i just rebuilt the heat riser with fire clay and perlite---6 inch inner diameter
guessing the riser is drying out and starting to insulate better because today the top of the barrel was red hot-- i filled a pot with water and set it in the center of the red area to cool it down a bit, and then let the fire go out
is this normal?
it seems prolonged burning like that would burn right through the barrel
am i just being a nervous nellie or do i need to use lower octane wood?
Congratulations, your rocket heater is working well!
You are appropriately nervous; at those temps, the steel in the top will eventually fail. Those temps are what you want, so you just need to handle them appropriately. One way to do this is...
I am a partner in DragonHeaters. We sell a 26" diameter barrel cap cast from dense refractory. You use it by cutting the end of your steel drum (which is 24" in diameter) out so that it is a cylinder. It comes with a ceramic fiber gasket to fit in the groove. The groove fits over the edge of the drum to form a gas proof seal. It weighs 72 pounds and can be painted with hi-temp paint to match your decor.
The refractory material absorbs the heat and stores it better than the cob in your bench. So, after the fire goes out, the barrel cap is still radiating heat into your room.
Wow! I sure would like to hear more basic details about your system that produces such high heat. It sounds like you are getting above average burn temps. Are you soaking the wood in nitro methane?
"Necessity is the mother of invention" That's why I'm a Jack of all trades, Master of some and have learned that Knowledge is power, but information isn't necessarily knowledge.
Location: Central Virginia USA
posted 6 years ago
as far as i know it's just a standard sort of deal
made a fireclay mix with lot's of perlite, cast the core 6" x 5"
i started with a double wall stainless heat riser cause winter snuck up on me and i had to do something fast, and it burned pretty hot,, burned out the inner wall about 1' up in the stainless, but the insulation was still in place and it was working fine when i upgraded to a new heat riser using an old piece of rusted 6 inch stove pipe (which i expect to burn out soon) and the same fireclay/heavy on the perlite mix, with a 10" outer stove pipe shell--- about a 3" gap to the barrel top
guessing for right now i've got super insulation, but wonder if at these temps i may be looking at the perlite glassing over, and not sure what that will do to the insulation/structure of the riser
i have noticed a general increase in temps since i ran out of trash branches and such, barely aged, no name wood and a little damp besides---and i tapped into a covered supply that's over 2 years old, red oak covered for the last year and a half
i was serious about lowering the octane of my wood,, i've got a bunch of sticks i've been pulling out of a beaver dam this fall and winter, nothing special, but some of them may be dry enough to burn and would probably moderate the temps a little
do you think keeping that pot of water on top may delay the eventual burn through
i do like the look of that dragon top, but 150$ + 75# worth of shipping charges,,, i'm thinking about buying some high temp refractory cement mix and trying to scrounge some mullite from the local kyanite mine and mixing up a custom top that i just cast in place,,, i've heard that mullite makes the mix super hard,, i think they use it for the space shuttle tiles