Modifying the baffle in my Old Fisher Stove

Hey community.

After reading a bunch of posts on Old fisher stove baffle plate

This is essentially what i used to have for a baffle

It worked ok. however smoke was still a serious part of the stove. And quite alot of the wood would burn up quickly. It took me about 40 minutes in the morning to get one liter of water boiled. Also i really had to gun the stove to get a hot fire. It heated well. Though it lost that heat just as quick.

I have since thanks to many threads on permies. Changed my baffle plate around and added a new one. See photo

Note not my stove.


I now have a better performing stove thanks to this simple addition. It heats up easier. it holds the heat for longer. It Smokes less. and as far as i can tell it uses less wood.

I have about three inches of clearance to the front door and three or so inches of clearance to the top of the stove.


Do not worry i am slowly experimenting with rocket stoves/mass heaters. My next project is making a rocket oven!

so i was not completely satisfied with the improvement. The old bricks i had cobbled together were slightly different heights. And they had more joints which meant more air gaps. The flame path was going every way.


I am not super stoked about these bricks. They are about 1000 grams lighter than the other brick i have




Than i decided to put myself in my firewood's position!


3 new bricks on each side and 3 smaller pieces for the back of the stove.


Now the flame path is pulling up to the front of the stove. Much better!


Top of stove with our hot water heater in the stove pipe.



I am soon to be getting a Infrared Gun!
 
So i will be able to get some temps on the stove.

Neat, good to see the impact.

I have the impression that back-when, the baffle was thought of as 'slow down the escaping hot air', and now.it is thought of as 'let's make the combustion more complete'..


I wonder what you would see if you doubled up on baffles...

Have you thought about adding a secondary air intake?

D Nikolls wrote:Neat, good to see the impact.

I have the impression that back-when, the baffle was thought of as 'slow down the escaping hot air', and now.it is thought of as 'let's make the combustion more complete'..


I wonder what you would see if you doubled up on baffles...

Have you thought about adding a secondary air intake?

yes. At the moment. I am not sure i have the clearance for double baffles.  Have any ideas D?

I am wondering how to add a secondary air intake I considered putting an old pipe in the ashes that leads to the back of the stove. Just to see the effects. I also have questions about where would the secondary air intake be placed?

Does anyone have any ideas? I am thinking i could drill a hole in the back of the stove and put some type of bung or something.


However, i am needing to keep in mind that the stove now gets much hotter. If the combustion became greater i would think i would have a harder time cooking on this stove. As we do cook on it exclusively from sept/oct - may really. Maybe if i added some type of stone to the top plate to offset the heat?

I have a Fisher Pappa Bear. I recall reading about them that they were designed not to need a gasket on the door. Mine did not seal as much as I wanted, so maybe the air leak was part of the design to add a little secondary air up higher than the dampers? The baffle was called an "ash fender," so my guess is it is designed to help prevent ashes from getting sucked into and blocking the horizontal area before the elbow. I've wondered about the possibility of making a small Walker-esque stove from it. Maybe some day...

Actually, the Smoke Shelf Baffle was designed in 198O by Fisher research and development for reducing smoke. It reduced particulate from 60 grams of particles for every kg burned down to 6. It was only used in the double door stoves with 8 inch outlet since the 6 inch stoves were normally connected to existing chimneys that were much larger built for fireplaces. So slowing the rising gasses and not allowing as much heat up the larger flue would create creosote problems. With the advent of secondary burn stoves and most all requiring 6 inch flues, adding a baffle with correct sized insulated flue works fine. That’s why the single door Bear Series didn’t have the factory baffle.
Coaly

Jordan Holland wrote:I have a Fisher Pappa Bear. I recall reading about them that they were designed not to need a gasket on the door. Mine did not seal as much as I wanted, so maybe the air leak was part of the design to add a little secondary air up higher than the dampers? The baffle was called an "ash fender," so my guess is it is designed to help prevent ashes from getting sucked into and blocking the horizontal area before the elbow. I've wondered about the possibility of making a small Walker-esque stove from it. Maybe some day...

The ash fender is the shelf under the door.

The baffle in the Fireplace Series, or double door stoves is patented as the Smoke Shelf Baffle.

The door seal was designed “air tight” with three sealing points all the way around. There is no clearance for gasket material. The center of the channel iron web contacts the raised portion of door and the edges of channel iron contact the back of door making the 3 points of contact. Cleaning the channel iron and door back is all that is necessary to seal. Worn door hinges or hinge pins cause air leaks. Glass door models use gasket material. When the doors were mounted, the stove was laid on its back and door centered on door sealing channel iron. The hinge plates were tacked in place and the door should lay flush against stove front. If the hinge plates were not exact, space exists at sealing area.

D Nikolls wrote:Neat, good to see the impact.

I have the impression that back-when, the baffle was thought of as 'slow down the escaping hot air', and now.it is thought of as 'let's make the combustion more complete'..


I wonder what you would see if you doubled up on baffles...

Have you thought about adding a secondary air intake?

The baffle was designed to reduce smoke. EPA rules went into effect in stages, and the baffle allowed production up until the last phase of regulation in 1988 when they didn’t reduce smoke particulate size enough. The particles collected went from 60 g for every kg of wood burned down to 6 with the factory Smoke Shelf Baffle in the double door stoves.

A baffle increases resistance within the fire box. A flue damper is a variable resistance that is used to slow an over drafting chimney. Every stove has a required draft measured at the flue collar. Doubling the path through stove increases the draft needed, so the chimney and connector pipe configuration becomes more important as well as using double wall pipe inside with the added resistance. There are calculations and the highest resistance is normally the air intake. More baffling slows the velocity allowing longer dwell time in stove, extracting more heat, causing condensing issues.

Fine line between how much you can remove before entering chimney. Only straight up, insulated flue the same size as stove outlet can operate with less heat. The main objective is staying above 250*f. all the way to the top. Below that critical temperature water vapor from combustion condenses on flue walls allowing smoke particles to stick. That critical temperature is only while smoke is present. You can see why manufacturers don’t double baffle not knowing what chimney and pipe configuration will be used on each stove. They have to err on letting more heat than necessary to prevent creosote formation.

So i ended up making a video of how the stove performs with the baffle plate altered. Here it is
Blurb from video;
So i changed the placement of the baffle in the stove. It now is lower and comes about 3 inches from the front of the stove(door). The stove was open 2 full turns for the first seven minutes and than moved to 1 full turn, than towards the end to about 2/3 full turn.
The readings for today were as follows;
8:25am - 63F
8:32am - 228f
8:45am - 422F
8:55am - 605F
9:05am - 630F
9:15am - 585F

So for about 90 dollars Canadian. I bought 1 sheet of 1" x 1' x 3' ceramic fibre board plus 7 Full size 2300F insulate bricks.

I cut the board into two 15"-3/4" x 12" sheets


I needed to cut the two of the bricks into 6" x 2.5" x 4.5"

the brick at the back could have been 2 inches and a full size brick. I cut it 1.5" and it has a small gap.


This left about 2 inches of gap up to the top of the cooking plate. so 2x16" = about 32. Which is what the flue pipe is.
I added two small fire brick splits to the edges(On top of the ceramic fibre boards). This made it so more of the gases went to the center of the cooking plate(hopefully)

The stove now has a rocket sound to it, when the door is open.



Finished!

Wanted to update. The stove has been run for a full season. The season went longer than usual with the west coast being cooler than average this year. We only really stopped having fires 4 weeks ago....


The ceramic fibre board has held up poorly. Maybe it would to better with supports running the length. Something like angle iron on both ends to support it. As it stands both pieces have cracks down the middle. The piece closes to the door would fall down, however I stuck some brick splits into the gap and sort of jammed the ends into the wall bricks. The board is flimsy....

I am looking for suggestions. I suspect splits would work better with angle iron supporting the bricks across the gap. I would need two single pieces of angle iron, and i suspect 2 pieces welded together to use in between the rows. 4 splits wide. This would end up somewhere around 19". I could make it 24" with a smaller piece of ceramic fibre board... Suggestions?


The other thing is I might be able to upgrade this stove to something better!!! I just have to get my partner to be on board!!!

Hi Jordan;
I've come to the conclusion that ceramic board has some quality's that just  do not hold up under intense fire.
I will not be using it in batchboxes anymore.
I'm experimenting with using RA330 sheet steel as a roof.
I have one sheet installed on my shop stove now. I'm seeing some warpage on it when heated up, that flattens out when cool.
I am currently rebuilding the studio batch.
I have another piece of RA to use on it.
I plan on using several pieces 3/4" angle tacked on top lengthwise as stiffeners, then super wool as insulation.
We will see how they work.