RMH smoking when going out

So my RMH project is working! Burning ash kindling it works well but when I want to let it go out it starts smoking back into the room. Obviously at this point there won't be the heat to drive the system so is there a good way to deal with this? I'm guessing you're going to tell me to cover the burn chamber but thought I'd ask first

What kind of chimney do you have? What kind of horizontal ducting, and what mass? If you have any thermal mass and a decent chimney, that should help the draft even as the fire dies down.

It's a 6" RMH about 8m horizontal run then exits and goes up 3m outside, the first 5-6m is packed in about 2tons of cob and brick. Part of the cob warms up but definitely not the whole thing. It does keep drawing for quite a long time after going out but it's very windy here so we get the odd back draft when it's not burning strongly

Tony Morse : so approximately 26 feet of horizontal run, Added to the straight ducting we must Count every 90º Elbow as the drag on the draft that it is .

Every Single Elbow needs to be counted as 5' more of piping ! You are almost certainly beyond the safe 30' for a 6'' J-Bend RMH.

Lets look at slightly more likely causes for your problem!

Your #1 clue that your Rocket is doing exactly what you want it to do is to listen to the strength of your rockets roar, any thing that increases this is a

good thing. ( There must be an exception to this rule, I just can't think of it !

It is important to use small, very dry finely split wood fuel to start your fire, ideally you place enough wood into the mouth of Your Feed Tube so that the

air channels between the individual pieces of wood act like individual Chimneys pulling in air that flows past them keeping the wood cool except at the tips

of the wood which are burning increasing temperature and Efficiencies ! To much Air can cause a cooling effect on your burn - again your ear is your best

clue as to what is going on inside the Burn Tunnel- It is also a clue to check the temperature of the Magnetic Thermometer on your Barrel/Drum.


When you are burning less than a full load of wood you will need to reduce the size of the mouth opening to reduce the amount of air drawn into the fire;

And direct it more directly down past and through your Wood Fuel ! At the end of every single RMH Burn there is a reduction of Fuel and an Automatic

increase in the amount of air fed to the fire ! This cools the fire and is a major cause for increased ashes and Charcoal building up in the Burn tunnel and

Constipating your internal plumping ! //// See link Below :

http://s65.photobucket.com/user/mremine/media/NYC%20Rocket%20Stove%20Build/P1030331.jpg.html?sort=3&o=6

THis is the way to both choke of excess air and more directly channel it to where it needs to go ! Again your ear is the best clue to what your RMH needs !

For the Good of the Crafts ! Big AL