[Tscarborough]

OK, i read the pamphlet. He makes some good points and some that are against what I have learned, but he makes a strong case for them.

I have observed a (horizontal) circulatory pattern in an oven similar to what he describes in a chimney, but I am not convinced that the same principle applies in a vertical application of the length of a chimney.

That is to say, he presumes that cold air is drawn from the top of the flue stack down the backside (of the flue) and mixed with the ascending air in the front of the flue, and this is the purpose for a smoke shelf.

It is certain that a roll of air forms in that position, but I have seen nothing to lead me to believe that air enters and descends from the top of the flue to contribute to the roll of air, or if it would even matter if it did.

He also draws the front of the throat as an angle not an arch, which may just be simplicity on his part, although I consider this feature to be critical to the Rumford design as it creates a venturi effect at the level of the damper.

I will grant that a sloped back is preferable, but not that it is necessary.

Overall it is a "book" (it is only about 60 pages) that anyone who designs or builds fireplaces should read. I wish I could afford to print and send copies to every architect in the US.

 

[cdkyle]

My question is, are the rumford design primarily for indoor use?

I am planning to build an outdoor unit at home for myself. I like the look of the rumford's taller opening and think it would be cool to do something a little different. But, it appears to me as previously mentioned, the depth of the firebox is much smaller and is going to limit the number or size of logs one may burn.

I have seen a few rumfords, but all in older homes. There are very few actual fireboxes even built in this part of the country. Most now are zero clearance metal units.

What do ya think would be good for an outdoor firebox, rumford or orton? I built many of the or tons over the years, but never a rumford.

Great topic, btw.

 

[Tscarborough]

There is no difference between a Rumford or Orton, they are the same thing. Orton is merely restating the design features of a Rumford design, and attempting to (briefly) explain their merits.

Indoor or outdoors makes no difference, other than including a damper, it will work in both instances.

 

[JBM]

I had an exterior chimney with a Rumford and it was excellent. If you look at the drawings on the rumford.com site it shows the depth to be 14" on a 36" opening. That doesnt allow for a face brick or stone veneer. It is a rough block number.

so when I build a rumford it is 18" as apposed to the standard 20" sqatty boxes that are standard.

That 2" does make all the difference in the world though, it makes the side walls much more pronounced, the back wall smaller.

Of coarse I did used to start my fires in a tee pee fashion. I was under the impression(of coarse this is correct) ,that the higher you could get the flame on a tall opening like the Rumford, the more you could utilize the radiant heat of the firebox. It wasnt because people were to retarded to know how to make wood smaller to fit intelligently. After an hour or so though, only an occasional log could be thrown on, it was too hot to sit within 10' of if it was roaring.

Regarding interior or exterior I dont think it would matter.

I personally would not use the damper they are sending out right now. They made a modification to keep the door from dropping down by adding a hook for the handle mounted between the throat and last firebrick. With the handle in the hooky thing, the opening isnt plumb, open, and a direct outlet. It is at a less the 45' angle, about 3-4" and opens directly to the wall of the throat system.(I called Superior Clay and the fella assured me this was perfectly fine)

The only way around this would be not to use the hanger gizmo for the handle and push the door open like we did for the last X amount of years.

I will from now on use a top mount damper, run the cable down and call it a day. Unless I can get the longer old style handles.

 

[Fancis Casini]

Rumford's footnote;but merely set down upon the hearth,

The Orton is a slanted backed firebox vrs. a straight, like Rumfords' first invention ''his prototype''.
The proto type was designed as a remedy installed into existing, thick front walled fireplaces, hence the straight backs and thicker front breast which demand rounding or risk smoke!

To function well the throat of a slant needs to be 8 or 9'' behind the face,. add a 4'' throat and a 6'' slant or so and you'll have a 19 to 20'' deep box.

Rumford did give some hint to lessening the acuteness of the side walls so as to receive longer rear logs.This is a nice option on a slant [ESPECIALLY FOR OUTSIDE] because when new logs get added they go onto the rear so the smoke gets carried up easier,...a handy trick which keeps the smokier logs at the back and up along the slanted wall and rule of thumb for all fps.
I feel the 180 chords or so I've burned the past 30 years taught me that much.
Any idea of a heat loss do to widening the back a bit to accept a longer log is made moot due to extra heat that radiates from the slanted rear wall.
Orton suggests a back that is between 2 and 3 times smaller the front width but try and keep closer to 3. Mine is 50'' at front and 36''at back and 20'' deep. At this angle the sides still can perpendicular-ly radiate heat out into the room without hitting the opposite wall,so no loss is had what so ever, in fact the wide angle is increased! As to depth I could easily do with 18'' but years back when cooking was common place in the FP it was handy.

Buckley plays games with his fire box plans which he affixes the name True Rumford to. He shows fireboxes with true Rumford depths on one side of the F.P. jamb, then on the other he adds a face of up to 5'' which is more the Orton without a slant, but certainly not exactly a true prototype.
If you look at his 6, 7, and 8' FP plans he adds double steel lintels and a cast iron damper [lips included] and a slant the top to accomplish some added depth.There is no other bigger smoke causing error than continuing to enlarge the depth of the breast to accomplish the above, hence the need for ti pi fires.

As to placing top dampers on a straight backed Rumford fireplace I don't
think they will hurt because the dampers can't really be choked to save heat due to the fact the throats do not run the entire openings length, and the breasts are thick to boot!
But on a Orton slant, the full length damper is needed when choked small.
Any choking at the top will be minimal and cause smoke.They can be draft inhibiting with different wind behaviors and turbulent in slow days.
''Smoke on a rope" is what they are to me.

Perhaps when I do my 2'' choked damper video some will understand the significance of a thin long opening along a true full length throat.

I'm pondering getting Lilly my 2 year old grand daughter, to help..lol ?

Here are a couple links to straight back Rumford situtaions. One is a reply to me about the throat kit and the other is a straight burning
with smoke stained front and if you look close it's smoking slightly which is the most aggravating eddy type. Both these problems can be location caused or short chimneys I don't know.

http://www.youtube.com/watch?v=ZTQ6jdQHJN8 smoke on face

a fire in a Rumford note his reply. http://www.youtube.com/watch?v=TnDu9Wf86Vc


This is Rumford's footnote referring to his experimenting on slants.I've read this a million time and just the last time I focused on the part where he mentions it can be sat on the hearth and separate from the chimney and used in new construction!
I immediately thought about him hiring a potter and the possibility of a
entire unitized ceramic slanted firebox and throat.One that just sat there and could be moved to any?

Any Thoughts? Could he have been aiming after the Franklin stove but with unitized masonry?....I'm positive Ben had the stove for 45 years already.

FOOTNOTE;

[353]
Of Chimney Fire-places. When the wall of the chimney in front, measured from the upper part of the breast of the chimney to the front of the mantle, is very thin, it may happen, and especially in chimneys designed for burning wood upon the hearth, or upon dogs, that the depth of the chimney, determining according to the directions here given, may be too small.
Thus, for example, supposing the wall of the chimney in front, from the upper part of the breast of the chimney to the front of the mantle, to be only 4 inches (which is sometimes the case, particularly in rooms situated near the top of a house), in this case, if we take 4 inches for the width of the throat, this will give 8 inches only for the depth of the fireplace, which would be too little, even were coals to be burned instead of wood. - In this case I should increase the depth of the fireplace at the hearth to 12 or 13 inches, and should build the back perpendicular to the height of the top of the burning fuel (whether it be wood burned upon the hearth, or coals in a grate), and then, sloping the back by a gentle inclination forward, bring it to its proper place, that is to say, perpendicularly under the back part of the throat of the chimney. This slope (which will bring the back forward 4 or 5 inches, or just as much as the depth of the fireplace is increased), though it ought not to be too abrupt, yet it ought to be quite finished at the height of eight or ten inches above the fire, otherwise it may perhaps cause the chimney to smoke; but when it is very near the fire, the heat of the fire will enable the current of rising smoke to over-
A A 3
[354]
Of Chimney Fire-places. come the obstacle which this slope will oppose to its ascent, which it could not do so easily were the slope situated at a greater distance from the burning fuel*.
Having been obliged to carry backward the fireplace in the manner here described, in order to accommodate it to a chimney whose walls in front were remarkably thin, I was surprised to find, upon lighting the fire, that it appeared to give out more heat into the room than any fireplace I had ever constructed. This effect was quite unexpected; but the cause of it was too obvious not to be immediately discovered. The flame rising from the fire broke against the part of the back which sloped forward over the fire, and this part of the back being soon very much heated, and in consequence of its being very hot, (and when the fire burned bright it was frequently quite red-hot,) it threw off into the room a great deal of radiant heat. It is not possible that this oblique surface (the slope of the back of the fireplace) could have been heated red-hot merely by the radiant heat projected by the burning fuel; for other parts of the fireplace nearer the fire, and better situated for receiving radiant heat, were never found to be so much heated; and hence it appears that the combined heat in the current of smoke and hot vapour which rises from an open fire may be, at least in part, stopped in its passage up the chimney, changed into radiant heat, and afterwards thrown into the room. This opens a new and very interesting field for experiment, and bids fair to lead to important improvements in the construction of fireplaces. I have of late been much engaged in these investigations, and am now actually employed daily in making a variety of experiments with grates and fireplaces, upon different constructions, in the room I inhabit in the Royal Hotel in Pall Mall; and Mr. Hopkins, of Greek Street, Soho, Ironmonger to his Majesty, and Mrs. Hempel, at her Pottery at Chelsea, are both at work in their different lines of business, under my direction, in the construction of fireplaces upon a principle entirely new, and which, I flatter myself, will be found to be not only elegant and convenient, but very economical. But as I mean soon to publish a particular account of these fireplaces, with drawings and ample directions for constructing them, I shall not enlarge further on the subject in this place. It may, however, not be amiss just to mention here, that these new invented fireplaces not being fixed to the walls of the chimney, but merely set down upon the hearth, may be used in any open chimney; and that chimneys altered or constructed on the principles here recommended are particularly well adapted for receiving them

 

[JBM]

Well it looks as if he is repeating the same thing I am, the fireplace gets to hot. He did mention that is occasionally smokes, dunno, it might be like a family room FP. Mine only smoked when the damper would fall down...

 

[Fancis Casini]

too hot ot abit

KIDO
any Rumford gets too hot with a bonfire...that's not what we want we want heat with small amount of fire and a lot of coal bed.
The old days had fp's in each room as well as ovens in the kitchen and the basement sometimes! My neighbor has a late 1700's house with an added wing built in the early 1800's.The the older part has a 7' walk in kitchen FP with a oven and 3 other fps one on in the 2nd fl bedroom.They all angled forward like the one on the cover of the Orton's Book which went plumb a bit too far before it slanted forward.
Makes me wonder because Rumford hadn't started his Rumford work yet? These fireplaces are square and about a foot deep to 16''on the bigger one accept the kitchen which was a bout 3' deep.
In the basement there is a huge stone beehive oven that's 6' in diameter probably one of the biggest around in the country. I never could see where it drafted to but the chimney was 5 by 5' and probably rebuilt so they more than likely closed it on the 1st fl.
Any how under the hearth of the huge kitchen FP was a stone foundation about 12 by 12' x 7' high, filled with dirt! I thought it shoddy but then I thought a bit more and figured what the heck...all that dirt and stone getting warm and being in the center of the house.....what a mass of radiant heat.They could probably shut everything down for a week and still have a house that would be in the low 60s.
I have a double set of 1775 andirons from the house,.. when the kids sold the house and had a tag sale. I think I paid 30.00 15 years ago. Funny the 1950's brass set was priced over a hundred.
About radiant heat,I designed my home so the FP was in the center.On the back side the brick wall is the dinning room wall with a small oven niche built into the back around 4'high. It is opposite the fireback and as the fireback leans forward it made room for the oven.
After I burn for about 6 hrs the back gets warm as does the side wall where there's another niche.These stay warm for days.On holidays I'll burn for 2 or 3 days straight and then everything stays very warm for about 4 days even the dinning rm floor near the brick wall. There is nothing like radiant heat as it has no on off clycles that old mason bones hate!
Bathroom mud jobs with radiant tubes are nice as are basement floors too. I have them and love it in fact last couple of years I rebuild a beach house my son bought and plumbed the kitchen and baths with infloor heat. No mud was used in the kichen I used those aluminum plates and under the plywood....nice. The plumbing gets involved but
it's a mechanics and I always loved it....had it not been for my father I'd a been a mechanical engineer......he sucked me in for cheap! lol.

u know your not far from me ...any time you want you can come and see my fp burn at the 2''. It's only 96 sq.inches on 2400 sq inch of opening......amazing vacuum stack....use the wrong damper and forget the tweaking to small gaps. IE any old hole won't do.

 

[Fancis Casini]

your damper

re;I personally would not use the damper they are sending out right now. They made a modification to keep the door from dropping down by adding a hook for the handle mounted between the throat and last firebrick. With the handle in the hooky thing, the opening isnt plumb, open, and a direct outlet. It is at a less the 45' angle, about 3-4" and opens directly to the wall of the throat system.(I called Superior Clay and the fella assured me this was perfectly fine);

Do they smoke at the 4'' or 3'' or at what opening size? They aren't built right.......either lay them at an angle by sloping the seat area. On a straight back they should hinge on the fire back wall side [like the cast irons]and at a minimum setting still be fairly open.....the problem is the throat system is built too short to choke unless under fantastic conditions with a warm and very tall chimney.
The cast throats need to be more the length of the opening and NOT THE REAR WALL? They are too far back where the narrow firebox back width dictates the short length. All they have to do is angle it forward from the opening height to the throat top....12 to 14'' Buckley has done this on his 7 or 8' fireplaces and condoned it as "works good".
Rumford frowned on any slant in the prototype only!

Many times when I use a cast damper on a slant aside from cutting the front lip off to give 4'' behind the face,I go to the next biggest length because the blades are too short and the housing is tilted in at the ends, and will cause eddys if a substantial choke is attempted.

Kinda like **** I guess...short fat dampers are worse if skinny! Put a pot belly [substitute for breast] in front and your sht outta luck! lol

 

[JBM]

KIDO
any Rumford gets too hot with a bonfire...that's not what we want we want heat with small amount of fire and a lot of coal bed.

u know your not far from me ...any time you want you can come and see my fp burn at the 2''. It's only 96 sq.inches on 2400 sq inch of opening......amazing vacuum stack....use the wrong damper and forget the tweaking to small gaps. IE any old hole won't do.

You are assuming that is what is required for the Rumford make the heat. It isnt, it made plenty of heat with just the coals, like you said.

Im not really sure what your arguing. You seem to be saying that your fireplace is better then the straight back Rumford, im saying that if it is, it might not be measurable. I also think the straight back looks better then an angle, although it isnt a deal breaker either way.

Im sure you build a great fireplace, im also here to tell you that the Rumfords Buckly sells, or designed is fantastic as well. You keep coming back stating that it isnt, i think, i dunno.

Ive only built maybe 300 or so chimneys, and only 15-20 or so of them straight back Rumfords with the kit. Im always up for better ways to do something, but it has to be better, and then it has to be faster or cheaper.

 

[Mooman]

I got to the end of this post where you were talking about the 1700's chimney all full of dirt and whatnot and realized you are the only person I have ever been able to chat with, that has dealt with these old behemoths besides myself. I love reading this, its like doing that project all over again.

Anyway, so that I am not taking away from this post, here is what I would like to say....

When I started this project, it was apparent that it was ready to fall down so the decision was made to take it all down to the 4 fireboxes on the first floor. Beneath all of this was in fact this 12'x12' base full of stone and dirt which I excavated further down til I got into the beehive shaped ash dump below. No one even knew it was there or once we did, what it was. At first it was thought to be another oven. The reason for this was there were no ash dumps in any of the boxes above, plus, the channel leading down to it really did look as if it could have served as an exhaust. Once I realized that there could have been dumps in the boxes, I got the OK from the architect to further dismantle and try and discover exactly what was going on.

This was all being documented by the Historical Society so every move was cautious at the least. Turned out, the dumps had been covered or plugged some eons ago. So I ripped out the stone box floors and started over while the boxes themselves(less the bread oven) were left untouched. I later rebuilt the bread oven with a few minor improvements. The owner did not want the dumps to be visible once completed therefore presenting a problem. Operational-YES, visible-NO. So I literally whittled stones with 45 degree bottoms to hold them from falling through and created notches for fingers to get a hold to lift out when and if ever necessary. The notches were cut so that through the use of angles, could not be seen when viewed from in front of the fireplaces.

Moving up to above the boxes, it was here where I made the decision to create my own chambers (and this is where I think some of you might cringe). I designed the smoke chambers to utilize Vestibule Dampers with 5" shelves, but, then I created spherical chambers with plum backs leading up to the first flue stack. Here, the 18" and 24" round clay tiles were set in place to continue the shape right to the top. Back down in the boxes, I wanted to reduce the turbulence it no doubt had from the many edges and cavities the original masons left due to no concern for detail. So I chiseled out all the stone from the top of the box, down about 12", and rebuilt the walls with absolutely no deviation from the vertical plane- smoothed to perfection. I then used a flap disk and smoothed and deburred the damper plates til they were perfect. I made the transition from the box walls-up through the damper and chambers, seamless. Also, much like Rumfords, I wanted to reduce turbulence as much as possible in this particular situation as I could- concerning the lintels. The existing lintels were of course massive 12' pieces of stone that spanned the entire chimney. They were of course cracked right dead center of the box openings. So I was forced to incorporate steel angle, catching 10" each side. I used an engine crane to lift the stone, then notched out the bottom(less 1" reveal to hide the steel), set the steel in place with insulation and breathed a sigh of relief it held together.

I could go on for days, but I just wanted to share some of that experience with ya'll and point out that when your cross-sectional math is correct, and things are smooth as a mirror, a chimney, (no matter what its intended design) can pull like a freight train and throw heat to the point where you really would consider opening a window. That being said, I am fully aware that the radiant heat X pattern works best when the sides are at proper angles and the back is sloped correctly( or perfectly straight depending on what your going for). But when existing boxes meet none of these specs, and you play with the physics, you can achieve great results. This project by the way, was an outstanding success. The boxes performed flawlessly with massive heat output. All done without changing the original look and meeting all codes.

One last thing, I have of course built traditional, Rumford, and modified fireplaces. I have seen first hand my own creations outperform all expectations. Great Post by the way. Thank you.

 

[Fancis Casini]

Similar Antique Rebuilds

Maybe that basement stone behive was a ash pit....I looked into it briefly and was going to stick bigger light into it but never did.

The neighbors had a builder whom they hired to do allot of work while I was doing the work.He was from Mass,his name was Ed Sunderland from Sunderland homes.
He was a nice guy but no mason although he thought he wrote the book on colonial F.Ps. He stuck his nose into my job when I was doing the kitchen fireplace over .He insisted the brick face firebox was original and I knew it was actually a Rumfordize attempt in front of the granite firebox.
He got the owners on his side till I went ahead and removed it and uncovered the original .....which we rebuilt sections of along with the entire throat and chamber, which had been fit with a homemade damper that was thin sheet metal and terribly wrong.

They burn the large kitchen FP allot as they sit and read and surprisingly the thing throws heat but has a large throat despite my closing it as much as possible before it'd smoke.

Here's a few pics with new plaster as was original.

 

[Mooman]

Maybe that basement stone behive was a ash pit....I looked into it briefly and was going to stick bigger light into it but never did.

The neighbors had a builder whom they hired to do allot of work while I was doing the work.He was from Mass,his name was Ed Sunderland from Sunderland homes.
He was a nice guy but no mason although he thought he wrote the book on colonial F.Ps. He stuck his nose into my job when I was doing the kitchen fireplace over .He insisted the brick face firebox was original and I knew it was actually a Rumfordize attempt in front of the granite firebox.
He got the owners on his side till I went ahead and removed it and uncovered the original .....which we rebuilt sections of along with the entire throat and chamber, which had been fit with a homemade damper that was thin sheet metal and terribly wrong.

They burn the large kitchen FP allot as they sit and read and surprisingly the thing throws heat but has a large throat despite my closing it as much as possible before it'd smoke.

Here's a few pics with new plaster as was original.

Wow! Its like looking at my job. Let me see if I can dig up some photos to show you. They look so much alike. I'll go look now, not sure what I have-if any, nor what stage of the process.

 

[Mooman]

Alright, found some. I think the ones of everything finished up, are on another memory card and I can't find that or the thing-a-ma-jig that is needed to plug the card into the printer or whatever. But these are what you and I are talking about anyhow....

 

[Mooman]

Others....

 

[Fancis Casini]

Oven

Did You use a sand form for the oven or just go slow. Oven looks good they are slow and tedius. I have 3 oven niches only about 12'' and 16'' deep as I didn't have room] they are a day's work each to get the joints nice. I made trowel lines in the joints looks nice but each one has to be done as soon as it's laid.
Many old ovens weren't laid fancy but they sufficed.

So you made all round passages[smaller flues] from the chambers of the various fireboxes leading into one big flue pipe?...it's hard to tell from the pics.

You work alone ..yes?

by the way nice dogs!.....love labs and retrievers

 

[Mooman]

Did You use a sand form for the oven or just go slow. Oven looks good.
So you made all round passages[smaller flues] from the chambers of the various fireboxes leading into one big flue pipe?...it's hard to tell from the pics.
You work alone ..yes?
by the way nice dogs!.....love labs and retrievers

Yes I did use sand(exactly 18 pails worth). And thank you, I was concerned that even though the oven looks 100 times better than it was, that it didn't look good enough. Never had feedback on that one to this day.
Either 2 - 18", or (15" I forget which)- round flue and 1 - 24" round flue were used to vent the 3 boxes. And for the bread oven, I used the 4" x 8" flue to vent it. I covered the dome with multiple layers, including 2 separate layers of insulation mortar before building supports for a cap to start building again on top of that.
All flue run right to the very top of the chimney with alternating termination points from one another above the wash. I am enclosing a photo of this shot(which happens to be in another post of mine), which clearly shows what you are asking.
Yes, I am the only employee of AJM, however, when its necessary to have help, I have another stone mason, who happens to be my ex-stepfather, help me-who is capable of some really nice work. Also, a tile guy, buddy of ours fills in as tender. I have hired guys in the past, but they didn't last long because they couldn't wrap their heads around "Quality". They just couldn't come even close to what I expect, so down the road they went.
Last, our 3 dogs....Red and Jackson(pure breed Black Labs) Brothers and quite the clowns. They are going to be 7 this year. That leaves Lola. She is our 3 year old Bull Mastiff/lab mix and is our little huggy bear! She is the worlds sweetest dog. Can't get enough attention.

 

[Fancis Casini]

heat and heat loss

re; You are assuming that is what is required for the Rumford make the heat. It isnt, it made plenty of heat with just the coals, like you said.

No you are thick! The radiation isn't all ther is!.. you are using a buckley designed throat situated at the extreme rear of your firebox. I think you said you had a 36'' rumford so that means your non chokeable precast throat is 4'' by 20'' long = 80sq.inchs
36x36''=1296sq inchs divided by 80 is 16.2.....you are 1/16 the opening...which means that rear throat is sucking alot of heat from the house.You may be toasty on one side but there is ice in your toilet.
This is opposite what Buckley has been saying about Ortons for some 30 years. Do you realize your un choked throat on a 36'' is 80sq inches and mine on a 50'' is 96sq.inches.That is just 16 square inches or 4'' by 4''.

You have a flat damper?.....as buckley promotes? This is because they already tested the precast throat design at 4'' and any less would be smoke prone.
This is what Jim had written to me years back when he said my throat was double his! That statement was the catalyst for my experimenting with my damper.

Have you ever bothered to try and choke any of your straights ???

Key point here is, all the sales pitch about breast rounding is an antique practice that "had to be incorporated by Rumford to get the smoke in past those THICK breasted EXISTING fireplaces".

Why in heck should anyone want to go back in time and have a thick breast to ROUND in efforts to aid a short and a rear positioned throat THAT NEEDS TO BE MADE DEEPER.. 4'' TO 5-1/2'' and bigger, and fitted with non adjustable type dampers. For looks??? The thicker, shorter, to the rear throat is a dead givaway where the problem lies! Yes they are easy builds, just read the advertisments ....they are aimed at a less skill demanding market as well as less labor. This doesn't bode well for our trade, it's already minimal.

Next superior should reread Rumford's footnote and do a unitized slant back[Orton] and get with the program!....but they also need to get a damper right because you can't cast 2'' throats. Access and draft variables inhibit a fixed small size.

Meanwhile The day I see a precast throat [the current style] sitting atop a straight back Rumford with a choked throat that equals 1/25 the opening, and burning smokeless for hours upon hours, and in any type weather, as mine does, I'll agree that both styles are close..although I do agree with Rumford and like watching the fire coming up the back of a extremely hot slant, and can't see cutting logs so short for the back.

Buckley is more than welcome to show his stuff to me and I'll do mine...heck I'm doing mine anyways amost nightly...In fact I will try for 1-3/4'' which will be close to 1/30th the opening of 2400 sq inches.

I would just want equal fuels burnt and chimney lengths....because the last time I talked to him he said he was burning Fir.....which is very hot and fast burning creating a force fire.[not fair]
In fact a horizontal fire would be unsisted on for both.

By the way last night at my son's house on the sound the wind was in the 60 to 70 mile an hour range.He had the FP going and it was eddying smoke.It's a 36'' very slight slant on an exterior wall [no where elas to put it].
It has a cut vestal because I didn't want to take a day and fab one of mine [should have] but it works fine on other days so I thought about the attic and the ridge vents sucking the house negative.It helped to block the attic door bottom but it was still happening.
When I did his chimney I puposely built the outside brick wall at the flue to retain heat, but the 12x16'' flue was never going to warm up in that very cold wind so I [Bit the bullet as Buckley would say when he slanted his 8' FP to get depth] and transformed the fire into a TI PI.
This was a first for me since I was a kid camping out....but it worked as it literally pushed it's way out despite dampening high wind and warmed the chimney.

This is testament though that almost any fireplace will work with a Ti Pi and shouldn't be judged while one is used unless it's the only fire that will ever work! In that case there's a problem with the integrals and a false sense of security is being displayed or enjoyed!

I read somewhere Buckley stating, If a cold chimney doesn't draw something's not right.......The only thing I could think of now is that the Ti Pi fell down!

 

[JBM]

Have you ever bothered to try and choke any of your straights ???

Key point here is, all the sales pitch about breast rounding is an antique practice that "had to be incorporated by Rumford to get the smoke in past those THICK breasted EXISTING fireplaces".

I really dont know what the difference is, aside from the height of the firebrick, what the difference is between this fireplace and the normal ones I build. It looks like the firebrick top opening is about 12, 12 1/2 inches. My standard opening is 14, for the vestal. Why didnt you use a 44" damper? You wouldnt have had to corbel like that.

Again, im not sure what we are speaking about, maybe you have it choked down above the damper? Im not sure, it has to fit the bottom of the flue. So regardless of the damper opening, there is a specific velocity number that is required to remove a certain amount of "smoke". To achieve the reqiured amount of velocity is going to be the same I would assume, the same based on the same amount of BTUs generated by the fire.

So heatloss is going to be relative to the amount of draw needed, based on the size of the fire.

Or are you saying you achieve a different velocity of draw (LESS), yet your fireplaces dont puff smoke?

 

[Fancis Casini]

Or are you saying you achieve a different velocity of draw (LESS), yet your fireplace

That damper cut measures 10'' from the fire brick jamb to the firebrick back top of wall. It is an inverted 3 1/2'' L iron on there,.. add the cast frame and its about 5'' to the throat from the jamb,..add 4'' for the brick face and it's 9'' face to throat! I usually do 8'' but a 2nd fl hall was causing a chamber reversal so I kept to a minimum the back wall tilt. Normal when tight framing is involved.

I have posted previously about widening the upper side walls to accommodate a throat that is full length....not the damper housing as you do.
The housing throat length is short the opening by alot and it's compound angled!

You may think I'm excessive but not when it can close to a smaller
area-ed throat. And if the chimney is sluggish it prevents lazy corner draft at each end of the inner breast.....a common place for puffs, as you call them.

The chamber closes the side to flue size but gradually. These cast-irons do the job but not nearly like my damper..that is unbelievably efficient at small settings less any turbulence.The cast would never get there it's built wrong....Is it just that I have a well built slant in a perfect draft assisting scenario well..
I do have a 36'' slant in the basement with a cut off cast iron damper.
I never installed the face on it but I could put a piece of dura rock on it and test the damper's limits with a fire. I'll do this after the video.

You'll hear claims that a long throat is not as good of a clean burner like the short deep straights, but I find the smoke mostly stays where the flame is anyhow...example, if you look up at each end of the inside breast wall at my fireplace, the brick and angle iron lintel are like new even after 18 years of very frequent use..... Does my fabricated damper extend past the opening? and do my upper side walls corbel out?. No not needed.

About any minimum throat opening per calculated theory? Rumford gave his throat dimensions per testing with a straight back and it's shorter throat positioned at the rear.
He found that 4'' was averaged to be best for most size F Ps but an increase to 5 or 6'' could be used on deep larger lodge fireplaces.
I think he also said 3'' could be used on very small F Ps. So much for theory....it becomes apparent to use what works less any smoke but try to keep it small as possible.
I can't imagine having a fireplace without an adjustable damper because some people have a perfect scenario to take advantage of it.
A flat damper atop those precast throats can't be choked well if at all, so some fireplaces will never be in tune.

All that inverted carburetor talk, fitted without a good draft governor,
why.

Re your statement;
''Or are you saying you achieve a different velocity of draw (LESS), yet your fireplaces dont puff smoke?''

Define velocity per a fireplace function. This is not a boiler! And what I achieved is a 1 to 25 ratio on a 50'' by 48'' high slanted [Orton] Rumford.

Now as to you are talking velocity.

It is understood that a draft coming through a thinner longer port will have stronger force [velocity] than a larger port.

A 1/25 ratio proves it is advantageous to keep this choked thin port and all it's suction/velocity as close [vertically over] where the two incoming currents are, "up close and along the entire front inner 8 or 9'' breast wall".
The natural attribute of a full length throat formed when a firebox rear wall is leaned forward has to my knowledge never been pushed to it's limits. we'll see soon

that's all

 

[JBM]

Since this thread is about making a traditional Rumford without the pre made throat, I thought some of the members would find this post on facebook interesting. And for those who have a passion for well built fireplaces, and Rumfords, buckley is on twitter and facebook now.

Anyhow this fellow in Turkey made a pretty decent Rumford by hand.
https://www.facebook.com/media/set/?set=a.10150895205694271.436635.634519270&type=3&l=5e8de87d0a