Rocket stove - hot plate.

Really pleased with to nights performance from the stove, this was the first time we have had it going for more than an hour.
Top plate reached an easy 403c I think it could easily reach 500c with a full fire box of wood.
The whole metal top plate formed a concave shape ....

Cool then.

There's one thing i saw yesterday.



I thought your chimney was all connected. But no.

A little more performance could be reached by insulating that spiral tube.

You must have some draft, otherwise you would be talking about puffbacks at least. But may be not as much as you'd wish for.

I did have the chimney going up and out but I disconnected it to experiment with te draw.

I have now discovered that by exposing the chimney outlet, I have the opportunity to adjust the draw through the system by closing down the hole size.
I will make a more permanent device but just by useing an old towel to partially cover the outlet i noticed it has as immediate effect on the draw.
I think this will be a great asset, I have found I can block off 50% and it still draws without smoking, the fire box starts to back burns at around 60% covered.

We cooked 40 mackerel fillets and I know from experience that 250c is a good frying temperature, I just used the towel to slow the draw and drop the normal running temp of 300c. Due the the thickness of the plate it takes a few minutes to adjust the plate temp but it really works!

I plan to line the slopping area above the fire box feed with polished stainless steel so it auto feeds a bit easier and show off more glow from the 🔥
I will try a P channel and insulating the chimney, I need to add some sort of gaurd  around the barrel to stop everyone touching the sides!i
I might cut a 4” hole directly above the heartriser so I can use a wok directly over the main heat source and be able to place meat skewers directly down the riser.

Also a removible oven dome above the hot plate......

About cooking in the riser, i can't see how that could be possible. Just a cast iron grid, above my riser, kills sausages in a few seconds.

The trick to protect the barrel, i would use a grid of perforated sheet metal.

https://www.google.fr/search?q=perforated+sheet+metal&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwitibz9z6DcAhVLDMAKHa6aDbUQsAQINA&biw=1228&bih=599

If you drill a hole for the wok, may try to find yourself a cast iron ring and cover to fit in there.

Did i show you this one?

https://permies.com/t/35569/Range-retrofit

Thank you for the links, great fun thinking about all the options.....
I am thinking my stove looks a pretty Steam Punk so I thought I might keep the theme going and add a sort of cooper tube railing effect around the drum.
Also adding some sort of heat shied in front of my actuall cooking position.
I am wondering if I can still get a log burning on top of the stove just for effect in the winter.

Can’t wait to build another one.....

I am a bit of a foodie, I love cooking and I often cook at extream temperature.
Tandoori work at extreme temperature, I think some moist marinated meat on a metal skewer lowered don the heat riser for a minute  or so might work very well.
I cook kababs in my wood oven at 500c it takes about three minutes but you need to keep them moving...

That's easy.

You have to remember that the temp in the heat riser is often between 800 and 1200C°

One more play with it today, we really fed it as much  as it would take useing dry soft wood ( I don’t know if hard wood actually burns hotter?).
I have found it takes at least an hour to get super hot but we saw the top start changing colour after around one hour fifteen at around 520c.
The very top of the barrel above the fire box was also glowing a dull red around 470c.
The single crack is now about 2mm wide and there are were few expansion creaks as it heats up but seems to run very well indeed.

Still thinking about putting stuff in the heat riser?

I am thinking about some novel way of heating some copper pipe filled with water so it blows a whistle.
My fist thought was to attach some pipe the the sides and I will try that but when I found out the cost of new 35mm cooper pipe, I almost fell over!
I wonder if different lengths and bores of pipe might signify the increase it temperature by whistling at different stages..... just for fun you. Understand!

https://permies.com/t/30379/NJ-Rocket

The link was bellow your thread.

Otherwise, i have no opinion!

Ha Ha, that is cool and pretty much what I had in mind although I will use more tube ( when I find some )
I went to a place called Omareau in New Zealand, it is classed as the Steam Punk capital of the world, we saw some great stuff there and that has given me a bit of inspiration.

I have had to get back to earning money so I have not had a chance to further improve my stove.
However we have used it quite a bit, just for shortish durations.
I have found that I can get max temps of around 420-460 in about one hour.
I have installed a rotating circle over the exhaust outlet, this works fantastically well!
I can regulate the temp to around 250c on the hotplate by closing down the exhaust to around 60% open.
By opening or closing the outlet, the effect is quite quick, I find 250c is a really good cooking temp to have in the centre, the outside of the plate will be around 120-160c.

I am really keen to build a mark two, I would like to see a faster warm up time, I think it is the density and thickness of the refactory that takes time to really saturate before the temperature goes up into the 400s.

A bit of alcohol enriched  fun with the stove...

I have been useing the stove for a few months now, overall it works very well but it does seem a little temperamental!

I say that as there have been a few occasions where i simply could not get it up above 220c and I am not really sure why?

I think it might be a combination of things... the type, the size and the dryness of the fuel wood and wood slipping into the burn tunnel.

Sometimes I get a really fast light up and a clean burning hot fire, other times I get a lot of ash build up and a lot of unburnt embers in the bottom of the feed chamber.

It could be the whole stove is effected by moisture as the unit is susseptible to the damp being housed in a basic outdoor enclosure but I mainly think it is due to unburnt wood lying in the burn chamber.  

If I were to build another one I would make some modifications to the basic design, a simple step in the bottom of the burn chamber would stop the majority of slipping wood and perhaps a method of removing unburnt embers in the fire box while the fire is running.
I am still learning how to get the best from the stove.....

I don't see any P channel.

No you are right, that might be just what I need, I will have to think of a way to get one working.

I am really tempted to build a new model.
There are so many videos and forum post ( many being quite dated) it is differcult to see if there really is a best way to go!

It seems secondary air needs to be pre heated and its entry point is quite critical but also it is best to restrict primary air if secondary air is to work efficiently.

I can’t understand why vortex designs are not more popular as they seem to be very effective at mixing gasses and heating the riser?

Having a hindged lid over the fire box seems to offer many more options with controlling air supply and pre heated primary air seems to work well.

Although for many it might seem wrong but useing a very small electric fan to supply hot air would seem to solve a lot of headaches trying to work out how to supply pre heated air. A 50mm pipe running through the barrel operated by a inline tube fan would supply hot air to any area.
A heat powered fan might work, a steam powered fan would be supper cool, you would than have a turbo power rocket stove.

Another thing I can’t get my head around is why the fire box, burn tunnel and riser all need to be the same size as the fire box gets filled with fuel and the burn tunnel gets lots of charcoal and wood sliding into it?

I built my stove around the standard recommended dimensions but it is not ideal to use with a standard barrel as the burn tunnel is to short to get the heat riser in the centre of the barrel.
It all good fun though and very interesting, I know that many people have dedicated huge amounts of effort into developing the concept but there still seems like there is room for much more development. I guess it would take a very large company to invest in development berfore a standard can be set.

I have made a few mods to the fire, the feed box is now 12” deep with a glass lid, I have secondary air working and a little glass plate on top of the plate.

Path of least resistance. It's going up the chimney, because the chimney is heated and gases there are far hotter than ambient, so less dense. Then there is less resistance. Eventually, it would "wash away" sucking colder air from the hole, cooling the chimney, and warming the gases above the hole.  I guess.

It was interesting anyway, I am going to make a 5min riser this afternoon.
I have an old 6” insulated flue pipe that I can use to form the blanket around but from my expereance the blanket is quire wirery or hairy and I don’t really want to have a hairy interior in the riser. I am wondering if I could lay out the blanket and dust it both sides with fondue cement give it a bit of a shake and dust it again until I get enough cement into the fibres then spritz it with water both sides, wrap it around the 6” pipe and encase it with the 10” outer pipe?
I think I will do an experiment first!
As I am still leaning the basics about how rocket stoves work, I am not sure how a low mass riser will work?
I guess I will get a faster warm up time but use more fuel, I think that once my high mass riser gets red not (2hours) it requires very little fuel to maintain the heat and offers very easy total combustion with the aid of secondary air?
I have been studying batch rockets but I don’t think they are the best design for my applications, so I have been thinking on a new vortex design J tube that will use a shorter low mass riser but still use a high mass fire box.
My present model uses a cement and vermiculite insulation,I would build the new one with ceramic fibre insualsion and a slightly thiner sided fire box.

You dont give a flying fanny fart about the roughness of inside the heat riser. It's even better to have it though, as it helps mixing gases. It's less work too, and less mass.

Ha ha well maybe but that is just not the way I see it.

I have just given it a try useing 2” blanket but I think maybe 2 x 1” might stay together better.
It does work ok but I am expecting some 1” to arrieve tomorrow and I will see if I prefer that.

I would like to get a fast and tight flowing vortex, I think that requires a smooth surface?

Smooth surfaces are over rated.

You polish the inlets into a head, when you have no more choice! First one is to enlarge, to have the boundary layer further from the main canal, which makes your main canal bigger.   In gas engines, a rough pipe helps further mixing of the air gas  mix. So, yes polishing helps sometimes, but it's not the miracle answer. And a turbulent flow can help with mixing. Well, that's engine theory.

Check this

http://donkey32.proboards.com/thread/1425/flow-visualization

Since rockets are more or less carburetor and ignition chamber, we are relying on the three T time turbulence and temperature.   So again, smooth is not the answer.

Ok thank you for your input, it is appreciated.
I spent much of my working life involved with fluid  dynamics.
I was certainly not the brains behind the work but I helped manufacture protein skimmers and C02 water reactors.
Anyway the work was heavily based around two concepts.. Venturi and Vortex... I am quite likely completely wrong in my assumptions that I can apply the same theory to a rocket stove but it is something I must try.

Getting back to the blanket, I tried cutting it on my big table saw so I could get a neat joint but I really need to sandwich it in a template to get the result I want.
I will have another go today. I think I might try to use three staggered 12” sections, I could easily stitch the outer 1” layer to the outer tube and then the inner layer might feel more secure....
I have taken apart a commercials used pizza oven so we could replace a cracked inner sectsion, the ceramic blanket was very brittle and not half as mailable as when it was fitted. The oven had been in daily use for around two years, considering the blanket was not actually exposed to any direct flame, I do wonder about how the blanket will stand up to prolonged use in a heat riser.

Most of the guys who have tried the five minute riser, seem to say, 2 inches is too thick.

http://donkey32.proboards.com/post/30096/thread

One inch inside a tube. And make sure you can replace when needed. Actually, i try to do that, keep things accessible, and replaceable.

About the old blanket. You don't know what you are dealing with, careful, very careful. Respirator, gloves, and even full body suit might be in order.  Same goes for new stuff, if it's not 607 superwool or the likes.


https://permies.com/t/93198/ceramic-fiber-blanket

And you know, i'm no brains about fluid dynamics, but understand more than the average joe  That's why i was being pompous about it.

5 minute riser made, more like three hours in my case!, anyway it is installed and tested.
Quite a difference in heat up time, more like one hour to 500c now and it might go higher but as the glass is only rated to 500 I stopped feeding the fire at around 520c.
Next up is to figure out a way to get a vortex spinning.....

Nice then.

Why do you want a vortex? to spin gases further out on the cooking plate?

So around three hours after I last fed the fire, with just a little bit of wood left burning, I can now see the down side of the low mass riser.
Barrel temp has dropped to 150c and the top to around 180c, if my high mass riser was in place I am sure the temps would be much higher.
I think the refactory riser weighs around 40kg and once hot stays hot for a long time.

I think a vortex will have quite an effect, it will dramatically increase dwell time of the passing gasses within the riser and I think heat it up a lot quicker and possibily get it a lot hotter.
If the gasses are spinning, then their travel to the top will take a much longer path so in theory I might be able to reduce the riser height.
I also think a vortex will mix the secondly air totally and very quickly, I really don’t know if the effect would carry on down the barrel but wouldn’t that be fantastic!

I think I would need to experiment with the vortex shape in order to get a perfect cyclone effect but even a basic spin should have an effect.
At the end of the day, my present fire is basically an experiment, I would really like to have the fire box higher off the ground and the hot plate slightly lower.

Maybe something like this, with an offset round riser and secondary air entry shown ....?

Fox James wrote:

I think I would need to experiment with the vortex shape in order to get a perfect cyclone effect but even a basic spin should have an effect.
At the end of the day, my present fire is basically an experiment, I would really like to have the fire box higher off the ground and the hot plate slightly lower.

You can always put mass around your new riser Firebricks stacked around it. That wouldn't hurt to gather the heat which goes up the chimney.

http://donkey32.proboards.com/post/26878/thread

Or something like this around the riser



For a higher firebox, i'm trying to develop a vertical batch. http://donkey32.proboards.com/thread/1803/peter-vertical-batch

And for a smaller heat riser, i will certainly enlarge the diameter. There is a point where the hot gases get too diluted in a huge heat rised, and the heat isn't contained anymore. Peter is somewhat working on this side of things.

http://donkey32.proboards.com/thread/3379/tapered-riser-batch-box-core

What you're thinking has been tried few times.

https://www.youtube.com/watch?v=iJoaXXefJ6g

https://youtu.be/otfZXmDqZu4

https://youtu.be/dhuRd_KbS1o

https://youtu.be/NJENCc3o_-Y

If you notice, it's all metal rockets. Yellow, or red flames.  Traces of soot in the risers etc.

Really, you don't need more than a batch or J tube for anything. It's a matter of KISS. All the enhancements, besides Peter's work, and a few others. Is overcomplexification of a simple design.  And if testo results aren't published, well, it's worth fcuk all!

I think there is plenty of potential to improve my own fire to suit my own needs.

Changing the riser has made a dramatic difference, even though I have yet to get my head around understanding the implication of high and low mass heat risers.

If the bottom of a dense cement riser is glowing red hot and holding that heat then that must offer something that a insulated riser does not.

I don’t know if the retained heat is a good or bad thing but it is must be a factor.

I like your idea of a vertical batch rocket feed, this is most definitely a direction I will be taking, I have never understood why the feed box needs to match the burn tunnel in a J tube?
I can see how a high breed of the two main designs would suit my needs, with a vertical feed in a sealed box with controlled air feed, a glass viewing panel in the front and a hinged glass lid, or even better a hinged front and top!
I can aslo see how the transfer port (sorry I have not studied batch rocket terminology) could be set at an angle in tangent with the heatriser to form a single vortex.
Potty, on YouTube uses a 9x9x19” fire box, a 5x 5.5” burn tunnel and a 6.25 heat riser and it all seems to come together!

So my target is to get a more visually experience of the actual fire, have a fast warm up time, have independent control over room temperature and cooking temperature.
It just a bit of fun for me in my retirement.

There is a way, i think, which is proven.

An horizontal batch, with a side window, and a top load.

http://donkey32.proboards.com/post/16159/thread  http://www.ecologieforum.eu/viewtopic.php?f=3&t=4610

Based loosely onto hendrik's build and some of mine.



http://donkey32.proboards.com/post/30192/thread

See the cast iron plate, here, on the firebox



Basically, instead of having a door in front, you could have just a piece of glass, and hinge the cast iron top as a lid on top. For horizontal batch, and top load. I am sure this one works. While the vertical, i'm not absolutely sure yet.

Hendrik's build, has a side window, instead of an end window. So either are doable.

Now the top of the firebox on my workshop heater has been changed for a proper cooking plate.



Which is unliftable.  But you could go for a decent "stir fry" plate there, as well as a lid.

Then, obviously you have seen the door in the metal tank. I've made a mistake there. I should have made it to the right hand side, to be used as an oven.

You could take on that idea.

Or leave the firebox on the floor. , the stir fry plate would be low, tho. And have another plate on top of the heat riser.  

http://donkey32.proboards.com/thread/2130/rule-thumb-scandalously-short-risers

As you have now.

Or if you keep my idea. You have the oven, to the side of the riser. And can make a lower "bench" at cooking height, with a big metal top, for a "simmering plate.

http://redirect.viglink.com/?format=go&jsonp=vglnk_153976146588614&key=bbb516d91daee20498798694a42dd559&libId=jncu54xv010004m6000DAfz9azk1v&loc=http%3A%2F%2Fdonkey32.proboards.com%2Fthread%2F1803%2Fpeter-vertical-batch%3Fpage%3D4&v=1&out=https%3A%2F%2Fpermies.com%2Ft%2F38889%2Fa%2F46625%2Fbatchetage2.skp%3Fdownload_attachment%3Dtrue&ref=http%3A%2F%2Fdonkey32.proboards.com%2Fboard%2F4%2Fexperiments-results&title=Peter%2C%20vertical%20batch%3F%20%7C%20Rocket%20Stoves..%20Experimenters%20corner..%20Answers%20questioned!&txt=permies.com%2Ft%2F38889%2Fa%2F46625%2Fbatchetage2.skp%3Fdownload_attachment%3Dtrue



See, many ways to kill a cat.

I have a short update, I managed to install a temporary insert to get a basic vortex spinning, just a bit of stainless steel bent and jammed in place.
The result is a cracked glass viewing panel and an overheated iPad!
The fire was working really well and I measured 500c after one hour.
Not surprisingly leaning over trying to take a video of the vortex was a bit uncomfortable but all of a sudden my iPad just switched off and it wouldn’t re start, then the glass cracked in two.
However I got a massive 547c on the glass just before it broke.

I don’t actually know if that is impressive compared to other stoves but it certainly impressed me.

I have managed to get the iPad working again but not properly, half my photos are missing and I have lost a huge amount of stored data but worst of all the camera won’t work. So basically I roasted the thing and I will have to but a new one.
I did manage to get this shot but not the 547c evidence.....

Ah sorry that was meant to show 524.5c but of course the iPad won’t post it... better get off to town and but a new one.
PS notice I have also melted the temperature gauge!

How do you manage to cook on such a hot plate? Don't things just burn?

Hi Graham, it is only the centre of the plate that gets that hot and it is quite easy to regulate the temp by adjusting the air flow and the amount of wood being burnt.
I have found 250c  is a good cooking temp and I can find that nearer the outside edge but now that winter is coming it is nice to have a warm room but in the summer I would not want it so hot!
I think that where I live, we get a very similar climate to where you live!

Fox James wrote:Not surprisingly leaning over trying to take a video of the vortex was a bit uncomfortable but all of a sudden my iPad just switched off and it wouldn’t re start, then the glass cracked in two.

Did you ever get a video of the vortex?  Can't you use a mobile phone instead, and hold it higher up?

Maybe taking picture/video with mirror? If it cracks, the loss is tolerable.