High powered wok cooking - what to use?

I was watching this and thinking how I could do this outside to avoid the inside air pollution?

I've only had experience with dry stacking fire bricks, and with L, J, mag and batch rocket stoves I got the most rising flame out of the latter.  I might have been overfueling it, but I got a fountain of fire coming up the riser which is what you need.

The videos on youtube seem to mostly use metal SHS to generate that amount of flame, and I guess metal is easy enough to replace.  Or they use high BTU butane gas burners.

So, what are people's experience in this sort of cooking?  What would you recommend?

Hey graham;  From the gaps in the doorway , there is no indoor pollution to worry about there. I think they were glad for the warmth and the wonderful smells coming from that wok!
Looks like a standard wood stove top with the pot lid removed. Huge firebox,and seemingly no worries about grease fire...  
You could cook over a riser like that . Batch box or J tube ' Just need to be up at the riser height.

Pretty ignorant here, but I think the wok evolved based on need. What kind of heat did they have that a wok served as the best cooking tool? I _think_, based on vague memories of a brief school enthusiasm, that woks may have been used to take advantage of a very small very fast hot fire. You'd want to check that, but IAC, the idea is to look at what the wok was designed for and then see whether you have a situation where it fits.

The temps, the length of time they are needed, the _size_ of the heat source (but that would be accommodated  by the correct size of wok)... The temps, attaining and regulating them would seem the questions to ask.  IIRC, the wok cooking is predicated on a very hot heat source.


Cheers,
Rufus

I guess I'm undecided about whether an open stove like the one pictured is bettered at all by a rocket stove for cooking.  Open fires lose most of their heat up the chimney when compared with modern wood burners with respect to heating, but that's what you want when wok cooking; you want the heat directly under the wok.  I've seen it claimed that 3 stone fires, well made, are pretty efficient though I've never made one.

Hey Graham, as you know I have have been delving into rocket stoves over the last few months but I have been outdoor cooking over my washing machine drum for 40 years!
To be more accurate, it’s  probably been around 10 different drums as they don’t last forever.

To be honest the drums are about 100 Xs more fun than my rocket stove, they offer much more radiant heat look fantastic, cook food to perfection but the main advantage is just how well a wok fits over the flame and how quickly it heats up!
The down side comes from the danger aspect of having an open fire and the amount of fuel required.
I use a 6mm steel cooking plate that just sits on the drum, this offered lots of cooking space and temperature variations, I have a little stand that fits over the centre hole and place my Wok on that.
Cost is minimal apart from the steel plate, they cost around £100.

I do a fair bit of wok cooking.  I have a propane wok stove with a low and high setting, made specifically for wok cooking.  It sounds like a jet engine while on the high setting, and will turn the bottom of an empty wok glowing red in probably less than 10 seconds.  I found it online at the The Wok Shop.  The food that comes from it tastes like restaurant style stir fry, which has a lot to do with the high heat that creates the Wok Hei.  I've thought about a wood fired wok stove a tiny bit, something that was able to produce very high heat at the exhaust/wok stove is what I would desire.

Fox - I've had several opportunities over the last few years to pull out the stainless steel drum of a washing machine to be used as a fire pit but the thought of using it as a wok fire source just never occurred to me!  But then I don't do the cooking  As a spectacle it certainly looks the part with the bonus of being able to cook over it.  But as you say, the wood consumption is going to be high and not viable for daily use.

Joshua - my brother had a LPG wok stove but his wife threw it out as they didn't use it much!  I did have a metal L style rocket stove I bought a while ago which I tried out last night.  Although it gives out a lot of flame it took a long time to heat up a water kettle.  And I think that's the problem.  There's only 8000 BTUs in one pound of wood and I've briefly looked at propane wok stoves which say that they provide 10,000 to 100,000 BTUs so I suspect a non batch style rocket stove is going to have trouble creating wok hei.

Edit: I just found this BTU thread where Peter calculates that a 6" Batchbox can generate about 77k of BTUs per hour. That sounds about right for a wok.

Using a wok fire ring on top of the riser is one of the most common ways I have cooked using my rocket stove.  I don't find that you need flames all the way to the wok for this to work well, because of how a well-insulated riser funnels all of the heat being generated to the very small space under the center of the wok.  It has been my experience that the metal ring a wok sits on is a great way of providing the ideal height for any pot or pan one might use with a rocket stove.  The ring for my wok is what I always use on my rocket stove, unless I'm grilling something.

Jason, what's the power of your rocket?  Or diameter?

Graham Chiu wrote:Jason, what's the power of your rocket?  Or diameter?

Graham, the riser on my rocket stove has an ID of 3.5".

All the tradespeople have departed for the Xmas holidays leaving the new granny flat at the rear of my house without water, power, and gas.  We are having to drop an extension cable into the house for temporary lighting.  I wanted to build a compost toilet but my daughter strongly objected to that!

And she has no cooking facilities either.  So, I tried to build a wok station for her but ran out of bricks.



I found a chimney but need to build the manifold to properly vent the gases away.  I'll finish this after Xmas when the rain is supposed to stop.

Now, does anyone know where I can get a metal plate with a pot cut out?  Maybe I need to find a metal fabricator to cut a circle out of plate steel?

Graham Chiu wrote:

Now, does anyone know where I can get a metal plate with a pot cut out?  Maybe I need to find a metal fabricator to cut a circle out of plate steel?

Are you in USA? in the last decade there have been a lot of cnc plasma shops pop up. Not to hard to find one. They could program and cut it in a few minutes. Most of them make metal signs above ranch gates.

Nope, not in the USA but I now know what search terms to use!  

In the USA  moderate sized cities often have a couple of metal vendors. Angles, sheets, tube, etc. Some of them also have a scrap yard where used metal can be plucked on it's way to recycle. There are couple/three in SF Bay area that are kind of a fairy land for certain types of artists and gear heads...

Might be worth a look around to see if you find anything like that near you. Steel may not be gold, but it's NOT free!


Cheers,
Rufus

Joshua Parke wrote:I do a fair bit of wok cooking.  I have a propane wok stove with a low and high setting, made specifically for wok cooking.

We also use a commercial propane stove designed for wok cooking.
Just remove the cast iron grate and drop in a wok.
Cooks just like a restaurant kitchen.

I picked up a wok from the shops today. Once it stops raining I'll see how it works over my now rectangular opening formed by the fire bricks to the burn chamber.

Just need some peanut oil.

I dry stacked a 5" batch box with fire brick and lined the floor and roof as well as manifold with ceramic fiber blanket.  I also built the riser using CFB to a height of 920 mm.  It's very clean burning, and virtually smokeless after about 5 minutes.

I am getting about 500 deg C at the top of the riser which sounds plenty hot enough.  I was sort of expecting to see flames shooting out of the top of the riser but it was just heat haze so it's only heat coming out.  But the 920 mm height is inconvenient for cooking  I might have to build a bench around it to stand on.

Over at Donkey's Rocket Stove Boards they shared a discovery, that risers need not be so long!
Essentially,  3 times the diameter, half the usual height,is tall enough.
It's explained  here: http://donkey32.proboards.com/thread/1845/scandal

Here is a nice hot plate rocket stove, very similar to what your going for,but at a nice cooking height.

http://donkey32.proboards.com/thread/3349/hot-plate?page=1

A video of it in action:

I have found that revising rocket stove technologies and even more so, development, is just about the most frustrating subject I have ever encountered!
To find out anything you need to do mutable cross references and try to read in between the the lines to fill in the detail.
Reference to the shorter riser, yes it does seem possible but at the price of a longer chimney.
As far as I can ascertain .. a 6” batchbox with a 2’ high riser needs a 25’ high chimney but I don’t actually know that!
Obviously development is happenings at a rate of speed that is differcult to keep up with.

I'm using a batch box, and the dimensions from Peter's spreadsheet.  As far as I know, if you shorten the riser, you need a longer chimney to compensate.
If you just want to cook over a short riser without an additional chimney you'll need to compensate for the lack of draft by using a fan to drive the air flow.
I bought a peltier module today to see if I can harvest the heat from the riser to drive a fan.

I ran another burn test with more pallet wood, and now reached 700 deg C at the top of the riser.



I was impressed because I was able to boil 10 cups of water in a wok in 10 minutes but the same amount of water took over 30 minutes on my gas stove!

Nice.  I've had it in my mind that it would probably require a fan to reach the temperatures desired.  I don't know what type of temperature my wok stove puts out, though I do I know that it's measured as a 35,000 BTU burner...if that's any help.  Some other thoughts I've had to design a wok rocket stove would be to insulate the core to maintain that heat where it's needed.  Using hard woods that generate more heat than other woods will probably be needed, I know that black locust is a good candidate, and if you can get osage orange, it would probably be one of the best.  Another idea would be to play around with the exhaust exit point shape, I've thought of using a, "nozzle", to concentrate more heat to a smaller area, the same way a rocket uses a nozzle to concentrate/accelerate the flow of burning fuel.

So most of this core was insulated with ceramic fibre blanket. I left the sides, and front of the combustion chamber facing fire brick only as I think you need some thermal inertia. Even then the outside of the blanket was recording 100 deg C and all the bricks started to heat up.

A pity that I didn't weigh the wood to see how much was needed to boil water. But I was impressed at how quickly it did boil the water compared with my gas stove. However, I'm sure my electric kettle would have been faster.