Author Topic: Rocket Stove Design  (Read 1404 times)

Rocket Stove Design
« on: November 08, 2019, 01:16:47 pm »
OK, it appears appropriate that having graduated to Shed 2, I should advance to Stove 2 in a similar vein.

This is for my allotment brew-up. My existing paint can rocket stove is this







Whilst it was functional, it lacked the rocket-y element, most likely an insufficiency of air. That could be seen in the not that impressive heating and comparative difficulty lighting.

For Stove 2, I have scored a bit of 100mm square section steel tube (for the purpose, lets ignore that it's 5mm and consider that an aid to longevity. When future archeologists unearth the evidence of the culinary habits of the agrarian members of the second elizabethan age, they won't have to wonder, as it will still exist)

My current thinking to create a simple L shape with a mitre, then a platform a third of the way up for the air/fuel. The platform would end before the combustion chamber.

Options are, a J shape (why?) another feed pipe for the fuel... any thoughts?

(Steadying pan supports with 6 & 10mm rod.)

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Rocket Stove Design
« Reply #1 on: November 08, 2019, 02:24:39 pm »
A few years ago Charlotte made a wood gasification stove using a Wilko's stainless steel biscuit tin, into which was inserted a Wilko's stainless steel coffee tin. Both had suitable holes for ventilation and there were a few other tweaks.  Thinking about it, it was more like 8 years ago.  If the search function here actually worked, I'd pop up a link.
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

Kim

  • Timelord
Re: Rocket Stove Design
« Reply #2 on: November 08, 2019, 02:29:17 pm »
A few years ago Charlotte made a wood gasification stove using a Wilko's stainless steel biscuit tin, into which was inserted a Wilko's stainless steel coffee tin. Both had suitable holes for ventilation and there were a few other tweaks.  Thinking about it, it was more like 8 years ago.  If the search function here actually worked, I'd pop up a link.

We appear to have a thread: https://yacf.co.uk/forum/index.php?topic=35564.0

I've still got the appropriate tins somewhere.  The prospect of drilling that much stainless put me off assembling the thing.
Careful, Kim. Your sarcasm's showing...

Tim Hall

  • I want to eat the fleeting shade of your lashes
Re: Rocket Stove Design
« Reply #3 on: November 08, 2019, 02:32:46 pm »
Phear mi l33t haxor skillz:

https://yacf.co.uk/forum/index.php?topic=35564.0

The key to drilling stainless steel, apparently, is to do it slowly. Very slowly.
There are two ways you can get exercise out of a bicycle: you can
"overhaul" it, or you can ride it.  (Jerome K Jerome)

fuaran

  • rothair gasta
Re: Rocket Stove Design
« Reply #4 on: November 08, 2019, 04:46:25 pm »
An Ikea Ordning cutlery stand is another option. It has plenty of holes, so less drilling required, £2.
https://www.ikea.com/gb/en/p/ordning-cutlery-stand-stainless-steel-30011832/
Or a taller style, £2.50. https://www.ikea.com/gb/en/p/ordning-kitchen-utensil-rack-stainless-steel-30131716/

Re: Rocket Stove Design
« Reply #5 on: November 08, 2019, 05:34:40 pm »
It appears that wood gassification =/= rocket, but I wouldn't swear to that, similar principles and effect seem to be in play

Re: Rocket Stove Design
« Reply #6 on: November 08, 2019, 05:45:05 pm »
A kelly kettle is pretty much a rocket stove (tall chimney, feed fuel through the side).  Key is being able to turn it round once going (so you can make best use of wind).

I think you are right about letting fuel in. I had a go at one once. Used a grill inside for the wood to rest on and extended it out through the fuel feed pipe. fuel burned too fast actually, but you could restrict fuel flow easily since the inlet was cool. The grill rusted and burnt through after a few uses.
<i>Marmite slave</i>

Re: Rocket Stove Design
« Reply #7 on: November 08, 2019, 06:29:05 pm »
The Kelly Kettle is a thing of awesomeness.  I bought mine from somebody otp and have been delighted with it.  So much so that only this afternoon  I was perusing accessories for it: a whistling bung and a hobo stove (simple pot stand) for cooking using the base.

redshift

  • High Priestess of wires
    • redshift home
Re: Rocket Stove Design
« Reply #8 on: November 09, 2019, 05:15:50 pm »
My preferred kayaking instructor is a chap called Huw Jones, and he runs a Kelly Kettle with a whistle for lunchtime brew-up, along with a very nice portable espresso maker.  I can vouch for the quality of both.
L
:)
Windcheetah No. 176
The all-round entertainer gets quite arsey,
They won't translate his lame shit into Farsi
Somehow to let it go would be more classy…

Re: Rocket Stove Design
« Reply #9 on: November 09, 2019, 05:22:45 pm »
The Plans. The idea is that the feed tube (with hinged cover) deposits fuel just where it is needed.






Re: Rocket Stove Design
« Reply #10 on: November 09, 2019, 05:36:32 pm »
I can see why that would work.

Kim

  • Timelord
Re: Rocket Stove Design
« Reply #11 on: November 09, 2019, 09:10:34 pm »
Thinking about it, and considering the photo in the OP, could the lack of rocketyness be due to the chimney being relatively short compared to the height of the burning fuel?
Careful, Kim. Your sarcasm's showing...

Re: Rocket Stove Design
« Reply #12 on: November 10, 2019, 02:32:54 am »
the OP stove looks as if there simply won't be enough air flowing through it; I think you would need many more holes in the platform for this. Even the fuel looks like it might restrict the flow; round sticks (at different angles) let air flow through more easily than squareish sticks packed parallel.

If you have a suitable punch there is no need to go drilling holes in (thin stainless) sheet metal; it is much, much faster to punch them. The other thing that works well for airflow  is to cut slits using a Dremel tool cutting disc, and then to pry these slits into wider openings (a bit like a cheese grater). You can buy 'expanded metal' mesh in steel or stainless steel and this makes for good airflow too.

If there is much of an air gap in the side openings (above the fuel)  then the stove may reduce in efficiency; the stove may just draw too much air into the flue above the fuel and this may be at the expense of the draw through the fuel. If you support long sticks in the right way, they can always bear against the top of the fuel access opening and this makes for good efficiency.

Taller chimneys are better and if you are going to have a pan support anyway , you may as well have a vertical flue. The other thing to bear in mind is that the volume of gas coming out of the top of the flue is vastly greater than the volume going into it; this means that if there is only a narrow gap between the top of the flue and the bottom of the pan, this may become the biggest restriction to the flow through the whole thing.

cheers

Re: Rocket Stove Design
« Reply #13 on: November 10, 2019, 07:07:00 am »
All of the above are possible, here is an alternative design. I like it in some ways because it is simpler.



There's a shelf on the bottom third, and a cover to ensure the airflow through the bottom, maybe that's not needed. Only, I'm not convinced about how the fuel will get delivered.

Of course, I could add those features to "design the first" and use whichever works better.

Another question, extend the platform to the line of the mitre or not?

ETA These scale drawings didn't seem to fit my minds eye of the piece of scrap I have. Went back to measure and it is a 65mm square section (so, 55 internal). Back to the drawing board (or, Corel in this case)

Re: Rocket Stove Design
« Reply #14 on: November 10, 2019, 08:24:46 am »
OK, now to correct scale using the metal I have


Re: Rocket Stove Design
« Reply #15 on: November 10, 2019, 01:40:25 pm »
David  Cambridge excels at many things including building a rocket stove.

Re: Rocket Stove Design
« Reply #16 on: November 10, 2019, 07:29:23 pm »
Thanks for that - reassuring. Looks like this design works. Without a plasma cutter I suspect I will place the feed tube right at the mitre junction.

Re: Rocket Stove Design
« Reply #17 on: November 11, 2019, 10:24:23 pm »
I went for the gap between the mitre and the feed tube inthe end.





Now, the pan support (with carry handle so I can move it when hot) and stand and I'm done

Re: Rocket Stove Design
« Reply #18 on: November 12, 2019, 09:31:15 pm »
Ready for test (tomorrow)



Modified the original plan so that the supports can be removed for more compact stowage, added handles to them otherwise they would fall off if you move the stove by the body, which could be sub optimal.

For those looking at it and thinking "Those welds aren't much to be proud of" please can I reassure you that (a) there are some joints that are reasonably welded and (b) it is quite possible for someone slightly soft in the brain cell dept. to shut off the gas whilst buggering around only to forget to switch it on before welding again. Two days in a row. And not realise that's why the welds are cr@p until going to shut off at the end and finding it off already. It is actually a testament to the preparation that the bits of metal are actually stuck together at all.

Re: Rocket Stove Design
« Reply #19 on: November 13, 2019, 09:22:51 am »
Success. Quick squirt of alcohol, it burst into life.






(oh yeah, if anyone could re-home a copper saute pan that needs retinning do shout. Currently sitting outside, the snail stew probably isn't it's best use)

Re: Rocket Stove Design
« Reply #20 on: November 13, 2019, 10:22:00 am »
Nice! 

A thought; could you add some means of regulating the air supply to the stove, in order to allow a low heat/simmer control?

cheers

T42

  • Tea tank
Re: Rocket Stove Design
« Reply #21 on: November 13, 2019, 10:39:41 am »
Very nice! 

Now if that were me I'd add a ring on top to take a round-bottomed wok...  ::-)
I've dusted all those old bottles and set them up straight.

Re: Rocket Stove Design
« Reply #22 on: November 13, 2019, 11:41:22 am »
Impressive  :thumbsup:

Re: Rocket Stove Design
« Reply #23 on: November 13, 2019, 01:22:51 pm »
Nice! 

A thought; could you add some means of regulating the air supply to the stove, in order to allow a low heat/simmer control?

cheers

Not sure it would be susceptible to that, bearing in mind the rocket-y nature. I suspect that at some point the chimney draft effect would drop off (as in Stove 1) and you just have  a bundle of sticks burning, not very hot.

Just checked the exif - from start to the second (close to boil) was 4 minutes. Houston, we don't have a problem.

Re: Rocket Stove Design
« Reply #24 on: November 14, 2019, 12:32:45 am »
Nice! 

A thought; could you add some means of regulating the air supply to the stove, in order to allow a low heat/simmer control?

cheers

Not sure it would be susceptible to that, bearing in mind the rocket-y nature. I suspect that at some point the chimney draft effect would drop off (as in Stove 1) and you just have  a bundle of sticks burning, not very hot.

Just checked the exif - from start to the second (close to boil) was 4 minutes. Houston, we don't have a problem.

possibly we are talking at crossed purposes here.  If you are after a fast boil there is basically no such thing as too much air coming in to the bottom of the stove, unless that air manages to bypass the burning stuff somehow.  In fact if you added a small battery powered fan the stove would probably go even quicker.

My suggestion is that if you want not to heat as fast as possible (eg for other forms of cooking) then you would be able to turn the stove down by restricting the air going in at the bottom. 

cheers