Wings Best Holes at Ash Drawer

KingCoal wrote:dlj,

wadr, you may very well be correct but,

if we look at virtually all the biggest and best mica radiators none of them have nor seem to have ever had a liner. just coal burning directly against the iron pot, with an air gap between that and the mica windows not only above the fire but the full depth of the pot down to the top of the grates.

i would have to say that the originators were pretty certain that no liner, in that instance, released more heat out of the stove at no peril to combustion eff.

.02 worth,

steve

But, remember, the mica firepot walls (and suspended pot stoves) are heated on both sides. Not as much to gain, if at all, by lining them.

Paul

joeq wrote:I would also agree with the liner having no insulator, that more heat would radiate from the stove. But, depending on stove design, I would think the bricks would be a good insulator and protector for the stove structure, in the case of an overheat condition. We all know how easy it is during tending, that some times the pot temps will be raised up higher than expected, because we walked away to do something else, only to return to a blazing fire. The firebricks will absorb more of that heat, than taxing the surrounding joinery or castings of the stove. I've heard people mentioning their potbellies glowing orange.
Unless some-one can convince me of a stove that is designed to take 900-1000° reliably, I'll keep to my brick lined pots.

Both potbelly stoves I've used - one small, the other a station master size - routinely had the bottom half glowing cherry red, hour after hour. Glowing brightly enough to easily be seen in a well lit room. That's up over 1000F. Didn't see any signs that was a problem for them.

But, they were never meant to have a liner either, so as Dave said, they may have had a different metallurgy ? Or, I wonder if it may have something to do with their compound curve shaped firepots ?

Paul

Sunny Boy wrote:

ddahlgren wrote:Possibly the question is, do you want more heat in the fire bed or on the other side of the fire pot? Intuitively for me more heat in the fire bed means higher temps for the fire bed and might fully burn the coal to fine ash getting every little bit out of it, possibly better at low firing rates. No liner should transfer more heat to the other side of the fire pot and where it goes has to be determined as useful or not to get more heat with potentially less complete combustion at anything less than a pretty brisk firing rate.

Which might make affect how low you can idle the stove down during warmer weather without stalling the fire ?

Paul

Just thinking out loud no expert here. I do need to sit down with a friend of mine that work in a coal burning power plant. We had a short chat a few days ago and the lengths they took to squeeze everything out were impressive to say the least.

Sunny Boy wrote:

KingCoal wrote:dlj,

wadr, you may very well be correct but,

if we look at virtually all the biggest and best mica radiators none of them have nor seem to have ever had a liner. just coal burning directly against the iron pot, with an air gap between that and the mica windows not only above the fire but the full depth of the pot down to the top of the grates.

i would have to say that the originators were pretty certain that no liner, in that instance, released more heat out of the stove at no peril to combustion eff.

.02 worth,

steve

But, remember, the mica firepot walls (and suspended pot stoves) are heated on both sides. Not as much to gain, if at all, by lining them.

Paul

then we seem to be in agreement. in some cases there is no need of a liner and in fact some times a pot can be in contact with the fire on one side and the super heated exhaust on the other and suffer no damage except by gross abuse and or neglect.

The mica stoves fire pots were insulated by air space. They were not directly exposed to heat loss, just as the modern Chubby fire pot is also shielded by air space.

The main function is to raise fire pot temperature to enable more complete combustion. The effect is most noticeable at moderate to low firing rates. At high output an unlined pot should work well also.

An unlined pot with exposed sides obviously will give off more heat than a lined one but does so at the cost of combustion efficiency at lower firing rates. Base heaters and those oaks with back pipe have increased heat exchange area to make up for the lower outer surface temperature of the lined fire pot, and the lined pot was standard in such stoves as the Glenwood base heaters.

Stoves like the Our Glenwood and others with suspended fire pot that carry flue gas down and around the fire pot carry this idea furthest. The results by users speak for themselves.

ddahlgren wrote: Just thinking out loud no expert here. I do need to sit down with a friend of mine that work in a coal burning power plant. We had a short chat a few days ago and the lengths they took to squeeze everything out were impressive to say the least.

Just bear in mind that we are talking naturally aspirated (no forced air) stoves here. Once you start adding in forced air things change. I think it was franco b (apologies if I'm not remembering correctly) that pointed out in in more modern combustion technologies, once you start adding in forced air and other fuel control systems, that the need to have an insulated fire box becomes much more important. A lot of modern coal burning power plants are using pulverized coal, injecting that into the combustion chamber along with controlled air control. That is a very different combustion technology from the stoves we are running...

dj

Steve.

Never having seen an unlined coal stove firepot that was damage by normal use, I can't say if it is really so good at protecting. My potbelly stove and both of my 118's appear to have never been lined. The pots are in fine shape, other than the typical small crack the Modern oaks are known for at the front base where there is a bolt hole.

Having used both unlined and lined firepot/firebox stoves, I can say that the lined ones can maintain a healthy fire at much lowed draft.

I'd be very interested to see if an unlined fire pot stove can maintain a .005 (yes, that's two zeros after the decimal point) for an overnight burn. My range with it's original fireclay bricks can do that easily, hour after hour until the fuel is expended without stalling the fire. And it can idle all day at .01 with outdoor temps of 75-80 degrees.

Mind you, I'm not trying to say that the liners don't help protect firepots. But, what I've seen is why I think the liner does more for coal burning ability over a greater range of conditions than for protecting the firepot.

Paul

As long as we are comparing apples to apples here the discussion has merit.

Let's not try to compare two different style stoves in the unlined vs lined debate

I.E. Glenwood base burner vs Glenwood base heater

Lined coal firepot verses unlined coal firepot. I don't see that it needs to be limited to one brand and model of stove when there are so many more examples that also apply we might learn from.

Besides, we've run out of stuff to say about the two holes in the ash drawer.

Paul

I think the 2 holes in the ash pan were to compliment the unlined firepot, and combustion efficiency.

I think the holes are to keep an eye on ash build up so you know when to empty the pan...

Ok, I was wrong. Just when it this thought that this tread was going to POT, I see you guys want to rehASH the wHOLE subject.

Paul

Stoves like my Crawford, Tom's 109 & Joe's 111, MUST have/run a liner. It's integral to the design and function of the stove. It was not an option to buy a brick liner. They were all originally supplied with one. The stoves fire pot would fail on the first run without one as the pot casting is only 1/8 to 3/16 thick.

Sunny Boy wrote:Yes, Dave. Seven red fireclay bricks in each of two rows. Nothing like the refractory materials we have now. More like red clay pots and the old clay bricks used to build chimneys. Very fine grained compared to modern bricks.

The bricks have "G B H 6" cast into the middle of each. With Wilson's help I was able to incorporate that detail into the brick molds I made, that he now has and is using for his #6 restorations.

There is a lip cast into the inner bottom edge of the firepot that extends upward. The bottom row of bricks have a notch cast into the inner edge of their underside that interlocks with and is retained by that lip.

The top row bricks just sit flat on the bottom row. They have a curved top edge to allow coal to fall back into the firebed while still able to support the gas ring at the very outer edge.

I'll mic the pot top in several places and post back.

Paul

Dave,

I mic-ed my GW #6 firepot in four places and about an inch below the top edge. Standing in front of the ash door and looking down at the firepot, the pot wall thickness measurements were taken at, 12, 3, 6 and 9 O'clock.

12 = .254 inch
3 = .243 inch
6 = .261 inch
9 = .276 inch

Since there is no indication that rust would account for the .033 variation, and that variation seems to indicate an offset, I think there was a slight misalignment of the mold cores when the cast iron was poured ????

Paul

Edit. The extension on my 4 inch mic wasn't seated all the way, thus causing an error of .030 inch. I corrected the numbers above after checking calibration and re-measuring the pot walls in the same areas.

The good news is that the GW #6 firepot walls are thicker than I first thought.

Paul

The core shift is approximately 0.016 and well within sand cast parts.