Marcia Selsor on fri 26 jul 02
Que quieres! (that's what they say in Spain)
Whatever you like. It is just a matter of preference. I have used 12 x 24 shelves
, two stacks for a few decades. I prefer the burners from the rear along a bagwall
with the shelves sitting on the bagwall. A few inches at the rear and a few
inches (maybe one extra inch ) at the front. I used a peep hole at the top and
the bottom. 36" wide x 36" deep and 45" tall to the top of sprung arch with the
specs from the AP Green brick guide book. It has the combos for sprung arches with
straights/arch brick combos.
Don't get Mel and Nils started on sprung versus flat tops!!!! not yet again.
My kilns were flat floor, 9" straight hard bricke on edge, sealing the flu from
the combustion area
(flame enters between the kiln wall and the bagwall and exits between the two
bagwalls up the flu).
The cube basis makes for an even firing.
Best wishes,
marcia selsor in montana
it is good to be home for a while
Paul Bailey / Janet Moe wrote:
> I am still finalizing my kiln design and gathering supplies. The
> question now is how to position the burners and whether to use a bagwall
> or not. I have read the archives (endlessly) but would like more
> opinions. I have four Ransome Venturi burners (MR750) rated at 77,400
> btu that I would like to use if possible. I am planning to use the Nils
> Lou double venturi flue box design and was thinking of having the
> burners come in from the front and back. However I notice that the
> designs like this tend to use only 2 burners coming in from the back
> with target bricks in the flame trench. Is it possible to use 4 burners
> and put target bricks in the middle of the flame trench with no bagwall?
> Would it be better to have the burners come in from the side and use a
> bagwall? or have the burners come in from front and back but use a
> bagwall? or have the burners come up from the bottom with no bagwall?
>
> Downdraft Kiln
> Fuel - Propane
> Shelves - 2 stacks of 12" x 24"
> Inside Dimensions (Approx.) - 31.5" deep, 45" wide- not sure yet, 45"
> height (incl. arch)
> Walls - 9" 2300 IFB
> Roof - arch
> Burners - 4 MR750 natural draft rated at 77,400 btu
>
> Thanks for any and all opinions!
>
> Janet, itching to get building on Denman Island, British Columbia
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
vince pitelka on fri 26 jul 02
> I have four Ransome Venturi burners (MR750) rated at 77,400
> btu that I would like to use if possible. I am planning to use the Nils
> Lou double venturi flue box design and was thinking of having the
> burners come in from the front and back. However I notice that the
> designs like this tend to use only 2 burners coming in from the back
> with target bricks in the flame trench. Is it possible to use 4 burners
> and put target bricks in the middle of the flame trench with no bagwall?
Janet -
First, I am assuming you are firing on propane, in which case you will be
able to get quite a lot more than 77,000 BTUs out of each of your GACO (not
Ransome) MR750 burners. Otherwise I am afraid you will never get to
temperature with four MR750s on natural gas with a kiln that size. The GACO
MR100 (available from Marc Ward) is a larger burner, and it would probably
work okay on natural gas.
There is nothing wrong with burners at the front and back with a double
target brick in the center, and you are correct that this would require no
bagwall. You mention that your kiln is 31.5" inside(which seems an odd
dimension, since it does not conform to any combination of normal brick
sizes), and when you add the wall thicknesses and divide in half, the flame
path for each burner would be a little less than 24" before the flames hit
the center target brick. I think that sounds fine. I have used this sort
of arrangement on several kilns, and it works very well.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Paul Bailey / Janet Moe on fri 26 jul 02
I am still finalizing my kiln design and gathering supplies. The
question now is how to position the burners and whether to use a bagwall
or not. I have read the archives (endlessly) but would like more
opinions. I have four Ransome Venturi burners (MR750) rated at 77,400
btu that I would like to use if possible. I am planning to use the Nils
Lou double venturi flue box design and was thinking of having the
burners come in from the front and back. However I notice that the
designs like this tend to use only 2 burners coming in from the back
with target bricks in the flame trench. Is it possible to use 4 burners
and put target bricks in the middle of the flame trench with no bagwall?
Would it be better to have the burners come in from the side and use a
bagwall? or have the burners come in from front and back but use a
bagwall? or have the burners come up from the bottom with no bagwall?
Downdraft Kiln
Fuel - Propane
Shelves - 2 stacks of 12" x 24"
Inside Dimensions (Approx.) - 31.5" deep, 45" wide- not sure yet, 45"
height (incl. arch)
Walls - 9" 2300 IFB
Roof - arch
Burners - 4 MR750 natural draft rated at 77,400 btu
Thanks for any and all opinions!
Janet, itching to get building on Denman Island, British Columbia
Paul Bailey / Janet Moe on sat 27 jul 02
vince pitelka wrote:
>First, I am assuming you are firing on propane, in which case you will be
>able to get quite a lot more than 77,000 BTUs out of each of your GACO (not
>Ransome) MR750 burners.
>
>There is nothing wrong with burners at the front and back with a double
>target brick in the center, and you are correct that this would require no
>bagwall. You mention that your kiln is 31.5" inside(which seems an odd
>dimension, since it does not conform to any combination of normal brick
>sizes), and when you add the wall thicknesses and divide in half, the flame
>path for each burner would be a little less than 24" before the flames hit
>the center target brick. I think that sounds fine. I have used this sort
>of arrangement on several kilns, and it works very well.
>Good luck -
>- Vince
>
Downdraft Kiln
Fuel - Propane
Shelves - 2 stacks of 12" x 24"
Inside Dimensions (Approx.) - 31.5" deep, 45" wide- not sure yet,
45" height (incl. arch)
Walls - 9" 2300 IFB
Roof - arch
Burners - 4 MR750 natural draft rated at 77,400 btu
The 31.5" comes from 3 and a half 9" bricks. That gives me 24" for the 2
shelves and 7.5" total for spacing between the shelf and back wall,
between the 2 shelves and the shelf and front wall. Is this enough space?
For the inside width of the kiln, how much space do I need between the
shelves and the wall, for the flame trench? Do I leave extra space in
case I decide I need a bagwall later?
The MR750 burners I have are old and rusty. Is there an easy way to
clean them up?
Thanks for any and all help!!!
Janet, enjoying a good hot summer on Denman Island, BC
vince pitelka on sat 27 jul 02
> bagwall. You mention that your kiln is 31.5" inside(which seems an odd
> dimension, since it does not conform to any combination of normal brick
> sizes
I don't know what I was thinking when I wrote the above. 31.5" is of course
exactly three and half lengths of normal firebrick, so it is a perfectly
appropriate interior measurement for a brick kiln. Lots of artists are a
little bit lysdexic, me more than some.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
vince pitelka on sun 28 jul 02
> That is more than enough space. It really won't hurt anything, but it
does
> cost more money to fire a kiln that is necessary for the desired setting
of
> shelves and wares.
Yep, Lysdexia. What that SHOULD have said is "it does cost more money to
fire a kiln that is larger than necessary for the desired setting of shelves
and wares.
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Marcia Selsor on sun 28 jul 02
> I think the 7.5" to be divided into the two flame channels seems tight to me. I
> would think you needed that much for one channel to provide a good combustion
> chamber.
Just my opinion.
Marcia
> Downdraft Kiln
> Fuel - Propane
> Shelves - 2 stacks of 12" x 24"
> Inside Dimensions (Approx.) - 31.5" deep, 45" wide- not sure yet,
> 45" height (incl. arch)
> Walls - 9" 2300 IFB
> Roof - arch
> Burners - 4 MR750 natural draft rated at 77,400 btu
>
> The 31.5" comes from 3 and a half 9" bricks. That gives me 24" for the 2
> shelves and 7.5" total for spacing between the shelf and back wall,
> between the 2 shelves and the shelf and front wall. Is this enough space?
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
vince pitelka on sun 28 jul 02
> The 31.5" comes from 3 and a half 9" bricks. That gives me 24" for the 2
> shelves and 7.5" total for spacing between the shelf and back wall,
> between the 2 shelves and the shelf and front wall. Is this enough space?
That is more than enough space. It really won't hurt anything, but it does
cost more money to fire a kiln that is necessary for the desired setting of
shelves and wares. I do not leave any space between the shelves, because
that eliminates the option of common-posting, where each post where the
shelves meet supports both shelves. Common posting uses a lot less posts,
which means quite a bit more room for wares, and it also produces a much
more stable setting. And actually, with the amount of room you have, you
could use two 13" by 26" shelves with no gap, and still have almost two
inches of clearance front and back, which would be plenty.
If you mount the burners front and back, you will not need a bagwall, but
you will want to leave a little more clearance than just the normal
firebox/flame trench width. For a regular oxidation/reduction kiln (not a
salt/soda kiln) with a bagwall, one brick's width (4.5") is fine for the
firebox/flame trench width, but I usually make them 5" wide to facilitate
placement and removal of target bricks. A bagwall is usually built of
bricks stacked on their sides, which adds 2.5", plus 2" clearance around the
shelves, totalling 9.5" on either side of the shelves if you use a bagwall.
If you use 12x24 shelves, then the minimum interior overall width (with a
bagwall) would be 43". The inside measurement of 45" that you stipulate
would allow you to use the 13x26 shelves with a bagwall.
Without a bagwall, I like to leave 7" between the inside wall and the
shelves. That seems to allow effective flame circulation without
excessively blasting the wares. So if you use 12x24 shelves, you really
only need an interior width of 38", and if you use 13x26 shelves, you would
need an interior width of 40", and in either case you would want to round it
off to 40.5", which is four and a half bricks. Either way, 45" is excessive
unless you decide to include a bagwall.
> The MR750 burners I have are old and rusty. Is there an easy way to
> clean them up?
You can have them sandblasted, but it is difficult to sandblast the inside
bore. If they are not badly rusted, it is not a problem. But as cheap as
they are, if they are badly rusted I would just get new ones. If you do,
get the MR100s instead of the MR750s. If you do use the MR750s be sure you
get an adjustable propane regulator to mount near the kiln, because you will
really have to crank those little suckers up high to get the BTUs you need,
and they will sound like little rocket motors. If you use the MR100s, you
will be able to run them a lot quieter.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Paul Bailey / Janet Moe on sun 28 jul 02
Marcia,
The 31.5" is the depth of the kiln not the width! I am now trying to
decide how wide to make the interior, so what would be the optiminum
width of the flame channels? Thanks for your opinions! Janet, on Denman
Island, BC where the tourists have finally arrived!
Marcia Selsor wrote:
>>I think the 7.5" to be divided into the two flame channels seems tight to me. I
>>would think you needed that much for one channel to provide a good combustion
>>chamber.
>>
>
>Just my opinion.
>Marcia
>
>
>
>>Downdraft Kiln
>>Fuel - Propane
>>Shelves - 2 stacks of 12" x 24"
>>Inside Dimensions (Approx.) - 31.5" deep, 45" wide- not sure yet,
>>45" height (incl. arch)
>>Walls - 9" 2300 IFB
>>Roof - arch
>>Burners - 4 MR750 natural draft rated at 77,400 btu
>>
>>The 31.5" comes from 3 and a half 9" bricks. That gives me 24" for the 2
>>shelves and 7.5" total for spacing between the shelf and back wall,
>>between the 2 shelves and the shelf and front wall. Is this enough space?
>>______________________________________________________________________________
>>
Brian Molanphy on tue 30 jul 02
vince wrote:
'For a regular oxidation/reduction kiln (not a
salt/soda kiln) with a bagwall, one brick's width (4.5") is fine for the
firebox/flame trench width, but I usually make them 5" wide to =
facilitate
placement and removal of target bricks. A bagwall is usually built of
bricks stacked on their sides, which adds 2.5", plus 2" clearance around =
the
shelves, totalling 9.5" on either side of the shelves if you use a =
bagwall.'
vince, how would you space the bagwalls in a salt/soda?
thanks, brian
vince pitelka on wed 31 jul 02
> vince, how would you space the bagwalls in a salt/soda?
Brian -
You need more space for vaporization of the salt, and the bagwalls
themselves are subject to a lot more wear and tear. I like to have at least
a 6" flame trench, and I always stack the bricks in normal "brick wall"
fashion for the bagwall, giving a 4.5" thickness.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@worldnet.att.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
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