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Welded Garage Rocket

Steve Blair


Joined: Oct 06, 2012
Posts: 6
Brand new here!

I just started building a 4" rocket stove for heating the garage.
Wisconsin winters can get to -20 deg F but more typical is between 10-20 deg low at the times I'm in the garage workshop.

I found a 16" diameter compressor tank, 4" inner dia. round riser pipe (1/4" wall) and 4" outer square feeder pipe (3/16" wall)

Have already cut open the tank and welded the horizontal feeder to the riser.
I plan to fit a vertical feeder to the horizontal one because the design goal was to stick a long 2x4 in the feeder and just let it be slowly consumed. I also have 100 year old dry lath that burns fast and HOT.

The combustion riser will be insulated with vermiculite inside a stove pipe.

No mass to speak of, just instant heat for taking the chill off the garage.

I tend to get artsy with some projects so the stove's feet will be like those curvy 1950s sci-fi rocket fins

I may later make a "nose cone" with multiple heat dissapating fins, to shape it more like a rocket ship and less like a bomb.

QUESTIONS:
About how long a horizontal exhaust can the stove push? Internal riser is about 24".
Can I go vertical out the roof? (~10ft)
I can send it out a window opening if needed.

If the stove proves itself, it may be rebuilt or prettied up and brought into our house.
A possible modification at that time would be to pump heated water down to storage barrels in the basement, either for radiators or just slow, passive heating of the basement space. Our gas forced air furnace will recirculate it throughout the house.
That is WAY in the future though.

I can post pics later if there is interest.

--Steve
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 971
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
First of all, if you want slowly consuming, you don't want a rocket.

Secondly, metal feed tube, burn tunel and heat riser don't work too well.

Here's a pic of one feed tube, burn tunel and turbulator after only about 40 burns. May be less.



And four inchers don't work well either. They are temperamental and need cleaning often.


God of procrastination (Pratchett's style) )
Steve Blair


Joined: Oct 06, 2012
Posts: 6
What is that one made from? I can't tell exactly what we're looking at.
I made the burn riser out of 1/4" thick steel so it would last longer, and the feeder is 3/16".
Standard wood stoves seem to be about this thick too.

I have also heard that 4" stoves are tricky but it's a bit of an experiment and primarily for the garage.
I'm also not pushing exhaust through a cob bench.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 971
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
Well, feed tube and burn tunel made of hydraulic pipe, 1/4 or more. Turbulator made out of an old gas container about 1/8 thick. What you see is heavy form of spalling, the metal deformed, and flaked. The bottom of the burn tunel turned into 3/4 puff pastry. Obstruing the burn tunel.
Weldon Carter


Joined: Oct 08, 2012
Posts: 4
I just built this exact heater Saturday from the same pieces you have. I used a 28" riser wrapped in insulation. I stuck a 5" exhaust stack inverted from the bottom of the bell.
My feed tube is only 10" tall or so.

First impressions are this thing rules for efficency, I have just burned twigs etc and it gets the upper 1/3 of the bell to 300+ in 60F ambient. the exposed portion of the burn chamber was at 900F on a infared temp gun.
Its a novelty at this point but I am going to build a 8" version for my shop (30X40).

The heater seems to want a 1/3 of the feed tube covered and burns with very low flow out the flue, the flue also stays under "skin burn" temperature which I like.

I will try and get some pix.
Steve Blair


Joined: Oct 06, 2012
Posts: 6
Hmm, I wonder if the hydraulic pipe has a different alloy than the steel I'm using or if both will end up spalling like that.
The insulated riser is a high pressure gas pipe meant for carrying natural gas at 3000+ psi. The square feeder is structural steel tube.
I know hydraulic pipe is quite soft, but very little beyond that.

I'll keep my eye on it and report back if I see anything weird going on when it starts getting use.

I bought a tube of 2000 degree wood stove sealant for repairing cracks. The inside of my welds could be better, so I'm going to seal them up with it. The outside welds look great, and should be easily gas tight if they don't crack horribly.

Pics of this other stove you built?
I have yet to take any good shots of mine as it's only half built.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 971
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
When i talk about hydraulic pipe, it's extremely tough. IIRC it's suposed to whistand 300 bar on a regular basis. It's tube recovered from the artificial snow circuit in the ski resort i work for in the winter.
Steve Blair


Joined: Oct 06, 2012
Posts: 6
The hydraulic tube is up to the job, I think.
I suspect the problem with stove in the photo above was that the primary burn chamber is of very thin material. I've welded a few propane bottles together (tiny 1lb tanks) and they're far too thin to use for this.

I lit the stove last night! It's only partially built - horizontal feeder and riser only, with insulation covering the riser and a small bit of the horizontal feeder.

It's 35 degrees outside - cold!
I initially put only a few pieces of lath in it - they kept going out. I put a chunk of 2x4 into it, which didn't work too well - I think not enough surface area to burn efficiently.
Then I stuffed 10 pieces of lath (.5"x1.5", about 12" long) into the feeder and boy did that thing rocket! It ran fantastically until the wood was mostly gone.

The barrel/compressor tank was placed over the top of the heat riser and I measured 450 degrees at the hottest point. The lowest edge of the tank was around 150-200 degrees. There's no exhaust port, so the bell was just resting on the feeder in the front, and a piece of 4" tube in the back - exhaust spilled out all around the rest.

So I've learned that it takes quite a bit of heat to warm up that 1/4" riser pipe! I think that stuffing a wax paper cup with tiny twigs would be a good way to light the stove. From there out, lots of little pieces will work best - I may have to give up on burning whole 2x4s, but I'll see how the horizontal feeder works - maybe it's still a possibility.

I'll get some photos tonight before the sun goes down.
Weldon Carter


Joined: Oct 08, 2012
Posts: 4
I will try and get some pix tonight of mine, I have been working out of town.

I have been using a map gas torch to light the kindling, the instant shot of heat really gets things going and as long as you have some smaller twigs in there they will light off pretty quick.

I can't believe the other stove shown above cratered like that. I built a fireplace grate out of the same tubing to use a blower on and fired it all last winter in the coals of a masonry fire place and it hasn't physically changed like that bell did.

I also am not sure it's going to matter much to me as I am only using this on weekends some and far less than the average RMH in a house.
Steve Blair


Joined: Oct 06, 2012
Posts: 6
Oi! Horiz. and vert. feeders together = worst idea ever.

At one point, I had the fires of hell belching out of the vertical feeder. Either the top or front opening needs to be closed or you get a very short rocket stove that exhausts into the room.
Some other technical observations have given me some ideas for tweaking, but as it is now, it's hard to start and very easy to overfuel or underfuel.

Learned a lot tonight.

Heat conducts into the steel vertical feeder, which is far too tall and appears to reverse the downdraft when enough fire builds up in the feeder.
The vertical sticks burn more and more, creating a fuel rich situation, the stove cannot pull enough air downward, and the stove starts to smoke. The only ways to correct this situation are to either remove burning wood from the feeder or open the front feeder hole. Opening the front hole without blocking off the top one IMMEDIATELY results in a spectacular fire breathing monster exhausting in your face.

Heavy modifications required, or maybe back to the drawing board...

Things that may help with the current design:
Larger exhaust - 6" or more (currently 4")
Taller heat riser
Shorter vertical feeder (less stack effect) with no front feeder
No top feeder at all
Insulating the feeder couldn't hurt I suppose...

I may have to build one with fire brick - I actually have tons of it.
Satamax Antone
volunteer

Joined: Sep 24, 2011
Posts: 971
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
    
  13
Steve Blair wrote:Oi! Horiz. and vert. feeders together = worst idea ever.

Insulating the feeder couldn't hurt I suppose...

I may have to build one with fire brick - I actually have tons of it.


Well, the horizontal and vertical feed tube being à bad idea has been documented here before. Thought, having a closed hole at the front helps cleaning.

Don't insulate the feed tube, i mean not too much. Actualy, it's a place where steel is good, if you can make the piece replaceable, since it transfers heat to the outside air, and fire doesn't tend to creep too much upwards. Insulating the bottom of the feed tube is good, and a bit of the sides, no more than four to six inches upwards. Depending on your feed tube.

And if you have firebrick, why insist to make a metal rocket which will burn out. Bottom of the feed tube, burn tunel, heat riser, or at least the first foot or two of the heat riser are subject to extreme heat. Up to 1200C°
Weldon Carter


Joined: Oct 08, 2012
Posts: 4
I fired it Saturday night (no camera though) to show a friend how it works. The wind was gusting 25+ and the temp was 80+ or so with 85% humiditity. I didn't figure it would even get up too temps since it was so warm outside. It quickly got up and rolling, zero smoke and good sideways fire in the feed tube. While it had been running for 15 minutes or so unattended we whent outside to check it out, the rh side of the burn tube was glowing red, I had never seen it do that yet and the radiating heat from the exposed portion of the burn tube was tremendous.
The heat from the bell was good too but I still wonder what it would be like with the correct gauge. I am going to build a 6" or 8" brick unit for my shop with the correct barrel, it is going to take quite a bit more output I think to warm it.
Weldon Carter


Joined: Oct 08, 2012
Posts: 4
Finally here are some pictures of my garage rocket turned outdoor party rocket heater.
We are having a halloween party Friday and it's supposed to be colder than hell so we'll get it stoked up really good and have the fam let me know if it's a keeper.
I am thinking that I am going to cut barrel in half at the bottom and redo the crappy insulation job and go woth a 6" duct lined with vermiculite or perlite or something to get the most bang for the buck.



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Steve Blair


Joined: Oct 06, 2012
Posts: 6
I think I'm going to have to redesign my stove.
I have a suspicion that the 4" round steel riser is just too small, and that it just takes too long to heat up.
I can't get it to stop smoking. Once in a while, it will run happily, but most of the time, the draft is so poor that it nearly goes out. I think to make the current stove work properly, I'd have to force a draft with a fan.

Here's the stove as it is now, but I've been looking into a 5-6" masonry riser, covered with the barrel. The exhaust is 6".

Ben Mosley


Joined: Nov 08, 2012
Posts: 42
Location: Upstate,SC Zone 7a
    
    1
Weldon Carter wrote:Finally here are some pictures of my garage rocket turned outdoor party rocket heater.
We are having a halloween party Friday and it's supposed to be colder than hell so we'll get it stoked up really good and have the fam let me know if it's a keeper.
I am thinking that I am going to cut barrel in half at the bottom and redo the crappy insulation job and go woth a 6" duct lined with vermiculite or perlite or something to get the most bang for the buck.



I am considering doing a heater like yours,except I would add a second barrel/tank off the side where the exhaust is.I'd install a U-pipe inside it and exhaust out the side.Then pack the barrel/tank with sand for thermal mass.These additional barrel/tank would be easily separated from the heater for clean out and mobility.
 
I agree. Here's the link: http://stoves2.com
 
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