Logan Oplinger on mon 15 mar 04
On Mon, 15 Mar 2004 10:40:52 -0600, Vince Pitelka
wrote:
>>Lajos wrote:
>>"I'm building a small test kiln. I made a flat top for it which measures
>>18"x18". I laid
>>K23 firebricks flat (8 pieces) and "glued" them together with refractory
>>mortar. It seems pretty strong, but I'm not sure if it's strong enough."
>>
>Lajos -
>I would not just leave it as-is. Why risk having it crack and collapse
>during a firing.....
>This works better on a polygonal lid (like on a toploader kiln), but even
>on a square lid (with corners rounded slightly) it should give plenty of
>binding force to keep your lid together indefinitely.
>
>A kiln lid assembled with a good high-duty mortar like Greenpatch 421,
>equipped with this kind of strip binding the perimeter, will last forever
>if properly cared for, and that includes periodically tightening the
>clamps.
>The latter is necessary because the strip and clamps will stretch slightly
>as a result of expansion and contraction of the bricks over time......
>
>Best wishes -
>- Vince
Dear Lajos, Vince,
With a lid this size, (18"x18") there is another method of using hose
clamps that does not require any drilling or pop rivets. Find eight
stainless hose clamps at least 7" diameter. If an auto store does not have
them, a hardware/plumbing store may have them. With four clamps, open the
clamps, and insert the tab end of one into the screw end of another until
you have assembled the four into a larger ring. Do this again with the
other four clamps.
With a square lid, the corners should be rounded off to a radius of about 1-
1/2" to 1-3/4". Place these two rings around the perimeter of the lid,
with the screws near the middle of each side. Tighten the rings by turning
the screws on each side the same amount until the rings are snug.
After the kiln has been fired, if the two rings loosen, they can be re-
snugged by re-tightening each of the four screws.
In the diagram below looking at an 18"x18" lid from the top, with staggared
bricks, the "o" and "O" are the rounded corners. The "////" are the clamp
screws. In the side view, the "e"s the screws viewed end-on.
Top View
O---------////--------O
| o--------|--------o |
| | | | | Side View
| |---|--------|----| | |------|-----------|------|
\ | | | | \ e============////===========e
\ |--------|--------| \ e============////===========e
\ | | | \ |------|-----------|------|
| |---|--------|----| |
| | | | | |
| o-----------------o |
O---------////--------O
I do not think I would attempt this method in making a larger lid.
I hope this is helpfull.
Logan Oplinger
Another Tropical Island
Vince Pitelka on mon 15 mar 04
Lajos wrote:
"I'm building a small test kiln. I made a flat top for it which measures
18"x18". I laid
K23 firebricks flat (8 pieces) and "glued" them together with refractory
mortar. It seems pretty strong, but I'm not sure if it's strong enough."
Lajos -
I would not just leave it as-is. Why risk having it crack and collapse
during a firing. I think the simplest reinforcement would be a variation of
what they use on toploader electrics. Get an appropriate-length strip of
sheet metal (stainless steel if possible), long enough to wrap all the way
around the lid with an overlap of a few inches at the joint. It will help
to round off the brick at the corners of the lid slightly. Get several
standard 3"-diameter automotive stainless steel hose clamps, unscrew them
all the way, and cut them in half (easiest to grind a groove with the bench
grinder and then just snap them and dress the raw edges on the grinder).
Drill 3/16" holes through the cut ends, and use #10 x 1/2" sheet metal
screws or 3/16" pop rivets to fasten them to the ends of the sheet metal
strip. Wrap the strip around the outer edge of the lid, thread the hose
clamps back together, and tighten securely. Normally you would use two hose
clamps, giving two clamps mounted parallel where the sheet metal strip
overlaps.
Of course you will have to bend the strip appropriately at the corners of
the lid, and prop the whole thing in place with bricks or whatever in order
to measure and mark for drilling and mounting the hose clamp ends. Be sure
that there is an overlap in the ends of the strip BEFORE the clamps are
tightened, and be sure to mount the clamps so that the ends can fully engage
before they begin to cinch tight, and will have plenty of remaining travel
to be further tightened periodically over the life of the lid.
This works better on a polygonal lid (like on a toploader kiln), but even on
a square lid (with corners rounded slightly) it should give plenty of
binding force to keep your lid together indefinitely.
A kiln lid assembled with a good high-duty mortar like Greenpatch 421,
equipped with this kind of strip binding the perimeter, will last forever if
properly cared for, and that includes periodically tightening the clamps.
The latter is necessary because the strip and clamps will stretch slightly
as a result of expansion and contraction of the bricks over time.
Toploader kiln lids to not get killed by expansion and contraction or by
careful routine use. They get killed either by being dropped shut, or by
having heavy objects placed on top of them. People say "Hey, that's a kiln,
it's sturdy, I can stand on it while changing that light bulb!" or "Hey,
just set that heavy box right here." Next thing you know, serious cracks in
the kiln lid and they are wondering why.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Vince Pitelka on tue 16 mar 04
Logan -
Your method is indeed easier, but are you suggesting using just hose clamps
with no sheet metal strip? If so, I would strongly advise against this.
The hose clamps will dig into the softbrick over time, will constantly need
tightening, and will create serious damage to the softbrick. A strip of
sheet metal spreads out the pressure of the hose clamps over the entire edge
of the softbrick, thus preventing damage. The drilling and pop-riveting are
all very simple. Pop rivets are very handy for so many applications, and
you can buy a decent pop rivet gun fir $20 at any good hardware store or
home improvement center.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Logan Oplinger on wed 17 mar 04
On Tue, 16 Mar 2004 09:03:43 -0600, Vince Pitelka
wrote:
>Logan -
>Your method is indeed easier, but are you suggesting using just hose clamps
>with no sheet metal strip? If so, I would strongly advise against this.
>The hose clamps will dig into the softbrick over time, will constantly need
>tightening, and will create serious damage to the softbrick. A strip of
>sheet metal spreads out the pressure of the hose clamps over the entire
edge....
>Vince Pitelka
Vince,
Yes, I agree, the hose clamps will dig into the soft brick over time,
especially at the corners if the lid is square. I would resolve this
problem by using scrap pieces of sheetmetal only around the corners since
this is where the compressive force on the fire brick is greatest. In
addition, I would bend the corner protectors so that there is a lip 1/2"
wide on the lower side to support the brick. Sheet metal screws placed at
the top edge of each clamp would transfer the load of the lid to the clamps
so they do not slide upward. In cross section it looks like this:
v sheet metal
FBFB|
FBF=|8 FBFB|| FBFB|
FBF=|8 FBFB|| FBF_|
Another way to make a compression band is with two pieces of 16 gauge sheet
metal strip, 2" wide, and four pieces of angle iron, 1/8" thick, 1" or
1.25" wide and 2" long. To make two clamps, the ends of the sheetmetal
strip are bent all the way around a piece of angle iron, and a 3/8" hole is
drilled all the way through where the sheetmetal wraps around the angle
iron. 3/8" bolts and nuts are used to pull the ends of the band together
on opposite sides of the lid to obtain compression. The bolts also serve
as handles for lifting the lid. A short piece of sheet metal placed
between the fire brick and the ends of the band prevent the band from
digging into the brick. I used this method for making the 13.5"x13.5" lid
for my small ^12 updraft reduction test kiln. The corners of the lid are
rounded w/ a 3" radius.
The clamp, viewed from top
FBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFBFB --------------------- ----------------| |------------- AAAAAA| |AAAAAA N|A|\\\\\\\\\|A|B |A| |A|
|A| |A|
--- ---
The lid, viewed from top:
N|\\\|B
/---| |---\//-----------\|| FB | ||
||-------| F ||
|| |/-\| B ||
|| F |\-/| || < circular flue opening in middle
|| B |-------||
|| | FB ||
\\-----------//
\---| |---/
N|\\\|B
Logan Oplinger
Another Tropical Island
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