Instead of a J tube, I am testing a T tube... Prototype design testing testing.

7 inch T tube with aircrete.       I am impressed with the height of the flame.!

Nice experiment. What this can best be compared to is an L-tube, rather than a J-tube. For your long bamboo feedstock, it makes sense. A fully functional rocket core doesn't have any coals to remove, just mineral ash, and a tiny amount of that that needs removal only every few days. Have you ever built a by-the-book J-tube, to have a baseline to compare your experiments with?

I think you'd get a more complete burn if you closed one arm of the T. The draught will pull harder through the remaining arm, but it will keep more of its heat, burning everything to mineral ash and obviating the necessity for a cleanout.

-CK

Another way to accomplish balancing the draft would be to make both lower channels half the height of the riser width. You could still push the long fuel through, but you would get the concentrated flow.

Or you could do what I have done in two rocket L-tube cores, and make the horizontal leg at least 2 1/2 feet long, to allow a long flame path on the fuel, reaching very high temperatures and completely consuming the fuel. In numerous wood-fired cob pottery kilns I have built, I have found that the best results had a horizontal firebox over 4 feet long.

Glenn Herbert wrote:Nice experiment. What this can best be compared to is an L-tube, rather than a J-tube. For your long bamboo feedstock, it makes sense. A fully functional rocket core doesn't have any coals to remove, just mineral ash, and a tiny amount of that that needs removal only every few days. Have you ever built a by-the-book J-tube, to have a baseline to compare your experiments with?

I have read books on the subject but I don't have hands on experimental testing of the full J-tube, I have seen Paul light them and get them to burn and see the sideways flame.  
I have been working out in my mind  what are the advantages of either system.      What I don't like about the standard J tube is that you have to keep feeding it on a regular basis, I have seen some designs that make a box or tube to go over the feed so that long sticks can go there.      the advantage of this design is I can load up several bamboo polls and the draw will go from both directions.

The disadvantage is I am probably not getting the most clean burn,  i was thinking of moving this to a barrel system where I could store thermal mass just like a standard  Rocket thermal mass heater.
Perhaps I will add in from the other side a pipe like Peter has for bringing in more heated air as in a batch box design.


I see coals as an advantage in my case as I am looking to make charcoal and if I can get them to charcoal level with the volitles burnt off I can use them in my charcoal gasifier.     With this system I am getting more benefit when making charcoal than if I just burnt off the volatiles in a cone charcoal pit.


I can always close up the end on this and run as a standard batch box, I just like testing to see what works best for me.

Thanks for your input.

Chris Kott wrote:I think you'd get a more complete burn if you closed one arm of the T. The draught will pull harder through the remaining arm, but it will keep more of its heat, burning everything to mineral ash and obviating the necessity for a cleanout.

-CK

I have been thinking about a damper on one end I am thinking of a plug.      It should be fairly easy to convert this to a standard J tube with the plug.

I may also try adding a fan to the setup and see how it reacts to force air with one end plugged.


This sure releases tons of heat in a short burst of time,   I would like to use this to charge a large insulated thermal mass outside and then pull that heat inside via a fan.    I really want the rocket stove outside  so that I load it up once and can then walk away. heating a thermal mass right next to it, and then I pull the heat in via a heat exchange.    ( my theory of how this could work )..   still in mental process of imagining an outside rocket stove design.

Glenn Herbert wrote:Another way to accomplish balancing the draft would be to make both lower channels half the height of the riser width. You could still push the long fuel through, but you would get the concentrated flow.

Or you could do what I have done in two rocket L-tube cores, and make the horizontal leg at least 2 1/2 feet long, to allow a long flame path on the fuel, reaching very high temperatures and completely consuming the fuel. In numerous wood-fired cob pottery kilns I have built, I have found that the best results had a horizontal firebox over 4 feet long.

Yes a square pipe on the bottom heating the air and feeding heated oxygen  the fury of the chimney just like Peter Van's design with a batch box.  

Mart Hale wrote:

Glenn Herbert wrote:Another way to accomplish balancing the draft would be to make both lower channels half the height of the riser width. You could still push the long fuel through, but you would get the concentrated flow.

Or you could do what I have done in two rocket L-tube cores, and make the horizontal leg at least 2 1/2 feet long, to allow a long flame path on the fuel, reaching very high temperatures and completely consuming the fuel. In numerous wood-fired cob pottery kilns I have built, I have found that the best results had a horizontal firebox over 4 feet long.

Yes a square pipe on the bottom heating the air and feeding heated oxygen  the fury of the chimney just like Peter Van's design with a batch box.  

The same could be done by simply filling the entire tube with wood all the way, restricting the air flow for more draw.      I might try just one side restricting the air...   and I might try multiple pipes

Glenn Herbert wrote:Another way to accomplish balancing the draft would be to make both lower channels half the height of the riser width. You could still push the long fuel through, but you would get the concentrated flow.

Or you could do what I have done in two rocket L-tube cores, and make the horizontal leg at least 2 1/2 feet long, to allow a long flame path on the fuel, reaching very high temperatures and completely consuming the fuel. In numerous wood-fired cob pottery kilns I have built, I have found that the best results had a horizontal firebox over 4 feet long.

Ok I re-read this,  and I got another nugget of info.

2 1/2 feet long,   I guess that you using a J tube with this long of a burn tunnel?

Interesting setup with 4 feet of burn tunnel horizontally.

A J-tube has a vertical feed; an L-tube has the horizontal feed like yours. A J-tube can only safely use fuel cut to a length that fits inside the feed tube (when you are outdoors this is less important), while an L-tube can be much longer and take longer fuel.

An outdoor core and mass with air or liquid to move the heat to indoors will have very large conversion and transport losses. If you are depending on it for serious, long-term heating, there are much more effective and efficient ways. If you just want occasional supplemental heating, it may work for you.

Glenn Herbert wrote:A J-tube has a vertical feed; an L-tube has the horizontal feed like yours. A J-tube can only safely use fuel cut to a length that fits inside the feed tube (when you are outdoors this is less important), while an L-tube can be much longer and take longer fuel.

An outdoor core and mass with air or liquid to move the heat to indoors will have very large conversion and transport losses. If you are depending on it for serious, long-term heating, there are much more effective and efficient ways. If you just want occasional supplemental heating, it may work for you.

I agree the more the heat has to move the more heat is loss in transit.

I am in Florida, so I don't have to heat as much the coldest it gets here is like 25 degrees at nite then it will be 50 the next day.     Then 70 the next day.

In that case, a heat storage mass remote from the living space, that can have heat moved only as required, makes perfect sense.