Coydon Wallham

thomas rubino wrote:
Shorty is a superior design, with more versatility and lower costs.

Do you explain this comparison in your book? I'm about half way through...

Peter van den Berg wrote:
Regarding your end question: yes it is, provided the calculation is done in a proper way. See the space above the riser as an imaginary ring. Think about it this way: the gases, rising out of the riser need to go through a 180 degrees bend in order to stream down.  When this ring's circumference, multiplied by its height is a figure that is twice as large as the riser's cross section area, then it's about the right size. Just by giving the gases ample space to round the bend without too much friction means a possible pinch point isn't there at all.
The same thing happens at the exit, the distance between the floor and the end of the pipe works the same way, although the change in direction is just about 90 degrees since most of the colder gases stream along the floor. So, in theory, the surface area of that imaginary ring should be at least 1.5 times as large as the exhaust pipe.

Calculating... the 8" pipe's csa is 50.26 sq. in. So, the imaginary exhaust ring's surface area should be at least 75.4 sq inch. Devided by the circumference gives the height of the ring. In your case, that would be 3" as the minimum distance from the floor, provided the exhaust pipe is free all around. As said before, the depression might be a negative factor.

The exhaust pipe is constrained some on the sides around it. Would cutting a vertical slit in the pipe and bending it back to enlarge the opening on the side toward the firebox be enough to increase the draw ability, or will it be necessary to break the cob, cut and reposition the whole pipe?

Glenn Herbert wrote:I don't see including some 1" iron pipe in the floor as doing enough to be worthwhile.

I ditched the pipe idea and put a sheet of .5" cement board on top of a grid of cement bricks to form the base of the firebox/barrel. The face of the bricks has been cobbed over, with channels left between them.

The bottom of the stratification chamber has wine bottles between each brick on the first course, completely cobbed in by thermal cob in the floor of the bench. Not sure if there will be any insulative benefit (from the bottles), but it has decorative qualities and saved on some cob requirements.

Yep, though one of the first additions will be a polished metal shield on the ceiling directly over the barrel intercepting the radiant heat there to reflect it towards the dining/kitchen area instead of the support beam.

The first firing went smooth, ran a couple of hours without incident. The following two days, it's been cold plugging severely. Even today with a few pieces of birch bark and some paper under the exit flue before starting, the firebox stalls out after ten minutes of a tepid burn. An hour or so of feeding the firebox a slight crack of air, as well as pointing a space heater directly on the base of the exit flue the whole time, is needed to get a draft going.

I'd say all of the wet cob (removing the cleanout covers after it plugs reveals moisture dripping from the roof of the bench inside) and ambient temperatures in the 60s F are clear causes for this and it is likely to be fine once the heating season starts, but am still not sure about placement of the bottom of the exit flue.

I created a ~2" depression in the stratification chamber bottom around where the flue would land, and set the bottom of the duct a little less than 1" above the rest of the floor of the chamber, so between 2-3" of space all around the opening to the 8" duct exit. Is using the inverse of the barrel top-riser clearance numbers a good guide for exit minimums?

In with the new. (Still waiting on more clay to finish the base layer of structural cob in a few spots...)

Out with the old...

Glenn Herbert wrote:I think they would work fine in the floor of a bell. I would bed them in some perlite-clay and space them enough to have perlite-clay struts between them, and a continuous layer above. It would probably be wisest to keep some space open at the base of the bottles so that air could flow from side to side under the bell to prevent heat buildup in a long firing.

I would want the brick walls to be supported on cob or on the floor with some gaps at the base; the base of the bell will probably not get too hot, but better safe than sorry.

A standard method of flooring a bell is to space some cement board up on bricks so air can flow freely underneath. This requires buying cement board, but is fast and easy, and takes little space from the height of the bell cavity.

Did your bottle experiment use bottles with the opening out, exposed to the room environement? I'm just planning to use them for the contained space, mouths blocked in.

Is there an expected temperature maximum that the floor would see in a properly ISA sized bell?

I was planning for the base of the brick wall to go brick>bottle>brick>bottle for the whole course of the exterior. The exterior wall would have 3" wine bottles, the interior floor 2" beer bottles. I'm not sure how tricky it would be to work in perlite-clay around those bottles while using regular clay mortar right around the bricks, or if that would make much difference. Would that be useful to prevent any thermal expansion from breaking the glass, or needed at all?

I also have a section of reclaimed pipe (1 1/4"OD) I planned to cut up and embed with the perlite-clay base under the firebox (with both open ends exposed to the room). Any potential problems there?

Ideally I'd say a column with "date added" would take care of it particularly if the table were sortable. Wikipedia pages have that sortability function, but I don't know how much trouble it would be for code ranch to implement here.

Having a "new" label like you mention would help if old ones were erased as new ones were added, but there might be trouble passing along that practice as time goes on and if third parties step in to help with this wiki.

Various things I'm not sure how to implement:
Floor insulation. For the stratification bell, I'd like to put down insulative cob on the wooden floor. I have horticultural perlite plus a number of wine and beer bottles (a nearby restaurant might supply some liquor bottles if they would be any better). The more bottles that can be used the better, since they would otherwise be headed for recycling and are much easier to deal with than perlite/cob mixture.

Any experience with incorporating bottles to insulate like this? Are they efficient? What kind of spacing would they require between the floor or each other?

When it comes to the brick walls of the strat chamber, could they go on the cob/perlite mixture, or would they need regular cob? How thick?