Steel drum rocket oven - lenghtier option (version 3)

[dvawolk]

Hi, all.

First it started with Rocket Ovens DVD from permies.
some photos here: (first/original version)

First i made oven with dimensions according to DVD and coupled it with 6 inch J-tube. It was a good use on our summer camps, baking two baking plates that were approximately 40cm x 25cm in dimension. Since the 6 inch J-tube was struggling with baking such a mass of food i decided to make a lenghtier drum oven and more powerful J-tube.

Photos and facts about the second version here: lenghtier version of a stove

This second version was coupled to j-tube with 18cm x 18cm heat riser. This one could bake three trays of lasagna, with GN1/1 standard dimensions (53cm x 32,5cm) and it really wasn't a problem to hold a temperature of 200- 230°C for this amount of food.

It also performed well when baking pizza, 45cm in diameter, with temperatures 300 - 350°C and baking time of 5-6 minutes.

So the second version was much more compatible with our summer camp's requirements.

But now i am in a need for a new model:

What i want for the next model is:
1. ability to cook/bake lasagna/potato+vegetable+meat/bread in two GN2/1 trays (65x53cm)
2. ability to bake one pizza at a time, square size of 65x53cm
3. posibility to be less high (use some other rocket heater instead of J-tube --> height problem)
4. Use oven door that wouldn't be on my way (maybe side opening to left+right)
5. Add a small window to oven door to check the cooking performance
6. (An option to heat water on the back side of the unit (to further use up generated heat after leaving the close-to-oven path).)
7. Stable outside design - metalwork.
8. Easy assembly/move of oven (upper part) and heater (lower part) with two persons.

Some facts about this build and main question:

- It is obvious that i can not use 200L drums, so it will be custom made with steel bending, welding, riveting.
- laser cutting of metal is an option
- oven inside will be stainless steel (in previous versions a lot of rust formed inside the oven because of high temperatures and high humidity)
- the compartment will not be cylindrical, but rectangular. This means that i can achieve the required size for the trays with the same volume as compared to version 2 that used cylindrical drums..
- even though there is the same volume to be heated, there is a significantly larger mass of food to be cooked/baked so i presume that the heater component should be more powerful. I could upgrade heat riser dimension of regular J- tube to 20cm x 20 cm (8" x 8") but that would not be compatible with my "lower height" compatibility. So i am inclined to use some other type of heater. What is your opinion on using a DSR2 open system for this kind of heater? Would you suggest some other type of heater The chimney should be no more than 1 meter high (this is a preference, not a rule), but the exhaust temperature would be quite high because of the specified usage...

I will be adding some sketches of this third version...

Thanks and have a nice evening.

[fuegos]

I would take a look at Matt Walkers riserless core oven which is what i built.In my case the oven is the same size as the footprint of the core - 50 x 50.as for temperatures i have a analogue dial type oven thermometer that i place on the floor by the door & 250c will cook a tray pizza in 5 to 8 miniutes.Im sure you could build an oven on top of this core to accommodate a bigger tray.
Also nice build, looks & preforms great 

[martyn]

Fuegos, how tall is your chimney?

[dvawolk]

There are some pictures that i made with sketchup.
Outside dimensions (without the chimney) are about 100cm long, 75cm wide and 53cm high.
There are three layers of sheet metal.
Inner two are stainless steel because in between these two gasses are travelling.
Outer layer is Zn platet steel or maybe Brown painted aluminum.
In between the middle layer and outer layer there will be 5cm of insulation.



If i take away the front steel plate (oven door is not sketched yet), you can see:
- inner layer of stainless steel (reddish) for white oven compartment.
- 25mm gap between reddish and yellow layer for hot gasses.
- middle layer of stainless steel (yelow) which is touches gasses from the inside and insulation from the outside.
- 50mm gap between yellow and gray layer for insulation.
- outer layer (Zn steel or Aluminum)

At the bottom you can see a square entrance for hot gasses from the burner. This sketch is designed for 15x15cm system or slightly larger...


Here is another image, you can see water heater for about 30L of hot water, also in this last picture you can easily see the path of gasses to the chimney.


Here is the sketchup file (v8): link (ignore the hidden parts)

[fuegos]

Oct 26, 2021 8:31:52 GMT -8 martyn said:

Fuegos, how tall is your chimney?

1.7 M in total -  from the oven floor to the top of the pipe.More than enough in this case, it pulls like a train.

[fuegos]

dvawolk i assume you are planning to put this oven on top of a core ? maybe the gap between the two metal skins might be too restrictive ?

[dvawolk]

Hi, fuegos.

Yes, the thing on the photo will be put on the top of the stove.. As you said about constriction - now it came to my mind: If using a J-tube it is not a problem of having a small gap for the gasses to pass in between the barrel and insulated heat riser... But with peter's batchboxes it was said that it is good if you have at least 30cm or so of empty space right outside of the heatriser.
Is this the same situation with DSR2 (open system) or with Walker's riserless core? Can these cores be used with gas channels instead of bells?

I checked the CSA of the gap (the rectangle below will be 25cm x 25cm, gap is 2,5cm), it gives a total of 250 square centimeters. This entrance is not yet correctly sketched.
System with 15cm x 15cm gives 225 square centimeters, so this should (?) be enough if the core would allow this kind of path of gasses.

[dvawolk]

Hm, matthewwalker, what is your opinion - can above be coupled to your riserless core reliably - provided that the gap inbetween the layers is the same or slightly above CSA of 6 inch system?

Regards,
Klemen