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Modifying the baffle in my Old Fisher Stove

 
master gardener
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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!


 
jordan barton
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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.
 
pollinator
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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?
 
jordan barton
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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?
 
gardener
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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...
 
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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
 
coaly Hearth
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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.
 
coaly Hearth
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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.
 
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