jonathan byler on tue 6 dec 11
Soooo, we finally got the roof up on the kiln shed. All metal
construction to keep the fire people happy. was a chore, getting the
framing done, but the 2' x 12' roofing sheets went on without a
hitch. scaffolding is a nice thing to have. makes everything so much
easier.
so now I just need to finalize the design and build the thing. We are
planning for a bourrey box type design, instead of the standard hobs,
I have 19" x 2.5" x 3" tall firebricks that I picked up for a song to
use as a fire grate. This will allow me to burn many different sizes
of wood, since we have access to lots of scrap in addition to actual
trees. was thinking to space the grate bars at least 3-4 inches apart
so as to keep pieces from getting stuck, yet still allow us to use non
uniform lengths if need be.
I have two basic designs that I have been thinking about, one utilizes
the same basic design as euan craig and lee love's downdraught design,
but moves the door to the side and puts a bourrey box on the front
flowing into the fireboxes. The path that the flames take would still
go under the floor, entering though the back of the kiln either side
of the flue trough. This would help keep the floor hot. The other
design is a more traditional cross draught design with a bourrey box
on it, and I'm not sure if it would fire so evenly, but it will
definitely have more of a uni-directional flame path.
I have figured out a way to bring preheated air into the firebox, both
from the chimney and from top of the kiln. I will share this info
with pictures once we start building the actual kiln in early january
after the christmas break. I am expecting to get some efficiency
increases from this relatively simple design addition, and will make
this air so that it can be cut off and all the primary air comes in at
ambient temperature in order to compare how long it takes to fire both
with and without the preheated air.
My main concern at the moment is to have the firebox big enough. so
how big is enough? I know you probably can't really do to big, but I
have a limited space in which to build the thing and don't want to
make it overly large if nThis kiln is going to be hardbrick lined,
with IFB/fiber blanket/castable type stuff on the outside. stacking
space will be on 24"x36" shelves, stacked maybe 45" tall at the
maximum under the top of the arch to the floor. the floor is going to
be 31.5"x54" or 45"x36" depending on design which of the two designs
that we go with. I have read that the fire grate area should be half
the area of the floor of the stacking space... but is that a
legitimate number? from reading other sources, I have determined that
heat input necessary to a kiln is more a function of the weight if the
ware and the furniture. hard to gauge this with wood, of course...
but if anyone has any thoughts on this matter, please share.
thanks,
jon
Steve Mills on tue 6 dec 11
Hi Jon,
Two thoughts:
1) St Fred of Olsen in his Kiln Book has some very good info on this, in pa=
r=3D
ticular Chapter 3 Principles of Design, Principle 3, which deals with propo=
r=3D
tions of grate, fire box, and flue, which from experience I cannot fault.=
=3D20=3D
2) The universal rule that it is better to be Over-gunned than under-gunned=
i=3D
s bang on; you can "turn it down" if it's too strong. But if you're flat ou=
t=3D
and it's not enough, you're stuffed!!
My latest construction has a very big Bourry Box compared to many in propor=
t=3D
ion to its chamber. No problem there!
Steve M
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my Ipod touch
On 6 Dec 2011, at 06:17, jonathan byler wrote:
> Soooo, we finally got the roof up on the kiln shed. All metal
> construction to keep the fire people happy. was a chore, getting the
> framing done, but the 2' x 12' roofing sheets went on without a
> hitch. scaffolding is a nice thing to have. makes everything so much
> easier.
>=3D20
> so now I just need to finalize the design and build the thing. We are
> planning for a bourrey box type design, instead of the standard hobs,
> I have 19" x 2.5" x 3" tall firebricks that I picked up for a song to
> use as a fire grate. This will allow me to burn many different sizes
> of wood, since we have access to lots of scrap in addition to actual
> trees. was thinking to space the grate bars at least 3-4 inches apart
> so as to keep pieces from getting stuck, yet still allow us to use non
> uniform lengths if need be.
>=3D20
> I have two basic designs that I have been thinking about, one utilizes
> the same basic design as euan craig and lee love's downdraught design,
> but moves the door to the side and puts a bourrey box on the front
> flowing into the fireboxes. The path that the flames take would still
> go under the floor, entering though the back of the kiln either side
> of the flue trough. This would help keep the floor hot. The other
> design is a more traditional cross draught design with a bourrey box
> on it, and I'm not sure if it would fire so evenly, but it will
> definitely have more of a uni-directional flame path.
>=3D20
> I have figured out a way to bring preheated air into the firebox, both
> from the chimney and from top of the kiln. I will share this info
> with pictures once we start building the actual kiln in early january
> after the christmas break. I am expecting to get some efficiency
> increases from this relatively simple design addition, and will make
> this air so that it can be cut off and all the primary air comes in at
> ambient temperature in order to compare how long it takes to fire both
> with and without the preheated air.
>=3D20
> My main concern at the moment is to have the firebox big enough. so
> how big is enough? I know you probably can't really do to big, but I
> have a limited space in which to build the thing and don't want to
> make it overly large if nThis kiln is going to be hardbrick lined,
> with IFB/fiber blanket/castable type stuff on the outside. stacking
> space will be on 24"x36" shelves, stacked maybe 45" tall at the
> maximum under the top of the arch to the floor. the floor is going to
> be 31.5"x54" or 45"x36" depending on design which of the two designs
> that we go with. I have read that the fire grate area should be half
> the area of the floor of the stacking space... but is that a
> legitimate number? from reading other sources, I have determined that
> heat input necessary to a kiln is more a function of the weight if the
> ware and the furniture. hard to gauge this with wood, of course...
> but if anyone has any thoughts on this matter, please share.
>=3D20
> thanks,
> jon
jonathan byler on tue 6 dec 11
Steve,
do you know if those proportions in the olsen book pertain also to
bourrey boxes? I have looked at a number of designs that claim to be
successful that don't go by his rules of thumb, i.e. the firebox is
smaller than one would expect. would you subtract the area of the
firebox blocked by a grate in a bourrey box kiln from the total area
when figuring these calculations?
thanks,
jon
On Dec 6, 2011, at 8:34 AM, Steve Mills wrote:
> Hi Jon,
>
> Two thoughts:
> 1) St Fred of Olsen in his Kiln Book has some very good info on
> this, in particular Chapter 3 Principles of Design, Principle 3,
> which deals with proportions of grate, fire box, and flue, which
> from experience I cannot fault.
>
> 2) The universal rule that it is better to be Over-gunned than under-
> gunned is bang on; you can "turn it down" if it's too strong. But if
> you're flat out and it's not enough, you're stuffed!!
> My latest construction has a very big Bourry Box compared to many in
> proportion to its chamber. No problem there!
>
> Steve M
>
>
> Steve Mills
> Bath
> UK
> www.mudslinger.me.uk
> Sent from my Ipod touch
>
> On 6 Dec 2011, at 06:17, jonathan byler wrote:
>
>> Soooo, we finally got the roof up on the kiln shed. All metal
>> construction to keep the fire people happy. was a chore, getting the
>> framing done, but the 2' x 12' roofing sheets went on without a
>> hitch. scaffolding is a nice thing to have. makes everything so
>> much
>> easier.
>>
>> so now I just need to finalize the design and build the thing. We
>> are
>> planning for a bourrey box type design, instead of the standard hobs,
>> I have 19" x 2.5" x 3" tall firebricks that I picked up for a song to
>> use as a fire grate. This will allow me to burn many different sizes
>> of wood, since we have access to lots of scrap in addition to actual
>> trees. was thinking to space the grate bars at least 3-4 inches
>> apart
>> so as to keep pieces from getting stuck, yet still allow us to use
>> non
>> uniform lengths if need be.
>>
>> I have two basic designs that I have been thinking about, one
>> utilizes
>> the same basic design as euan craig and lee love's downdraught
>> design,
>> but moves the door to the side and puts a bourrey box on the front
>> flowing into the fireboxes. The path that the flames take would
>> still
>> go under the floor, entering though the back of the kiln either side
>> of the flue trough. This would help keep the floor hot. The other
>> design is a more traditional cross draught design with a bourrey box
>> on it, and I'm not sure if it would fire so evenly, but it will
>> definitely have more of a uni-directional flame path.
>>
>> I have figured out a way to bring preheated air into the firebox,
>> both
>> from the chimney and from top of the kiln. I will share this info
>> with pictures once we start building the actual kiln in early january
>> after the christmas break. I am expecting to get some efficiency
>> increases from this relatively simple design addition, and will make
>> this air so that it can be cut off and all the primary air comes in
>> at
>> ambient temperature in order to compare how long it takes to fire
>> both
>> with and without the preheated air.
>>
>> My main concern at the moment is to have the firebox big enough. so
>> how big is enough? I know you probably can't really do to big, but I
>> have a limited space in which to build the thing and don't want to
>> make it overly large if nThis kiln is going to be hardbrick lined,
>> with IFB/fiber blanket/castable type stuff on the outside. stacking
>> space will be on 24"x36" shelves, stacked maybe 45" tall at the
>> maximum under the top of the arch to the floor. the floor is going
>> to
>> be 31.5"x54" or 45"x36" depending on design which of the two designs
>> that we go with. I have read that the fire grate area should be half
>> the area of the floor of the stacking space... but is that a
>> legitimate number? from reading other sources, I have determined
>> that
>> heat input necessary to a kiln is more a function of the weight if
>> the
>> ware and the furniture. hard to gauge this with wood, of course...
>> but if anyone has any thoughts on this matter, please share.
>>
>> thanks,
>> jon
gary navarre on tue 6 dec 11
You are correct about subtracting the brick grate area from th=3D
Jon,=3D0A=3D0A=3DA0You are correct about subtracting the brick grate area f=
rom th=3D
e actual useful open area of the hob's exposed to the coal pile. I've had t=
=3D
he luxury of forest land so I don't need to depend on odd sizes of wood and=
=3D
cut mostly 32"-36" for the Bourry box and save the under sized sticks and =
=3D
logs for the Pignose or side stoking. So, if you want to stoke odd sized wo=
=3D
od you'll need more brick for a larger box. I've probably reached the lengt=
=3D
h of fuel limit for easy stoking from the side of the Bourry box so any lon=
=3D
ger would need some kind of center prop for the middle of the fuel.=3D0A=3D=
0A=3D
=3D0A=3DA0Another element to consider is the area of the throat arch and ex=
it f=3D
lue in relation to the Bourry grate area. I expanded my Bourry by 6" so the=
=3D
the throat arch and wood exposed to the coals might be about equal or more=
=3D
than the Bourry. and the exit flue is reduced with some brick and pots for=
=3D
the next firing.=3DA0 =3D0A=3D0A=3DA0=3D0AGary Navarre=3D0ANavarre Pottery=
=3D0ANavarre E=3D
nterprises=3D0ANorway, Michigan, USA=3D0Ahttp://www.NavarrePottery.etsy.com=
=3D0Ah=3D
ttp://www.youtube.com/GindaUP=3D0Ahttp://public.fotki.com/GindaUP/=3D0A=3D0=
A=3D0A=3D
=3D0A________________________________=3D0A From: jonathan byler MAIL=3D
.COM>=3D0ATo: Clayart@LSV.CERAMICS.ORG =3D0ASent: Tuesday, December 6, 2011=
1:3=3D
8 PM=3D0ASubject: Re: [Clayart] wood kiln firebox sizing... thoughts?=3D0A=
=3D0A=3D
Steve,=3D0A=3D0Ado you know if those proportions in the olsen book pertain =
also=3D
to=3D0Abourrey boxes?=3DA0 I have looked at a number of designs that claim=
to =3D
be=3D0Asuccessful that don't go by his rules of thumb, i.e. the firebox is=
=3D0A=3D
smaller than one would expect.=3DA0 would you subtract the area of the=3D0A=
fire=3D
box blocked by a grate in a bourrey box kiln from the total area=3D0Awhen f=
ig=3D
uring these calculations?=3D0A=3D0Athanks,=3D0Ajon
Steve Mills on wed 7 dec 11
Short answer: yes.=3D20
We've recently been involved in building a twin Bourry Kiln for a friend in=
C=3D
harleston SC. Where I was largely responsible for its design. Each Bourry h=
a=3D
d three brick Hobs, which, when deducted from the Grate area gave us approx=
5=3D
0 Sq Ft for each, totalling a shade over 100 Sq Ft grate. Flue exit area: a=
p=3D
prox 15 Sq Ft bringing it fairly close to Fred's 7 to 1 ratio. Setting area=
i=3D
s about 24 cube plus.=3D20
First firing went pretty well all things considered, though we concluded we=
'=3D
d made the flue a bit too tall and not compensated enough for that as the f=
r=3D
ont was a bit cool. We still got some racers out of it though. We're lookin=
g=3D
forward to the next firing.=3D20
Steve M
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my Ipod touch
On 6 Dec 2011, at 19:38, jonathan byler wrote:
> Steve,
>=3D20
> do you know if those proportions in the olsen book pertain also to
> bourrey boxes? I have looked at a number of designs that claim to be
> successful that don't go by his rules of thumb, i.e. the firebox is
> smaller than one would expect. would you subtract the area of the
> firebox blocked by a grate in a bourrey box kiln from the total area
> when figuring these calculations?
>=3D20
> thanks,
> jon
>=3D20
>=3D20
> On Dec 6, 2011, at 8:34 AM, Steve Mills wrote:
>=3D20
>> Hi Jon,
>>=3D20
>> Two thoughts:
>> 1) St Fred of Olsen in his Kiln Book has some very good info on
>> this, in particular Chapter 3 Principles of Design, Principle 3,
>> which deals with proportions of grate, fire box, and flue, which
>> from experience I cannot fault.
>>=3D20
>> 2) The universal rule that it is better to be Over-gunned than under-
>> gunned is bang on; you can "turn it down" if it's too strong. But if
>> you're flat out and it's not enough, you're stuffed!!
>> My latest construction has a very big Bourry Box compared to many in
>> proportion to its chamber. No problem there!
>>=3D20
>> Steve M
>>=3D20
>>=3D20
>> Steve Mills
>> Bath
>> UK
>> www.mudslinger.me.uk
>> Sent from my Ipod touch
>>=3D20
>> On 6 Dec 2011, at 06:17, jonathan byler wrote:
>>=3D20
>>> Soooo, we finally got the roof up on the kiln shed. All metal
>>> construction to keep the fire people happy. was a chore, getting the
>>> framing done, but the 2' x 12' roofing sheets went on without a
>>> hitch. scaffolding is a nice thing to have. makes everything so
>>> much
>>> easier.
>>>=3D20
>>> so now I just need to finalize the design and build the thing. We
>>> are
>>> planning for a bourrey box type design, instead of the standard hobs,
>>> I have 19" x 2.5" x 3" tall firebricks that I picked up for a song to
>>> use as a fire grate. This will allow me to burn many different sizes
>>> of wood, since we have access to lots of scrap in addition to actual
>>> trees. was thinking to space the grate bars at least 3-4 inches
>>> apart
>>> so as to keep pieces from getting stuck, yet still allow us to use
>>> non
>>> uniform lengths if need be.
>>>=3D20
>>> I have two basic designs that I have been thinking about, one
>>> utilizes
>>> the same basic design as euan craig and lee love's downdraught
>>> design,
>>> but moves the door to the side and puts a bourrey box on the front
>>> flowing into the fireboxes. The path that the flames take would
>>> still
>>> go under the floor, entering though the back of the kiln either side
>>> of the flue trough. This would help keep the floor hot. The other
>>> design is a more traditional cross draught design with a bourrey box
>>> on it, and I'm not sure if it would fire so evenly, but it will
>>> definitely have more of a uni-directional flame path.
>>>=3D20
>>> I have figured out a way to bring preheated air into the firebox,
>>> both
>>> from the chimney and from top of the kiln. I will share this info
>>> with pictures once we start building the actual kiln in early january
>>> after the christmas break. I am expecting to get some efficiency
>>> increases from this relatively simple design addition, and will make
>>> this air so that it can be cut off and all the primary air comes in
>>> at
>>> ambient temperature in order to compare how long it takes to fire
>>> both
>>> with and without the preheated air.
>>>=3D20
>>> My main concern at the moment is to have the firebox big enough. so
>>> how big is enough? I know you probably can't really do to big, but I
>>> have a limited space in which to build the thing and don't want to
>>> make it overly large if nThis kiln is going to be hardbrick lined,
>>> with IFB/fiber blanket/castable type stuff on the outside. stacking
>>> space will be on 24"x36" shelves, stacked maybe 45" tall at the
>>> maximum under the top of the arch to the floor. the floor is going
>>> to
>>> be 31.5"x54" or 45"x36" depending on design which of the two designs
>>> that we go with. I have read that the fire grate area should be half
>>> the area of the floor of the stacking space... but is that a
>>> legitimate number? from reading other sources, I have determined
>>> that
>>> heat input necessary to a kiln is more a function of the weight if
>>> the
>>> ware and the furniture. hard to gauge this with wood, of course...
>>> but if anyone has any thoughts on this matter, please share.
>>>=3D20
>>> thanks,
>>> jon
jonathan byler on thu 8 dec 11
I assume with olsen's book, he is talking about hardbrick kilns? ours
is most likely going to be hardbrick lined, both for durability and
because it is what we have. If that is the case and we were to switch
to IFB on the interior, I would assume we could get away with smaller
firebox grate area and smaller flue sizes.
On Dec 8, 2011, at 6:15 AM, Paul Haigh wrote:
> Sidestoke.com to the rescue! What a great site
>
> Single Bourry critical dimensions- I used this and Olsen in
> designing my kiln, and would use this again: http://sidestoke.com/bourryk=
iln/bourry.html
>
> Someone's twin Bourry: http://sidestoke.com/inferno/ti.html
>
> More links: http://sidestoke.com/
>
>
>
> Paul Haigh
> Wiley Hill Mudworks
> Web: http://wileyhill.com
> Facebook: http://www.facebook.com/pages/Wiley-Hill-Mudworks/1081451392306=
52
> etsy: http://www.etsy.com/shop/WileyHillMudworks
Paul Haigh on thu 8 dec 11
Sidestoke.com to the rescue! What a great site
Single Bourry critical dimensions- I used this and Olsen in designing my ki=
ln, and would use this again: http://sidestoke.com/bourrykiln/bourry.html
Someone's twin Bourry: http://sidestoke.com/inferno/ti.html
More links: http://sidestoke.com/
Paul Haigh
Wiley Hill Mudworks
Web: http://wileyhill.com
Facebook: http://www.facebook.com/pages/Wiley-Hill-Mudworks/108145139230652
etsy: http://www.etsy.com/shop/WileyHillMudworks
Steve Mills on fri 9 dec 11
Jon,=3D20
I wouldn't make that assumption.=3D20
IFB's better thermal efficiency won't compensate for reduced volume or flow=
.=3D
=3D20
With our last kiln in SC the fireboxes and stack were hard brick, and the s=
e=3D
tting area high temp IFBs.=3D20
Board insulation was added to all exteriors except the flue.=3D20
Steve M
Sent from my iPod
On 9 Dec 2011, at 05:57, jonathan byler wrote:
> I assume with olsen's book, he is talking about hardbrick kilns? ours
> is most likely going to be hardbrick lined, both for durability and
> because it is what we have. If that is the case and we were to switch
> to IFB on the interior, I would assume we could get away with smaller
> firebox grate area and smaller flue sizes.
>=3D20
>=3D20
>=3D20
> On Dec 8, 2011, at 6:15 AM, Paul Haigh wrote:
>=3D20
>> Sidestoke.com to the rescue! What a great site
>>=3D20
>> Single Bourry critical dimensions- I used this and Olsen in
>> designing my kiln, and would use this again: http://sidestoke.com/bourry=
k=3D
iln/bourry.html
>>=3D20
>> Someone's twin Bourry: http://sidestoke.com/inferno/ti.html
>>=3D20
>> More links: http://sidestoke.com/
>>=3D20
>>=3D20
>>=3D20
>> Paul Haigh
>> Wiley Hill Mudworks
>> Web: http://wileyhill.com
>> Facebook: http://www.facebook.com/pages/Wiley-Hill-Mudworks/108145139230=
6=3D
52
>> etsy: http://www.etsy.com/shop/WileyHillMudworks
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