Fisher Papa Bear - Need Baffle Info.

[Scout_1969]

I have had the stove for 15 years and it didn't have a baffle when I got it. FYI- There is no name plate on the stove. I have identified it by some posted info. here as the Papa Bear and other than the door having Fisher on it there are no other markings.

While replacing the fire brick I noticed two 1.5" angle iron clips on each side, just above the side fire brick, about 2/3 the way back as shown in the pictures. I'm pretty sure they are for a baffle. They are just wide enough for a fire brick too, which has me puzzled.

The manuals I found online don't show this model in detail to show the baffle. I have found some similar but I wanted to see what was OEM. It appears that the Mama Bear would be similar.

Does anyone have pictures, a diagram etc. showing the OEM baffle assembly that they could post here or send me?

Are there any home-brew improvements to the baffle assembly that I could make?

Are 'secondary air tubes' something worthwhile to fabricate/use on this stove?

Thanks.

 

[webbie]

Ah, they didn't show a baffle because I think it didn't have one.......
https://www.hearth.com/econtent/index.php/wiki/File:fisheradrear.jpg/
(see cutaway).....

 

[Scout_1969]

Thanks for the reply.

The clips look the same as the others so I thought they maybe OEM. I can't find online info. for my stove, but here's something for the Grandma/Grandpa Bear 3's that reference a baffle--https://www.hearth.com/econtent/index.php/wiki/File:fischermanual.pdf/.

Any ideas what the clips might be for?

 

[tickbitty]

Send a PM or email to Coaly on this board. If you do a search for Fisher he comes up in most of those threads. He's the resident Fisher stove junkie and I'm sure he can tell you whatever you need to know!

 

[WES999]

I have a Fisher Grandma bear, it looks very similar to yours. There is a small plate welded to the back of the stove under the exhaust hole.
I have made several modifications to my stove, (others on here have also).

see post #6 https://www.hearth.com/talk/threads/17993/

Pics of a baffle someone else made.

https://www.hearth.com/talk/threads/48532/

The first version was a simple piece of 1/4" pate wedged between the plate on the back of the stove and the exhaust tube.

The second version was a baffle with secondary air to my stove.

I am currently working on a updated secondary air system. I will post more info when it's done.

A baffle is a simple mod that should improve the stove performance.

 

[Scout_1969]

I'll PM coalie to see what he has.

WES999-

My stove also has the rear flue.

Is the air fed directly to the manifold by some sort of pipe/tube or does it work like the front damper/knobs?

Does your baffle go completly to the back and side walls?


Thanks.

 

[WES999]

https://www.hearth.com/talk/threads/17993/

read post #6 and #9 that should explain most of it.

Yes the baffel goes all the way to the back and side to side.

 

[Scout_1969]

It looks like the hole in the back of the stove lines up with one of the side tubes and just butts up?

 

[coaly]

That Papa Bear had no smoke shelf baffle.

Angle Iron was all I've seen used for the brick retainers. (except on the XL with a T piece to allow a second course of fire brick) However, I've seen quite a few bend upward due to heating the angle iron. It must have internal stress that allows it to open up the angle, and the horizontal piece of the angle curls upward making it look like someone tried to bend the angle iron to get the bricks out. I believe someone welded the additional spacers above the angle iron to prevent them from curling up and allowing the bricks to loosen. At least that's what the added pieces would do welded where they are. They would also conduct heat and carry it away from the exposed angle iron keeping it much cooler.

My thoughts on a homemade baffle would be to make a flat horizontal plate (5/16" thick) supported just under the flue outlet, tight against the rear of the stove to about 3/4 the way toward the front. This would be like the design used in the UPLAND. A proven design that used a baffle above the fire to force the rising gasses to move TOWARD the air intake to get above the baffle and out the flue. The Upland had the air intake on a side door, making the firebox long and deep like the Papa Bear. This reverse burn method (burning towards the air intake), against the natural draft direction prolonged the burn to create a good bed of coals and would have been my favorite stove had they ever been made with steel plate! You do have to burn this type a little differently. You end up with LOTS of coals, so you push them toward the back of the stove. Then fill it up with logs and as it burns near the back of the stove, you'll notice how the smoke has to come toward the air intake in the front to get out. It needs to make a U turn around the front of the baffle to get to the flue. The flow of air coming in prevents this, so you get a long glowing burn that is hard to beat.

 

[webbie]

I would try to save work and make the baffle out of relatively light ga stainless steel......which I would bend or roll to add stiffness. A flat plate of thick steel is likely to warp quickly.

A piece of koawool could be set on top of the baffle to retain heat below it.

 

[Scout_1969]

Coaly-

Thanks for the info. I was hoping mine was a newer version with baffle like it appears the grand bear 3 are, but I guess not. It does appear that where the addition clips are at is the hottest part, based on white/gray discoloration on the sides.

I took quick measurements this morning and it looks like the deflector? under the flue pipe is about 2" under the low portion of the top of the stove. At 3/4 of the way back the plate would extend about 9" past the upper/lower transition and about 9" to the door.

The 5/16" plate weights about 38 pounds. The door is 10" X 11" I believe with a diagonal of about 14-1/2". So I'm thinking of two 8-1/2" wide X 25" long pieces with a piece of 3/8" channel at the joint. I'll have to make a stand similar to one I've seen posted here that had fire brick on it. I'll have to do some figuring on this. Ideas/pictures would be greatly appreciated.

Webmaster-

The stainless sounds like an interesting option. I guess it would be thinner/lighter than the steel, more costly probably.

In general-

I'll get some accurate measurements and check on materials.

Any ideas what increase in efficiency I might see with this?

Would another baffle on top of this one help much?

Thanks.

 

[coaly]

I mentioned a piece of 5/16 plate because they didn't seem to warp on the newer UL listed stoves. But they were not horizontal like a shelf above the fire. They were an angled plate inside at the rear only extending into the fire box 6 inches from the rear of the stove, just enough to roll the unburned particles back into the fire, and prevent a straight line up the stack.
Another option on materials to prevent warpage would be fire brick, but the thickness would have to be taken into account so the open space above it at the front would not be smaller than the square inch area of the flue. One support down the middle, lengthwise with the stove, and shelf brackets on the sides to support the bricks would work. It would be adjustable as far as the depth (length) by adding or removing bricks. Easy to experiment with as well. (and they're cheap)

Steam locomotives had pipe welded to the back head, (the rear wall of firebox where the door is) and ran forward, then bent down in an arch shape toward the front of the firebox. Arched pieces of large fire brick laid on them at the front to create a baffle to prevent the fire from being sucked out the flue pipes too rapidly. Also when the door was opened, cool air wouldn't rush in and hit the flues to chill them causing contraction and leaks. This is known as the brick arch. So the material worked well for that.

 

[Captain Hornet]

Gentlemen, I am interested in this Fisher modification but was wondering about a couple of things. First, It looks to me that with your plate in place there would be a considerable reduction in firebox area. The one good thing about the Fishers is the huge firebox and your modification works directly against that. Secondly, without the plate there is a huge amount of heat that goes up the flue. My Fisher is a top vent and with a large fire I can see flames being pulled up the flue. Your plate would make the flue run much colder causing problems with creosote. If I run my stove hot or with a normal sized fire I do not have creosote problems and I do not want to change that. Burning a little extra wood is a small price to pay for keeping the flue clean. David

 

[WES999]

One thing to keep in mind withe the 2 piece baffle is to allow room for heat expansion.
The baffle I had in warped quote a lot. I think it was because there was not enough room for expansion.
The next version I am thinking of using 2 pieces of 1/4" stainless covered on both sides with kaowool.

 

[Scout_1969]

I'm thinking of trying the angle iron and fire brick. Seems within my skills, a reasonable cost, durable and insulated (I guess that's the term) etc.

I may have to stop it short of the stove transition from high to low, as I only have 2" now from the low part to the flue. Based on the sq. in., I only have about a 1/4" (the thickness of the plate??? how ironic), or maybe add a small piece of metal towards the door. I guess the longer I can keep the burned air in the stove the better.

The fire brick will be tight but not air-tight like the other options, is this a big deal? Or could I use some high-temp sealant between the joints?

As far as having less space- I have humped the wood up a bit before, but we're talking roughly an 1.5" under the flue for the baffle. I'm hoping the efficiency will make up for the reduction. We'll see.

I'll have to watch the creosote too.

I know there are variables, but what efficiency increase might I expect?


Thanks guys.

 

[coaly]

The little space between the bricks shouldn't make a noticeable difference. I get some fly ash that settles on top of the baffle plate. That may eventually fill any voids between bricks anyway. A strong draft with newspaper and kindling doesn't seem to pull it up the stack or move it.

The added bricks are going to add heat retention that a steel plate wouldn't as well. When kindling a fire, those hot bricks are going to release heat up the chimney after the kindling is gone. That could be a very good thing, if the wood isn't going very well, it should continues to draft better than it normally would without the bricks. That rising warm air from them would give the barely started fire the oxygen it needs through the wide open intake at this point.

The smoke shelf baffle as added to the UL listed stoves after 1980 went from 40 to 60 kilograms smoke for every kilogram burned to only 6 grams smoke per kg. burned in the redesigned stoves with baffle. (covered in the "Everything Fisher" thread with baffle picture on page 6, post #119 here) https://www.hearth.com/talk/threads/53332/
The baffle plate didn't cover the entire raised section, it only prevented the unburned particles from rushing out the stack. ANYTHING is an improvement over the open stack.

Remember the chimney is the engine that drives the stove. The better drafting the chimney, (lower pressure in the chimney) the more baffle and the smaller the holes in the damper when closed is needed. So your chimney size and type can have a lot to do with the baffle size needed too.

I only burn my Fishers that have the baffle, and never tried any modifications to them myself. The older models I have without baffles are collector items that have never been fired, or have the first of the cast doors without trees that were very thin and could crack if used again.

 

[Scout_1969]

Thanks coaly.

I put my 'feelers out' for some scrap metal... as luck would have it, I'm going to be picking up some 3/16" stainless plate and some 1/4" or so flat steel plate this weekend.

If I made the plate just under 14" X 17.5" I could get it through the door diagonally. I could use the additional clips as hangers for some legs, it's funny that the clip furtherest from the rear is at 14" . With my flue out the back and plate an additional 6" longer, I would think it would work atleast as good as the one shown in the link (I think it's a Grandma/Pa). This would be an easier fix. Plus there's room to put a slope on the plate.

It sounds like the longer the plate, the longer hold time, the better. A baffle plate at 3/4 of the fire box depth will need to be flat or it could stop shy of the low portion of the top to have an angle. It would seem the angled baffle allows a little more wood in the firebox. I think there was a thread/post on the site saying that the slope had no noticeable affects.

The stainless may be able to be arched/rolled to fit through the door in one piece. The steel could be two pieces. I'll see what I come up with on the scrap metal.

Also, it sounds like the fire brick would offer some advantages as well, I may try a combination.

I'll post back what I find and do.

Thanks.

 

[WES999]

Here is a simple baffle design. This was how I made my first one. The baffle was a piece of 1/4 diamond plate just a bit smaller than the diagonal of the door opening. This will give you a baffle that has about an inch or two space on each side. If you make a two piece baffle you could probably get it to come right up to the sides.

It had a bend to angle it up towards the top of the stove, it was clamped with beam clamp hangers to the small existing baffle welded to the back of the stove. Your stove looks similar to mine so I think it would work.
I sketched the new baffle in red on the cheesy paint drawing.
Good luck.

 

[vvvv]

pretty cheap to stick a piece of fluepipe into existing outlet from the inside of the firebox?

 

[pen]

Here is what I did w/ my grandma bear fisher.

You can read all about it here.


https://www.hearth.com/talk/threads/31420/
pen

 

[Scout_1969]

WES-
The existing flue plate is just a little wider than and projects out from the flue. I guess I could attach with slits in the plate for the clamps. This has me thinking of maybe using trying to put the 3/16" stainless between the flue and the existing plate, maybe with some angle iron long ways as guides and for rigidity.

Last night I tried a mock-up using cardboard and two firebrick in the four extra clips. Possibly cutting fire brick at a slope (not sure? some say 5⁰ others at 30⁰, while others are flat) and resting the plate on the brick and under the flue plate. I could make collars with angle to secure it to the brick.

VVV- That's an interesting thought. It seems simple and inexpensive enough. I'm wandering why more stove's with the rear flue don't have that. I'm sure others will weigh in on this.

Pen- Your's is one of the designs I noticed before joining Hearth.com and someone posted a link to yours above. I may end up doing something similar, but my stove with the rear flue, flue plate, small door and the extra clips give me some other challenges and options. Did I mention small door..yeah I did

What are the thoughts on:

>The ability to slide the baffle forward a little to start a fire? I saw that posted somewhere, but all the ones picture/described are fixed or not easily slid.

> Does the baffle need to have the plate fully secured? It looks like it will be high in the fire box.


Thanks all for the ideas and effort.

 

[pen]

Here's what I did.

1. I bolted the whole angle iron assembly together so that I could loosen up the bolts and do whatever it took to get it in the stove, then tighten everything together in there.

2. My stove had an 8in flue collar which has an area of 50.24 inches. When designing my baffle, I kept the area that the smoke could move around the front of the baffle at roughly 55 inches so that more smoke could get around the baffle than could leave the stove. By doing that, I never had any smoke come into the house because of the baffle and could still run the stove as a fireplace w/ the screen that I had.

3. Wess's stove is a rear exit if I remember and he used a baffle w/ no problems. I don't see where you'll have an issue.

4. You wouldn't want to move that baffle once installed. Done properly, you won't need to on startup.


pen

 

[Scout_1969]

If I go the stainless plate route and used the ceramic wool blanket, is 1/2" thick enough?

Is foil faced on one side prefered? If so, which side is up?

Can it just be help in place with a few strips of scrap steel plate?

 

[Scout_1969]

Here's the pictures of the baffle assembly I made up and how it burned.

The 3/32" stainless sheet has a 3/4" lip around the outside. The front lip is angled slightly down like some others I've seen.

It was bent in half to get through the door then straightened with a lot of leverage once in side.

There are two firebrick in the extra clips that the plate rests on and the lip goes between the stove wall and firebrick. The baffle is not sloped front to back like some others I've seen.

The 1/2" ceramic wool is foil side down on top of the stainless plate and the stainless wire grid to hold it in place.

I think the fire is doing what it supposed to with the baffle. It surely wasn't going straight up the flue.

The approx. 3 hour fire seemed to get very hot, but it was a 77 degree day. The plate didn't distort during or after the fire. Everything seems to be just how it was installed.

Flue temp was highest at about 750 degrees and the stove top was highest at 450 degrees.

>Does it look like it's working correctly?

>Are there any 'tweaks' I should make

Thanks.

 

[Redbear86]

I was wondering if your still having good results with your baffle as I was planning on making one soon?