rocket ovens

I have a lot of rocket oven stuff to put here.  But I wish to start with this:

What is a rocket oven?

Paul, do you think a reburn chamber would help these designs?  

William Wallace wrote:Paul, do you think a reburn chamber would help these designs?  

After the heat riser, what is left to burn?

paul wheaton wrote:

William Wallace wrote:Paul, do you think a reburn chamber would help these designs?  

They After the heat riser, what is left to burn?

Thanks for responding Paul.  It seems that I was mislead with how the barrel works early on in my RMH education.  

After the riser, all that is left is pretty much steam and co2.  What are you thinking of burning?

In Rocket Woodburning Technology, the insulated Heat Riser is the reburn chamber.

The fuel burns in the burn chamber and the particles burn through the burn tunnel and up into the riser.

I found my misunderstanding =)

Now I see your misunderstanding. The barrel isn't a reburn chamber, it's a radiator. Those gasses cool off the second they touch the top of the barrel.

The complete burn happens through the burn tunnel and heat riser.

Kyrt Ryder wrote:Now I see your misunderstanding. The barrel isn't a reburn chamber, it's a radiator. Those gasses cool off the second they touch the top of the barrel.

The complete burn happens through the burn tunnel and heat riser.

Kyrt, thanks for taking the time to understand my premise ..... even though it seems that it was completely flawed!  I can't remember where I got that from, but I realize that isn't important.  

How does a rocket oven work?

Paul you say to check the oven temperature every few minutes while getting the hang of operating one of these...

But how do you make adjustments if it's too hot?

Kyrt Ryder wrote:Paul you say to check the oven temperature every few minutes while getting the hang of operating one of these...

But how do you make adjustments if it's too hot?

You have to open the door to see the thermometer.  That will let a lot of heat out.  

In general, when you want it hotter, add a lot of small wood.  If you want it cooler, less wood and bigger pieces of wood.  

There is always the option of letting it run out of wood.  

Comparing a rocket oven to a cob oven

race to 350 degrees:  rocket oven vs electric oven

how much wood does a rocket oven use?

the carbon footprint of a rocket oven

My rocket oven kickstarter has started!   Here is the video:




CLICK HERE to go to the kickstarter

We had such an awesome time baking with this oven during our workshops!  
It was quick and easy enough to use that the students were baking at least 3x per week.
Easier to bake fresh bread for sandwiches than drive into town between class days.
(Although, stale store bread might have lasted longer...)

So much delicious FOOD!

We used it for some things you might not expect, too, like kale chips (<200F) and hot water.  
Most of our students found it easier to pop a few pans of wash water onto empty racks while baking other things, than to fire a separate rocket water heater/canner.

paul wheaton wrote:race to 350 degrees:  rocket oven vs electric oven

Paul, this test could prove interesting to refine.

Calculating the weight of the wood, before and after, to know what weight is exactly used. And monitoring the electric power with an amp clamp.

Satamax Antone wrote:Paul, this test could prove interesting to refine.  

I think erica holds the record at 9 minutes.  But I suspect that somebody could go a bit further and ....    well .... with "fire starters" maybe something under 7 minutes could be achievable?  

Paul, it could reach 350 in a few seconds, with an acetylene burner of 40kw!

What i was trying to imply, is, two competing ovens, should not only be timed, but also monitored for power consumption.

If you put say, 5kw of electrical power, and 10 of wood power, and the difference between the two is only 2 minutes. There is some energy wasted. If the rocket reaches it's temp faster using less power, then it's real bragging rights! :D  

The thing I was worried about that the video clarified was "do you have to wait longer to use a rocket oven than an electric oven?" - and the answer is:  a rocket oven heats up faster than a fancy and expensive electric oven.  

Mission accomplished!  

Of course, it would be fun to say that an 8 inch rocket oven will reach 350 in half the time of that same oven.

There's another test one could do.  Compare how long it takes an electric oven to heat up to 350F versus a Rocket Oven when the electric grid is down due to a snowstorm, or hurricane, any other occurrence that might make the lights go out.

My money is on the Rocket Oven winning.

We had a pizza party with our mostly built rocket oven on Sunday - it went very well.

We were able to get the oven well past 600 degrees Fahrenheit with just twigs and branches that had fallen from our apple trees.  All the wood was small enough to break into pieces by hand

We used a pizza peel and a pizza stone. The crusts were just delicious - crispy on the outside and soft on the inside.

Has anyone used a material other than fiberglass insulation (I hate that stuff) for the outer insulation layer?
Maybe sheep wool insulation? https://goodshepherdwool.com/

Might be hard to find just one piece though.

Ours has rock wool, not fiberglass.  Rock wool is heat resistant.

Thanks Julia. Your pizza looks delicious!

I have Tim Barker's book.
I'm torn between building a black oven or a white oven.
The white oven made with the barrels seems fairly complicated to construct but really cool, while the black oven is simply repurposing an old oven. Did this take you a long time to build?

I'm also wondering if you could make the entire j tube out of fire brick, and cover that with cob (he uses the metal tubes packed with perlite).

Nathan Strumfeld wrote:
The white oven made with the barrels seems fairly complicated to construct but really cool, while the black oven is simply repurposing an old oven. Did this take you a long time to build?

I cheated.  Tyler had started a rocket oven for Paul's feature length instructional and I bought it from him (and hired him to bring it from Seattle down to Portland and install it).

I'm also wondering if you could make the entire j tube out of fire brick, and cover that with cob (he uses the metal tubes packed with perlite).

I'm pretty sure that you could, if you weren't looking for portability.  My oven has a J-tube built from bricks, but lined with the heat resistant material whose name I'm forgetting right now. .. .  Covering the heat riser with cob will hopefully lend some insulative properties, to enable the "domesticated chimney fire" effect of a rocket stove.

Wow, that's convenient!

Is it ceramic fiber board? (the j tube). That seems like a good option too.

Yes, I think that's what it is.  It's fairly expensive - I think there was $150 worth in my oven's j-tube.  

Thanks Julia. I’m looking forward to building one. They cut down a huge oak tree near me so I gathered, chopped and split a bunch of logs. Inoculated a few mushroom logs, but I still have plenty to burn.

Is there anything you would change about yours if you could have a new one built?

Do you have any pictures of the full oven?

What if you applied a 2" layer of cob to the inside of the oven?
Of course it would take longer to heat up, but there's something nice about cooking inside an earthen material instead of metal. Plus, it would still be way more efficient than a brick or clay oven. Maybe you could even sculpt some side rails for the oven racks.