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Pocket Rocket Force air heater with Mass Storage?  RSS feed

 
Logan Jonker
Posts: 17
Location: Missouri
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Long Time visitor, first post. No pics today, but more to follow.

Today I built a 30 gallon pocket Rocket with 8 x 24 feed tube and a 6 x 72 Oval flue. I ran the rocket for a couple hours to burn off the pain as well as burned off the paint on my 55 gallon Juice Barrel with removable top.

My aim is to put a 6 inch hole in the base off the 55 gallon drum (bottom, center) to put an elbow in for a cool air feed. Bricks will then be put in the bottom of the barrel to make up the difference of the heights bettween the barrels and raise the Pocket rocket about 4 inches +/- from the cold air intake. I intend to put the pocket rocket inside the drum and then vertically place bricks up the sides in the space between the two barrels, this will create channels for the air to travel up around the sides of the pocket rocket. I make use soda cans, with the tops and bottoms cut off, to act as spacers between the brick columns as well as extra surface area for heat transfer. near the top of the 55 gal, I will put an 8 inch duct in for the hot air out.

On the burn of the pocket rocket, the bottom few inches went cherry red/orange and the grass in a 12 inch perimeter around the base ignited from the heat alone, so the rocket works. My theory as to why the bottom gets so blazing hot is that the ground is insulating it allowing massive amounts of heat to build up. I believe that with the cold air intake just below the bottom of the pocket rocket, the cold air will absorb a good portion of that heat, expand and race upwards to the top of the barrel and out the exhaust.

Then I want to drive some t-posts of extra tent pipe that isn't being used to form a perimeter around the barrels and fill it in with earth/rockets, then cover that with insulation.

So the P-Rocket will run as normal, the second barrel will allow the air to get heated, and any excess heat might bleed off past the seoncd barrel, warming the mass allowing for some continued warming of the air flow after the rocket has finished firing.

Thoughts, tips Questions?


Thanks!
 
William Bronson
Posts: 1446
Location: Cincinnati, Ohio,Price Hill 45205
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forest garden trees urban
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This sounds great, a really smart,cheap and simple way to move heat from the outdoors to the indoors.
It is said that most of the heat in a pocket rocket goes up the stack.
Perhaps a second barrel or a stovepipe as another shroud/envelope to capture that heat would make sense?
 
Logan Jonker
Posts: 17
Location: Missouri
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Thanks for the reply- I will eventually look at adapting the exhaust in this fashion:


I am going to be making aluminum foil gaskets for my connections/unions. Should I worry about them off-gassing or melting like Galvanized metal?

I had to use a chisel and hammer to make my holes and they are imperfect to say the least. I did a test burn without sealing up the joints just to see what needs to be done and to dry out the system from the past couple days snow/rain mix. So far my measurements have been correct on sizes and layout of the barrels and vents. Pics tomorrow.
 
Logan Jonker
Posts: 17
Location: Missouri
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Some Pics of the Work so far.
P1000932.JPG
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Base of Rocket Stove
P1000933.JPG
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Cold Air Intake on heat exchange barrel, unturned
P1000936.JPG
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Cold Air Intake and Hot Air Output on Exchange barrel
 
Logan Jonker
Posts: 17
Location: Missouri
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The Boy in the above pic is my son who wanted to help build our heater.
P1000951.JPG
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Cold Air Out to Heater, Hot Air in to House.
 
Logan Jonker
Posts: 17
Location: Missouri
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So- Initial burns resulted in about 200 degree heated air coming out of the exchange barrel, So I thought the the flexline insulated duct would work fine.


HA!

I had made some tweaks in the design- instead of the circle of 6 bricks in the heat exchange barrel, I move to 4 bricks in a t pattern to increase air flow.

Well, I setup the thermometer after insulating the pipes and ran a burn- over 450 degrees pipe temp and air temp! Melted the plastic in the insulation. I pulled it apart and built a double wall insulated pipe using black pipe and surrounded the pipe with bricks in the wall, so the exterior pipe temps and the temps on the surrounding wall are not very high, just the hot air.

I am planning on surrounding the heat exchange with bricks and cob. I am also looking at using the flue pipe to heat water (looking forward to seeing boom squish DVD) and using some of the hotwater line to heat another layer of cob around the heat exchange barrel. I am considering a design like this:


Issues:

My feed tube is filling with coals tonight- I can't just leave a few pieces of wood or the fire goes out, but prolonged burns fills the tube with coals and chokes off the air intake.

Do I need to lower the feed tube close to the bottom of the barrel? Or put some bricks in the bottom (to raise the floor)? Or do I need to simply clean it out each day?

Is the fire suppose to stay at the bottom of the barrel? it seems to crawl up halfway the tube, but still burns down though...

My feed tube is an 8 inch tube, should I go down to 6 inches?
 
Cindy Mathieu
Posts: 242
Location: near Houston, TX; zone 8b
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Feed tube, burn tunnel, heat riser and stove pipe should all be the same size. Consequently, if you have an 8" burn tunnel and a 6" stove pipe, its not going to work properly.
 
Logan Jonker
Posts: 17
Location: Missouri
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Cindy Mathieu wrote:Feed tube, burn tunnel, heat riser and stove pipe should all be the same size. Consequently, if you have an 8" burn tunnel and a 6" stove pipe, its not going to work properly.


It's not an RMH, but a pocket rocket. I used the specs for a 25-30 gallon pocket rocket from their book. It is sitting inside a 55 gallon drum that acts as the heat exchanger.
 
Cindy Mathieu
Posts: 242
Location: near Houston, TX; zone 8b
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When I said stove pipe, I meant the exhaust pathway that goes up through the roof or out the window. This has nothing to do with whether you are attempting to store the heat or use it right away. I believe it explains the fire crawling up the wood in the feed tube.
 
Logan Jonker
Posts: 17
Location: Missouri
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Cindy Mathieu wrote:When I said stove pipe, I meant the exhaust pathway that goes up through the roof or out the window. This has nothing to do with whether you are attempting to store the heat or use it right away. I believe it explains the fire crawling up the wood in the feed tube.


but the specifics on the pocket rocket state that the feed tube should be bigger than the exhaust, as most of the heat leaves through the exhaust. This slows the heat escaping.

http://www.rocketstoves.com/pdf/pocketrocket.pdf

I couldn't get 4 inch pipe so I smooshed 6 inch pipe into an oval.

I calculated that the feed tube should extend about 7/6ths to the bottom of the barrel.

So My feed tube is getting "too Much" oxygen, allowing the fire/draw to work its way up the tube? It's tough fine tuning the amount of wood into the tube to keep it burning without choking it out, but I do notice a better burn when I place a cover over the feed tube.

BTW- the entire unit is outside, if that matters- I think I may be fighting the exterior temps sometimes as well.


 
Logan Jonker
Posts: 17
Location: Missouri
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I haven't taken any pictures of the unit due to freezing rain the past few days and my 3rd shift job, but here:
P1000938.JPG
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The Build the first night- only full body shot we have of the unit
 
Logan Jonker
Posts: 17
Location: Missouri
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well- we were losing too much radiant heat outside through the exterior barrels and up the chimney. So I have moved it inside and made the following modifications:
Instead of air flow between the inner burn barrel and the exterior 55 gallon drum, I have filled that in with pea gravel.
I have also filled the burn chamber with several gallons of pea gravel capped with a clay sand mix. The Interior burn chamber is now closer to 20-25 gallons
I have capped bother barrels with cob to level the tops, seal any gaps and provide additional mass.
I still have an 8 inch feed tube and a 6 inch flue.

This sucker is HOT.
Flue temps are about 600 degrees,
The cob top and sides of the 55 gallon barrel get between 200-300 degrees.
My feed tube extends through about 4 inches or so of Cob and then about 17 inches down with a 2.5-3 inch gap below it to the bottom of the burn chamber.
The burn is actually occurring about 10 inches above the ground, on top of steel, pea gravel, steel, pea gravel and cob, The base of the barrel doesn't get as hotas the upper walls and top, by design.
It heats up fast, warming the room up fairly quickly.
I did have bricks lining it, but they acted more as insulation rather than storage, so they are gone, allowing the heat to get out more quickly.
I know I am losing massive amounts of heat out the flue, but I am working on a solution for that as well.


Issues:

It doesn't hold heat for more than a few hours, which is understandable as there is only about 2 inches of pea gravel as mass between the walls of the pocket rocket and the exterior barrel. Would Adding about 6 inches of Cob heat up and radiate longer through the night?

Fire is climbing up the feed tube again, but only about as far as the feed tube is in the burn chamber, so I think it has to do with 600 degree radiant Heat around the tube at that point. Flames sometimes lick higher and a briefest puff of smoke might come out of the feed but gets sucked back down again. I have a removable 8 inch round, 9 inch tall ceramic section of pipe I have resting on top to the feed tube (this makes it easier to clean, light and provides better draft)

Is there a way to slow down the burn, if that is a solution? Either Go to 6 inch feed tube or move the feed tube lower? Would slowing down the burn keep it at about 400-500 degrees for a longer time.

Thanks for the input.

note: this is a Pocket Rocket, not an RMH. Thanks (at least I think there are some technical differences in how they run)

 
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