Rocket mass autopsy

Hi All; I built my first RMH in 2013. An 8" J tube with traditional piped mass.
I had hardly a clue how to proceed. Thanks to Permies I learned a lot. I also made contact with Matt Walker of Walker stoves who gave me some great advice.

My mass was by the book. 8" pipe. With a 180 degree turn at the far end before returning almost to the core and then rising up to the ceiling.
I knew I should put a cleanout at the 180 but space was tight so no cleanout was installed.

Its 2020.  I just updated my 8" J to a 6" Batchbox.  It was time I fixed my cleanout problem.
Took the better part of a day to dig my way down 28" thru the mass.  
I finally located the 180.  After careful digging I unseated it from the horizontal pipes.
More digging to lower the floor to act as an ash pit. I built a red clay brick wall on the cement board side. Stopping apx. 8" from the top of the mass.
Some scrap sheet metal as a roof, some recycled bed frame angle iron as support legs .
Some 1/4" hardware cloth to mate up with the existing mass. Using reconstituted cob and a fraction of the shale I removed I refilled above the roof.

Now instead of having to traverse a 180 degree turn. The hot gasses have a small bell to give off some extra heat and  will travel up and out of the system with less friction..

Was too hot this afternoon to light it off.  Tomorrow morning  it will be plenty cool enough to let her rip!
I'm looking forward to it!

My arms are sore from just looking at the pictures.  

Fired it up this morning!  Lots of little smokes , some I cobbed shut , some just stopped on their own as things start to dry out and heat.
I needed to use my "bypass" to encourage the smoke to head up the chimney.   Heating the stack red just as it comes out of the mass really does the trick!

Its the little modifications like this that really are important to the long term functioning of a rmh that are easy to skim over when your first building it because you just want to get it burning.
I know the feeling all too well. Thank you for sharing Thomas.

Hi All;
Back with an update.  I spent about 5 days attempting to dry out and make this chimney draw.
A dismal failure I'm afraid.  
Seems that 11' away from your core there is not enough heat being generated to have an 18" bell...
Would work for a while and then decide to smoke back thru the intake...

Yesterday I had had enough!  I removed the almost dry cob and my new bell roof system.
I placed 4 horizontal insulated bricks directly across from the incoming and outgoing pipes.
I created a new roof with hardware cloth and cement board.  Sitting on the horizontal pipes and the insulated brick, it create's a small clay box .
Apx. 10" tall x 20" wide and 12" deep. It worked perfectly as soon as it was lit! Wet cob and all!

Lesson learned)  With a piped mass, A SMALL bell works with less restriction than a 180 degree piped turn.
A large bell doesn't work well at all.