Richard Gralnik on thu 7 may 98
I'm trying to build the arch for my kiln, and I'm running into a
reality gap between what the book says and what I'm actually
encountering.
According to the AP Green catalog, my 3' span arch with 2.302"
rise per foot should use 1 straight and 18 #1 arch bricks per
course. Well, I can't get those 19 bricks to make a curve that's
6.906" inches high in the center. I ran the formula for figuring
the radius of the circle my sprung arch describes (well,
suggests actually), and the curve of a circle with a radius of
26 29/32" doesn't match the curve my bricks create.
At this point I'm still standing bricks on end on the ground trying
to see what kind of curve they make. Should I just draw the
curve the formula dictates, build my form and hope the bricks
behave? Should I make as smooth a curve as I can with the
bricks and let that dictate the shape of my form?
Can anyone with *experience* in this advise me? The old
truth "Measure once, cut twice. Measure twice, cut once." is
the theme of my kiln building experience. I'd rather get the
measurements right than cut bricks (especially arch bricks).
Thanks,
Richard
ThePottery on fri 8 may 98
In theory (like so many other things in life) you should be able to do a
perfect curve but none of my kilns have come out this way. This usually means
that the bricks DO NOT ALWAYS FIT THE DIMENTION STATED ON THE BOX. This
applies to hard brick also. The other problem is that I have never cut a
perfect arch form. The one time it did work was when I put a double layer of
1/4" tempered masonite over the arch form. I think it helped even the errors
in the first layer. I try to be as carful as possible and when I put up the
arch I work from both skew blocks at the same time and make sure that the
brick is flat to the arch form and flat to the brick it lays against. Also if
when you get to the Key brick there are different ways to work with if a
standerd brick does not fit. If the space is too narrow...just raise the arch
a little and this will expand the opening enough to drop in the key bricks and
vice versa if the space is allready too large to fit tightly you can drop the
arch a little at a time until the key is tight. Then you can avoide the whole
thing and cast the key brick in place to get a perfect fit.
Good luck Tracy Penland NC
PS..Of course the first thing you need for a good arch is to make sure that
the whole kiln especilly the last layer of the wall and the skew blocks are
SQUARE,PLUM AND LEVEL....
David Hendley on fri 8 may 98
Richard, I'll take reality over theory anyday.
My M.O. has always been to use the tables as an estimate of
what bricks are needed, but I make the arch form to fit a
configuration that is actually laid out on the ground.
You may well get contrary advice, as I think this is a matter
of personal biases, training, and experiences.
My experience is practical rather than theoretical.
I'll be laying out an arch myself next week, and will be using
a collection of 'odds and ends' bricks, and will lay out the arch
without ever looking at a table.
By the way, if you are using insulating bricks, 'shaving' a brick
or two per course to fit is really no big deal. Just rub it on concrete
until it fits.
David Hendley
Maydelle, Texas
At 08:37 AM 5/7/98 EDT, you wrote:
>----------------------------Original message----------------------------
>I'm trying to build the arch for my kiln, and I'm running into a
>reality gap between what the book says and what I'm actually
>encountering.
>
>According to the AP Green catalog, my 3' span arch with 2.302"
>rise per foot should use 1 straight and 18 #1 arch bricks per
>course. Well, I can't get those 19 bricks to make a curve that's
>6.906" inches high in the center. I ran the formula for figuring
>the radius of the circle my sprung arch describes (well,
>suggests actually), and the curve of a circle with a radius of
>26 29/32" doesn't match the curve my bricks create.
>
>At this point I'm still standing bricks on end on the ground trying
>to see what kind of curve they make. Should I just draw the
>curve the formula dictates, build my form and hope the bricks
>behave? Should I make as smooth a curve as I can with the
>bricks and let that dictate the shape of my form?
>
>Can anyone with *experience* in this advise me? The old
>truth "Measure once, cut twice. Measure twice, cut once." is
>the theme of my kiln building experience. I'd rather get the
>measurements right than cut bricks (especially arch bricks).
>
>Thanks,
>Richard
>
Leslie Norton on fri 8 may 98
Richard,
I have built nearly 75 kilns over the last 20 plus years. I have never been
able to get the AP Green formula to work. They must include some amount for
mortar or some other magic number. The way I usually do it is:
I draw an arch that I want to make, on a piece of plywood (this works for
both catenary or sprung arches). I then arrange the bricks on end along the
arch, using straights, #1, #2 or #3 arch shapes. Keep the bottoms of the
bricks as flat as possible to the arch. You can even us pieces of paper,
shaped like arch bricks, to figure out the number bricks you need to buy.
To save money on bricks and fuel, only make a 4 1/2" arch and put 2 to 4
inchs of fiber over the top (I did this on my newest kiln and it works
great).
Make sure the form is at least 1" smaller, al the way around, so you can get
the form out. Save the form, someday you will want to take the arch down
and it's nearly impossible to do without the form.
Hope this helps.
-Leslie
-----Original Message-----
From: Richard Gralnik [mailto:richardg@desktalk.com]
Sent: Thursday, May 07, 1998 5:38 AM
To: Multiple recipients of list CLAYART
Subject: Arch brick configurations - theory and reality
----------------------------Original message----------------------------
I'm trying to build the arch for my kiln, and I'm running into a
reality gap between what the book says and what I'm actually
encountering.
According to the AP Green catalog, my 3' span arch with 2.302"
rise per foot should use 1 straight and 18 #1 arch bricks per
course. Well, I can't get those 19 bricks to make a curve that's
6.906" inches high in the center. I ran the formula for figuring
the radius of the circle my sprung arch describes (well,
suggests actually), and the curve of a circle with a radius of
26 29/32" doesn't match the curve my bricks create.
At this point I'm still standing bricks on end on the ground trying
to see what kind of curve they make. Should I just draw the
curve the formula dictates, build my form and hope the bricks
behave? Should I make as smooth a curve as I can with the
bricks and let that dictate the shape of my form?
Can anyone with *experience* in this advise me? The old
truth "Measure once, cut twice. Measure twice, cut once." is
the theme of my kiln building experience. I'd rather get the
measurements right than cut bricks (especially arch bricks).
Thanks,
Richard
Marcia Selsor on sat 9 may 98
I always use the APGreen charts and find they work great. I also use a jack to
adjust and drop the form to make the bricks fit into place. I also use
threaded rod for the tension supports and adjust them as well.
My arches really have gotten to fit much to my happy satisfaction. I think it
is crucial to use the correct size of feather edge bricks before starting your
courses across.
Marcy in Montana
Leslie Norton wrote:
>
> ----------------------------Original message----------------------------
> Richard,
>
> I have built nearly 75 kilns over the last 20 plus years. I have never been
> able to get the AP Green formula to work. They must include some amount for
> mortar or some other magic number. The way I usually do it is:
>
> I draw an arch that I want to make, on a piece of plywood (this works for
> both catenary or sprung arches). I then arrange the bricks on end along the
> arch, using straights, #1, #2 or #3 arch shapes. Keep the bottoms of the
> bricks as flat as possible to the arch. You can even us pieces of paper,
> shaped like arch bricks, to figure out the number bricks you need to buy.
> To save money on bricks and fuel, only make a 4 1/2" arch and put 2 to 4
> inchs of fiber over the top (I did this on my newest kiln and it works
> great).
>
> Make sure the form is at least 1" smaller, al the way around, so you can get
> the form out. Save the form, someday you will want to take the arch down
> and it's nearly impossible to do without the form.
>
> Hope this helps.
>
> -Leslie
>
> -----Original Message-----
> From: Richard Gralnik [mailto:richardg@desktalk.com]
> Sent: Thursday, May 07, 1998 5:38 AM
> To: Multiple recipients of list CLAYART
> Subject: Arch brick configurations - theory and reality
>
> ----------------------------Original message----------------------------
> I'm trying to build the arch for my kiln, and I'm running into a
> reality gap between what the book says and what I'm actually
> encountering.
>
> According to the AP Green catalog, my 3' span arch with 2.302"
> rise per foot should use 1 straight and 18 #1 arch bricks per
> course. Well, I can't get those 19 bricks to make a curve that's
> 6.906" inches high in the center. I ran the formula for figuring
> the radius of the circle my sprung arch describes (well,
> suggests actually), and the curve of a circle with a radius of
> 26 29/32" doesn't match the curve my bricks create.
>
> At this point I'm still standing bricks on end on the ground trying
> to see what kind of curve they make. Should I just draw the
> curve the formula dictates, build my form and hope the bricks
> behave? Should I make as smooth a curve as I can with the
> bricks and let that dictate the shape of my form?
>
> Can anyone with *experience* in this advise me? The old
> truth "Measure once, cut twice. Measure twice, cut once." is
> the theme of my kiln building experience. I'd rather get the
> measurements right than cut bricks (especially arch bricks).
>
> Thanks,
> Richard
Roger Korn on sun 10 may 98
You wrote:
----------------------------Original message----------------------------
Richard,
I have built nearly 75 kilns over the last 20 plus years. I have never bee
able to get the AP Green formula to work. They must include some amount fo
mortar or some other magic number. The way I usually do it is:
I draw an arch that I want to make, on a piece of plywood (this works for
both catenary or sprung arches). I then arrange the bricks on end along th
arch, using straights, #1, #2 or #3 arch shapes. Keep the bottoms of the
bricks as flat as possible to the arch. You can even us pieces of paper,
shaped like arch bricks, to figure out the number bricks you need to buy.
To save money on bricks and fuel, only make a 4 1/2" arch and put 2 to 4
inchs of fiber over the top (I did this on my newest kiln and it works
great).
Make sure the form is at least 1" smaller, al the way around, so you can ge
the form out. Save the form, someday you will want to take the arch down
and it's nearly impossible to do without the form.
Hope this helps.
-Leslie
I don't have nearly your experience, only seven kilns in my past, but your cut-o
layout method is what I've come to. The mortar allowance may work for a full-tim
brick mason, but just confuses things for me.
The cleverest insulation scheme I've seen is used by George Wright, who just
celebrated his 80th birthday. He uses just 4 1/2 inches of IFB, covered with 1"
2300 fiber, then covers that with 3 1/2" of kraft-paper backed fiberglass insula
with sheet metal over the top. The paper burns up the first time the kiln is fir
the added insulation saves fuel, is cheap (read free - he's the world champion
dumpster diver), and slows the cooling rate of the kiln to a more acceptable rat
Another trick of George's is to make a gable kiln roof out of finger-jointed mul
shelves with fiber and glass insulation on top. If he needs to fire a tall piece
just takes the roof apart, adds a few courses of bricks, and puts the roof back
together.
He's the epitome of a natural engineer, he'll do for a nickel what any fool coul
for a dollar.
Roger
| |
|
