Welcome back to our stove upgrade series!
This time I’m installing secondary burners.
Once again, I’m going to subject you to some of my fine artistic skills.
Looking at the side-view of the stove, when starting the stove, fresh air comes in through
the bi-metal thermostat damper.
The air comes up through the ash grate and stokes the fire and coals.
The gas and smoke mix with some fresh air from the new burners, but since it’s not
hot enough, it doesn’t yet combust.
There’s also a new ceiling above the burners to force the air forward and up into the secondary
chamber, then venting through the stack.
This chamber will be used for the last phase of this project.
As more fuel starts to burn and the burn chamber gets hotter, the wood gasses start to combust,
and as the stove continues to heat up, the damper door automatically closes, choking
most of the fresh air intake from the bottom and slowing down the burn rate of the wood.
There is still a small amount of air that comes through here to help stoke the coals
through the grate.
Since there is a strong draw pulling up the chimney, this causes more fresh air to get
sucked into the stove through the secondary burners and igniting a large portion of the
wood gases.
There’s enough added air where the flames are getting drawn up into the upper chamber
creating a “rockety” effect.
From a top view, fresh air is drawn in through the side of the stove where it travels through
the central tube.
The goal was to preheat the air before it combines with the wood gas.
With it only traveling roughly 25 inches through 1/8” thick steel, I doubt the temperature
has a significant increase.
The air then travels down two burner tubes injecting air into the fire box causing the
wood gas to ignite.
The central tube is made from 1-1/2” steel box tubing.
The steel should last for a couple of years and is really just for experimenting.
When it wears out, it will need to be replaced with stainless.
The burn tubes are 1” box tubing so the inside profile of the 1-1/2” tubing is slightly
greater than two of the 1” tubes so it won’t restrict the air flow.
The holes are drilled along the sides of each tube every 1/2".
When drilling it was easy enough to go all the way through so it basically drills two
holes with one pass.
After drilling the first tube and seeing how misaligned the holes were, I wised up and
clamped a backstop to the drill press.
It makes it look much better even though no one will ever see this inside the stove.
With surgical precision, I needed to cut some holes in the sides of the tubing so the air
could flow properly.
My 4” cutoff wheel is precise enough for the job and to get into the tight corners,
I wore through a dozen cutoff blades with my knock-off Dremel tool.
Now that all the pieces are cut, the tubes are laid out, aligned and tack welded together.
Once I knew it was set up properly, all the seams were welded.
I must admit that having a MIG welder is one of the best investments I’ve made for my
tool collection.
A few pieces of scraps are welded over some of the ends and cut down to the proper size.
One last addition is to weld a flange near the opening so there’s a way to mount the
burner to the stove.
Here’s the finished burner showing the mounting flange, the two burner tubes with holes coming
through horizontally, and a small leg to help add support at the rear of the stove.
The burners mount through the side of the stove so a few more modifications to the stove
are needed.
These are slightly larger than the burner so there’s a bit of slop left for adjustments.
Two holes are drilled through which are used to mount the burner to the stove.
Mounting each burner was fairly easy and they fit right into place.
It’s always nice to see these fit together the first time…especially when it’s difficult
to patch misplaced holes.
I used stainless bolts to minimize corrosion so it’s easier to dismantle.
I debated putting a gasket between the burner flange and stove wall but it doesn’t appear
to be leaking through this area.
Here they are mounted in place.
You’ll see one has already been tested prior to this filming….just to make sure it was
going to work properly.
The last step was to add was a ceiling above the burners to help keep the gasses near the
burner and to create a section above it for the next phase of the project.
The stove came with this bi-metal thermostat that’s linked to the damper.
As the stove heat up, the damper will close choking some of the burn.
Keep in mind that the secondary burners continue to burn so the stove will continue to produce
a lot of heat until there is no fuel remaining.
While it’s burning, it’s impressive to see the secondary burner suck air in.
Here’s a good example of the burners in action.
You can’t see the wood, but there are a couple of small flames coming up from them,
a few flames around the glass, mainly because there some air leaking around it.
It’s tricky to see, but right at the top center, you can see the flames looping back
up into the upper chamber.
The stove usually stays around 500 degrees.
Without the burners I’ve seen vary all over the place, sometime hitting 700.
It’s not rocket mass heater temps, but the cooler temp should help keep the stove from
wearing out.
That’s about it for now.
I have one more addition planned for this stove so please “’like” this video and
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Thanks for watching!