I suck! unfortunately my rocket stove does not.

[morpho]

Thought that might get your attention!
This used to be in the thread "minimize me" but it's a whole new problem.


Ok....I am now on version 4 of the 6" stove (Yes that is 7 trials in total in two days) and I can not get the 6" one to function. It simply does not create enough of a draw. The flames simply climb up the kindling in a sad unimpressive way. No cool rocket sound...just a lot of smoke and flames in the feed tube.
The tunnel is half the height of the riser....all the interior dimensions are 5"x6" Nothing is smaller than the tunnel. I tried making the feed tube a bit smaller. I tried making the tunnel a bit smaller. I tried praying to the fire gods.
Anyone have any advice?

Thanks.

[swizzlenutz]

Do you have any pics? What is the length of the burn tube and the riser? Swizzle

[morpho]

Hi Swizzlenutz.
Thanks for the response.
I could take all sorts of pictures....there is no way my interweb connection will send them though.
The burn tunnel is 12" inches long and the riser comes in at 32"
I've tried them both in different configurations etc.
Is it possible that with the smaller dimensions any and all openings between the bricks just makes it to...sucky ....everywhere else other than where I need it? (remember this is a mock-up not a finished unit)
hmmmm?
Sounds like a chance to play with more fire.

Any thoughts?

[grizbach]

Howdy Morpho, I am experimenting with a new rocket also. Mine is a 5 incher though. Do you have a burn barrel on it? The draw really slows down once the barrel is placed. I actually increased the area between the riser and barrel to twice the recomended size to get a good pull. It still dosen't roar like my pocket rocket though.

[swizzlenutz]

If you want you can send me the pics and I'll see if I can't resize and post them for you. You could be getting a bit to much air flow in between the bricks. Maybe slap some mud on the cracks and crevises just to see what happens. I would try to add another layer of brick around the top of the riser to make it a tad taller. I've only built one decent backyard model so far so please don't think I'm an expert on this. These are just things that I would try. Once I had mine going up the chimney I would start by closing the front off the stove off on the top half and leaving the bottom open. At night to close it down I would place a couple of bricks that have the holes molded into them in front of the opening and by morning it'd be all ash. My riser was a 8 inch pipe about 36" long and my opening was made out of 4x8x16. The opening must have been pretty close to 8". I have a lot more experimenting to do. Swizzle

[Donkey]

The mess is outside, I'm assuming from yer earlier posts..
Make sure all the cracks are sealed up. Schmeer 'em with mud like swizzlenutz said.
Start the stove with the barrel off and see how it runs like that. It should just scream along. Get a friend to help lower the barrel on, but don't seal it with the base, make sure that the flow just wooshes out at the bottom of the barrel.
If the fire peeters out at this point, the gap between the barrel and the top of the heat riser is too small. Adjust till it runs well again, then seal the bottom of the barrel with your manifold/piping in place. If the stove fails at this point, either there's a constriction at the manifold end (the most common), a constriction somewhere down one of the pipe runs, or the runs are too long and leaving too little heat left over for a vertical chimney.. Pop the vertical chimney off and see if it improves. If it does, shorten yer runs till it works or perhaps step down in pipe size.

[hpmer]

I think insulation is an important component as well. Since it is a mock up, I assume there is no insulation which perhaps is not allowing the burn tunnel to get hot enough?

[swizzlenutz]

Hmm...I was thinking about my outdoor set-up. I was actually thinking about using the top and sides of the burn tunnel as extra mass with the tunnels running down at least one side of it. Would that be considered insulation? Swizzle

[Donkey]

The burn tunnel and heat riser should be as insulated as possible. Don't, I repeat, DON'T take heat away from the exhaust until it's left the top of the heat riser.

That said, your outdoor model should still run without the insulation. Especially with the barrel off, though it should work with the whole thing closed in and no insulation, just not as well.

[morpho]

Yup, that was it. Once I sealed up the cracks it went like a charm.
So now I'm hoping that once the barrel is on it it keeps drawing.
How much loss in "rocketness" should I expect once the barrel is on it?

Also...this thing is getting pretty freakin tall as i have it built up with an air pocket over the wood floor then the insulation etc. The whole thing will be sitting close five feet tall when the barrel is on it.
What would happen if I shortened the burn tunnel, shortened the riser to the correct ratio and then cut the barrel down a bit?

Oh what a tangled web we weave when first we practice to make heat.

Thanks everyone!

[Donkey]

umm.. Shortening the riser (as long as the tunnel is shorter too) might work, though it's best to get the riser as tall as is practical.
If you've got room to shorten the tunnel, I'd say do it no matter how tall the riser is. Best to make the burn tunnel as short as possible.

As to loss of "rocketness" it all depends. You can't expect the lusty roar of a pocket rocket or a naked riser. Whatever happens, it should still all go in the right direction AND do it snappily.

[morpho]

Thanks for all the info and thoughts everyone.

Seems to be working well now and i think i will just try and keep the barrel the normal height.
I have another question....go figure!

So I am looking at the diagrams, reading the book again and nowhere does it mention or show that the riser insulation needs to be cut and shaped around the burn tunnel and made to continue down to the bottom of the whole assembly on the opposite side, but I am assuming that is how its done. Am I wrong?

Thanks anyone.

[Donkey]

I've seen it work fine without.. Sometimes it's not entirely practical, so you can fudge it.
But, I'd say the best policy is to get as much insulation around the burn tunnel and heat riser as you can. If you can wrap the whole mess, do it.

[morpho]

ok, thanks.

Can anyone tell me if the heat exchanger be too close to the feed tube?
In the current design it comes within about an inch of the edge of the feed tube.
The tunnel is currently 10" long....should I increase it a bit to separate them or is a short tunnel a greater imperative?

[morpho]

Well, I got sick of testing so I just put my nose to the grindstone and built it inside the shelter.
The mock-up worked well outside. (after version 9)
I built it with extra care.
I stood back and lit her up today.
It went pretty well all things considered.
As it burnt it progressively became less able to draw.
More and more burning up the firewood past the burn tunnel height.
It really seemed to have a hard time just burning the ends. There seemed to be pretty good draw so I'm not sure what's wrong. If I didn't tend it constantly it just crept up and out of the feed tube. I hope it's just my inexperience with stoking it. Otherwise it's going to be a very long winter looking down the feed tube to make sure I don't burn down my winter shelter!

About an hour after it went out the CO alarm started yelling at me to run for my life.
So I opened the door.....which let out the heat i had produced...kinda counter productive in the end.

Any words of advice?

Thanks anyone.