Tommy Humphries on tue 22 jan 02
To all the kiln makers out there, a simple plea...
Please use stainless screws and hardware on your kilns from now on...OK?
**small rant alert**
Yesterday, I was firing a load of decals in our big oval blue diamond kiln
at work, when I think I hear the kiln sitter drop. Thinking it is way too
soon for that (especially in this kiln) I go to look, and am surprised by
what I find. The entire control box had fallen away from the side of the
kiln and was being supported only by the wiring. All the screws holding the
box in place had completely corroded away, leaving only a tiny bit of screw
left attached to the head. All appeared to be standard galvanized sheet
metal screws. I checked the other kilns around the shop, and my personal
kilns at home and found this to be the standard screws for all the different
makes of kilns I saw ( blue diamond, paragon, skutt, american beauty all of
them) and most all of them were in various stages of corrosion.
**Large Rant Alert**
On another note about this blue diamond kiln...the element connections here
were Pathetic. Simply a loop bent into the ends of the element tails with
the power supply connected with brass nuts,bolts and washers. This isn't an
old kiln, only about 4 years old, and fired maybe 20 times altogether, but
most of the element connections were badly corroded, and some of the
connection bolts had to be replaced, as they were badly burned. Others
snapped when I tried to tighten them (you could wiggle the wires by hand
between the washers).
Looking at the wiring for this kiln made me sick, as good money was paid for
this thing. The first time it was attempted to reach ^6 it took well over 24
hours on high to get there...The company sent a service technician to look
at it, said it was underpowered, so we got a step up transformer just for
it... solid 240 volts at the control box... still takes forever to fire to
^6...3 service calls later...no difference. Finally said there was nothing
else they could do to it, and refunded part of the money spent on it, and
let us keep the kiln for low temp work. I guess the customer service was OK
though it did take some doing to get through to them... They did try, but in
my opinion the substandard workmanship on this kiln defeated them soundly.
My 20 year old american beauty kiln is in much better shape, both
structurally and electrically than this "new" blue diamond on was on day
one.
Rant over,
Tommy Humphries
vince pitelka on tue 22 jan 02
> To all the kiln makers out there, a simple plea...
> Please use stainless screws and hardware on your kilns from now on...OK?
Hooray Tommy. I have been meaning to ask the same thing, especially
regarding the screws. It would be such an insignificant increase in cost,
and it would mean SO MUCH to us.
In the mean time, I keep several boxes of hex-washer-head sheet metal screws
of the appropriate sizes around, and every time I remove the control boxes
or kiln setter, if there is any sign of corrosion I replace the screws.
They are very inexpensive. But you are right, it would be far better if
they were stainless steel, saving us all this bother.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Stephen J Lewicki on fri 25 jan 02
L&L changed over to all stainless steel hardware both for mechanical
fasteners and for our element connection bolts about 2 years ago. I don't
know why this hadn't been done years ago - old habits die hard I think.
When I took a close look at how these zinc and nickel plated screws held up
over time I realized that they were the weakest and cheapest link in our
whole system. I would see kilns that were perfectly good except for the
screws that held things together. It was a Homer moment. By the way we also
spent considerable time and expense converting and upgrading stands and our
notoriously cheap hinge system to heavier corrosion resistant materials. My
appologoes to older L&L kiln owners. Also we are i the process of upgrading
all our element connection boards to a very cool virtually non-destructable
ceramic block (the DaVinci & J2900 series kilns have had these now for
about 1 year).
By the way you typically have to use 400 series stainless steel for the
mechanical fasteners because the 300 series is too soft and the screws just
strip. Unfortunately 400 series is not a corrosion resistant as 300 series
but it is a zillion times better than the zinc or cadmium plated screws.
Stephen J Lewicki
President, L&L Kiln Mfg.
william schran on fri 25 jan 02
Stephen - Thanks for finally getting around to these much needed
upgrades. I have literally replaced all screws holding the kilns
together and metal parts of the electric hook up blocks in our five
L&L's with stainless steel parts over the past several years. Never
could understand why anything other than stainless steel was used.
I'd like to suggest the next item to think about is replacing the
bolt, washer, nut connection between element pigtail and wire leads
with a good terminal block that you could push the leads into a hole
and secure with a screw. This would eliminate the ring terminals for
which I have had to replace numerous times due to
corrosion>arcing>failure.
Thanks for making a good product better.
Bill
Craig Clark on fri 25 jan 02
I'm finally getting around to replacing the elements in an old test kiln.
I've been told that the crimp type connectors that come with the elements
aren't that great and was going to use split bolt type connectors instead.
What do you think of this?
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From: "william schran"
To:
Sent: Friday, January 25, 2002 3:10 PM
Subject: Re: hardware quality in electric kilns
> Stephen - Thanks for finally getting around to these much needed
> upgrades. I have literally replaced all screws holding the kilns
> together and metal parts of the electric hook up blocks in our five
> L&L's with stainless steel parts over the past several years. Never
> could understand why anything other than stainless steel was used.
> I'd like to suggest the next item to think about is replacing the
> bolt, washer, nut connection between element pigtail and wire leads
> with a good terminal block that you could push the leads into a hole
> and secure with a screw. This would eliminate the ring terminals for
> which I have had to replace numerous times due to
> corrosion>arcing>failure.
> Thanks for making a good product better.
> Bill
>
>
____________________________________________________________________________
__
> 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.
>
vince pitelka on sat 26 jan 02
> requires no special tools or expertise to make it tight. I wasn't aware of
> the ring terminals corroding - and I very much appreciate getting that
> feedback. I will look into how that is done and if it can be done better.
Stephen makes some good points, and I am pleased to hear that they are using
all stainless hardware on the newere kilns. I replaced the studs, washers,
and nuts with stainless steel on our L&Ls the first time I replaced
elements. In my experience, the ring terminals corrode badly from
overheating if they are inadequately tightened.
For anyone replacing elements on an L&L, it is critically important that the
right tools be used to tighten the nuts ont he terminal studs, and most
people just use pliers or an adjustable wrench, which is not adequate. The
stud is of course just a machine screw, with the head on the back side of
the terminal block, and a nut up against the terminal block locking the
screw in place, making a convenient stud for the terminal connections. If
that bottom nut gets loose, the whole terminal board must be removed from
the kiln in order to get a screwdriver behind it to tighten the screw.
Otherwise, the tools needed are a small, thin 3/8" open end wrench, and a
socket wrench with a deep-well 3/8" socket. When loosening or tightening
the terminal nut, the wrench should be placed on the bottom nut against the
terminal board, preventing it from turning.
Whenever I install elements on the L&Ls, I always wrap the element pigtails
securely around the studs, place a stainless steel washer over the stud,
then put the ring terminal on the stud, another stainless steel washer, and
then the final nut. Tighten down securely, with the wrench on the bottom
nut and the socket wrench on the top nut.
If the ring terminals show any corrosion at all, they should be replaced.
You can purchase the proper uninsulated copper terminals (they are usually
plated - silver in color) at Lowe's or Home Depot or at any electronics or
electrical supply store. The stud is #10 - 3/16" diameter, so be sure to
get ring terminals to fit that size stud. You will also need a set of
crimping pliers. DO NOT try to crimp on wire terminals using normal pliers.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Stephen J Lewicki on sat 26 jan 02
To Bill -
Thanks for your comments. One reason I know the plated type fasteners were
used in the past on at least our kilns is that they were easy to use. Even
the 400 series SS fasteners sometimes strip which is a real pain during
manufacturing. However, the end result of a durable kiln obviously
outweighs this issue. On the element connection front - a couple of
thoughts I'd like to pass on to you, Craig and others. L&L uses, as you
pointed out, a terminal bolt, washers, lock washers and nuts (all of which
now are stainless steel). The element end gets twisted around this terminal
bolt and then a cord (to connect our ring to the control panel) with ring
terminals on the wire ends goes over this terminal. I like it because it
requires no special tools or expertise to make it tight. I wasn't aware of
the ring terminals corroding - and I very much appreciate getting that
feedback. I will look into how that is done and if it can be done better. I
mentioned that some of our kilns and soon all of our kilns have or will
have a completely molded ceramic terminal block. One nice thing about this
is is consistancy and the fact that the terminal bolts are held in place by
the molded ceramic. On the older connection boards sometimes the terminal
screws would turn making it harded to get that all important tightness.
I have looked at other terminal ends - crimp connectors, machined tubes
with with screws that impinge on the element ends. My father even tried to
do use something like that on a cheaper line of kilns L&L made for awhile.
It was a total disaster. The element ends get hot and they expand and
contract which can cause them to get loose. Once loose they get real hot
and fail - which is expensive to fix. The problem that I have with crimp
connectors is that they require a special tool and they are somewhat
dependent on strength and technique to get right. They have the advantage
of being cheap and for all I know they do a great job. I really don't know
how much of a problem that is in practice - just some offhand comments that
I hope won't get me in trouble. I am not familier with the split bolt
terminal that Craig talks about or perhaps I don't know the terminology. I
would be very interested in hearing other comments from kiln users about
their experiences with element terminations - the good the bad and the ugly.
Stephen J Lewicki
President, L&L Kiln Mfg.
Paul Gerhold on sat 26 jan 02
Dear Stephen,
I have three old electric kilns which get a lot of use including an antique L&
L which I really like. I have probably had to redo 20 or more ring terminals
over the years but never have I replaced due to failure a tube connection or
a crimped element connection. Of course I do have a proper crimping tool. I
don't think you can put enough pressure on the connection without one. And of
course a loose connection will fail eventually.
I agree with previous posts about stainless fasteners. Ihave just about
replaced every screw on every kiln, Your decision is to be applauded. Now if
only someone can figure out a good way to attach the hose clamp pieces to the
outer jacket most of the annoying problems will be behind us. Spot welds
don't last nearly as long as a well maintained kiln.
Thank You For Thinking
Paul
Ceramic Design Group on sat 26 jan 02
on 1/25/02 4:40 PM, Craig Clark at mudman@HAL-PC.ORG wrote:
> I'm finally getting around to replacing the elements in an old test kiln.
> I've been told that the crimp type connectors that come with the elements
> aren't that great and was going to use split bolt type connectors instead.
> What do you think of this?
> Craig Dunn Clark
> 619 East 11 1/2 st
> Houston, Texas 77008
> (713)861-2083
> mudman@hal-pc.org
We have replaced all the other/misc type connectors on our electric kilns
with split bolt connectors. They work fine and in my experience, have not
shown any degradation over time, meaning that elements are easily replaced
by loosening the nut on the connector. We use a nut driver on one end of the
connector and a small open end wrench on the other to loosen. Just be
careful not to put any unnecessary stress on the element pigtail or the
element itself.
Jonathan
Roger Korn on sat 26 jan 02
The corrosion problem at the clamp-to-jacket connection is a well-known problem
with stainless. It's called stress corrosion and is caused by accelerated corrosion
of the ferrous content of SS under stress. I've been replacing the spot welds with
3/16" aluminum pop rivets for several years. No problems so far, but a couple of
years isn't long enough to say that this is a real solution. Brazing works great,
but is expensive as a production method, plus it distorts the jacket to a visible
degree, so that's not acceptable either. Probably TIG welds using a 400- series
filler would be ideal, but that's another expensive production process.
Anybody got The Answer?
Roger
Paul Gerhold wrote:
> ... Now if
> only someone can figure out a good way to attach the hose clamp pieces to the
> outer jacket most of the annoying problems will be behind us. Spot welds
> don't last nearly as long as a well maintained kiln.
>
> Thank You For Thinking
> Paul
>
> ______________________________________________________________________________
> 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.
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
Roger Korn on sat 26 jan 02
Hi Stephen,
I really appreciate your willingness to get "down and dirty" on these issues. Kiln
repair, design, and construction has been a sideline of mine for some years now
(it's a great way to meet other potters), so I see the results of many different
approaches. The current "group think" approach to this thread on Clayart has been
very positive in its ability to focus attention on an issue where the status quo
("that's just the way it is") has been accepted for too long.
Thanks,
Roger
Stephen J Lewicki wrote:
> To Bill -
>
> Thanks for your comments. One reason I know the plated type fasteners were
> used in the past on at least our kilns is that they were easy to use. Even
> the 400 series SS fasteners sometimes strip which is a real pain during
> manufacturing. However, the end result of a durable kiln obviously
> outweighs this issue. On the element connection front - a couple of
> thoughts I'd like to pass on to you, Craig and others. L&L uses, as you
> pointed out, a terminal bolt, washers, lock washers and nuts (all of which
> now are stainless steel). The element end gets twisted around this terminal
> bolt and then a cord (to connect our ring to the control panel) with ring
> terminals on the wire ends goes over this terminal. I like it because it
> requires no special tools or expertise to make it tight. I wasn't aware of
> the ring terminals corroding - and I very much appreciate getting that
> feedback. I will look into how that is done and if it can be done better. I
> mentioned that some of our kilns and soon all of our kilns have or will
> have a completely molded ceramic terminal block. One nice thing about this
> is is consistancy and the fact that the terminal bolts are held in place by
> the molded ceramic. On the older connection boards sometimes the terminal
> screws would turn making it harded to get that all important tightness.
>
> I have looked at other terminal ends - crimp connectors, machined tubes
> with with screws that impinge on the element ends. My father even tried to
> do use something like that on a cheaper line of kilns L&L made for awhile.
> It was a total disaster. The element ends get hot and they expand and
> contract which can cause them to get loose. Once loose they get real hot
> and fail - which is expensive to fix. The problem that I have with crimp
> connectors is that they require a special tool and they are somewhat
> dependent on strength and technique to get right. They have the advantage
> of being cheap and for all I know they do a great job. I really don't know
> how much of a problem that is in practice - just some offhand comments that
> I hope won't get me in trouble. I am not familier with the split bolt
> terminal that Craig talks about or perhaps I don't know the terminology. I
> would be very interested in hearing other comments from kiln users about
> their experiences with element terminations - the good the bad and the ugly.
>
> Stephen J Lewicki
> President, L&L Kiln Mfg.
>
> ______________________________________________________________________________
> 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.
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
Stephen J Lewicki on sat 26 jan 02
Paul - thanks for your comments. I am going to look into the ring terminal
problem. I have to really thank this forum - it is a great way for us at
L&L (and presumable for other kiln manufacturers) to get this sort of
important feedback. It is very hard to sift for gold during the typical
day.
I know I have seen some kilns with rivits on the hose connectors. Anyone
out there have an opinion about this? I do know we are paying more
attention to quality of our spot welds - and that may be the real issue. I
can remember seeing some really bad spot welds in the past.
By the way, I don't imagine I can catch hell for plugging a competitor, but
I believe Skutt also uses stainless steel fasteners.
Stephen J Lewicki
President, L&L Kiln Mfg
Fredrick Paget on sun 27 jan 02
This topic of reliable connections is one that cropped up several times in
my other life. Once we received a shipment of computer hardware back in the
50's. This was before transistors were in use and these had 3 or 4 vacuum
tubes per board. It was made with some of the first printed circuit boards
and these were on hundreds of phenolic laminate boards 1/4 inch thick.
They were double sided and connections from front to the back were made
with rigid rivets and soldered. During the transcontinental trip in the
middle of the winter from the east coast factory to our California location
the temperature dropped well below freezing in the truck. As a result many
of the solder connections from front to back of the boards cracked. At
first we were mistified as the device would work for a while and then fail.
We ran dozens of tests and a mechanical engineer made a mathematical
analysis that proved that there was nothing we could do to that kind of a
joint on such a thick board because the thermal expansion would crack the
solder every time. We had to hand wire with wire from front to back and
resolder thousands of connections.
This kind of an analysis can be made of a crimped joint. The main thing to
be sure about is that the materials of the joint are only stressed and not
strained. That is, to stay within the part of the stress strain curve of
the material where it acts like a spring and is not stretched. If this is
true it won't loosen and will spring back to its original shape as it is
temperature cycled.
Copper is a tough material to connect to since heat will form an oxide that
is not such a good conductor. Silver plating is often used to help. Another
thing is to use nickel sleeves instead of copper. The crimping tool should
be one of the kind that seizes the connector and has a sort of ratchet that
won't let go until the pressure reaches the recomended level. These tools
are relatively expensive - 1 or 2 hundred dollars - but they make a gas
tight connection.
Fred
>I can check our UL reports to see what temperature they see (I think this
>is one of the points they measured in the testing). Any heat will cause
>some expansion so the presure is there to cause a loosening of the
>connection. There is a coefficient number of expansion, which I am sure
>with the temperatures involved and diameter of the wire is infinitesimal.
>On the other hand it is irresistable - the expansion has to go somewhere.
>How that plays out in actual use is the issue. I'm not sure there is a
>perfect connector but I am finding this thread facinating as I am sure
>others are.
>Stephen J Lewicki
>President, L&L Kiln Mfg.
From Fred Paget, Marin County, California, USA
Jennifer F Boyer on sun 27 jan 02
This thread has been GREAT!! The only thing that ever goes wrong
with my J2927 L&L(used for bisk) is the ring terminals burning
out. Thanks to everyone for all the detailed info....now I know
a lot more about how to maintain my kiln better.
Jennifer, perusing the MSC catalogue for stainless steel stuff
and a deep well socket wrench.....
vince pitelka wrote:
>
> > requires no special tools or expertise to make it tight. I wasn't aware of
> > the ring terminals corroding - and I very much appreciate getting that
> > feedback. I will look into how that is done and if it can be done better.
>
> Stephen makes some good points, and I am pleased to hear that they are using
> all stainless hardware on the newere kilns. I replaced the studs, washers,
> and nuts with stainless steel on our L&Ls the first time I replaced
> elements. In my experience, the ring terminals corrode badly from
> overheating if they are inadequately tightened.
>
> For anyone replacing elements on an L&L, it is critically important that the
> right tools be used to tighten the nuts ont he terminal studs, and most
> people just use pliers or an adjustable wrench, which is not adequate. The
> stud is of course just a machine screw, with the head on the back side of
> the terminal block, and a nut up against the terminal block locking the
> screw in place, making a convenient stud for the terminal connections. If
> that bottom nut gets loose, the whole terminal board must be removed from
> the kiln in order to get a screwdriver behind it to tighten the screw.
> Otherwise, the tools needed are a small, thin 3/8" open end wrench, and a
> socket wrench with a deep-well 3/8" socket. When loosening or tightening
> the terminal nut, the wrench should be placed on the bottom nut against the
> terminal board, preventing it from turning.
>
> Whenever I install elements on the L&Ls, I always wrap the element pigtails
> securely around the studs, place a stainless steel washer over the stud,
> then put the ring terminal on the stud, another stainless steel washer, and
> then the final nut. Tighten down securely, with the wrench on the bottom
> nut and the socket wrench on the top nut.
>
> If the ring terminals show any corrosion at all, they should be replaced.
> You can purchase the proper uninsulated copper terminals (they are usually
> plated - silver in color) at Lowe's or Home Depot or at any electronics or
> electrical supply store. The stud is #10 - 3/16" diameter, so be sure to
> get ring terminals to fit that size stud. You will also need a set of
> crimping pliers. DO NOT try to crimp on wire terminals using normal pliers.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> Home - vpitelka@dtccom.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> http://www.craftcenter.tntech.edu/
>
> ______________________________________________________________________________
> 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.
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer mailto:jboyer@adelphia.net
Thistle Hill Pottery
95 Powder Horn Glen Rd
Montpelier, VT 05602 USA
802-223-8926
http://www.thistlehillpottery.com/
Never pass on an email warning without checking out this site
for web hoaxes and junk:
http://urbanlegends.about.com/
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Stephen J Lewicki on sun 27 jan 02
Vince -
Thanks. If you don't mind I may lift some of your comments here and put
them in our instruction manuals - very well described and helpful for
people doing repairs. It is not as easy for the terminal screws to move on
our new ceramic blocks - especially the ones for the J230s and J18s.
Stephen J Lewicki
President, L&L Kiln Mfg.
william schran on sun 27 jan 02
Craig - I've replaced the crimp connections many times on kilns that
get lots of use & abuse and find if you have a proper crimping tool
you can get a good tight connection. This has been my observation
replacing the elements a few times on the same kiln and not finding
any corrosion/arching at the connection. Only problem is having to
cut back the lead wire each time which will eventually make it too
short and thus having to replace it. Have also replaced these
connections with split bolt when the wire was going to be too short
if I cut it any more.
Bill
william schran on sun 27 jan 02
Stephen - Thanks for the answer about connectors. I was encountering
a problem with the ring terminals on the jumper cords corroding and
the wire breaking at the point where it connected to the terminal.
This was happening on a J2927. Had 3 or 4 break this way, twice in
the top ring. After some conversations with folks at L&L, it was
decided the area was getting too hot and I stuffed some small pieces
of fiber blanket in the insulator tube where the pigtail comes
through. This seems to have corrected the problem.
You spoke about the problem of expansion/contraction of the elements
as they heat /cool. Do they undergo much expansion where the
connection is made?
Bill
Stephen J Lewicki on sun 27 jan 02
Bill -
I can check our UL reports to see what temperature they see (I think this
is one of the points they measured in the testing). Any heat will cause
some expansion so the presure is there to cause a loosening of the
connection. There is a coefficient number of expansion, which I am sure
with the temperatures involved and diameter of the wire is infinitesimal.
On the other hand it is irresistable - the expansion has to go somewhere.
How that plays out in actual use is the issue. I'm not sure there is a
perfect connector but I am finding this thread facinating as I am sure
others are.
Stephen J Lewicki
President, L&L Kiln Mfg.
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