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 My first rocket stove space heater

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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 18, 2014 9:48 am

Mr. Heater wrote:
It looks like the hole through the sawdust is smaller (about 1/4 the size) than your primary air pipe. That may be choking off the primary air. Maybe just a larger hole through the sawdust the same size as the primary air pipe will fix it.

Also, the hole in the top of the firebox lid may be too small.  I would make it as large as the primary air intake pipe to the heater.  You can always put a damper on it to slow down the air intake (burn).

The hole in the sawdust worked better when it was smaller, as there were more flames and a better draw. I had the lid open to let more air in and all that happened was that smoke came into the room.
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 18, 2014 9:55 am

2ndburn wrote:
:) 
Hi Mr,
The hole will become bigger as it burns, but I think it would be something simple to put it right.
It maybe that there is too much secondary air or that air is coming in from somewhere else, making for a weaker draw would not pull enough air in through the fire box and would account for the smoke.
When James posts a video we may see what the problem is.

The secondary air comes in between the fire box pipe and the RS pipe. The fire box pipe measures 5.5" and the RS pipe is externally 6". This leaves an area of 4.5" sq for the secondary air. Is this too small or too big? Also what could be effecting the draw is the old chimney being used.
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Mr. Heater

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PostSubject: Re: My first rocket stove space heater   Tue Feb 18, 2014 11:59 am

To eliminate a few variables:

* Try dry wood first instead of sawdust.  Try to build the fire right inside the fire box pipe (inside the fire box) at first so it preheats the heater and chimney.

* Try blocking the secondary air completely.  Maybe stuff some fiberglass insulation in between the two pipes, and tape off the air holes.  If the draft and performance increases, you may have to decrease the gap between the pipes, and/or cover some of the air holes.  If the draft is the same as before, you can suspect the chimney isn't drawing properly.  You won't get much draft from a cold masonry chimney if the room temperature is also cold.

* Worst case, you could roll the heater outside, and try it with just the steel pipe chimney.  From the picture, the chimney looks tall enough to produce a strong draft by itself. If it works outside, you will have to find a way to preheat the building chimney to get it drafting.
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 18, 2014 6:48 pm

Thanks for the ideas. I will try them  :) 
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Wed Feb 19, 2014 12:05 am

Here is yesterdays burn. Today was better because I used wood and there was no smoke Very Happy

http://youtu.be/_8T5-cJkOYk
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Mr. Heater

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PostSubject: Re: My first rocket stove space heater   Wed Feb 19, 2014 12:57 am

Great news. You have a "beast" of a heater there ! Great build job.  Very Happy 
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2ndburn

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PostSubject: Re: My first rocket stove space heater   Wed Feb 19, 2014 5:00 am

 :) 
Hi James,
How long did the sawdust burn for?
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Wed Feb 19, 2014 5:18 am

2ndburn wrote:
 :) 
Hi James,
How long did the sawdust burn for?

It burnt for around 3 hours then left about 2/3rds of the sawdust, which then just smouldered. Tomorrow I am going to put a plate above the pipe exiting the burn chamber, with a central 3' hole to see if this will produce a more even burn. If it does I will build another burn chamber with a pipe coming out of the base and then into the RS.
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Hitchhiker



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PostSubject: Re: My first rocket stove space heater   Thu Feb 20, 2014 7:53 am

Congrats!
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Thu Feb 20, 2014 9:18 am

Another firing today with sawdust. The first sawdust firing left a lot of it smouldering, as the pipe was to one side, so I put a plate in with a central hole 3" on top of the pipe going to the RS. See below.



The sawdust burnt nice and evenly, but I had to put wood down the centre to get it going for the first 30 mins. There was smoke for the first 30 mins but when it got up to temp the smoke disappeared.









The flue temperature stayed around 110C for most of the time.

I think that the hole in the plate needs to be bigger so I will increase it to 4"
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Bezman

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PostSubject: Re: My first rocket stove space heater   Sun Feb 23, 2014 7:00 pm

Blooming Hell James,

You have made some amazing progress since our phone conversation! The stove looks fantastic. I think I need to be calling you when I next get some time to 'tinker' with the stove.

Looks like a really well put together heater, I hope you have enjoyed it. Only problem you have now is that firing these things up in the UK now is pretty much just an admission of pyromania as it isn't cold enough to justify  :shock: 

Great build chap, I hope you solve the sawdust burn challenge.

Bezman
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Sun Feb 23, 2014 7:16 pm

Hi Bezman,

Yes, it is coming together nicely.

It is typical that it is so warm :) 

I am going to go in two directions with the stove. Firstly with the sawdust I am going to go build a more traditional 8 hour burner like this one

http://www.youtube.com/watch?v=Qj7X9X8LTe0

and then attach it to the heat exchanger. Secondly I want to develop the wood burning side. This works with existing setup but there is a lot of some coming out when I put wood in.

Speak to you soon

James
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 25, 2014 2:08 am

Fired up again today with sawdust, but this time instead of a 68mm (2.6") hole in the centre I put a 100mm (4") hole which worked much better although burn quicker.

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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 25, 2014 2:10 am

Fired up again today with sawdust, but this time instead of a 68mm (2.6") hole in the centre I put a 100mm (4") hole which worked much better although burn quicker. Sorry about the back ground noise it is from the workshop machinery.

Click on the photo to see the video.

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twistedkarma

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PostSubject: Re: My first rocket stove space heater   Tue Feb 25, 2014 8:47 pm

your into my realm of stove.

you are preheating, making gas ect, and downdrafting it , into a rs.

So, when you make too much gas in first tower. and raise the lid at wrong moment (adding fresh air to 600 degree gas), you will burn your hands and face.

now that we have the safety talk out of the way, this design, works .
Heat has to build in first chamber, and cant leave till it gets pulled threw coals at bottom, gas and smoke get spontaneous at bottom and rolled into rs riser.
mine chugged, blew itself out, when it reignights, that's when it gets nasty.

corn runs good in mine.
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Tue Feb 25, 2014 9:40 pm

You only can lose the hairs on your arms once on each firing. Very Happy 

My stove chugged to start off with but then behaved once it was hot enough.

Having a first chamber is more of an incidental thing for me as I wanted to have a central hole to burn sawdust instead of a side hole, but it is interesting having the first chamber. You can watch the flames swirl around and I think that it would be interesting to have some secondary air coming into this chamber. The only drawback to this system is lighting it.

I don't have any corn but I bet it is a good fuel and a good for the environment as it is a waste product. :) 
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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 6:31 am

jameshookway wrote:





ive got to ask but what is that white insulation stuff around vortex tube spotted it via ppottys design was considering using fire blanket to smother flames out as i believe its roughly the same stuff as i only need a few items to weld all this up and complete the build

insulation, welding rods 309, and the fire silicone is all i need now to be able to get on with it all
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hermetic



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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 8:42 am

Hi, I noticed on the commercial sawdust stoves they put a thin layer of sand on the top of the sawdust fill "to stop the top burning" Have you tried that? It may get the stove to burn from the bottom up (they light from the underneath via the ashpan) , and not leave unburnt sawdust. I note also in the commercial version, they don't mention how you get the sand out again!!!
Phil
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 10:37 am

Hi Phil,
I have not tried using sand, but I am going to. I presume that when the stove is cold the sand is scooped out.

The commercial stoves burn with the flames going up. I was trying to see if I could get the flames to go down. Which I did manage. Have done this experiment I have decided to try the commercial method as one of my goals is to get an 8 hour burn from one load, but using the efficiency of the rocket stove to clean the smoke and extract the maximum heat. All I need to do is to build it :) 

James
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twistedkarma

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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 11:09 am

If I could get some sawdust, id; put it into my boat ancor, and see if it gets a 8 hour.
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 7:01 pm

A lot of small joiners cant get rid of it and are happy for you to collect it.
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hermetic



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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 8:03 pm

Hi James, I had assumed that the flue on the commercial sawdust burner went to the bottom of the burn chamber as it appears to do in the video, and the flames went down through the hole in the bottom where the filling tube is inserted. The air is going in through the hole in the top of the outer drum, and it seems to make sense that the flames are burning down. Having said that, I like your design more than the commercial one! I think you need to let more air into the burn chamber, so you can run with the lid closed, but have a means of varying the amount of air to find the "sweet spot". On the commercial burner they appear to have a fixed diameter hole air inlet, the size of which is sufficient to keep the stove burning, but not to allow it to run away and overheat. They have probably achieved this through trial and error. You need to allow sufficient air in to get the rocket stove pipe hot, to create the draught, and the draught needs to be flowing straight down the hole in the sawdust. If you increase the size of the draft hole in the top of the burner chamber, and put a regulator on it, and top off your sawdust with sand, I think you will be on a winner! The commercial stove limits the air intake to extend the burn, and stop overheating. A rocket stove will not work with a limited air supply as it will not get the rocket pipe hot enough to create the draught.
Phil
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jameshookway

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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 8:44 pm

HI Phil,

The sawdust burners I have seen burn up. So I am think that the second chamber on my stove would do two things firstly clean the smoke up with the secondary air intake and secondly extract as much heat as possible.

At the moment the chamber is too small as it burns out within 2 hours. I have now drilled holes at the bottom front of the burn chamber so the lid does not need to be propped open. This worked well as it let less smoke out. So some more work required.

James
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twistedkarma

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PostSubject: Re: My first rocket stove space heater   Wed Mar 05, 2014 9:20 pm

yes and no Phil. Mine will sometimes never use the RS riser on it.
The first chamber, burns at 550 , it is restricted, and will secondary burn in the ceiling of the hopper.
The coals are at bottom, and smoke will pass past em, and incinerate remains.

after some time, james will realize that his second hopper is just a backup, only used once in a while. Mine riser does not produce the heat until I get a large load, and coals lay in the bottom at start of RS riser.
http://youtu.be/o8A62YRvPmw

I'm building a new stove on the mistakes I have learned from.
I was debating on just adding a large door to my hopper, but still uncertain.

the coals laying in the bottom of the riser works great, I don't know if new design will work without it

Keep playing with hopper and downdraft James. just watch out for gassing and adding air while it is gassing, keep it safe.
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PostSubject: Re: My first rocket stove space heater   Thu Mar 06, 2014 11:57 am

jameshookway wrote:
Hi Phil,
I have not tried using sand, but I am going to. I presume that when the stove is cold the sand is scooped out.

The commercial stoves burn with the flames going up. I was trying to see if I could get the flames to go down. Which I did manage. Have done this experiment I have decided to try the commercial method as one of my goals is to get an 8 hour burn from one load, but using the efficiency of the rocket stove to clean the smoke and extract the maximum heat. All I need to do is to build it :) 

James

James you could make a thin metal plate with burn hole to cover the top of shavings, make enough clearance around the sides so it moves down with the shavings as they burn. Some brackets welded to the sides of plate like legs would stop it tipping as it slid down. Point legs down to stop plate hitting bottom.
The commercial stove shown will only really produce heat from the lid and flue, I know because I burned shavings like that for many years, you will eventually get some heat from the sides just over half way into the burn. 80% heat probably going up the flue making the burn clean.
Using a rocket down burn you will exchange far more heat than the oil drum up burn.
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