I suck! unfortunately my rocket stove does not.

[swizzlenutz]

It may be due to the whole thing still being wet. Sometimes it takes a firing or two to dry out the concrete or cob. Check the whole thing over good when its hot, you might be getting some cracks that aren't showing on a cold stove. I would definitely wait for Donkey and some of the others to chime in first before firing it up again though. Until then pull out the sleep bags and thermals and bundle up. Good luck and please do all your testing well your awake. I'd hate to see a fellow "Cob" jobber get hurt playing with fire. Swizzle

[Donkey]

Could be wet cob.
Did you run it as you built it, or did you build the whole mess before you lit the fire? It's REALLY helpful to find out at what point it starts acting up. There might be a constriction somewhere. Sometimes, early on with wet cob, there can be a WHOLE LOT of water vapor in the exhaust stream, it will go down-pipe and condense out on some cob, making it too wet, so it will slump. Cob slowly slumping into the exhaust path can give really confusing results.

If you are using soft wood, that could be part of the problem. Softwood tends to allow fire creep. Hardwoods tend to keep the fire down where you put it.

How long is the bench, what side of the house is the chimney on? It's possible that a long bench and a chimney on the north, in the shade can cool down (things) enough to keep gasses from rising out while your coals are still smoldering.

[morpho]

Nope still no go.
Last night was another lackluster burn. I managed to keep it going for 4 hours, but I was constantly having to fiddle with the wood. It would pull fine...then all of a sudden it would start to rapidly eat its way backwards in the feed tube...then rapidly up the feed tube, then i would rapidly do the fire dance and then rush to open the door to let out the smoke.
My little Carbon Monoxide alarm has been working overtime!
I have now pulled the barrel off....added another course of brick to the riser. It is now a little over 4 times the length of the burn tunnel!
I'm running out of sand, I'm running out of brick, I'm running out of patience.

P.S. I'm sorry I can't reply to everyones posts personally. My internet connection is so slow. It can take me an hour to get connected and sometimes 5 minutes for the rocket stove log-in page to appear more time for the page to load up etc. etc.
Ain't technology great?!?

[morpho]

thanks swizzle!
I am doing my best to not die.

there wasn't any slumping that i could see after I took the barrel off.
The bench is short...like 4 feet short...not cobbed yet....just the pipe.
The chimney is on the south side and without a vertical stack for the moment.
The wood could be the issue. I'm in Western Canada....all we have is softwood.
I have some old oak flooring a buddy is bringing out to me to burn....maybe the local high school gym will mysteriously get stripped of its floor this winter!
I don't know....I guess I'll build up the base some more....lower the barrel...cobb her in place and fire her up again.

thanks!

[swizzlenutz]

Maybe try cutting your wood in half. Shorter pieces should be less likely to burn back up the burn tunnel and hopefully keep the fire where its suppose to be. I don't expect you to answer my post. I know how slow the internet can be and what a pain it is. Just answer the experts and get it done right. Hopefully you can get it up and running before old jack frost comes charging in full blast. Swizzle

[grizbach]

It's been my experience that short wood heats up quicker and is more likely to smoke back.
You said that it starts off with a good draw. Could it be you are getting a lot of coals at this point and this is creating too much heat in your burn tube?

Since you don't have any mass yet your exhaust is probably pretty warm. Use this energy to create more draft. Vertical stack! You will be suprised what 5 ft. will do!

[Donkey]

The breathing in and out pattern I've seen before in stoves that have a constriction down the run somewhere. It will run forward, then back up and smoke, then run forward again, etc, etc..

You're gonna hate this, but you've got to open all the doors and windows in your house, pull the barrel off and the piping back, start the stove and add each component till it fails again.
It feels to me like you've got a constriction or narrowing or some kind of mismatched volume down the pipes somewhere.
Through the process of elimination, you will find the culprit! But, yer gonna have to smoke the house. Actually, with the rocket running well there should be VERY little smoke. You shouldn't see smoke till you find your problem area.

Yikes, be careful.. You live in a wooden house, don't you?

[morpho]

Lots of advice.
Thanks.

Short wood longer wood not enough heat too much heat.....
I'm sure there is a solution.

The best luck I had so far was burning a single 2x4 pushed flat against the burn tunnel and then a brick up against the 2x4 so the draft had to pull past the 2x4...it still crept up once in a while but it was way better.

I fired her up without the barrel on it today....went fine. I put the barrel on.....went fine-ish (to be expected I guess when you add the barrel.) I had to stop the experiment as it was getting to dodgy inside here!
Sure was smoky in the old refugee hut!

Donkey the "house" is literally a 20x20 temporary post and beam around my little old trailer. This is all wrapped in vapour barrier and then wrapped in unplastered strawbales. 2 tarps are secured over the whole mess. Open flame? what me worry?!?! Naw!

Its kinda cool....really ghetto...and I don't mean north american ghetto. We are talking third world ghetto!
My niebours are less than impressed.

Ok.
I'm going to cob the barrel on and go scrounge some wood.

Thanks again for all the advice everyone.

[Donkey]

You might want to try lifting the barrel up an inch or so.
At the top of the heat riser is a pretty classic choke point, and I think that the gap there should be a little larger than the math (the book) says.

[morpho]

cough!
well it burned pretty well, then the wind came up and shot flames and smoke into the place....that was fun.
The next burn went pretty well...very little smoke and flame creep as long as I tended it pretty closely.
So be it! This is an experiment and a way to keep warm for a few months until spring comes. I will be able to see if this will be something that gets built into the new house.

The barrel is actually 3 1/4 inches above the riser so I would hope that is enough space.
Either way... it is what it is.

I'll keep monkeying with her a bit and post any results.

Has anyone employed a little DC fan at the end of the stack to create a bit more draw?

My wife had a great idea for all those people who wish they could watch the flames.....(we find ourselves standing above the feed tube all the time watching it and not just because we are worried about the fire creeping up) She said: "we just need to get a little web camera and project the fire onto the wall, then we can sit down and stop straining our necks"

Thanks everyone.

[canyon]

Nov 20, 2009 9:15:07 GMT -8 morpho said:

Has anyone employed a little DC fan at the end of the stack to create a bit more draw?

She said: "we just need to get a little web camera and project the fire onto the wall, then we can sit down and stop straining our necks"

Did you add a vertical stack outside yet as Grizbach mentioned?

How about a mirror?

[morpho]

yup the vertical stack may have helped a bit.
Hmmmm? a series of mirrors. I like that even better.
Maybe add one of those old fresnel lenses people used to put in front of the TV so it looked bigger. This way it might look like an 8" system!

[morpho]

So about an hour into the last two burns I did the flames start to dance back and forth into the feed tube. I can reach into the tube and it does not seem all that hot. The surrounding cob is not all that warm either. But with that said after an hour the still exposed stove pipe is barely warm. I'm sure this means something is not working right. I'm losing too much heat somewhere I "don't need it".
I insulated as much of the burning areas as I could. I'm at a loss.
The only solution I have so far is to let the longer wood burn down when it starts to fluctuate and then start feeding 3 inch pieces of wood into the burn tunnel so there is no chance anything can come back up into the feed tube. (the flame still fluctuates, but it never actually sends smoke into the tube.) I have looked inside the clean out and see no slumping, nothing seems to be blocking the flow. I seem to have enough room all the way around....I have measured and remeasured the feed tube, burn tunnel and riser and nothing is out of proportion.
So I don't know.
Maybe I am destined to have forced air heating.....sigh....or maybe version 10.0 will be the magic one that really works.
I think next time I would look harder for 8" pipe and make the riser even higher! And maybe add an alter to the stove so I can make offerings to the draw gods.

Thanks everyone.

[Donkey]

OK.. Perhaps you are loosing so much heat to the system that the chimney won't work right.

Try this, at the end of the run reduce the size of the pipe you are using. Try reducing to a piece of 5 inch or 4 even inch pipe. The flue gasses should cool and contract considerably by the time they get to the end of the run. Smaller pipe diameter will run hotter and perhaps draft better under the circumstances..
It'd be good to find a way to try it out before buying fittings and things that you might not be able to use. ... Umm, maybe take your 6 inch chimney piece, open it at the seam (they are just pressed closed), roll it a little tighter and perhaps use some bailing wire to hold it that way. As a temporary measure, you might be able to cob it in to get a good seal. Or if you've got access to a dump (or transfer station) that takes metal trash AND will let you scavenge, maybe you can just pick up some 4 inch pipe and what-not.

How long is the total run anyway??

[morpho]

Well, I'm not sure what changed....I fired it up this morning and it went like a charm.....more or less...better than it has been working.
I will add a smaller diameter length though just to see what happens.
The total horizontal run is only four feet. I know this is not the prescribed idea, but I have very limited options in this temporary set-up and I just wanted to build one and see if I liked it.

Hey! We had our first Rocket stove espresso this morning! Was great to sit back and drink a cup and not have to stand over the feed tube with a fire extinguisher and a look of dread on my face!

Thanks everyone for all your input and advice......now if I can just figure out how to replace the shattered glass in the scavenged solar panel we will have electricity!