jonathan byler on tue 15 jun 10
Hi all,
I was wondering what people's experience is building chimney stacks of
around 16-20 feet tall, and whether they bother to put lightning rods
on them or anything like that. I was planning on building the one for
our wood kiln with a metal frame so that I would not have to mortar it
together, and was wondering if simply grounding this frame with a
heavy cable to a ground rod is sufficient, or whether it needs
anything at all. It won't be the tallest structure in the
neighborhood by any means, but I do feel the need to get it up above
the roofline of the building it will be near.
-jon
gary navarre on wed 16 jun 10
Ya Jon,=3D0A=3D0A Grounding the metal wouldn't harm but I doubt you will ha=
ve a=3D
problem with lightning striking your tower if there are taller targets. Ho=
=3D
wever, you better duck when Mel strikes you with lightning for making the f=
=3D
rame...=3D0A=3D0A"so that I would not have=3D0A> to mortar it=3D0A> togethe=
r,"=3D0A=3D
=3D0A One thing he and I agree on is a tight stack. I like the heat sink of=
b=3D
rick too and I'm up to 14' (tapered up to about 10') double walled hard bri=
=3D
ck liner with house brick skin starting about 8'. At about 5' up on the out=
=3D
side I set a layer of splits to stagger the horizontal seams between the la=
=3D
yers of brick so there is no leak. After the second firing I've decided to =
=3D
add another couple feet or more if needed. The only metal I might add is so=
=3D
me sort of contraption to slide the chimney cap open or closed from the gro=
=3D
und. I once saw some guy online at his stoke box with a chain in his hand t=
=3D
hat looked like it went to the stack but I don't recall his link. That woul=
=3D
d save a lot of climbing to make adjustments after firing for three days. L=
=3D
et us see some pictures and stay in there eh!=3D0A =3D0A =3D0AGary Navarre=
=3D0ANava=3D
rre Pottery=3D0ANavarre Enterprises=3D0ANorway, Michigan, USA=3D0Ahttp://ww=
w.yout=3D
ube.com/GindaUP=3D0Ahttp://public.fotki.com/GindaUP/=3D0A=3D0A=3D0A--- On T=
ue, 6/15=3D
/10, jonathan byler wrote:=3D0A=3D0A> From: jonathan b=
yler=3D
=3D0A> Subject: [Clayart] lightning rods on chimney?=
=3D0A>=3D
To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Tuesday, June 15, 2010, 3:00 PM=
=3D0A>=3D
Hi all,=3D0A> =3D0A> I was wondering what people's experience is building=
=3D0A> =3D
chimney stacks of=3D0A> around 16-20 feet tall, and whether they bother to =
pu=3D
t=3D0A> lightning rods=3D0A> on them or anything like that.=3DA0 I was plan=
ning o=3D
n=3D0A> building the one for=3D0A> our wood kiln with a metal frame so that=
I w=3D
ould not have=3D0A> to mortar it=3D0A> together, and was wondering if simpl=
y gr=3D
ounding this frame=3D0A> with a=3D0A> heavy cable to a ground rod is suffic=
ient=3D
, or whether it=3D0A> needs=3D0A> anything at all.=3DA0 It won't be the tal=
lest s=3D
tructure in=3D0A> the=3D0A> neighborhood by any means, but I do feel the ne=
ed t=3D
o get it=3D0A> up above=3D0A> the roofline of the building it will be near.=
=3D0A>=3D
=3D0A> -jon=3D0A> =3D0A=3D0A=3D0A
Louis Katz on thu 17 jun 10
If you do put up a lightning rod I would make sure to follow your local
code. If your wood kiln is in a separate structure, and the structure is
metal, what function will this serve other than to provide some protectio=
=3D
n
to the electronics you might have such as a pyrometer?=3D20
If you do use a lightning rod it is really important that you isolate it
from your house electrical system or perhaps ( a question for experts) th=
=3D
at
the ground rods are properly tied together. Doing a bad job is potentiall=
=3D
y
more harmful than not doing anything. Bleeding off even a small proportio=
=3D
n
of the power of a lightning strike is enough to be deadly or very damagin=
=3D
g
to electronics.=3D20
Good luck finding good information on this. I am not a source of it.
Grounding antennas and antenna towers properly is a subject of some debat=
=3D
e
in the amateur radio community.
Louis
Who has an antenna up at only 35 feet and five 8-12 foot ground rods bond=
=3D
ed
with #6 copper for his radio equipment. (He also should buy a Polyphaser
lightning protector for the tallest antenna that stays connected during s=
=3D
torms).
David Woof on fri 25 jun 10
Hi Vince=3D2C =3D20
Regarding shorter wider/too tall/thin chimneys: you are right=3D2C and I sh=
ou=3D
ld have qualified my "shorter" and "too tall and thin" to be efficient=3D2C=
e=3D
xtremes. Your points are well taken. I am chagrined but still exuberant!! =
=3D
=3D20
=3D20
I still remember the feelings of consternation from the late 80's when wood=
=3D
firing interest really took off and as I traveled=3D2C I saw so many beaut=
if=3D
ully built kilns=3D2C but abandoned in frustration=3D2C because of tiny fir=
ebox=3D
es=3D2C and exit flues and chimneys built on the size and principles of for=
ce=3D
d air gas firing and with "wattle and daub" chimneys so loose you could see=
=3D
the flames dancing inside.=3D20
=3D20
If I were to build a Groundhog I would use a wide=3D2C but narrow depth=3D2=
C ch=3D
imney with a split wall inside to create two flues and port these into the =
=3D
back of the kiln in two widely spaced exit flues. Passive damper pull bri=
=3D
cks for each side would regulate the draw and thus the pull of the gasses t=
=3D
hrough each side of the kiln. I could then pull more heat from the hotter =
=3D
side of the kiln into the sluggish side=3D2C and thus ventilate this side w=
it=3D
h a stronger draw and so even out the kiln. And no doubt I would keep stac=
=3D
king bricks to an efficient height for that given altitude and physical cha=
=3D
racteristics of that particular kiln site...while still wrapping and unwrap=
=3D
ping my brain around the concepts of volume=3D2C mass vs velocity in a give=
n =3D
tapering space vs height. =3D20
=3D20
I think Groundhogs were/are great kilns if one remains true to the original=
=3D
tradition that is intrinsic to their mystique=3D2C Tied irretrievably to=
a=3D
vailable local materials to make the kiln=3D2C fire the kiln=3D2C dig the c=
lay =3D
from pits in the creek bottoms=3D2C fill in the hole you dug so the neighbo=
rs=3D
cow didn't fall in. Usually a single native clay that would stand the "bla=
=3D
sting" and the heavy reduction=3D2C and basic alkaline glazes......A way o=
f =3D
life. =3D20
=3D20
I know that the ideal in some folks mind is the dream of a gathering where =
=3D
we collectivly arrive at the ultimate formula for everything=3D2C but as w=
e =3D
have written many times past=3D2C (the archives are full of good informatio=
n)=3D
=3D2C the variables are so many that one size or formula will never fit eve=
ry=3D
terrain=3D2C artificial physical features=3D2C elevation....
=3D20
Take for instance the kiln experience you've cited=3D2C you had a good one =
th=3D
ere=3D3B no doubt built from experience and a willingness not to know every=
th=3D
ing as you also invented and tryed new ideas and technology.........I am re=
=3D
fitting two kilns built by others before me at Yavapai College with new chi=
=3D
mneys=3D2C venturis and stacks tall enough to get the salt and soda fumes a=
bo=3D
ve the nearby roof lines of the high walled kiln yard so they don't get suc=
=3D
ked into the building. Welding metal frameworks and steel tubes as well. T=
=3D
oday one of our Techs tossed an empty clay bag into the open salt chamber a=
=3D
nd I noticed the dust swoop thru the exit flues with some velocity. Good s=
=3D
ign. With everything overbuilt and plenty of passive controls at stratigic =
=3D
places and Mark Ward's new burners designed for this kiln we will have some=
=3D
salty fun.
=3D20
We move across campus in two years and then will deal with new challenges r=
=3D
egarding physical features and prevailing winds......=3D20
Passive dampers will help accommodate a wide range of atmospheric and geo v=
=3D
ariables. and for the kilns at Yavapai=3D2C the control of those chimneys=
=3D2C =3D
volume and velocity of gasses=3D2C as well as control of the kiln=3D2C make=
a p=3D
assive dampering system a must.
=3D20
I especially like your application of the internal flaring of the nozzle po=
=3D
rt inserts. I have the reverse so as to entrain more air around my old atm=
=3D
ospheric burners on an adjustable height gas kiln here at my personal studi=
=3D
o. I think you are dead on with the almost venturi=3D2C "blunderbuss" agit=
at=3D
ion of the gasses as they enter the kiln from the forced air burners.
=3D20
This subject is near to my heart....Get me started...shut me up....or I rat=
=3D
tle on....
=3D20
Best regards=3D2C=3D20
=3D20
David
________________________________________________________________________
1d. Re: Subject: lightning rods on chimney?
Posted by: "Vince Pitelka" vpitelka@DTCCOM.NET=3D20
Date: Sat Jun 19=3D2C 2010 10:14 am ((PDT))
David Woof wrote"
"A shorter chimney with larger volume will draw as well or better vs a
taller one with narrower dimensions once it is heated sufficiently and it
has the added feature of physical stability."
Hi David -
The physical stability part is certainly true=3D2C but otherwise=3D2C it is=
not=3D
true
that a shorter=3D2C wider chimney will draw as well as a tall narrow one=3D=
2C u=3D
nless
the tall one is too narrow and thus restricts the draft. A chimney is a
convection tower=3D2C and any observation of the old Industrial Revolution
chimneys tells you that a tapered one is the very best. A tapered one
allows the speed of the gases to increase as they rise up the tower=3D2C wh=
ic=3D
h
increases the draft at the bottom. Before the advent of forced-air burner
systems=3D2C the draft provided by those chimneys was the primary "force"
supercharging combustion in a kiln or furnace=3D2C and thus the millwrights=
o=3D
f
the time experimented with every possible way to increase draft. The tall
tapered chimney is the most efficient. The primary flaw of the groundhog
kiln is the short=3D2C wide chimney and thus the inadequate and uneven draf=
t.
I built a 100-cubic-foot natural-draft natural-gas car kiln in California
was one of the smoothest=3D2C most even-firing kilns I have ever used. I
attribute that to several things=3D2C including the tall=3D2C tapered chimn=
ey=3D
=3D2C which
was 13.5"x13.5" inside at the bottom where the flue entered=3D2C 9"x9" at t=
he
top of the brick=3D2C with a length of 10" steel well-casing on top=3D2C an=
d a =3D
total
height of about 14 feet. That much height was not necessary for the
operation of the kiln=3D2C but was required to clear the height of the adja=
ce=3D
nt
studio roof peak. The flue exited the center-end of the studio and the
chimney was outside. For chimneys of that height=3D2C I would add several
passive-damper ports near the bottom to temper any excessive velocity in th=
=3D
e
flue.
One other thing I did that made that kiln so controllable - I formed IFB
burner port inserts with a round hole slightly larger than the diameter of
the burner tip=3D2C and with the opening flaring larger towards the inside =
of
the kiln.
And for Jon=3D2C lightening was very rare in coastal Northwestern Californi=
a=3D
=3D2C so
that was not a concern. The chimney described above was encased in an
angle-iron frame=3D2C which is a must for any tall=3D2C narrow brick chimne=
y=3D2C
especially in earthquake country. It was also required for this chimney in
order to provide something to weld on the additional length of well-casing.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net=3D3B wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
=3D20
=3D20
=3D20
=3D20
=3D20
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