J-tube optimization

This has inspired me to do a simple and cheap destructive test.

Simply dangle three wires down the risers. One of aluminum (1221F), one of copper (1983F), and one of steel (2600-2800F).

Naturally, the hitch is that steel and aluminum will burn. I regularly see the reminders of this in Talent, Oregon near where I live where whole swaths of mobile homes and trailers went up in the Almeda Fire last year.  Also, have you seen any of the new Fords catch on fire? Aluminum burns in relatively low temperature fires. https://static-11.sinclairstoryline.com/resources/media/4ea39405-a32a-4bda-8bdb-292da0c8f7cb-large1x1_truck3.jpg?1577231444781
 They don't leave puddles of aluminum. Most of it is just gone.

Steel burns or at least rapidly disintegrates in RMH temperatures so that might not be as useful. It's not going to melt, at any rate, unless temperatures are getting into wildly optimistic ranges that I just don't believe when people talk about them.

That leaves copper. With its melting point and resistance to burning, I think it would be an excellent destructive test in this context.

Cool idea Solomon;

I see a stumbling bock though.
How will you suspend those wires?
Anything you use will bend.  
Draping them over an edge might work but the center of the riser is the hot point.

As far as your question of how hot to qualify as a rocket stove?
The answer, is as absolutely as hot as you can!
The design of a J tube alone promotes a good fire.
So any J tube build no matter how sloppy funky it might be... its still a rocket stove.
To be a rocket mass heater it needs to be tight enough to flow hot air thru the mass.

Innovator's like Peter Berg , Matt Walker, Ernie & Erica Wisner.  
Have made extensive modification's and experimentations to make the J-tube as hot and clean burning as possible!

With the J tube design Peter took it a few steps further in efficiency.
He then sold the design & rites of those improvements to  "Dragon Heaters".
With Peters improvements using a cast core they are the Cadillac of J tubes.

thomas rubino wrote:He then sold the design & rites of those improvements to  "Dragon Heaters".

Not entirely correct, sorry. They took a 5-year license for the whole of North America back in 2010 or 2011 and didn't renew it since then. So the design is open source for years now. It's also not easy to produce for just one cast, the molds are pretty complicated. That said, I shaped the first pair of molds in extruded polystyrene foam and got away with it, so it can be done.

Incidentally, the guys in Bulgaria building the Gamera rocket heaters asked they could use the design and are implemented it in their newer models.

Peter van den Berg wrote:

thomas rubino wrote:He then sold the design & rites of those improvements to  "Dragon Heaters".

Not entirely correct, sorry. They took a 5-year license for the whole of North America back in 2010 or 2011 and didn't renew it since then. So the design is open source for years now. It's also not easy to produce for just one cast, the molds are pretty complicated. That said, I shaped the first pair of molds in extruded polystyrene foam and got away with it, so it can be done.

I've been unable to find the exact design, is it available somewhere? A sketchup model or diagram?

If you are interested, I can delve through the pile of files and drawings.

thomas rubino wrote:I see a stumbling bock though.
How will you suspend those wires?
Anything you use will bend.  
Draping them over an edge might work but the center of the riser is the hot point.

I don't think it's a problem. At the top of the riser, steel doesn't burn out, especially not in one firing, not going to melt or bend appreciably. Another option would be a piece of copper pipe, I have some of that laying around.

All this is assuming temperatures are high enough for copper to melt at 1983F.

I just thought of something else, say the temperature gets hottest at the midpoint of the riser, maybe that's 1984 degrees and so the middle of the wire melts but not the bottom.  But, I guess you'd know because intact wire would be laying on the bottom of the riser.

At any rate, I am going to try this when I get to testing this core which should be sometime this week.

I'm officially naming it "The Solomon Test." (Since everybody seems to like to name things after themselves around here.)

Peter van den Berg wrote:If you are interested, I can delve through the pile of files and drawings.

If you have time, that would be wonderful. I like the concept of the Dragon Heater and I thought of experimenting with building my own version of that design, but I tend to want to pay people for their work. Now that I know they haven't paid their license and it's loose in the ether, I would love to play with it.

Do you have a way that people can give you donations? I have certainly gleaned value from your work and would like to offer you gratuity for it.

@Solomon, here's the 6 inch design drawing of the Dragon Heaters J-tube. It's provided as is, no further development is or will be done since the release of this drawing in 2012. There is a secondary air provision that at the same time cools the upper part of the feed tube, which is the only steel part of the core. This steel part is designed in such a way that it can be turned over in two directions, providing four edges that will be worn out eventually. The two halves of the core are strapped together with two small and long hose clamps, ceramic felt between all parts that need to be sealed.
https://pberg0.home.xs4all.nl/Bestanden/J-tube/6inch-Jtube.skp

There's an evaluation report about the core online at Donkey's: https://donkey32.proboards.com/thread/803/evaluating-6-dragon-burner

About donations: can be done through PayPal, I'll provide a mail address by personal message.

Got it, thanks.

Is the 8" core just scaled up from this?

I'm presently 3d printing a 25% version for close inspection.

Maybe I'll start a new thread about possible modifications. Do you have any suggestions or do you think it's as good as it gets?

This thread might interest you ?
https://donkey32.proboards.com/thread/1058/core-tripwire-channel-kicktail-design

Solomon Parker wrote:Is the 8" core just scaled up from this?

Not entirely, no. The notable exeption is the trip wire, being around 1/4 inch high. That should be the same height while the design is scaled up or down.

Solomon Parker wrote:I'm presently 3d printing a 25% version for close inspection. Maybe I'll start a new thread about possible modifications. Do you have any suggestions or do you think it's as good as it gets?

You do the 3D printing directly from the SketchUp drawing? Interesting!
In my view, this is as good as it gets, there's very little room for improvement and a whole lot for killing off the present behaviour. Only a rigid test program could establish whether or not any modification is worthwhile.

What I did was upload the file to the free online version of Sketchup, then delete all the parts I didn't need, then save each piece as a separate file, then export each file as a .stl and then printed those from the normal slicer, I use Cura. .stl is the standard 3d printing file.

Peter, there was some mention of ash buildup in one spot of the back wall curve suggesting the possibility of some slight adjustment to the curve.

I wonder if an insert could be created to stick into my ceramic fiber board core to emulate the dragon core.

Thinking out loud. I'm not there yet. I'm sure I'll end up with a batch box eventually anyway.

Solomon Parker wrote:Peter, there was some mention of ash buildup in one spot of the back wall curve suggesting the possibility of some slight adjustment to the curve.

Yes, that's true. It's a spot where a small amount of ash will come to rest, just before the ramp of the back sweep starts. That patch is there always, it doesn't grow so I wouldn't use the phrase "accumulating" for that. Interestingly enough, it happened to be the same in my development model so in the final design the back sweep was made sligtly longer. But as Donkey reported the patch is still there, all other ash in the burn tunnel will be blown out and settles in the bell, manifold or other wider part in the system. In itself, this is a huge improvement as compared to the simple shape of the original which can be easily clogged up completely by accumulating ashes.

So you could try to resolve this particular small niggle, but my guess would be: another spot will hold some ash, possibly more than before. As long as the back sweep ramp itself stayes free, it's a hard surface where ash is blown off quite easily. In contrast with a large patch of ash forming a soft surface which could lead to building up.

I doubt it's worth worrying about.

I'm nearly finished printing, I have the core and riser done, just need to do the wood feed piece.

At any rate, I'll stop going off topic on Mr. Woodford's thread.

You are right Solomon. Is it possible to split the relevant posts off to a separate thread? Any staff person that has more experience handling that type of problem than me?

Edit: OK, it turned out to be very easy, so have done it already.

Thanks Peter.

For anybody interested, the print is done and we've started off on possibilities with printed molds for castable cores.  Check it out here:  https://permies.com/t/155825/printed-Peter-Van-Den-Berg#1220996