Rick A. Lawrence

Fox James wrote:Hi Rick, there are hundred of detailed builds on this forum thread, some feature very basic construction methods others use the latest high tech materials.
So the best know workable formula for a J tube design is based on a 1-2-4 format ie the feed tube is 1 foot the burn tunnel is 2 feet and the riser is 4 feet.
We try to avoid any deviation from the system size, so if you build a six inch diameter feed tube then the burn tunnel, riser and chimney will also be six inch diameter.
You want to avoid as many bends as possible and ideally there would not be any elbows or bends after the barrel exit.
You will get a better performance using a bell rather than a piped mass.
It is possible to deviate from the tried and tested dimensions but not recommended especially for a first build.

I'm an inventor and I never just go off the plans of others in anything I do. I have built everything from a builders foam mini bass boat

to a complex trebuchet from my own plans having never done it before.

I would much rather experiment and fail, if that is how it turns out with my own designs. If I fail I try to figure out why, make the needed changes, and try again. That's the only way to come up with truly new ideas. I do however listen to opinions of others on subjects I'm not skilled in and make tweaks to my design if I think it's needed.

Glenn Herbert wrote:

A nitpick: I see your drawing shows flame in the burn tunnel/riser base, then smoke in the riser, then more flame in the donut at the top of the riser. I know people have talked about a "reburn" at the top of the riser, but from my experience that is not how it happens. The air and fuel gases mix in the burn tunnel and more in the riser, and all of the combustion happens there. Sometimes the flames end well before reaching the top of the riser, sometimes they do reach the top depending on conditions, but they do not burn again after leaving the riser.

I have seen this talked about in many of the sites I have done research at before I drew up my plans. I'm not sure one could prove or disprove this theory without making one out of glass, so you can see what happens. I was just assuming it was a fact due to my lack of knowledge on the subject.

You don't mention the space this system is intended to heat. A 6" J-tube system can heat a small house or large room in a real winter climate, while an 8" J-tube can heat an average house that is compact and not chopped up into little rooms. This is assuming the structure is reasonably well insulated. Some more information will help us give the best advice here.

The area I plan to heat in cold winters here in N. Idaho is about 1400 sq. ft. with a half basement and I think I'm planning to put this in the basement with heating/AC ducts to the main floor.

Phil Stevens wrote:I'm referring to the horizontal section from the 90-degree bend after the dampener and leading to the tee with the fan.

OK tnx, another question.  Doesn't cob turn rock hard after it is fired? I don't see how you could reuse it.

Consider a Consider a stratification chamber (a bell) instead of the piped mass.  (a bell) instead of the piped mass.

Also, I dont know what stratification chamber or piped mass means.

Phil Stevens wrote:


1)  That long horizontal run of the flue is not a good idea. The fewer bends and departures from vertical in your chimney the better it will draw. Ideally, you'd go out the back of the mass and straight up through the roof. You probably won't need the fan if you build everything according to fully tested and debugged plans.

Phil,
Do you mean the Part between the labeled L and the fan or the part labeled J?

I want to build my own design of rocket stove with some ideas I came up with. He is the basic plan. The Idea is to build a stove that will burn a small fire many hours very efficiently. It will use some heavy wall pipe and a 55 gal. drum as well as 8" stovepipe. It will also use a fan to help create a draft to get the fire started as well as dampeners to control the burn and turn the fan air off. Looking for any ideas on if there is something I missed or suggestions on how to improve this idea.  I plan to build a small scale working model this summer first to test it out before a make the large scale one in my home. I don't have any sources of clay near my home. So I was thinking of using concrete, but not sure how well it would handle the heat.