Fisher Grandpa Bear X Wide Rear Exhaust Baffle

[egordons24]

Hi, I picked up a Fisher Grandpa XW stove to restore. It is rear outlet. Does it need a baffle ? If yes, what is best ?

 

[coaly]

The Series III were fitted with factory baffles. If your stove has angle iron corners that become legs, it did not have a factory baffle.

Depending on venting system, it is recommended to add one.

 

[egordons24]

Here are pictures of my stove. I believe it is a X Wide Grandpa built by the Dunn Brothers, now my work in progress. Angle iron sides with hinges welded to them. Setup for a second course of fire brick on the sides. Are they needed ?? It will be hooked to 7 inch insulated pipe. What design baffle would be best ?? I'm wanting to make this the best heating stove I can. The last picture is the stove I'm heating with now, top vent Grandpa it has never had a baffle in it. I didn't know it needed 1 when I bought and put it in my shop last September. I joined here in October when I purchased a 76 Grandpa and needed info on it and restoring it. Thank you Coaly for all the info and pictures you have put on here I haven't read every post on Fisher Stoves on here but I'm working on it.

 

[coaly]

Your starting point with 7 inch diameter would be minimum 38.5 square inch opening for the smoke path. Cut a template from a piece of cardboard sitting on rear shelf, angled upward towards front. It can come up to the lower bend or past it, just as long as the opening is not smaller than chimney flue cross sectional square inch opening.

Setting baffle on bricks at sides allows it to be adjustable by lowering the baffle if smoke rolls in opening doors, depending on chimney draft. If no smoke rolls in opening doors with draft established, that minimum opening is where to leave it.

The second course of brick is optional. It was added to increase firebox temperature.

 

[egordons24]

If I cut down the small baffle plate that is in the stove now to a 1 inch shelf and set the new baffle on it, it will be touching the outlet pipe. Is that ok? Or is there a minimum distance from the baffle plate to the outlet pipe ? This stove is 29 5/8 inside so will 5/16 plate take the 29 3/8 width or is 3/8 needed ? If I put the edge of the baffle 1 3/8 in from the bend in the top that is just over 40 square inch of opening. A Grandpa has about 10 inches from the bend to the front plate on the inside this X wide Grandpa has 8 1/2 inches. Will that shorter and wider distance of this stove effect the 40 square inch opening ? I measured the 3 sections of the tops on Grandpa and X wide grandpa and the have the same square inch of surface. Thank you

 

[coaly]

If I cut down the small baffle plate that is in the stove now to a 1 inch shelf and set the new baffle on it, it will be touching the outlet pipe. Is that ok? Or is there a minimum distance from the baffle plate to the outlet pipe ? This stove is 29 5/8 inside so will 5/16 plate take the 29 3/8 width or is 3/8 needed ? If I put the edge of the baffle 1 3/8 in from the bend in the top that is just over 40 square inch of opening. A Grandpa has about 10 inches from the bend to the front plate on the inside this X wide Grandpa has 8 1/2 inches. Will that shorter and wider distance of this stove effect the 40 square inch opening ? I measured the 3 sections of the tops on Grandpa and X wide grandpa and the have the same square inch of surface. Thank you

That’s fine. I never cut the original shelf under outlet. Sometimes the rear outlet pipe prevents the baffle from touching the rear wall. Baffle normally touches outlet pipe on bottom.

The wider stove should be fine with the slot that size. New stoves have baffles that come right up to within inches of the front. Some leave no error for weak draft without spilling smoke inside too.

That’s why I never recommend welding angle iron to the sides for a baffle support. Too many variables with draft. The differential temperature between inside and outside of flue is a main factor. Double wall insulated, or insulated liner being the best. Height increases draft to a point, cooling exhaust gases as they rise higher with diminishing returns. Altitude lowers atmospheric pressure the higher you are, detrimental to draft, and everything else decreases draft, such as screen at top, elbows, and horizontal runs all add resistance. The baffle adds resistance in the firebox itself by changing from diagonal flow to a S flow through firebox.

5/16 thick plate was used in the wider XL. If there is any sign of warpage, just flip it over, or in worst case scenario, drive over it, or a sledge with hearing protection makes them flat again.

I see an immediate smoke reduction starting fires with a baffle installed.

 

[egordons24]

I ordered the plate 10 3/16 x 29 3/8. If it rolls smoke, raising it is easy to gain area, would stepping the front outside edges like a factory baffle, not easy, but have any advantage ? I read the 7 pages of questions about baffles on the other Fisher thread and didn't see any with an X wide stove so I started this new 1. Coaly from reading all this stuff I can tell, You have been there and done that. Thank you for your help !!

 

[coaly]

Haven’t installed one in the wide body stove, but I tried them all on the same 6 inch straight up chimney. The only issue I had was fluttering in the Baby Bear.

My most memorable was showing up where the customer had a larger than desirable coal pile glowing, so I did that one with it lit!

I set the side bricks upright and wedge a stick across to hold them tight to the sides. Then carefully set the baffle plate horizontal on top, and slide it rearward to let it drop into position at rear.

 

[bholler]

Haven’t installed one in the wide body stove, but I tried them all on the same 6 inch straight up chimney. The only issue I had was fluttering in the Baby Bear.

My most memorable was showing up where the customer had a larger than desirable coal pile glowing, so I did that one with it lit!

I set the side bricks upright and wedge a stick across to hold them tight to the sides. Then carefully set the baffle plate horizontal on top, and slide it rearward to let it drop into position at rear.

Hot stoves are always so much fun to work on

 

[egordons24]

Installing it will be easy. Stove is laying on its back. The stove has T channel on the sides for the fire bricks so the top course of fire brick just set in it. I will put the plate in place, mark the sides of the stove, cut fire bricks to the mark, angle. If I need to raise the front of the plate for more square inch I'll just cut the front block down from 4 1/2 and slide it back. I am going to drill 2 holes in each side of the baffle and put nails in them to hold the top of the fire bricks. I read that someone on here did that, excellent idea and easy. I will post pictures when it is finished. Thanks again