About to get started on my build, but I keep coming up with last minute doubts.
My wife refuses to have a 55 gallon barrel in the house so I salvaged an old 35-ish gallon boiler.
The top (the part sitting over the heat riser) is concave/convex (depending which side you're looking at it from).
From the point of view of the heat riser, the center of the boiler is higher up than the sides, i.e. concave.
Is this usable? How do I calculate an appropriate gap given that the gap at the center will always be
larger than on the sides?
That boiler should work fine. The top distance that matters is at the edge of the riser. If it is too complicated to measure and subtract heights, you can put a ball of soft clay on top of the riser edge, put the barrel over it in the desired position, and see how much the clay is flattened. Adjust from there.
I've often wondered the same question and for the most part I would imagine the reason people use the 44gal drum is for ease of access through the lid to clean/inspection but can not for the life of me understand that if steel is basically a no no because of the temps reached why so many people aren't using something stronger/thicker like the OP mentioned.
Location: Upstate NY, zone 5
posted 2 years ago
The reason is that steel in the barrel location is not subject to the extreme heat and atmospheric conditions of the burn tunnel and heat riser. Ordinary steel drums have lasted over 20 years so far without failure, and would be easy and cheap to replace if needed, as well as not failing catastrophically as barrel stoves are known to do.
The steel outside the "firebox" and internal chimney; where the very low carbon flame and extremely high temps exist. Is perfectly fine. And it makes a nice radiator. It can even resist a blasting from the heat riser, because it's not insulated, and sheds heat very fast.
Your wife will probably be even happier because with the round shape there will probably be less of a hot spot above the heat riser which tends to degrade the black paint over time and turn it white. There are several Youtube projects using compressor tanks which have worked very well.
I used a hot water boiler. The material is very good. Its quit stylish also I find, disadvantage is that you can't heat stuff on it (well yeah I think of welding a rack/tray on it so one can, but like this one cannot).
I removed all the paint with an anglegrinder to not have the fumes of weird paint. The colors got amazing, rainbow colors actually although that is not so obvious to see in this image.
It's a beautiful shape in a bedroom, like this one is