FISHER Grandma and Grandpa Bear Details (Fireplace Series)

Chuck D

New Member
Jan 7, 2017
2
SE MI
I've been reading all day trying to ID my "fireplace" Fisher. So here some measurements.
Top plate is 29 1/2"
Depth with tray 28 3/4"
Door opening is 17 x 10.5. Stamping on the left door - 594 GM1 GML MI Right door - 593 GMR MI
My door seal is C channel on the stove and square stock on the doors.

As shown in post #139 I have grandma doors. But that GM hinges are welded to the outside of the stove. My hinges are welded on the front of the stove.
So I'm thinking that I might have a GP stove with GM doors. Built in 79'
What do you guys think?
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Yes, you have a Grandpa Bear box with Grandma doors. Likely that the fabricator ran out of Grandpa doors and was in need of a Grandpa to complete the sale. Are the doors flat across the top or arched? Pictures of the doors or description of spring style, draft cap fins and bends if any on the handles will help date it.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Anywhere between 1979 and end of production in '88.
Many fabricators made the old style box with angle iron corners as an unlisted cheaper alternative to the listed version. They were $100 less when UL Listing wasn't necessary on a non-combustible floor or hearth.
 

svlmustang

New Member
Nov 3, 2016
5
Creekside, PA
Hi
I bought a grandpa bear lll 2 months ago. I have the one with the shields for the nickel plating. Any suggestions on how to Polish it easily? Also it has a c clamp inside to close the door. The handle on the right door cinches up against it but I have to loosen and move it back into place after a month. Thanks in advance.
 

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Nothing abrasive on door. Only metal polish.
I prefer Maas metal polish. You can use any polish for precious metals such as silver, brass, gold........ Maas leaves a protective residue to prevent constant polishing.
There should be a tab welded inside at top right door for the latch rod to contact. You should have to rotate handle up to crack open slightly, then rotate downward to disengage tab to open fully. This creates a second or so delay when opening door to allow draft to increase and prevent smoke roll in when opening door too fast.

Canadian Teddy Bear H632878 4.jpg Teddy Bear 7 inch inside.jpg
 

svlmustang

New Member
Nov 3, 2016
5
Creekside, PA
Nothing abrasive on door. Only metal polish.
I prefer Maas metal polish. You can use any polish for precious metals such as silver, brass, gold........ Maas leaves a protective residue to prevent constant polishing.
There should be a tab welded inside at top right door for the latch rod to contact. You should have to rotate handle up to crack open slightly, then rotate downward to disengage tab to open fully. This creates a second or so delay when opening door to allow draft to increase and prevent smoke roll in when opening door too fast.

View attachment 192420 View attachment 192422
Ty I took a picture of the clamp
 

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svlmustang

New Member
Nov 3, 2016
5
Creekside, PA
Nothing abrasive on door. Only metal polish.
I prefer Maas metal polish. You can use any polish for precious metals such as silver, brass, gold........ Maas leaves a protective residue to prevent constant polishing.
There should be a tab welded inside at top right door for the latch rod to contact. You should have to rotate handle up to crack open slightly, then rotate downward to disengage tab to open fully. This creates a second or so delay when opening door to allow draft to increase and prevent smoke roll in when opening door too fast.

View attachment 192420 View attachment 192422
 

svlmustang

New Member
Nov 3, 2016
5
Creekside, PA
Hi
I bought a grandpa bear lll 2 months ago. I have the one with the shields for the nickel plating. Any suggestions on how to Polish it easily? Also it has a c clamp inside to close the door. The handle on the right door cinches up against it but I have to loosen and move it back into place after a month. Thanks in advance.


Cleaned the nickel plating with never dull
 

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
If you want to paint the doors, it's as simple as spray painting with Satin Black (Stove Bright) and wipe paint off polished raised areas when dry with mineral spirits before firing which gives it the final cure. Same way with draft caps.
 

jpregman

Member
Oct 1, 2017
3
bigdog
I have what I believe is a Grandpa Bear based on the dimensions. In great shape. Trying to figure out year built. No "76" in star on door. No baffle on inside before exiting exhaust opening. Round silver ball feet. Has the nickel screen for open viewing.

What do u guys think?
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
'78 or '79 Grandpa
 
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jpregman

Member
Oct 1, 2017
3
bigdog
I'd love to put it in my basement fireplace, but the top vent setup doesn't work for me. Would have to be a rear vent opening to make it work.

Sent from my SM-G935V using Tapatalk
 

espchris

New Member
Oct 3, 2017
1
Glenwood Springs, CO
I am new to the site and have been reading through as much as I can, but have some questions I am hoping someone could answer. We just purchased a house with what I think is a Grandma Bear stove. I am curious if the stove is setup properly with the baffle type thing on the back. Seems like it should be sealed up in back if I am using the top for the chimney? I am also confused on the box shaped part inside the stove covering the rear vent. Can anyone perhaps enlighten me on this, and if this seems like it is setup properly? Thanks so much in advance.
IMG_0268.JPG
IMG_0266.JPG
IMG_0265.JPG
 
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I am new to the site and have been reading through as much as I can, but have some questions I am hoping someone could answer. We just purchased a house with what I think is a Grandma Bear stove. I am curious if the stove is setup properly with the baffle type thing on the back. Seems like it should be sealed up in back if I am using the top for the chimney? I am also confused on the box shaped part inside the stove covering the rear vent. Can anyone perhaps enlighten me on this, and if this seems like it is setup properly? Thanks so much in advance.
View attachment 200860
View attachment 200861
View attachment 200862

sorry Coaly can better answer this, but that appears to be the barometric draft option. I am not sure how it works per se, but it is used when burning coal as it (in some fashion unknown to me) allows for finer control fo the draft when burning coal. If I remember from an earlier post it also is dangerous if you get a chimney fire as it would open fully and feed the chimney fire more air. contact coaly about this i thought he recommended blocking it or something when using strictly for wood. best bet is to read some more in this thread as that's where I cam across this info. (excuse me if I was mistaken)
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Yes, that is a barometric damper installed properly as an air intake to reduce draft. Remove it and cap the rear opening.

Atmospheric pressure is what makes any stove work. The temperature difference between inside and outside of the chimney flue causes air to feed oxygen to the fire through the intakes by creating a lower air pressure in the firebox allowing the higher air pressure outside of the stove to push in. This controls the negative pressure (slight vacuum) in the stove. There is a box inside the top outlet which separates the exhaust from the rear intake, allowing indoor air into the chimney.

They should not be used for wood burning since you will develop creosote in the chimney flue and if it ignites, the damper flap OPENS to allow cool inside air into the flue. During normal operation, the flap opens when there is too much draft, or the chimney is too hot. Cooling the flue slows the draft which in turns slows the incoming air into the stove. This was done to make the stove more efficient by keeping the exact draft required constant. This type of damper controls the draft very well by automatically changing with atmospheric changes, temperature, and indoor air pressure. It should be used on all coal stoves since the draft on them is more critical than burning wood.

When the flapper is CLOSED, the chimney is too cold, such as in your picture and is the same as a manual damper being wide OPEN. As the chimney heats, the flapper OPENS which is the same as a manual damper being CLOSED. The weight is adjustable to adjust the draft for the manufacturer recommended draft required at the stove outlet where the draft is measured. This controls the air flow through the stove. The problem is in the case of a chimney fire. It is designed to control the draft and fire in the stove. When the fire is in the chimney, the damper responds by opening the flap (when you would close a manual damper) to cool the chimney. But since it uses cooler indoor air to slow the draft, this feeds the fire in the chimney more oxygen. Coal does not create creosote, so there is no chance of creosote fueling a chimney fire using them burning coal.

You will find more info here searching threads in this Forum using "barometric" as a search keyword using the search feature at top right of each page. (the magnifying glass) The word barometric is used when atmospheric pressure is measured.
 
Yes, that is a barometric damper installed properly as an air intake to reduce draft. Remove it and cap the rear opening.
Thanks for your input Coaly, it is always timely, and well appreciated. Now that I have shined the apple some ;) got a question for you. a typhoon rolled in this weekend and in the space of literally one hour, my stove went from king of the hill to oh my god I can't keep it lit....How much of a difference does the outside baro pressure make?

literally the stove worked great for 30+ hours easily adjusted, all tempt were good, and then the bottom fell out and I could barely keep it lit and it all went to a bed of coals with almost no flame. I tried opening the primary feed more, tried closing and playing with the secondary feeds to see if I could trick it, nothing...like beating a dead horse.

Last month I added that extra section to the outside chimney and extended it by 3 more feet. I think/thought that it might allow the outgoing exhaust gasses to cool too much do you think this is the cause? Temp was only 3 degrees (centigrade) cooler than the prior week, but once again typhoon brings a pressure change (lower I think) . if so does this mean I should make my stack shorter again or leave it alone? desperately studying this crap, but your brains are leaking more knowledge in this area then i will ever amass so please spill the beans and thoughts on this.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
The temperature difference between the inside and outside of the flue is what brings air into the stove. The larger the temperature difference, the stronger the draft.
So the chimney creates draft, and everything else reduces draft. Connector pipe, elbows, spark screen, even the resistance of the shape or baffles in the firebox are resistance in the system, the damper being the variable resistance. So you can see why smaller diameter pipe increases the resistance as well as not leaving enough heat escape to increase the draft. Here's what the negative pressure from draft does;

. When the atmospheric pressure is high, you have higher pressure pushing the air with oxygen into the stove to fill the void created by the chimney. The higher the altitude, the less pressure on a good day...... When a low pressure area moves over the stove intake, there is much less pressure to push oxygen into the stove. The larger the air intake, such as leaving the door open, the more square inch area the atmospheric pressure has to push in with. So larger outlet for more heat to rise through, and larger intake for the lower atmospheric pressure to use to get in.

To give you an idea of how minute the negative pressure is, the lowest pressure is at the stove connector measured in inches of water column.
1/2 PSI is about the normal pressure of propane line pressure for an indoor appliance. This is 11 inches of water column. Natural Gas is about half that, which is less than your breath. A U-tube manometer is used to measure this low pressure, which is simply clear vinyl tubing bent at the bottom in a U shape. Add water in the tube and it will find its own level. If you put a ruler behind it, when pressure is applied to one end, the other left open, the pressure will displace the water pushing it down on the pressure side and the water comes up the same amount on the side open to the atmosphere. You add the two together (rise and drop) and the total you get is inches of water column. So 1/4 PSI will move the water about 5 inches up one side and 5 inches down the other. This is the difference between the pressure side and atmospheric pressure at any given time.
Your chimney should be capable of producing .045 inches - notice that is decimal zero four five of an INCH. That would move the water 1/2 that much up and down the water tube scale. We're talking minute pressure. Every stove manufacturer will have a draft requirement for a stove. Normally coal and wood stoves are between .04 and .08 inches. Obviously when your chimney is undersize, temperature inside and out isn't extreme, like below 10*f. and you have a low pressure area, you aren't going to get the pressure low enough in the stove for indoor air to push oxygen into the stove. Opening a window to allow full atmospheric pressure at the stove intake may help, but a draft inducer such as a blower or electric heater in the stack may be required to force a draft.

I fired steam locomotives, and when you have steam pressure, you open a steam line that shoots steam up and out the stack to make an artificial draft through the exhaust tubes which makes a low pressure area in the firebox allowing atmospheric pressure to push through the firebed. In certain cases you need more "vacuum" than the stack or your chimney can give you. It's not you or the stove, you can have borderline conditions that won't allow enough oxygen into the stove. Same as a normally aspirated engine. When the piston goes down on the intake stroke, you only have atmospheric air pressure pushing into the intake. So at high altitude with less pressure, less power. During a storm with very low pressure, even less horsepower is available. Same as your normally aspirated stove which uses the chimney as an engine to make it go.
 
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Gonzo64

New Member
Dec 11, 2017
2
Usa
Wanted to say hi and purchased this old Fisher for $100. Needed draft knob fixed. (Rusted open). New fire brick. Brick is pita take out. I am assuming it's a 76 grandma. Also needs paint
 

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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Welcome to the Forum, you'll be amazed how fast it cleans up. Bricks are not the fun part. Wire wheel, paint and you're good to go.
 

Don H

Feeling the Heat
Aug 19, 2015
280
Maryland
Soak that draft knob in penetrating oil for a few days and hopefully it will free up. Then lube the threads and hinge pins with a small amount of Never Seize.

Don't do what I did with my first stove rehab, that was to use Stove Black. The proper paint is Forrest Products Stove Bright in satin black.
http://forrestpaint.com/stove-bright/high-temp-stove-bright-aerosols/high-temp-aerosol-paint/ or you can get creative and choose another color.

There's lots of great information here. Good luck.
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,053
NE PA
Another trick I found that works great loosening stuck draft caps is after soaking with penetrant, (I find Kano Aerokroil is the best) pour hot water over the draft knob without heating door. Then near boiling water over the center of knob expanding the aluminum knob and steel insert nut inside cap. Turn open by hand and clean threads behind cap with a small wire brush for cleaning copper tubing fittings. Grease threads and it should spin freely.

I think Don means Satin Black, not Flat?
 

Gonzo64

New Member
Dec 11, 2017
2
Usa
I just broke the bolt off and drilled it out and retapped the hole. No problem now works fine. Little never seize works great. Got all the fire brick out and man the rust behind them was crazy. Also noticed up front there is a small sliver of fire brick by the doors. Should I worry about putting new there?