When you run your Dragon long and hot you can expect to have take her into see the rocket scientist's.
My 7" shop dragon gets lit off around 7-8 am everyday. It runs full bore until late afternoon and into the evening.
The secondary air stub is a known wear point on a working batchbox.
In normal use (2 burns a day) an air stub can be expected to last two seasons and maybe more.
In severe duty use (all day everyday) with a stock, carbon steel stub, not more than 1 season, probably half a season.
I got 3 months from mine before the cobra head came off !
My six inch batch also sees severe duty daily. It is at two months now and showing wear. I'm hoping it will last the season.
Repair consisted of removing the door and then unbolting the door frame.
The door frame and the secondary air tube are tacked together, they come out as a unit.
Once in the vice. cutting the remains of the old stub off and grinding it clean took just a few moments.
Fabricating a new stub is easy enough(for some of us)
Weld it into place and reassemble.
Build a new fire and take that dragon for a test flight!
I make it sound easy...
Does the stub (cobra head?) need to be welded to the tube? Might there be a way to make a stub that can be replaced by someone who can't weld? Drop in, bolt on, swap out, etc. Just thinking of potential business opportunities and ways to make these stoves even easier for someone to want to own.