James L Bowen on wed 23 feb 00
------------------
We finally got the bricks on the form. We have a couple on the ends of the
courses near the top that are loose enough to take out by hand.
So, one opinion is that they will be tighter after we take out the form. =
The
courses are all interlocked instead of individual rows. I noticed if we =
tighten
the rods on the angle iron to put more pressure on the side skews the arch =
can
raise up off the form. Is this where the term =22sprung arch=22 originated? =
My
concern here is expansion. The framework puts pressure on the walls of the =
kiln
when we tighten the rods. Is expansion a problem with IFB kilns? Should the
frame work be used only to reinforce the arch or to lift it? Should it be
loose, snug, tight or?
Marcia Selsor on thu 24 feb 00
Get some (car)valve springs from a junk yard and put them on the
threaded rod behind some big washers to put some give for the expansion
and contraction. The sprung does spring! (Gee, I love sprung arches,
sorry Nils)
You can tighten the arch up just enough to get it off the form. I always
use a few shims under the form to let it drop when they're pulled. That
is an exciting moment.
Good luck.
Marci in Montana
James L Bowen wrote:
>
> ----------------------------Original message----------------------------
> ------------------
> We finally got the bricks on the form. We have a couple on the ends of the
> courses near the top that are loose enough to take out by hand.
> So, one opinion is that they will be tighter after we take out the form. The
> courses are all interlocked instead of individual rows. I noticed if we tighte
> the rods on the angle iron to put more pressure on the side skews the arch can
> raise up off the form. Is this where the term "sprung arch" originated? My
> concern here is expansion. The framework puts pressure on the walls of the ki
> when we tighten the rods. Is expansion a problem with IFB kilns? Should the
> frame work be used only to reinforce the arch or to lift it? Should it be
> loose, snug, tight or?
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
CYoung/NCzuchra on thu 24 feb 00
James,
I built a sprung arch kiln in 1984 and am still using it. I'm not an
engineer, but the bricks should fit the form. Sprung arch means the
pressure is outward, so I would not tighten the sides. Once the form is
removed, all the pressure will be outward, and it will support itself thru
any expansion.
Hope this helps.
Norm Czuchra
ferenc jakab on fri 25 feb 00
All,
I've found that car valve springs can be too tight and the kiln cracks. I
periodically loosen the retaining bolts as the temperature rises and the
frame tightens.
Feri
Marcia Selsor on sat 26 feb 00
My kiln have lasted +20 years with car valve springs and I opccasionally
hane to tighten them over the years.
Marcia Selsor in Montana
Montana State University-Billings
ferenc jakab wrote:
>
> ----------------------------Original message----------------------------
> All,
> I've found that car valve springs can be too tight and the kiln cracks. I
> periodically loosen the retaining bolts as the temperature rises and the
> frame tightens.
> Feri
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
ferenc jakab on sun 27 feb 00
Marcia, yes I have seen a lot of kilns with car valve expansion springs that
are still going well, but I have seen a small number which did crack. As my
kiln is a single layer, catenary arch, insulating fire brick with fibre
over, I decide to go the manual route (not much mass), and be safe rather
than sorry. Never the less the spring loaded expandable frame is a good idea
but the strength or compressibility of the springs needs to be considered
carefully.
A lot of Kiln frames are over engineered and excessively robust for an
expansion mechanism.
Feri.
rickmahaffey on sun 27 feb 00
Hello Marcia and Ferenc,
As a motor head, I could not resist pointing out that valve springs are
not created equal.
If you feel that most are too strong look for valve springs from a car
that uses two on the same valve, and use one of them. I remember that
Fiat 131 uses a two valve spring set up. Good luck trying to find a 131
in a wrecking yard. :)
Way back in about '77 we built a kiln with aircraft cable and
turnbuckles in it. One of my students was an Engineer at Boeing and SHE
calculated the stretch on the cable and chose a 3/16" cable so that it
would have just enough give to allow the arch to expand. Worked great.
The cable was stainless so corrosion was not a problem.
Rick mahaffey
Ps. My car kiln was a Flat top with a sprung arch. lasted for about 400
firings then we lost the space and dismantled the kiln and sold it.
ferenc jakab wrote:
>
> ----------------------------Original message----------------------------
> Marcia, yes I have seen a lot of kilns with car valve expansion springs that
> are still going well, but I have seen a small number which did crack. As my
> kiln is a single layer, catenary arch, insulating fire brick with fibre
> over, I decide to go the manual route (not much mass), and be safe rather
> than sorry. Never the less the spring loaded expandable frame is a good idea
> but the strength or compressibility of the springs needs to be considered
> carefully.
> A lot of Kiln frames are over engineered and excessively robust for an
> expansion mechanism.
> Feri.
Marcia Selsor on mon 28 feb 00
Catenary arches are beautiful. We have a small soda catenary kiln which
I had to build on a shoe string. The base is bolted but wants to "walk".
As MIchael Cardew said,"some potters are mud people, and some are fire
people". Kilns occupy the thoughts of fire people.
Marcia
ferenc jakab wrote:
>
> ----------------------------Original message----------------------------
> Marcia, yes I have seen a lot of kilns with car valve expansion springs that
> are still going well, but I have seen a small number which did crack. As my
> kiln is a single layer, catenary arch, insulating fire brick with fibre
> over, I decide to go the manual route (not much mass), and be safe rather
> than sorry. Never the less the spring loaded expandable frame is a good idea
> but the strength or compressibility of the springs needs to be considered
> carefully.
> A lot of Kiln frames are over engineered and excessively robust for an
> expansion mechanism.
> Feri.
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
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