Ratnesh Mathur

Glenn
So I implemented all the 5 suggestions - and the test fire was super success. The burn was awesome, no smoke, and wood sticks burning properly.
See video here https://www.youtube.com/watch?v=8fQk7A0KDdM
I think we are ready for doing the cob insulation.
Here are our current dimensions:
Feed Tube: Depth: 11", cross section - 7" sq
Burn Tunnel: Length 19": cross section - 7"sq
Heat riser (without pot) - 40" (with pot it will eventually go upto ~ 58")

Thanks Glenn for the quick response. Based on your comments - this is what i will try tomorrow (its night time here in India) and update:
1) Reduce the length of feed tube
2) Make sticks in feed tube vertical
3) Cut sticks to size slightly longer than the feedtube (11inches in our case)
4) Keep feed tube filled up
5) Increase the space between top of riser and pot to about 2 inches (right now its about 1/2 inch)

One question - if the sticks are vertical - where exactly does the sticks burn (flame) below the opening of the feed tube or below the burn tunnel?

SO here is a tiny video of the test fire we did after plastering the fire bricks (not yet insulated them with cob).
https://www.youtube.com/watch?v=bd3q27AV9r8
The ISSUE that is still bothering us is that after some 15-20 min of good burn the fire goes off. The long stick remains unburnt - sticking out of the feed chamber. How do we ensure that fire keeps burning - and yes why is it getting turned off?

The dimensions i currently have
A1 - we have is 11 - i can easily increase it by another brick to 15.5 - though not sure longer feed tube will make any difference.
B1 in our case is also 12 - making B3 as 26 (adding 7+7 width of both feed + riser)
R2 in our case is 38 as compared to 51 of your setup. Let me increase this by two bricks (9") to 47 and see how it goes
Will clay mortar it tomorrow - and test fire it day after and let you know how it goes
thanks

Thanks Thomas for sharing your dimensions - that would certainly help - only i am confused from where to where are you measuring. Just to be sure and clear - pl see the diagram below and clarify for me:

1) feed tube which is 16" deep is A1 or A2
2) Roof length of burn tunnel is 12"  is B1 or B2 or B3
3) Riser is 51" tall is R1 or R2
(All dimensions internal)
thanks

Yes Burra Maluca in the pic one layer of brick is missing in riser - which we added after the photo was taken.

Thanks Thomas
I like your suggestion of mortar with clay to close gaps and then try. Will do that tomorrow morning and update/
Also we did lift the pot up by placing two sticks between the bottom and the top brick
You said to shorten the burn tunnel - what ratios work best?

​I ma making a rocket stove J - using fire bricks.
This is for heating water for bathing in a pot
I am doing this in two steps​ -
First step (is where I am) we made the basic rocket stove stacking the fire bricks, test it, make any changes if required.
After rectification i will add Cob insulation around the firebricks and around the pot too. The heat riser will continue around the pot and then via a chimney the exhaust will be let out.

We built the rocket stove using 65 firebricks of 9x4.5x2 inches size
​Various dimensions are shown in pic below (all dimensions are internal). Pl note the pot and its insulation will have gap around it - to function a further heat riser.

See photos of our test construction and test fire here

QUESTIONS:
The heat we are generating feels less - what could be the reasons?
Fair amount of smoke comes out of the heat riser - its not smoke less - why?
The wood sticks do not keep going inside (gravity feed) - rather some of them just stopped burning after 30min or fell inside and stopped burning
We see fair amount of ash - what could be the reason for that?
Also we found it was not easy to start the fire - the fire kept coming out of the feed chamber only inside of going into the burn tunnel?

So here is my revised design (based on feedback of William & Glenn) - these are the changes:

Removed AshPit and side air-intake (B & C removed)
Lowered the exhaust chimney to bottom of the pot (I)
Added insulation of COB (L)
Heat riser is now partly the riser (E) and partly duct around the pot (H)
Move pot stand wedges to the outside edge of the pot (F)
Added dimensions in the sketch (not to scale)

Also considering doing away the masonry bricks totally and replace the whole structure with COB (ensuring the top of the whole system has a roof to save from rain)

Also need help with the material of the burn tunnel (D) and heat riser (E)
Are fire bricks better or should we choose metal pipe of 6" dia

Thanks in advance

Thank you William & Glenn for all the thoughts and suggestions. Am slowly absorbing them and will soon post a revised design - sketch based on them. That would also give me opportunity to see if I have understood your thoughts clearly. Thank you.