Rocket Stove vs Hobo Stove

[Ulu]

This winter I have been building some experimental hobo stoves. I didn’t follow any particular pattern, but built about 8 different versions or modifications.

My efforts culminated in a stove you would hardly want to take backpacking, but it works ok in the boat yard.

So far I am only using this to heat water for tea and warm my feet.

Anyhow, I have burned a few of these tin stoves out, and was thinking of something more sturdy and durable when I found these old boat seat pedestals. Rocket stove material, for sure!

Trying to minimize cutoff waste, I nest the cuts together.

I test my pipe fitting skills.

Not straight yet. Just a bit more grinding needed . . .

I removed one flange and cut/shaped the other three smaller.

Close enough so far . . .

Ah yes, the metric square! (There is some myth that it is more square than the English square.)

Lots of hacking with grinders and then smoothing with the wheels and belt sander.

Drilling out the ends. This was the hardest part. Too tall for my tiny drill press.

Soon to be welded. I still need to make the fire grate and the ash door.

 

[Ulu]

Shaker grate inside:

Cleanout and air door:

First burn:

 

[Ulu]

I made the grate from 14 ga sheet metal, bent as a channel in the vise, and slit with the grinder.

This came from some gray painted Air Force junk, in my collection since 1973.

It wants a little handle to shake it, and the air door wants a handle too.

The first burn went OK last night, and I successfully made cocoa on the new rocket stove. But it isn’t perfect.

I found I can boil water easily over the chimney, but not so easy on the little platten. It sheds too much heat, and there is a trick to lighting it off.

The trick is to load 2 sticks (I was burning 18” western red cedar, split into sticks 3/4”x3/4”) then stack the chimney with small tinder, and light the chimney on top. That burns fast, and drops coals on the grate, starting the sticks.

It is easy to make a hot fire with two sticks, but 3 cuts the airflow and makes smoke. Otherwise it is a little blast furnace if you point it into the wind.

And it is sensitive to wind direction.

The big flanges on the ends shed a bunch of heat, and I thought that maybe I should reduce them. But instead I may sheath this stove with sheet metal and load it with thermal mass. Clean sand, small gravel, or things like pearlite and vermiculite can be used for the mass, allowing the stove to conserve heat.

 

[Ulu]

I decided to open up the fire grate, add a shaker handle, add an air door handle, and make a heavy duty pot stand.

This reduced smoking and eased operation. It wants a spring on the air door. Maybe a bit more venting on the grate.

Pot stand.

I may relieve this to improve draft.

Shaker handle.

Adding an air door handle.

 

[Ulu]

Death tribute to the tin hobo stove:

Rust in peace…

 

[Ulu]

Ruined freon compressor might make a potbelly rocket, with some heat capacity.

 

[MattiThundrrr]

I like this one using nothing but 4 cinder blocks, takes literally seconds to make

 

[Ulu]

Looks fast and easy if you want to cook on a construction site.

BTW, they do not actually still use cinder block in Canada, AFAIK.

Nobody here in California has made blocks with cinders for nearly 100 years. Since the 1920s they all use small aggregate and air.

Those “cinder blocks” in the video are called CMU in the business: Concrete Masonry Units. Zero cinders are used.

These blocks now cost $3.26 each with tax at Lowes, so no labor to stack them up, but it would cost over $13 total to make that stove, plus a trip to Lowes.

I spent about $4 on argon and $2 for AC power.

The next one will cost the same. Built from junk I already own. But for now, I will go back to work on the car, unless it starts raining again.

 

[Oldbiscuit]

Careful using concrete blocks. If they sit outside and get wet, a fire can make them pop, split , even explode from the expansion of the boiling water vapor!

 

[MattiThundrrr]

Similar in concept, this is the Kelly Kettle I inherited from my father in law.

Double wall chimney that fills with water, detachable fire bowl at the bottom, can boil water in minutes using twigs as fuel source.

Attributed to Irish fishermen, because you gotta have proper tea to catch fish

 

[MattiThundrrr]

These blocks now cost $3.26 each with tax at Lowes, so no labor to stack them up, but it would cost over $13 total to make that stove, plus a trip to Lowes.

I spent about $4 on argon and $2 for AC power

How much did your welder cost?

 

[Ulu]

I didn’t buy it just to weld stoves. Stoves are for fun and practice.

 

[MattiThundrrr]

I didn’t buy it just to weld stoves. Stoves are for fun and practice.

Thanks. Great info. I don't have a welder, so here's instructions for a rocket stove that doesn't require a bunch of expensive equipment

https://www.rootsimple.com/2012/03/a-rocket-stove-made-from-a-five-gallon-metal-bucket/

 

[MattiThundrrr]

When we were kids, my friend's dad was a Scout Master, he taught us to make tuna can stoves. Not the best thing for cooking, but a fun little project for the kids nonetheless.

https://randomcreativity.wordpress.com/2012/01/31/tuna-can-burner/

Hadn't thought of those things in ages, I might have to make a few with the lads, teach them to be prepared for power outages

 

[Ulu]

Teach them to make the double wall gassifier hobo stove. You need some empty cans an ice pick or nail, boyscout knife or old kitchen knife, small log to beat on, hammer or small log to beat with. A beer can opener helps.

This thing can cook when made from just a dog food can and a soup can. Much hotter than a tuna can stove.

This is a 3-can model sitting in a cookie tin for heat reflection.

Zero cost, maybe an hour to build .

 

[twojs.bike]

I always wanted a rocket stove. Not sure why. Maybe we should have a rocket stove build off?

 

[68z27]

I doubt there is any connection, but as soon as I saw the "torso shaped" metal kettle, the name and that its from the British Isles, , I instantly thought of the "Kelly Gang" of Australia.....

 

[Ulu]

I thought of a samovar, and I’m not even Russian. I have UK & German ancestors.

No time to burn here.

Still in the aftermath of our broken sewer line.

I had to bring in 1 yard of soil and remove 1 yard of saturated clay. Anyhow, I moved all that clay in a wheelbarrow.

 

[Ulu]

The weather has turned wet and windy so I can’t weld on the car. I’m back to working on the next little stove.

So this is the compressor from a small refrigerator. The steel is substantially thick. 3mm before pressing.

I cut it apart in the vise with my fake sawzall. The top and bottom are electric seam welded, and they leave a convenient little groove to get your saw started.

So what’s inside this is, a small amount of lubricating oil, 3 short wires, copper thermostat tube, and a brushless 120vac 60hz synchronous electric motor that drives a piston pump.

Synchronous just means that it will try to run at some multiple of that 60hz frequency. (50 Hz in Europe and other places.)


Notice how the extra counterweight is riveted to the crankshaft.

Cute little piston pump!

The only connections from the motor and pump assembly to the case are three springs and three wires. The 2 larger tubes coming into this case connect only to the case.

There’s a little plastic scoop on the piston pump, which is the freon pump intake, and it is positioned very closely to the freon line coming into the case.

Pressure from the piston pump just exits this hole into the case & simply flows out of the case through another line to the condenser coils.

There are no gas-tight connections to the pump. It just bobbles around inside on its 3 little springs. It sucks up Freon spewing in through the open copper tube, compresses it, and spews it into the steel case.

There is almost no way to break this thing unless you cut the wires or one of the three copper tubes. Cutting the tiny third tube which controls the thermostat will also leak out the Freon.

But, A big dent in the case would probably not effect the operation at all. You could literally throw this thing off a truck onto the ground and it wouldn’t hurt anything inside of it.

So all the little parts come off with grinders and drills. I drilled out the factory welds and brazing. This little lip came off with the sawzall.

Drilling out the electrical connector, I used the Uni-bit and just powered through it. The electrical pins have some very tough glass insulators that will shatter.

This was electronically welded steel, where it appears that the three copper tubes were furnace brazed in place. I’m gonna grind off every trace of copper before I try to TIG this.

Here is the empty case, before completely removing the copper (and 3 thin electrical pins,) and you see three 6mm dia steel pins, where the isolator springs are retained.

 

[Ulu]

I cut off one of the feet and reshaped it with the grinder so it fits under the front edge of the stove like this when I tip it up.

I think it will stand vertically like this.