Jeff Osborne on sun 15 jul 01
I just purchased a L&L JD 2927 will all options. I test fired to cone 5,
didn't quite make it. during firing I watched as the
lid on the kiln became bowed and the front lip started to rise up. then at
about cone 3 or 4 the lid was sitting about 3/8 to
1/2 inch off the top of the kiln. the red heat was pouring out. does any
one know if this is normal and if this could be the
reason for the kiln not achieving it set temp on the controller? please help.
Jeff
Osborne Designs
hand made tile
william schran on mon 16 jul 01
Lid on a L&L 2927 we have at school cracked after 5 firings and
little bit of bowing. Flipped the lid over, been fine, crack and all,
for 7/8 years. Only fire to bisque in this kiln. Find it way under
insulated, taking long time to reach cone 5/6. If you have 240V
elements, check electrical input - you might only have 208V.
Bill
Wayne Matthews on tue 17 jul 01
What did L&L say? I just fired a Paragon to cone 10. The space between the
lid and top of kiln was about 1/8 inch. That seems normal to me from my
experience with Skutt, Paragon and Cress kilns.
Wayne Matthews
Innvironments Studios
Potter and Sculptor
Ojai, CA 93023
805.646.7338
on 7/15/01 1:39 PM, Jeff Osborne at osbornedesigns@HOME.COM wrote:
> I just purchased a L&L JD 2927 will all options. I test fired to cone 5,
> didn't quite make it. during firing I watched as the
> lid on the kiln became bowed and the front lip started to rise up. then at
> about cone 3 or 4 the lid was sitting about 3/8 to
> 1/2 inch off the top of the kiln. the red heat was pouring out. does any
> one know if this is normal and if this could be the
> reason for the kiln not achieving it set temp on the controller? please help.
>
> Jeff
> Osborne Designs
> hand made tile
>
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Arnold Howard on thu 19 jul 01
The lid rises in the front when the hinge is not adjusted properly
or is binding.
During firing, the wall bricks expand. This pushes the lid upward.
If the hinge does not have sufficient play, the lid will rise at
the front.
If this happens, please do not put a weight on the lid to hold it
down. That will only damage the lid. Instead, check for play at the
hinge, or for binding.
Arnold Howard
Paragon Industries
--- Jeff Osborne wrote:
> I just purchased a L&L JD 2927 will all options. I test fired to
> cone 5,
> didn't quite make it. during firing I watched as the
> lid on the kiln became bowed and the front lip started to rise
> up. then at
> about cone 3 or 4 the lid was sitting about 3/8 to
> 1/2 inch off the top of the kiln. the red heat was pouring out.
> does any
> one know if this is normal and if this could be the
> reason for the kiln not achieving it set temp on the controller?
> please help.
>
> Jeff
> Osborne Designs
> hand made tile
>
>
______________________________________________________________________________
> 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.
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Dan Ody on wed 1 aug 01
Jeff Osborne brought to our attention a subtle design flaw in our new J2900 =
Series Spring Hinge. To help clear any confusion that may exist surrounding =
the L&L J2900 lid, we thought we would relay all of our information about this =
design.=20
The lid on a J2900 is a 12 sided polygonal lid nearly 35 inches across at =
its widest point. Constructed of cemented K23 insulating firebrick, it has a =
reversible linear expansion of .6% at 2000 degrees F. This tells us that at =
2000 F, the lid will expand nearly a quarter of an inch in width. However, the =
outside face of the lid stays well below these temperatures, and therefore does =
not expand nearly as much. It is this temperature / expansion differential =
that causes the lid (and all polygonal lids) to flex into a shallow bowl shape. =
(Put a straightedge across a polygonal kiln lid at the height of your firing =
and notice how the center of the lid is lower than the edges.) This is more =
pronounced in a 3" thick lid, as opposed to a 2 1/2" thick lid, because the =
thicker insulation keeps the outside temperature lower, making the hotface / =
coldface differential greater. It is also more pronounced at higher =
temperatures, again making the differential greater. =20
We had decided to completely support these larger lids on 29" interior =
diameter kilns from both the front and back to prevent stress on the brick when =
it gets opened. The support beam, however, in its first design iteration, was =
restricting the expansion of the firebrick. This forces the lid to fold, =
rather than form the shallow bowl shape it would naturally assume. As soon as =
we discovered this problem -thanks to Jeff Osborne- we quickly came up with a =
design change that fixes the problem. We tested the fix on a kiln firing to =
cone 10 and feel confident that we have completely solved the problem by =
decoupling the vertical support of the lid with the horizontal restriction. =
Concern over a poorly adjusted hinge pin is irrelevant, as the L&L design has a =
vertical slot rather than a hole for the hinge pin, allowing for the expansion =
of the walls of the kiln. =20
We are in contact with the few people who received the first hinges and are =
implementing a field fix. The revised design is shipping as of today. Any =
questions about the kilns are welcome, either via email, Dan@hotkilns.com or by =
phone, 610-485-1789. Best Regards -
Stephen Lewicki, President L&L Kiln Mfg., Inc.
Dan Ody, Technical & Sales Representative, L&L Kiln Mfg., Inc.
POB 1898
Boothwyn, PA 19061
Phone: 610-485-1789
Fax: 610-485-4665
Email: dan@hotkilns.com
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