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3" Rocket Heater with 7 Gallon drum  RSS feed

 
craig offret
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I have researched these heaters for a long time, I got so much info from this forum.

I Really wanted to make a very small version of the rocket heater, I really am not to fond of having a 55g drum in my living room i think it looks kind of janky.

Using zero's fact based formulas I scaled down the size of my heater to less than 3"

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craig offret
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I used insulated fire bricks they are lightweight and very easy to cut and shape, so the entire Utube and riser are cut out of the bricks, I think it took less than 10 to make the firebox


The input tube is 6" long 2.25 x 2" opening

The horizontal burn chamber 9" long 2.25 x 2.75

The Riser 21" long 2.5 x 2.75

The exhaust 3" diameter
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craig offret
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I used a 7 gallon air tank as the drum, I offset the riser opening to one side to make room for an exhaust out the bottom. This saved quite a bit of effort trying to seat the bottom of the drum on the bricks, the square opening to slip over the riser is pretty tight so there isn't any real exhaust leak to speak of.

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craig offret
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The trial burn on the porch went well, it only fits a couple 1x2s in the feed chamber at a time, it heated the tank hot enough to burn the paint off after a couple reloads of wood, it gets pretty hot and there is zero smoke when its running right, I tried to open the front and load up the horizontal chamber and it smoked for a bit, If I just keep putting the 1x2s down the feed inlet and let them consume it runs smokeless, the exhaust isn't really that hot, maybe 90-100 degrees maybe. the fire bricks hold the heat in pretty well.

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John McDoodle
Posts: 524
Location: ontario, canada
fungi tiny house transportation
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That's a neat little unit.
 
allen lumley
pollinator
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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Craig Offret : Take that bad boy outside to burn the paint off of the tank and heat it until several vertical feet of the galvanized pipe is no longer a shiny silver,

and instead is a dull grey. Burning off that stuff inside will give you a monster headache. The Heat Riser should be at least 1/2 again as long as the Burn Tunnel,

I can't tell from the pictures just how long your parts are ! Be prepared to spend a lot of time feeding your Rocket, it is not likely to support more than a token

Thermal mass ( I Think ) . It is pretty though

For the good of the Crafts ! Big AL

Late note : Looks like I was typing as you were posting - You probably will need more insulation under your Rocket than just what you've got now Your length to

height ratio looks good. A.L.
 
craig offret
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I just hope it puts out 25k btu or better or Im going to have to Scale up to 4" I burned it out on the porch for 3 hours I had to add sticks every hour or so. I think I have the arrangements of feed, burn, riser correct the fire runs as its supposed to. After the cool down I can see the sweeping 90 Upward has seen the highest heat as the bricks are in that area are discolored the most. I could never get it hot enough to burn the paint off the lower half of the tank. I might do it manually with a bonfire.

I am only heating a 16 x 16 cabin with it, I was thinking of putting the exhaust through 2 masonry bells... Dragon heater style. I just wish I could do something with the tank to dress it up a bit.

for now I think I will wrap the burn chamber in bricks for thermal mass storage. my goal is to exhaust cold air

I am really happy with the zero smoke output though, and zero ash.. it is quite impressive as this is my first rocket project..

 
Satamax Antone
gardener
Posts: 2280
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
55
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I quite like the thing. I love insulating firebricks. For burning your "barrel" a daft idea I've used before on 55gal ones. Wrap it in rockwool/roxul.

http://donkey32.proboards.com/thread/989/burning-paint-off-minutes-tops?page=1
 
Glenn Herbert
gardener
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Location: Upstate NY, zone 5
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Good work on stretching the lower size limit on functional J-tube rocket almost-mass heaters! I have heard seriously tiny rocket stoves (straight through, no barrel) can work easily, but your use of insulating firebrick must be what allows you to get the contained flow. Now to see if you can get a usable amount of heat from it.

You say you are feeding once per hour... that is quite an achievement. What fuel are you using - size, shape, length, wood species? Is it all just 1x2s?

If the exhaust (at the top of the chimney?) is 90-100 degrees F, there is no more heat available to power a bell. You are radiating all of the heat from your barrel. If you want a bell, you will need to increase your system size. A 6" system has something like half the power of an 8" system, a 4" system would have less than half the power of a 6", and a 3" considering the extreme surface-to-volume ratio would probably put out much less than half of a 4" system.
 
F Styles
Posts: 447
Location: climate zone 6b
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great pocket rocket buddy. have yo uthought about building a brick box around your bell to hide it and use bricks with holes to allow air flow?

 
craig offret
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Wood so far has been 1x2" kiln dried fir so it burns and feeds itself real well as it is smooth a couple 18" sticks are about all that fits in the feed tube, Im sure things will change when I try to put split alder in there. I was really trying to make a dragon heater and send the fire out the riser to bells, its challenging to put a refractory top on the bells as its so non structural an delicate. I went with the tank as it was a pretty easy solution.

For now I'm pretty versitile as nothing is cast into place. Im going down to the cabin tomorrow to set it up I am set up to put in some type of mass but I haven't decided yet, for now I know I can capture heat for mass around the burn chamber but not much else, I can imagine how terrible the tank will look if I try to wrap it in concrete or brick. Im going to try to make some castable refractory from all the dust I collected from the bricks.



 
F Styles
Posts: 447
Location: climate zone 6b
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have you thought about building a little batch box in front of it or a larger feeding chamber with a lid and access port at the bottom of the J so that you can load larger sticks?

have you thought about buying paint remover to melt the paint off to the bare metal then paint it in high temp paint?

have you thought about adding more insulation like perlite in between your riser and larger duct around the riser?

have you thought about maybe building it inside a oval large wash tub and then filling around it with sand and have wheels on the bottom so you can move it around or outside to save space in the small cabin in the summer?

they make different color high temp spray paint maybe you could get creative with the paint job so it doesnt look so drab?

i think yo have created a very handsome unit and cant wait to see more pics.

keep up the good work.


 
craig offret
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I think Glen is right on target with the 50% scale down on heat.

I took the bricks apart this morning in the daylight for analysis and I don't think I'm as impressed as I was initially, except for the burned board on the deck.

I fired it up without the tank and i can't get any flame in the riser, it seems like a large majority of the heat is being dissipated in the burn chamber.

Plus I couldn't get the tank hot enough to melt the stickers off the side. I think this configuration might work if I was trying to heat a 6x8' bathroom or something
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F Styles
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Location: climate zone 6b
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i wouldnt be so disappointed yet. one thing that has not been tested or figured in yet. although Glenn may be correct you still have not pointed the bricks or insulated the burn chamber or heat riser yet and could be tested in that oblong wash tub i suggested with ease and with out doing anything permanent. put your pocket rocket into the tub and fill it with sand (its been done before) and wrap your heat riser with fiberglass insulation and there you go a better test with out the bias of a leaky insulated setup. this way you could put the tub on blocks in a safe location in your house and run the exhaust duct through some tin with a hole in it that is placed in an open window as a temporary test to see how it heats a room in your house? i would make sure the bricks are pointed for the test and that there are no leaks to poison the air. its weird how disclaimers must be put for people that are bent on making stupid decisions and is not meant for you.



16gal oval hotdip washtub

run exhaust out window for a short test only to see how heat is working. maybe a garage would be a safer test start to see if it can heat that?



 
Glenn Herbert
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Location: Upstate NY, zone 5
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Thank you for your thorough assessment of the experiment. You can clearly get a good burn going in this, but two 1x2s burning at their ends simply does not give much heat energy per unit of time no matter how efficient the burn is.


I will be interested to see how a 4" unit of the same construction will work for you. A comparison with as many variables as possible eliminated (same tank?) would be instructive. I think you will be pleased with how that will work. Your insulating firebricks are the ideal material as long as you can feed carefully to avoid abrasion damage to the feed tube and burn tunnel.
 
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