Mama Bear Secondary Burn

JWIW465

New Member
Dec 10, 2017
3
NE IL
Any chance you could sketch out what this looks like in profile? I'm afraid of blocking the flue too much to meet the angle and height from the inside-top of the stove.

I believe my stove is a Momma Bear -- that's what I was told -- but my measurements seem much different from yours. Inside width (minus a half inch) is 16.5-in. The 6-in flue is not flush with the inside rear wall, but protrudes 2.75-in inside the firebox. For me to set a 5/16-in steel plate inside at 45-degrees and 2-in from the inside-top of the stove, it would need to be about 10.5-in wide.

You used a 15 x 8 x 5/16 plate but I think that would be too small for my stove. Am I missing something?
Just finished refurbishing firebrick, adding upper row, adding baffle (15x12 1/2) and adding secondary burner (3/4 pipe). Going to make some better draft controllers but the ball valves will be OK for now. Thanks to everyone on the site for the valuable information. Hope someone can use something from these. Here are some pics.
 

Attachments

moresnow

Minister of Fire
Jan 13, 2015
1,667
Iowa
Just finished refurbishing firebrick, adding upper row, adding baffle (15x12 1/2) and adding secondary burner (3/4 pipe). Going to make some better draft controllers but the ball valves will be OK for now. Thanks to everyone on the site for the valuable information. Hope someone can use something from these. Here are some pics.
Let everyone know the flu temp diff. while running the burn system.
 

JWIW465

New Member
Dec 10, 2017
3
NE IL
Just bought the stove and only ran it HOT to burn out the creosote before working on it. So, I have no baseline temps, but will measure the various locations and time the progress. Merry Christmas to All!
 

JWIW465

New Member
Dec 10, 2017
3
NE IL
Any updates on how your secondary burn system worked?
Hi all, just following up a little and apologizing for the delayed response. Had a little matter of some skin cancer stuff to get resolved and got behind on a number of responsibilities.
The stove works pretty nice, but I don't have before and after data for comparison. I can report that flue temperatures are under 300 while firebox temps at the top are over 500. Closing the secondary inlet valves slows down the combustion considerably so I don't think that throttling down the fire is the best use of the stove. I plan on adding a liquid heat loop at the top/rear and a heat exchanger in a ballast tank. I'll be looking for ideas that have been proven to work as well as balance theory from some of my pipe fitter gurus. I believe that full combustion that captures the heat coupled with controlled release of the stored heat will prove to be the most efficient. Getting to that point using an adjustable passive circulation system will be an interesting challenge. I am happy with the heat that is being thrown off by the unit, as it is, but the burn time is a little short. A full load of dry hardwood does hold a fire for well over 12 hours but the heat output drops off considerably after about 4-6 hours. All night fire but not all night heat. Any ideas/experiences with heat exchangers would be greatly appreciated. Thanks!
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,179
NE PA
show pics on where pipes are mounted and where they come into the stove.. Show pipes inside the stove
Are the pics working for you in the OP's first post? 16 of them with the first showing the two intakes through the front at top.

If you want to build a secondary air system, I recommend coming in through the exhaust outlet so the stove needs no modification. Also starting with a glass door model is a plus.