to cramped compromises.

Thank you Peter and Thomas for you expert opinions -alas,  I will take down the J tube...spring is here anyways.

One last question, can I still run the exit gases out my cob bench?     (say yes say yes please say yes....unless it really won't work)

Of course you can still use the cob bench. If you have a 6" system, you would benefit from a bigger mass and more heat exchange surface, even for a J-tube, and especially for a batch box.

[quote=thomas rubino......
About your J tube build. Is that metal I see at the top of your riser ?


Now I understand your question about metal in the riiser.   For those who haven't listened to this podcast uncle mud part 3, you might not know that metal in the core (feed, burn tunnel, or riser),  is a bad thing unless you have a specially desgined 4" system.  I'll change my blog too.

Wow things have really changed for RMHs....metal risers were all the rage 10years ago......listen to the podcast.....and you won't have to replace your core in one year or two!!!