Build a J-Tube RMH - PEP BB rocket.straw.build

Can't believe I'm the first here, I thought I'd be scrolling through pages of wonderful creations to upload my evidence.

We built our rocket in 2015 and I've at long last gathered the evidence for this, my first BB! I've put the full build (as well as the changes we made in 2019) into an 8 minute video. If this is not acceptable I can post the separate pictures as you wish.

Going to try for the RMH build.

This was my first attempt in our under construction house.

I'm missing the video for running the RMH so I'll add that later but don't want to have to upload all this again.

This project was MASSIVE for me! Not just because of the pieces that had to be assembled, but also because of all the tasks which required leaning. Angle grinding, brick cutting, and figuring out cob, to name a few. Here's a thread I made, documenting my journey:
https://permies.com/t/270223/Rebekah-inch-RMH

I built this RMH, which I have named Daisy, in my greenhouse (this same building used to be a chicken coop/barn) Daisy is replacing an old camping stove with a lousy old, 6-inch black stove pipe that went all the way through the roof. Big improvement.

Alexandra Malecki showed me this design, which uses 4 barrels and way less pipe. She helped me know the supplies and specs and tools I would need! Thanks, Alex! For helping me figure out so much 🥰

Once I had the design, parts, tools and space for this project, then I had to figure out what material to use for the mass. Jeff Bosch taught me SO MUCH about cob. He answered a hundred questions from me about cob and rockets and helped me troubleshoot things like cracks. Thanks, Jeff!!!

I built the core from firebrick and the ceramic wool, 5-minute riser. I welded a frame for it from rebar, since I had a difficult time locating a 10-inch stovepipe. Thanks to my patient husband for teaching me to weld!!! The manifold barrels came from Clay McGowen, who brought them to me. Thanks, Clay! They're straight-sided, which gives Daisy's bell a lovely shape.

I used perlite cobbish to further insulate the core, and the first round of cob to level the manifold. The manifolds exhaust is an 8-inch pipe that leads to two barrels, which I welded together. Don't look too close! (I'm a welding noob and it's ugly...) but it sealed.

The vertical chimney juts into the stratification chamber over halfway to create a "juice box effect." 🧃 it then meets the ceiling with an appropriate box to transition to the double-wall pipe that goes above the roof. I placed a silicone boot over this exterior double-wall pipe, to help prevent any leaks. The code in my area requires a spark arrester, which I made from a dryer vent, and welded into place.

There are two cleanouts in this system. Besides the removable bell over the manifold, the stratification chamber barrels have an original lid and clamp that remains openable at the end of the bench. There is also a cleanout T in the vertical chimney.

The system has had very little smokeback ever since the first firing. I have lit it several days now to help dry the cob. Here is the video of me lighting it:

https://youtube.com/shorts/bjqpzZYFvow?si=fKd6RJZe40THtI7g

Finally, I spent two weeks cobbing Daisy into place. I searched FOREVER to find a local source of clay. Thanks, Downey! After making test bricks, I decided on a 1:1:1 ratio of sand, clay and soil from near my duck pond. Then I finished the cob with a layer of wheat paste finish cob, and used a yogurt lid to gloss over it, as Jeff taught me.

I am really happy with the process and the finished product!

I built an 8in J-tube rocket mass heater with an 8in exhaust. For this experiment, I dry stacked the firebrick (which I won't do again since the cob can shift the brick), made a "5min riser" (which actually took far more than 5min to build), and a juice box exhaust out of a double barrel bench. I also included a p-channel, version 2 ash scoop, metal dragon art, and a feed cover.

The radiator barrel is a functional cleanout and the end of the double barrel bench is also a functional cleanout. This system is very easy to maintain and works very well; no smoke <5mins.

I added a bonus photo of my cold start access showing an eyebolt attached to a handle to hold the kindling --> Uncle Mud's idea from the red cabin rocket that I think I made nicer.

Here's my video of starting the rocket: