great forum, I have questions about a rocket build.

Hi there all.


Great forum here, so I get already a question.


I have drawn a rocket mass heater and want to build, I did however saw that the burn tunnel needs smaller as te rest and the wood chamber the same as the chimney pipe and rizer.

idea was the rocket and a brick tower for heat battery, and up to chimney on the roof 7 meters high, I do need a resporator on it with a motor, I do build these and tig welding it together,
that way with a regulator the rocket is more easy to ignite and also I make the chimney virtual bigger in diameter.

I go use concrete slabs and a layer of 30 or 50 mm  calcium silicate plate a layer of firebricks 210 x 105 x 30 mm and the rest with 210 x 105 x 50 mm firebrick, the yellow ones and
the tower is blue concrete bricks who work fine as a battery, she do not spattering because there the heat is not high enough but it do charge very good.


Thanks on forehand for your help, in dutch ecologie forum I did get no right answers.

regards

Hi Kees;  Welcome to permies!

I will try to answer your questions as best as I understand them.  Please forgive me if I misinterpret your questions.
Your sketch up of the base looks very good. I think that looks like a properly built safe base.
Your design of a rocket core and riser also looks good (must be sized properly)
Your last sketch up is the most confusing for me. This looks to be a chimney cap ? Hand made,  possibly a revolving cap ?  Do I see a size change in the construction?  
If I understand your question) you are wondering if you need a fan (blower) on the chimney stack ? If that is the question the answer is No.
 Of course there are exceptions where a fan might be needed to start a draft. But as a general rule in most builds , a properly built rmh with a proper warm chimney stack , will have no need of mechanical assistance.

thomas rubino wrote:Hi Kees;  Welcome to permies!

I will try to answer your questions as best as I understand them.  Please forgive me if I misinterpret your questions.
Your sketch up of the base looks very good. I think that looks like a properly built safe base.
Your design of a rocket core and riser also looks good (must be sized properly)
Your last sketch up is the most confusing for me. This looks to be a chimney cap ? Hand made,  possibly a revolving cap ?  Do I see a size change in the construction?  
If I understand your question) you are wondering if you need a fan (blower) on the chimney stack ? If that is the question the answer is No.
 Of course there are exceptions where a fan might be needed to start a draft. But as a general rule in most builds , a properly built rmh with a proper warm chimney stack , will have no need of mechanical assistance.

Hi Rubino

The chimney cap you see is a ventilator with a motor, as you look well you see the fan itselfs between the plate.


The reason is I have a chimney of 11 cm diameter, and the rocket is for 15 cm chimney, smaller is not possible then I get trouble with wood blocks, I can not use a bigger pipe, it do not fit, so I go virtually make the pipe bigger, I can go as high as 20 cm virtually, and a
nice side effect is I have always draft, I build a regulator for the motor rpm, so I can adjust when needed,


The rocket is not yet properly adjusted in dimensions because I do not now what is the best, on our dutch forum there is a guy Peter van den Berg who did experiment with a kind of plate or modelled stone for afterburn support, that did work very nice see the movie
here.

https://www.youtube.com/watch?v=VEAJSP4D9Mo

Did use concrete stone for street, but for test it was fine, as not insolated it did burn nicely.


I did hear that rocket do not smell to smoke outside, so it is interesting because of complaining nabures, I have now a steel box as a heater, a normal woodstove.

I did also read a suare from red stone blocks, filling it with perlite and then there a layer of fire stone do also work? the calcium cilitate is expensive.


regards

What is the length of the 11 cm portion of chimney? How much of it can not be made bigger due to existing holes or whatever?

If you can make most of the chimney bigger, you may be able to work with a constricted part of the chimney... this will depend on a lot of factors in your situation, so the more detail you can give about your house, the better the answers we can give.

With a restricted chimney size and thus system size, I would recommend you look into a batch box instead of a J-tube core. A batch box delivers heat much faster for the same system size compared to a J-tube, and the firebox of a batch box will be significantly bigger than a J-tube feed. Peter van den Berg is a world leader in batch box research and design, so you can get the best information directly from him, as well as from his website batchrocket.eu.

Glenn Herbert wrote:What is the length of the 11 cm portion of chimney? How much of it can not be made bigger due to existing holes or whatever?

If you can make most of the chimney bigger, you may be able to work with a constricted part of the chimney... this will depend on a lot of factors in your situation, so the more detail you can give about your house, the better the answers we can give.

With a restricted chimney size and thus system size, I would recommend you look into a batch box instead of a J-tube core. A batch box delivers heat much faster for the same system size compared to a J-tube, and the firebox of a batch box will be significantly bigger than a J-tube feed. Peter van den Berg is a world leader in batch box research and design, so you can get the best information directly from him, as well as from his website batchrocket.eu.

hi Glenn


I do now the batch rocket, but need some extra difficult work like a door and glass, I do like the old fashion rocket much more, and the chimney ventilator I do build myselfs, even a electrostat fine particles filter I did want to make, I can al do this myself because I am technical engineer and do electronics, so this is not the trouble, buying a ventilator is very expensive above 500 euros and closer to 1000, I can tig weld so that is made myself very easely including the regulator.


Mine chimney is 8,40 meters long in center of the house, until the roof, it is a flex tube put in the old measonry chimney who has leaks and now it is oke again. The only part that can be 15 or even 20 cm is the part in mine home, wh is then around 2 meters until it dissapairs into the channel.


Maybe in the future I do try the batch, but for now I stick to a  J-tube.


Do you now what the calculations are for a 15 cm j tube? I do read that these are not equal everywhere and that this is important. The burn tube for example is smaller but how much? is there a formula for that?


I did want to use a 200 liter oil drum, however this is quite big for a room of 27 square meter and 240 cm high, I did read 60 or 100 liter drums are also used, but then maybe the rizer get to short.


thanks in advance.

If your chimney is that tall and in the center of your house, you will probably get better draft from it than you expect.  I would not hesitate to design a 12-13 cm J-tube for that situation, a 15cm might work but I couldn't guarantee it.

A J-tube core is ideally the same dimensions throughout, but if the burn tunnel is a bit smaller, that is okay. So make it all 15 cm square. The riser can be 15 cm diameter and work as well, since square channels have about the same capacity as round of the same diameter due to poor flow in the corners.

I have a 7" wide x 7 1/4" high burn tunnel and feed tube, and a 7 3/4" diameter riser that is several inches shorter than optimum, in a masonry bell, leading to a 6" diameter temporary stovepipe that is only 12' tall above the feed level. It drafts fine.

If you want to use a smaller drum, you can set the base of the drum on some layers of brick to raise the top to the height you want. You just need to make sure there is enough space around the riser for gases to flow freely - the free drum cross section space should be at least 2 or 3 times the system size.

Hi All


Thanks for the tips.


I had seen on a dutch site that the burn tunnel is smaller, and that did confuse me because other like here say it needs the same all over. I can
imagine me that a smaller burn tullen can give more turbulency, one of the pics is from a kwown book who says also C is smaller the the other channels.

So a lot of different setups and succes rates.


see pic.

Note that the diagram says that C can be less than OR EQUAL to A and F... just not larger.

Glenn Herbert wrote:Note that the diagram says that C can be less than OR EQUAL to A and F... just not larger.

That it can not be larger I now, on the internet are a lot of builds, I keep it equal for shure then.

thanks.

Hi all


I have redrawn the rocket, the concrete is gone, I did use not red stones filled with perlite or other good insolation material please advice what is best.


This way it fit better in mine place, now I need the thermal batterie design, idea was a square tower whith on top mine shimney output it needs te be a downdraft
if this will work because the rocket allready has one.


thanks for advice.

kees