I used up all the board with only the off cuts from the circular cut outs left! I will have to use to them in pieces to finish the front to get 3’’ all around.
I have glued and screwed it all together and I will build a box for it to go in with another few inches of rockwool all around.
I am thinking about lining the fire box with 6mm stainless steel, my friend only intends to use this stove occasionally and for relatively short periods to cook food so I think the steel should last but there is only one way to find out.....
I will make it as a replaceable drop in box anyway.
High temperature silicone and stainless steel screws .
I have just noticed a new product that I have not seen before, a hard surface, non insulating fire board, i have just sent an email to find out its température rating .
I have spent four hours this morning trying to tune the fire.
I have used a few bits of glass to line the fire box and a 32” steel pipe riser.
At first it was not working as I hoped and in fact hardy spinning at all and the flame was mostly going straight up the riser.
I also had black smoke puffing out .... anyway after trying out dozens of configurations and using scraps of fibre board to block off air and close down the throat I started getting better results .
However it has really made be realise how much experimentation it will take as the smallest changes can make a big difference.
I have a feeling my nice neat box will be trashed by the end of this ha ha ....
I am going back down the garden in a few minutes to give it a bit more, I have narrowed the throat right down from 5” to 3” but I want to try reducing the height next .
Just a suggestion: try to position the throat in the middle and a bit lower than the firebox. And the cross section area of that throat about 70% of the riser behind it. Then you would end at the batchrocket specification which is tried and tested by now about 500 times using a gas analizer.
Mind you, it can also be done employing a single vortex, i.e. the venturi opening at the side. In that case the csa should be a bit smaller, say 60%, and the opening should be lower than the firebox again. The bottom of this throat, gate, port or whatever one would call it always at the level of the firebox floor. During a lot of experiments the single vortex results always weren't as excellent as its double counterpart.
Thank you Peter, i dont doubt your findings for one second but i have my own reasons for wanting a vortex .
My present rocket stove is already more efficient or perhaps more accurately .. more effective.. than I need and this one is indicating that it will also exceed my expectations.
I want to use the Vortex effect as a decorative feature .
I found out this afternoon that i can easily obtain a double vortex but i really want to see the spinning flame exit the riser top so it can be viewed through a window.
Anyway I have definitely managed to form a powerful vortex effect and it is definitely capable of spilling out of the riser!
If anything it seems too powerful and was eating wood far to quickly, to be honest i have spent six hours on it today and i have not really got anywhere with the air supply as yet!
The throat size that seemed to work the best was 3’’ wide and 5’’ tall.
The ceramic board is getting more and more damaged as i have taking it apart several times, it is not something i enjoy working with, i think. I will use a Compromising refractory mix for the next one but the board is so good for making ajustements or pining in an extra bit i cant think of a better material to use for experiments
I have been using lots of ceramic board over the last 7-8 years as it plays a part in my pizza oven construction where a 2’’ sheet is placed on top of 4’’ of vermiculite and under the fire brick cooking base. However i have never had to cut it up and work with it.... horrible stuff really.
I will have a look at air inlets tomorrow but any advice would be very welcome....
We all strive to have the fiercer, hotter burns possible, in order to achieve the best burn efficiency. And the idea of letting the fire out of the riser, which for most of us happens during the bad portions of a burn. You trod a somewhat beaten path with this single vortex. Peter has tried it, and some others too, nearly the way you have implemented it this time. You'll have to sniff in the old posts at Donkey's.
If you really want to make your fire turn one direction. I'd say, go the cyclonic route. A J tube entry, round if possible, finishing into a neutral vane into a big burn chamber, even better if it's conical, like a cyclone.
I forgot to say, iirc, for a good cyclonic burn chamber with not too much drag, you need at least 3x the riser size on big systems, on small ones, you can go up to 8x, this is to avoid as much drag as you can.