Flue outlet size

If you calculate your stoves nominal commercial rating for BTUH using my simple formula, and then go to the InfoPedia charts I linked to, you will find your requirement for minimum flue diameter based upon the stoves maximum BTUH and its chimney height. It doesn't get much easier than this.

The fire pot volume will reduce in size by the same ratio as the smoke pipe, so no need to alter from half scale.

franco b wrote: ↑

Thu. Oct. 12, 2017 9:24 am

The fire pot volume will reduce in size by the same ratio as the smoke pipe, so no need to alter from half scale.

Yup, but only for a round firepot.

Halving the diameter of both the firepot and pipe will keep the same ratio. But for a square, or rectangular firebed, reducing it and the pipe size by half the dimensions will throw the ratio off. Gotta be done by ratio the area of cross section then.

Paul

Fred, This entire adventure is not one I ever plan to sell to anyone.This is just for my better understanding and a grand experiment to more fully appreciate what the manufacturer goes thru to get a stove together. My hat is already off to all of our manufacturers we have surviving yet in this country. Mike

Paul, Then it would stand to reason that if I cannot find the exact one half sized main body I could get the next closest size and scale all else by the ratio of the metal I will be using to the full sized original, how does that sound? Mike

Mike,
As evidenced by the Glenwood examples, I believe there is some leeway in that firepot to pipe ratio. Remember that the flue gas can change speed, which will allow it adjust to minor differences in the ratio.

If the pipe is at the small, workable end of the ratio, the gases will just flow faster. That is, up to the point of where the pipe is getting a bit too small. Then it acts like a partially clogged pipe would affect a full sized stove. The stove just becomes sluggish to damper settings.

At the big end of the ratio, or if the pipe is a bit too big, it will still draft well up until the pipe is too big then the draft becomes weaker. But the pipe would have to be absurdly over sized, like garbage can sized.

So, I think that if your going with a round fire pot, then as Franco said, scaling the pipe to the pot in close to the same ratio, it should work fine.

And remember that you have to scale down the coal somewhat, too or it will affect the depth of the firebed that burns better. Example; use nut coal at half it's usual firebed depth of 8 to 12 inches for ranges and many stoves and it may not hold a fire as well. But using pea coal at half the depth of a nut coal bed will likely draw and burn better ?

You can test a lower firebed depth with smaller coal size with something as simple as an empty paint can, with lots of holes punched in the bottom, using a screw driver or chisel, and a small diameter stove pipe bent-tab attached to the can's lid. Cut lots of slots in one end of the pipe. Bend every other "tab" out at 90 degrees. Put all the unbent tabs though the hole in the can lid. Then bend those inner tabs out 90 degrees inside the lid to sandwich the lid between the tabs above and below the lid. If the hole in the lid is very close to pipe OD, that should seal well enough for an experiment.

Paul

A real life example is the Godin 4 inch smoke pipe with a fire box volume of about 3/4 of the height of the stove.

franco b wrote: ↑

Thu. Oct. 12, 2017 2:24 pm

A real life example is the Godin 4 inch smoke pipe with a fire box volume of about 3/4 of the height of the stove.

Franco,
What size coal works best in that, and would it still work well with less firebed height ?

Paul

Nut coal and it needs the height to counter the large front grate that can let air bypass the coal.

The biggest hurdle I see with this working is the depth of the coal bed. It probably won't be deep enough to perform well.

coaledsweat wrote: ↑

Thu. Oct. 12, 2017 2:59 pm

The biggest hurdle I see with this working is the depth of the coal bed. It probably won't be deep enough to perform well.

True, a deep firebed burns best. But that may not rule out a shallower firebed working also. The range that Wilson has does not have a proportionally tall firebed.

And, the working half scale model kitchen range I saw in an antique shop has coal grates and it's firebox was to scale. The fire box is about half the depth of my range, and my range is at the small end of range sizes in it's day.

To give you some idea, the red handle of my Swiss Army knife in the picture is 3-1/2 inches long. The fire box is maybe 4 inches deep, and the range shows signs of use.

And full sized ranges have a low firebed compared to heating stoves of the same era. My range's firebed is only 7-8 inches deep and it runs fine on nut or stove coal even as the firebed level is getting low.

Paul

It seems like smaller coal in a shallower bed would perform similar to bigger coal in a deeper bed with similar burn times but proportionately different BTU output. The coal depth in a stoker is only an inch or two right?