Rafael Molina on fri 12 mar 99
Clayarters:
I concur with Gavin's distinction between an anagama and a noborigama. It
also brings to mind another question. In all of the reading I've done
noborigamas are multi-chambered climbing kilns which feature arches sprung
from vertical walls. I don't recall ever seeing a noborigama with catenary
arches whose walls and roof are one unit. Is the popularity of the
multi-chambered climbing kilns with catenary arches a recent American
innovation (see Ruggles/Rankin) or is there a Japanese antecedent?
While we're on the subject will members of the list make a distinction
between a Catenary arch derived from hanging a chain/rope from two points
that mark the span to a point which marks the rise and a Parabola? From a
mathematical perspective are they one and the same or are they merely very
closely related? TIA.
Rafael
-----Original Message-----
From: Gavin Stairs
To: CLAYART@LSV.UKY.EDU
Date: Thursday, March 04, 1999 6:49 AM
Subject: Re: Wood kiln for rent
----------------------------Original message----------------------------
At 08:55 PM 03/03/99 EST, you wrote:
>----------------------------Original message----------------------------
>Another posting for a friend:
>
>East Meets West Pottery has a 30-foot single chamber noborigama kiln
>located in the rural setting of Walton, NY (3-1/2 hours NW of New York
>City). It is availiable May through Sept. '99 for rental and/or as a
>site for wood-kiln workships. If interested, contact Reinaldo (voice
>mail) 212-726-8733, or Maxine Krasnow, 4027 E. Santa Barbara, Tucson,
>AZ 85711, 520-327-3949
I think I'll be pedantic with this: As I undertand the terms, a single
chamber, hill climbing, Japanese kiln is an anagama. A noborigama is a
multi chambered, hill climbing, Japanese kiln. Both are usually fired with
wood, and nowadays for ash effects. Originally, they were not fired for
ash, but because they were the most efficient kilns of their day. That is
no longer true, so they are fired for ash, or for the romance of riding the
dragon.
Gavin
Gavin Stairs on sat 13 mar 99
At 03:32 PM 3/12/99 EST, Rafael wrote:
....
>While we're on the subject will members of the list make a distinction
>between a Catenary arch derived from hanging a chain/rope from two points
>that mark the span to a point which marks the rise and a Parabola? From a
>mathematical perspective are they one and the same or are they merely very
>closely related?
Hi Rafael,
They are of different families. The parabola is a conic section, a
quadratic curve, y(x)=a*x^2. The catenary is related to the hyperbolic
functions: y(x)=a*cosh(x/a). A hyperbola is also a conic section, but the
name hyperbolic function is justified by a parametric relationship, and not
because they are based on the hyperbola. Because the catenary is a
trancendental function, it is somewhat more difficult to design with and
plot than the parabola, so the parabola is often substituted, with
reasonable results.
Gavin
Gavin Stairs on sat 13 mar 99
In addendum to my previous post, a late breaking bulletin:
I just got this off the web. Note in particular the point about the
parabola and the catenary. I didn't know this. Learn something every day.
"The catenary is the shape of a perfectly flexible chain suspended by its
ends and acted on by gravity. Its equation was obtained by Leibniz, Huygens
and Johann Bernoulli in 1691. They were responding to a challenge put out
by Jacob Bernoulli to find the equation of the 'chain-curve'.
Huygens was the first to use the term 'catenary' in a letter to Leibniz in
1690 and David Gregory wrote a treatise on the catenary in 1690. Jungius
(1669) disproved Galileo's claim that the curve of a chain hanging under
gravity would be a parabola.
"The catenary is the locus of the focus of a parabola rolling along a
straight line.
"The catenary is the evolute of the tractrix. It is the locus of the
mid-point of the vertical line segment between the curves e and e.
"Euler showed in 1744 that a catenary revolved about its asymptote
generates the only minimal surface of revolution."
Gavin
Gavin Stairs
Stairs Small Systems (S3)
921 College St., # 1-A
Toronto, Ontario, Canada M6H 1A1
(416)530-0419 stairs@stairs.on.ca
Vince Pitelka on sat 13 mar 99
>I concur with Gavin's distinction between an anagama and a noborigama. It
>also brings to mind another question. In all of the reading I've done
>noborigamas are multi-chambered climbing kilns which feature arches sprung
>from vertical walls. I don't recall ever seeing a noborigama with catenary
>arches whose walls and roof are one unit. Is the popularity of the
>multi-chambered climbing kilns with catenary arches a recent American
>innovation (see Ruggles/Rankin) or is there a Japanese antecedent?
Raphael -
I have seen images of historical Chinese and Japanese multi-chambered kilns
with modified catenary arches (but I cannot remember where!!). I say
modified because the low side of the arch was catenary, while the high side
meets the low vertical wall of the next chamber, from which springs another
catenary arch. Essentially it is like a catenary arch on one side and a
sprung arch on the other, in sequence up the hillside, if that makes any
sense. Our two-chamber modified noborigama, designed and built by Doug
Casebeer, uses that design.
It is hard to tell whether the multi-chamber climbing kiln originated first
in China or Japan. Single chamber crossdraft high-fire kilns appeared very
early in China, and by the Song Dynasty multi-chamber kilns were being used.
They seem to have appeared in Japan at about the same time, and there is
some conjecture that Japanese potters traveled to China and brought back the
technology of the chambered kiln, plus Song glaze technology including
celadons and temmokus. And within the Japanese tradition there is a lot
more variation in noborigama designs than you might expect. The concept of
the multi-chamber climbing kiln seems to have spread very quickly in
medieval Japan, with a lot of adaptations in design from on region to
another. Some regions, such as Tamba, retained the Korean tube-kiln design
(right up to the present!) while the multi-chamber design seems to have
found favor in most other areas.
>While we're on the subject will members of the list make a distinction
>between a Catenary arch derived from hanging a chain/rope from two points
>that mark the span to a point which marks the rise and a Parabola? From a
>mathematical perspective are they one and the same or are they merely very
There is no difference. A hanging chain forms a parabola.
Best wishes -
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
paul on sat 13 mar 99
Rafael,
A catenary will take weight on the very top, if you apply equal pressure on
the sides it will collapse. A parabola is designed to take weight at equal
intervals throughout the arch. They look very similar but mathematically
they do differ.
Paul Wilmoth
earthenware, and wood/salt stoneware
pwearthenware@email.msn.com
-----Original Message-----
From: Rafael Molina
To: CLAYART@LSV.UKY.EDU
Date: Friday, March 12, 1999 3:33 PM
Subject: Sprung Arches and Cats was Re: Wood kiln for rent
>----------------------------Original message----------------------------
>Clayarters:
>
>I concur with Gavin's distinction between an anagama and a noborigama. It
>also brings to mind another question. In all of the reading I've done
>noborigamas are multi-chambered climbing kilns which feature arches sprung
>from vertical walls. I don't recall ever seeing a noborigama with catenary
>arches whose walls and roof are one unit. Is the popularity of the
>multi-chambered climbing kilns with catenary arches a recent American
>innovation (see Ruggles/Rankin) or is there a Japanese antecedent?
>
>While we're on the subject will members of the list make a distinction
>between a Catenary arch derived from hanging a chain/rope from two points
>that mark the span to a point which marks the rise and a Parabola? From a
>mathematical perspective are they one and the same or are they merely very
>closely related? TIA.
>
>Rafael
>
>
>-----Original Message-----
>From: Gavin Stairs
>To: CLAYART@LSV.UKY.EDU
>Date: Thursday, March 04, 1999 6:49 AM
>Subject: Re: Wood kiln for rent
>
>
>----------------------------Original message----------------------------
>At 08:55 PM 03/03/99 EST, you wrote:
>>----------------------------Original message----------------------------
>>Another posting for a friend:
>>
>>East Meets West Pottery has a 30-foot single chamber noborigama kiln
>>located in the rural setting of Walton, NY (3-1/2 hours NW of New York
>>City). It is availiable May through Sept. '99 for rental and/or as a
>>site for wood-kiln workships. If interested, contact Reinaldo (voice
>>mail) 212-726-8733, or Maxine Krasnow, 4027 E. Santa Barbara, Tucson,
>>AZ 85711, 520-327-3949
>
>I think I'll be pedantic with this: As I undertand the terms, a single
>chamber, hill climbing, Japanese kiln is an anagama. A noborigama is a
>multi chambered, hill climbing, Japanese kiln. Both are usually fired with
>wood, and nowadays for ash effects. Originally, they were not fired for
>ash, but because they were the most efficient kilns of their day. That is
>no longer true, so they are fired for ash, or for the romance of riding the
>dragon.
>
>Gavin
James Blossom on sun 14 mar 99
Hi all.
Catenaries and parabolas are different beasties indeed.
The determining characteristic of catenaries is that the tension in
the (cable, chain, rope) is equal at all points. This leads to the
equation Y= 1/a cosh ax = H/w cosh ( w/H )
Where:
a = w/H
H = T cos phi
(phi = the instantaneous angle (angle at every point) with respect to level
of the chain)
T = tension in the rope , chain, etc.
w = weight of a (tiny) chain, rope, etc. section
H = horizontal component of the force vector at a particular point
(how hard each link in a chain pulls left or right)
A parabola is a relatively simple relationship between a line
(the DIRECTRIX) and a point (the FOCAL POINT)
The standard equation is Y = X** / 4p
where X, and Y are coordinates of any point on the parabola
and p is some number where the line y = -p (a straight line) is the
directrix
this equation also has the form y = ax** + bx + c ( called a QUADRATIC)
and Y = a( x - h)** + c (** == squared)
The chief use of parabolas is as focusing devices, as any ray approaching
the open end of a parabola *and parallel to the directrix* will be
reflected
to the focal point. Uses include antennae, reflectors for spot lights, and
telescopes.
A parabola *APPROXIMATES* a catenary, but the stronger shape is the
catenary.
That's why catenaries are used in bridges, and engineers get to learn
hyperbolic
functions
Hope this helps as much as confuses
j.b. in Albuquerque, where we just got our first real snow (thank the gods)
and the cherry
blossoms are clothed in white.
"A sharp spear needs no polish" ... Zulu proverb
"
-----Original Message-----
From: Rafael Molina
To: CLAYART@LSV.UKY.EDU
Date: Friday, March 12, 1999 12:33 PM
Subject: Sprung Arches and Cats was Re: Wood kiln for rent
>----------------------------Original message----------------------------
>Clayarters:
>
>I concur with Gavin's distinction between an anagama and a noborigama. It
>also brings to mind another question. In all of the reading I've done
>noborigamas are multi-chambered climbing kilns which feature arches sprung
>from vertical walls. I don't recall ever seeing a noborigama with catenary
>arches whose walls and roof are one unit. Is the popularity of the
>multi-chambered climbing kilns with catenary arches a recent American
>innovation (see Ruggles/Rankin) or is there a Japanese antecedent?
>
>While we're on the subject will members of the list make a distinction
>between a Catenary arch derived from hanging a chain/rope from two points
>that mark the span to a point which marks the rise and a Parabola? From a
>mathematical perspective are they one and the same or are they merely very
>closely related? TIA.
>
>Rafael
>
>
>-----Original Message-----
>From: Gavin Stairs
>To: CLAYART@LSV.UKY.EDU
>Date: Thursday, March 04, 1999 6:49 AM
>Subject: Re: Wood kiln for rent
>
>
>----------------------------Original message----------------------------
>At 08:55 PM 03/03/99 EST, you wrote:
>>----------------------------Original message----------------------------
>>Another posting for a friend:
>>
>>East Meets West Pottery has a 30-foot single chamber noborigama kiln
>>located in the rural setting of Walton, NY (3-1/2 hours NW of New York
>>City). It is availiable May through Sept. '99 for rental and/or as a
>>site for wood-kiln workships. If interested, contact Reinaldo (voice
>>mail) 212-726-8733, or Maxine Krasnow, 4027 E. Santa Barbara, Tucson,
>>AZ 85711, 520-327-3949
>
>I think I'll be pedantic with this: As I undertand the terms, a single
>chamber, hill climbing, Japanese kiln is an anagama. A noborigama is a
>multi chambered, hill climbing, Japanese kiln. Both are usually fired with
>wood, and nowadays for ash effects. Originally, they were not fired for
>ash, but because they were the most efficient kilns of their day. That is
>no longer true, so they are fired for ash, or for the romance of riding the
>dragon.
>
>Gavin
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