Vortex JTube

[martyn]

Thanks, perhaps I should look into installing one.

[treebased]

Nov 10, 2023 10:02:52 GMT -8 Vortex said:

Looking great, Martyn. Have you ever tried a draft regulator? I find they really help in that kind of weather.

That or a Wind Directional Chimney Cap. I really like mine, spins with the wind like a weather vane so the wind always draws over the top of the chimney creating a slight venturi effect. Of course, I live in one of the lowest wind areas in the usa, so results may vary.

[martyn]

All ready to rock for Christmas…..

[fruitbat]

That thick sheet steel top with expansion piece over the riser is smart, durable and overall a great solution Martyn. I well remember my kettle always doing a bunny-hop as the barrel end dished out with a bang as it came up to temperature, back in the early J-tube days....

[martyn]

I have noticed an interesting fact that occurs with the stove.
It seems that the highest temperature I can record on top of the barrel, directly above the riser happens within the first 10 minutes of lighting.
This is around 550c (or just turning red hot) but by 20 minutes and there after, it operates around 375-400c and I cant seem to get it to go any higher.
This is not actually a problem for me but why does this happen?
I assume it has something to do with the air feed temperature restricting the air once the stoves gets really hot?

[martyn]

I tried a double vortex before but this time it really seems to work well, I will fit it in a barrel to see how it works as a portable patio heater and steak cooker….

[peterberg]

Looks good! Funny to see an idea from as long ago as 2009 being incorporated in a J-tube with a batchrocket-like centered venturi. Is the narrow gate reaching up to the ceiling of the burn tunnel?

Now that you have this setup, I'd suggest to try the same trick as I did with the Shorty batchrocket core. When the riser above the core is becoming much wider this will slow down the gas speed. In fact, it'll stop the flames from coming up and out of the riser.
The total volume of the riser should be about the same as the normal straight riser. The exit being the same as the original riser's cross section area. Not sure how it would work in these circumstances, the best results I got while using a slit, the same csa as the chimney.

[martyn]

There is already a slight increase in volume to allow for expansion but yes I can try a few different aspects. I am going to switch my attention over from the vortex stove to this much easier project.

So the feed is 100 x 100mm, burn tunnel is 100 wide and 125 high, vortex slot is 32 x 125.

The bottom 125mm of the riser has angles in the corners then the next 100mm above is square, so a little bit more volume, then it goes into the 100mm chimney.

The flame is mostly staying in the bottom apart from initial start up can see sparks coming out the top.

I am going to build a new experimental version with sliding restrictions (like two sliding house doors) so I can adjust the width of the slot while the stove is running and even run it as a single vortex for comparison.
But yes I will pursue the expansion chamber too… would you like to suggest some starting point dimensions?

I love the ease of use you get from a J tube, I need a break from the temperamental vortex stove…. It was so satisfying to build something that runs beautifully straight away!

[martyn]

New short video….

[Sprocket]

I see that the net that you have in between the feed tube and burn changer needs to be replaced very often. Have you thought of using a titanium net? That'll last. They are a bit expensive, but to me it would be worth it since the stove seems to be working very well and I assume you're going to keep it like this.

Something like:
www.winnerwell.online/a-65580041/shop-all/winnerwell-grill-grate-titanium/ and I guess they are available in the UK in various places for outdoor life and camping. Maybe you have to search around for a net in the dimensions you need if these grill nets are not large enough?

[Sprocket]

Jun 28, 2024 8:05:27 GMT -8 peterberg said:

Looks good! Funny to see an idea from as long ago as 2009 being incorporated in a J-tube with a batchrocket-like centered venturi. Is the narrow gate reaching up to the ceiling of the burn tunnel?

Now that you have this setup, I'd suggest to try the same trick as I did with the Shorty batchrocket core. When the riser above the core is becoming much wider this will slow down the gas speed. In fact, it'll stop the flames from coming up and out of the riser.
The total volume of the riser should be about the same as the normal straight riser. The exit being the same as the original riser's cross section area. Not sure how it would work in these circumstances, the best results I got while using a slit, the same csa as the chimney.

This is something I'd like to try. I'm thinking of making a very small rocket heater for my tiny house, and the J-tube seems to be the best (only?) choice for something that will use a 75 mm chimney. The chimney is already there, originally it was a diesel heater installed. I will not be able to have much of a mass heater because of weight restrictions, only a metal bell/encapsulation of some sorts, and it would be beneficial to have as low height as possible of the stove in whole. Realistically it will be a hit or miss construction, but I will off course start off by looking at the proportions of your shorty construction. I can always sigh, go back, and do a normal J-bend stove if forced to.

But if possible I'd very much would like to hear your thoughts about my ideas of how to scale it down.

Some important aspects of all these varieties of batch box stoves seem to be the relationships in between volumes for the burning gasses, the volume of the spaces in which they are, and the area of the ports/exit. Those things seem more or less fundamental, and then there are details like port shapes, stumbling blocks and such, that can make or brake things. But those details seem rather unpredictable.

Of course one can just scale existing stoves down, but looking at how things change when scaling, it seems to me that when going this much smaller than existing and proven constructions, it could be a good idea to take into account that volumes and areas scale differently. So for a small stove one would increase the volume of the Shorty riser, comparatively, and use slightly smaller ports. I have not at all looked into how large these changes could be, but it shouldn't be anything major, more like tweaks in only one direction.

(I have to admit I'm not 100% familiar with the lingo yet, for example I just became unsure if the exit from the riser is really called exit, or if it's the second port...)

[peterberg]

Sprocket, the smallest workable batchrocket of whatever design is a 100 mm system. Since you want to use your 75 mm chimney, a J-tube seems to be the one to go for. A smaller than 100x100 feed tube still works, but it's let's say... rather cramped.

[paganodimelito]

I think I read there where batch boxes all the way down to 75mm... Didn't they work well?

[fruitbat]

martyn Really sorry if I've missed this in any of the videos, but what is the riser made from, the second one which replaced the ceramic fibre version? The insulation is vermiculite, obviously...

[martyn]

I have tried a few different materials ranging from dense cast refractory cement to lightweight insulating cast refractory but at the moment it has a ceramic fibre riser coated with Vitas ceramic fibre rigidiser, I think I gave it 5 coats last year.
The riser its self is only 22” inches tall with a total height from the base of the stove to the top of the riser of 31”.
Next time I will try vermiculite board.