Andrew M Casto on thu 10 aug 06
Nathan,
Sounds like you built Mel and Kurt's flat top, but as a wood burner. I'm
sure they can give you advice on your sag problem - maybe steel rod rather
than threaded? I do not know, but there are many flat top folks on the list
that I'm sure will offer help. It would be good to get Nils Lou's "Art of
Firing", which has LOTS of info on flat tops. In considering your question
about a castable roof, you should factor into your calculations the weight
of a piece of castable that big. It would need to be thick enough to not
break or crack in the middle, and probably reinforced with something to add
strength. It will likely be heavier than you would want to pick up and put
on each time you fire this kiln, so I would devise a pulley system with a
counter weight that would aid in manueverablity. The bottom half of my door
on my wood kiln is cast from insulating castable. I would say that a 15" h
x 1' w x 9" thick piece weighs about 50 - 60 lbs.
Good luck
Andy
www.redbridgepottery.com
I think I've narrowed down my choice of roof replacements
to three options:
1) use four 12" x 24" x 2" hard bricks
2) use one or two sheets of fiberboard
3) make a sectional roof from castable
Nathan Miller on thu 10 aug 06
Greetings and reductions unto the list! I recently built a small wood-fire
kiln using plans found in an issue of Pottery Making Illustrated from a
little over a year ago (I think). The plans call for constructing the roof
by stringing several IFB onto a 1/2" threaded rod. 5 of these units make up
the roof. During the maiden firing, which lasted 11 hours, the rods
softened and the roof sagged. Its bricks shifted and a lot of heat and
smoke escaped between the chinks. I don't think this roof will survive
another firing. I think I've narrowed down my choice of roof replacements
to three options:
1) use four 12" x 24" x 2" hard bricks
2) use one or two sheets of fiberboard
3) make a sectional roof from castable
Which should I use? Are there other options I should consider? The hard
brick would be more durable, but the fiberboard would be lighter (definitely
a consideration, since the kiln is top-loading, so the roof will be removed
each time the kiln is loaded and unloaded) and the castable would give me
flexibility and more control over slab size.
Nathan Miller
Thistillium Pottery
Newberg, OR
curtis adkins on thu 10 aug 06
Nathan,
I am taking a stab at this but can you get a higher grade of rod to hang your brick with because the metal in your rod may have fatigued due to poor materials used to make some all-thread rod and other hot rolled steels whether it was nickel or chrome plated or not...ie...It is quite easy to take a 7/8's hot rolled rod and bend it with a very small hobby sized propane torch! I hope this helps...or I may be way off base! Let me know.
Curtis Adkins
Nathan Miller wrote: Greetings and reductions unto the list! I recently built a small wood-fire
kiln using plans found in an issue of Pottery Making Illustrated from a
little over a year ago (I think). The plans call for constructing the roof
by stringing several IFB onto a 1/2" threaded rod. 5 of these units make up
the roof. During the maiden firing, which lasted 11 hours, the rods
softened and the roof sagged. Its bricks shifted and a lot of heat and
smoke escaped between the chinks. I don't think this roof will survive
another firing. I think I've narrowed down my choice of roof replacements
to three options:
1) use four 12" x 24" x 2" hard bricks
2) use one or two sheets of fiberboard
3) make a sectional roof from castable
Which should I use? Are there other options I should consider? The hard
brick would be more durable, but the fiberboard would be lighter (definitely
a consideration, since the kiln is top-loading, so the roof will be removed
each time the kiln is loaded and unloaded) and the castable would give me
flexibility and more control over slab size.
Nathan Miller
Thistillium Pottery
Newberg, OR
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pdp1@EARTHLINK.NET on thu 10 aug 06
If suspending a flat roof of a Kiln, whose roof
Bricks are aligned by a rod ( threaded or
otherwise ) passing through them or better yet,
through their made-to-be-accomidating joins...
It would be best if the 'rod' itself at each
Brick-seam, were suspended by wire to a simple
super-structure such as stount angle Iron or
channel...which is a few inches above.
So that the 'rod' itself is in effect an alignment
device or recourse merely, and the weight of the
bricks themselves is held by the little wires...
Phil
Las Vegas
pdp1@EARTHLINK.NET on fri 11 aug 06
Hi Kurt, all...
My thought...is that if the Bricks are to be
vertically suspended, if the Bricks are in a
vertical orientation for the cieling/lid...one can
have half-circle 'notches' on each Brick side some
certain and regular distance from what will be the
'top'...one could make a simple jig to do this...
Then, the 'rod' acts as an alignment device...and,
between or 'in' each otherwise snug seam, a thin
but adequate wire is bound to the rod and goes
up...
On the Kiln's top then is a simple girder or other
stout cross member for each Brick row's seam, and
these wires then connect to this simple low
superstructure...thus suspending the whole safely
from any transmitted heats or from the 'rods'
themselves having to be the only or actual
unsupported 'support', where of course they would
likely sag...
Phil
Las Vegas
----- Original Message -----
From: "Kurt Wild"
> The roof over the chamber of our former small
train kiln at Hay Creek
> consisted of three cast slabs 12" x 24" x 2-1/2"
thick. I don't remember the
> weight but they required two of us to set them
in place and/or removed them.
> Stainless steel pins (specifically designed as
reinforcement material) were
> added to the castable.
>
> On another note: The PMI kiln plans of Mel and
myself were for
> a gas fired, front loading Minnesota Flattop.
We did not suggest
> stringing insultaing brick on rods for a roof.
That method was first
> developed by Jim Mckinnel in the late 1950's.
>
> Kurt
John Anthony on fri 11 aug 06
Hi Nathan-
I built a small flat top, gas fired, a couple of years ago. For
the top I used IFB held by compression in a framework of
lightweight metal angle and threaded rod. It was quite heavy, and I
used a Harbor Freight hoist to lift it
for loading and unloading. It did very well for eight or so firings;
I would sometimes need to tighten up the
threaded rods to snug it up a bit, and I always had to cover the top
layer of pots with shelves to keep dust
from the bricks out of them (the lid would sort of thump down, as the
hoist only has one speed).
Last winter the top of the kiln was inadvertently exposed to the
elements for a time. Water invaded the
softbrick and then froze, with predictable results. I opted to
replace the softbrick with fiber - I used
2" fiber board with 2" of kaowool on top, and some wire and mud over
that. I fit the board into the old framework that had held the
IFB. I fired some L shaped ceramic "corners" to cone 8, and used
Kanthal wire wrapped around them
to tighten the board to the framework.So far I've fired it three
times that way and it's holding up very well.
I think its a better choice than something as heavy as hardbrick.
I put a photo of the original lid in the photos section of the
clayart yahoo groups page, if you have a yahoo id.
http://ph.groups.yahoo.com/group/clayart/photos/view/3679?b=1
This is a during-construction photo. The whole kiln is wrapped in 2"
of wool and covered with mud.
Fires very evenly with two burners to cone ten in 7 hours or so.
cheers
John A
Kurt Wild on fri 11 aug 06
The roof over the chamber of our former small train kiln at Hay Creek
consisted of three cast slabs 12" x 24" x 2-1/2" thick. I don't remember the
weight but they required two of us to set them in place and/or removed them.
Stainless steel pins (specifically designed as reinforcement material) were
added to the castable.
On another note: The PMI kiln plans of Mel and myself were for
a gas fired, front loading Minnesota Flattop. We did not suggest
stringing insultaing brick on rods for a roof. That method was first
developed by Jim Mckinnel in the late 1950's.
Kurt
Ron Roy on sun 13 aug 06
Hi Phil,
That is how I built may suspended flat top back in the 60's.
Nichrome wire around 1" cold rolled rods - only need 5 wires for the 4 foot
span. The cold rolled did not last that well - maybe 500 firingd - I
replaced them with stainless when needed - that kiln gave me 900 firings.
Interesting that you would come up with the same solution.
RR
>If suspending a flat roof of a Kiln, whose roof
>Bricks are aligned by a rod ( threaded or
>otherwise ) passing through them or better yet,
>through their made-to-be-accomidating joins...
>
>It would be best if the 'rod' itself at each
>Brick-seam, were suspended by wire to a simple
>super-structure such as stount angle Iron or
>channel...which is a few inches above.
>
>So that the 'rod' itself is in effect an alignment
>device or recourse merely, and the weight of the
>bricks themselves is held by the little wires...
>
>
>Phil
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
pdp1@EARTHLINK.NET on sun 13 aug 06
Hi Ron,
I was aware of people building Kiln roofs useing
the round solid stock, usually with holes bored
through the bricks for the rods to pass through,
to suspend them and align them...
But it would not set well with my mind to do that
as all there is for holding them against gravity
and heat migrations...it is bad engineering...and
also may allow a Brick to fracture at the bore
hole which would of course occasion a possible
falling onto one's Pots of the birck piece(s).
Something else I wondered about, was whether one
could bore a small 1/4 inch hole into each brick's
top end, three inches deep or something, and
refractory cement a small rod ( maybe with a
wiggle-bent length to grip better) and for these
small 'rods' then ( or even all-thread pieces with
a small bend or two to grip better, to then
attatch to a simple super-structure above, to
suspend the brick's weight while remaining far
clear of the migrating heats...this would be a
little tedious I suppose...but was one of my
museings...
Really, a thin wall 'pipe' or even de-plated
Conduit, would be better anyway than solid 'rods'
for the going through the Bricks of their
seams...and having each brick's side with a
half-hole to share the grip on the round that
way...as you did...
as it would weigh less, and when suspended from
above with wires, would be all the strong one
might wish for...
Anyway, if I ever build a 'flat top' Kiln, I would
try the latter I think...
Phil
Las Vegas
----- Original Message -----
From: "Ron Roy"
To: "Clayart"
> Hi Phil,
>
> That is how I built may suspended flat top back
in the 60's.
>
> Nichrome wire around 1" cold rolled rods - only
need 5 wires for the 4 foot
> span. The cold rolled did not last that well -
maybe 500 firingd - I
> replaced them with stainless when needed - that
kiln gave me 900 firings.
>
> Interesting that you would come up with the same
solution.
>
> RR
>
>
>
> >If suspending a flat roof of a Kiln, whose roof
> >Bricks are aligned by a rod ( threaded or
> >otherwise ) passing through them or better yet,
> >through their made-to-be-accomidating joins...
> >
> >It would be best if the 'rod' itself at each
> >Brick-seam, were suspended by wire to a simple
> >super-structure such as stount angle Iron or
> >channel...which is a few inches above.
> >
> >So that the 'rod' itself is in effect an
alignment
> >device or recourse merely, and the weight of
the
> >bricks themselves is held by the little
wires...
> >
> >
> >Phil
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
>
>
W J Seidl on sun 13 aug 06
When we built Lisa's kiln in NC, Mel had us lay out the base on top of =
the
concrete slab from concrete blocks.
On top of those, he used "expanded metal" grating to allow for movement, =
air
flow, etc. with soft brick on top of that, IIRC. It worked amazingly =
well.
If one were to lay atop the kiln walls a layer of kaowool board (the =
stiff
stuff), followed by a layer of expanded metal and another layer or two =
of
kaowool board, would that not be sufficient? The expanded metal grate =
would
add strength enough when "sandwiched", the (3)insulated board layers
providing (duh) insulation, and it would be light enough to be easily =
moved
if all "stitched" together, perhaps with kanthal or nichrome wire. The
inside of the bottom layer could be sprayed with ITC. One person could
probably lift it easily, if hinged on one end.
Anyone?
Best,
Wayne
wondering what force counter to gravity manages to hold up all those =
girdled
bricks anyhow
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of
pdp1@EARTHLINK.NET
Sent: Sunday, August 13, 2006 2:38 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Retrofitting the roof on a wood kiln
Hi Ron,
I was aware of people building Kiln roofs useing
the round solid stock, usually with holes bored
through the bricks for the rods to pass through,
to suspend them and align them...
But it would not set well with my mind to do that
as all there is for holding them against gravity
and heat migrations...it is bad engineering...and
also may allow a Brick to fracture at the bore
hole which would of course occasion a possible
falling onto one's Pots of the birck piece(s).
Something else I wondered about, was whether one
could bore a small 1/4 inch hole into each brick's
top end, three inches deep or something, and
refractory cement a small rod ( maybe with a
wiggle-bent length to grip better) and for these
small 'rods' then ( or even all-thread pieces with
a small bend or two to grip better, to then
attatch to a simple super-structure above, to
suspend the brick's weight while remaining far
clear of the migrating heats...this would be a
little tedious I suppose...but was one of my
museings...
Really, a thin wall 'pipe' or even de-plated
Conduit, would be better anyway than solid 'rods'
for the going through the Bricks of their
seams...and having each brick's side with a
half-hole to share the grip on the round that
way...as you did...
as it would weigh less, and when suspended from
above with wires, would be all the strong one
might wish for...
Anyway, if I ever build a 'flat top' Kiln, I would
try the latter I think...
Phil
Las Vegas
----- Original Message -----
From: "Ron Roy"
To: "Clayart"
> Hi Phil,
>
> That is how I built may suspended flat top back
in the 60's.
>
> Nichrome wire around 1" cold rolled rods - only
need 5 wires for the 4 foot
> span. The cold rolled did not last that well -
maybe 500 firingd - I
> replaced them with stainless when needed - that
kiln gave me 900 firings.
>
> Interesting that you would come up with the same
solution.
>
> RR
>
>
>
> >If suspending a flat roof of a Kiln, whose roof
> >Bricks are aligned by a rod ( threaded or
> >otherwise ) passing through them or better yet,
> >through their made-to-be-accomidating joins...
> >
> >It would be best if the 'rod' itself at each
> >Brick-seam, were suspended by wire to a simple
> >super-structure such as stount angle Iron or
> >channel...which is a few inches above.
> >
> >So that the 'rod' itself is in effect an
alignment
> >device or recourse merely, and the weight of
the
> >bricks themselves is held by the little
wires...
> >
> >
> >Phil
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
>
>
_________________________________________________________________________=
___
__
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.
Ron Roy on tue 15 aug 06
Hi Phil,
I forgot - the rods were 3/4" and the holes were 1" to give space for
expansion and to let some cooling air through. It all worked very well - if
there was some spalling - and there was on two rows - I just took the row
out and rethreaded some new brick.
Had springs on each end to adjust for heating and cooling movement.
The inspiration came from a APGreen brick catalogue - had some hard brick
for kiln roofs with a T slot (picture the T upsidedown) in the top - for
threading on to i beams.
I notched each brick from the top of the 1" hole to the top of the brick -
for the wires to fit in and to add some cooling.
The hardest part was finding the way to hold the wire to the angle iron -
finally found some clamps with screws.
RR
>I was aware of people building Kiln roofs useing
>the round solid stock, usually with holes bored
>through the bricks for the rods to pass through,
>to suspend them and align them...
>
>But it would not set well with my mind to do that
>as all there is for holding them against gravity
>and heat migrations...it is bad engineering...and
>also may allow a Brick to fracture at the bore
>hole which would of course occasion a possible
>falling onto one's Pots of the birck piece(s).
>
>
>Something else I wondered about, was whether one
>could bore a small 1/4 inch hole into each brick's
>top end, three inches deep or something, and
>refractory cement a small rod ( maybe with a
>wiggle-bent length to grip better) and for these
>small 'rods' then ( or even all-thread pieces with
>a small bend or two to grip better, to then
>attatch to a simple super-structure above, to
>suspend the brick's weight while remaining far
>clear of the migrating heats...this would be a
>little tedious I suppose...but was one of my
>museings...
>
>Really, a thin wall 'pipe' or even de-plated
>Conduit, would be better anyway than solid 'rods'
>for the going through the Bricks of their
>seams...and having each brick's side with a
>half-hole to share the grip on the round that
>way...as you did...
>as it would weigh less, and when suspended from
>above with wires, would be all the strong one
>might wish for...
>
>Anyway, if I ever build a 'flat top' Kiln, I would
>try the latter I think...
>
>
>Phil
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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