J tube Rocket failure, thinking about converting to Batch box

My several year old j tube it starting to experience catastrophic failure of the feed tube.  I think it might be in part to wiggling wood and trying to get it to fit. I was considering converting it to a batch box?  Anyone have any tips or experience in doing such a thing?  Threads you could point me to in the right direction? Thanks!

Hi Eric;
Sorry, your J is feeling poorly.  Here is the thread with converting my studio stove to a batch.
https://permies.com/t/148226/Dragon-Transformation-tube-Batch-Box
And here is Gerry's conversion
https://permies.com/t/132799/tube-Batch-Box-Conversion
Here is my shop stove being converted
https://permies.com/t/138779/Breaking-News-Shop-Dragon-admitted
This is my mockup before changing the shop stove over from a J to a batch
https://permies.com/t/136577/Mocking-batch-box-core
This is my shop stove getting rebuilt after using the low temp bricks.
https://permies.com/t/140568/Dragon-flames

This should keep you busy for a bit this morning.

Hey Eric,
Does that fissure in the cob extend all the way into the core with the firebricks cracking as well?
If my memory serves me correctly, your feed tube faces a corner wall.
In case I'm wrong, could you re-post the link to your build so we can see more of what you have and what your dealing with?
Assume your doing research and planning on building after winter is over?....or are more like me and just went for it while the snow was still flying?

PS... Here is another example of a conversion:
J to batch conversion

Gerry Parent wrote:Hey Eric,
Does that fissure in the cob extend all the way into the core with the firebricks cracking as well?
If my memory serves me correctly, your feed tube faces a corner wall.
In case I'm wrong, could you re-post the link to your build so we can see more of what you have and what your dealing with?
Assume your doing research and planning on building after winter is over?....or are more like me and just went for it while the snow was still flying?

PS... Here is another example of a conversion:
J to batch conversion

Not in a corner.  The crack is on both sides and extends into the firebox, the bricks arn’t cracked but have pulled away from each other.  ( I think my wife really tries to shove stuff in there that clearly doesn’t fit)

My build is located here

https://permies.com/t/89382/RMH-Builders-guide-build-pic


It really hasn’t affected performance, but I have noticed a Smokey smell and I couldn’t pinpoint where it was coming from. I think I found the culprit.  I’m not going to address it until after this winter.

thomas rubino wrote:Hi Eric;
Sorry, your J is feeling poorly.  Here is the thread with converting my studio stove to a batch.
https://permies.com/t/148226/Dragon-Transformation-tube-Batch-Box
And here is Gerry's conversion
https://permies.com/t/132799/tube-Batch-Box-Conversion
Here is my shop stove being converted
https://permies.com/t/138779/Breaking-News-Shop-Dragon-admitted
This is my mockup before changing the shop stove over from a J to a batch
https://permies.com/t/136577/Mocking-batch-box-core
This is my shop stove getting rebuilt after using the low temp bricks.
https://permies.com/t/140568/Dragon-flames

This should keep you busy for a bit this morning.

Thanks so much! I’ll let you know if in a few weeks after I go through it if I have any questions. Bahahahaha

More pictures

Eric, what about troweling a little fireclay mortar into those voids? It's an inelegant kludge but it might solve the smoke issue for the remainder of the heating season until you tear it down and rebuild.

I have a pretty long 8” tube in my mass, borderline as long as you can make one based on the calculations in the rocket mass heater book.

If my 8 inch j tube runs the long pipe without any trouble, a batch box should work well with it also correct?

I’m trying to figure between a 7 inch batch box and 8 inch…… how much height should be between the top of the riser and the lid of the barrel, I’m having trouble finding this dimension.  I’m limited to an 8 foot ceiling, so I’m not sure I will have the space available to pull off an 8 inch batch box system with a tall riser and a tall distance between the riser and barrel.

How close can the barrel be to a sheet rock ceiling?

Dimension wise I can pull off a 7 inch pretty easily I think, but can a 7 inch drive through my existing ductwork in my bench.

Thanks for looking at my ramblings!

Hi Eric.
A batch box of the same size will be a lot more powerful!  
I think you could get away with a 6-7” in gap above the riser but there seems to be no upper limit so basically the more the merrier.
I saw a good analogy from Peter saying that a J tube just burns the tips of the wood but, a batch box burns a whole load at once making it much more powerful.

Fox James wrote:Hi Eric.
A batch box of the same size will be a lot more powerful!  
I think you could get away with a 6-7” in gap above the riser but there seems to be no upper limit so basically the more the merrier.
I saw a good analogy from Peter saying that a J tube just burns the tips of the wood but, a batch box burns a whole load at once making it much more powerful.

This is great news!

I have another batch box question. On my j tube I have to close up the feed box with bricks when not in use to prevent warm air from getting sucked out of the house.

Does the secondary air port on a batch box need shut off when the stove isn’t burning for the same reason?

Eric Hammond wrote:I have another batch box question. On my j tube I have to close up the feed box with bricks when not in use to prevent warm air from getting sucked out of the house.

Does the secondary air port on a batch box need shut off when the stove isn’t burning for the same reason?

I always closed my combined air port after the fire was out for that same reason.
The thermometer I had in my chimney stack always dropped quickly after I did this which proved to me that it was worth it.