Cracked fire pots?
spaco
firepots, one vendor to another?
That is: do some mfr's (or sellers) firepots crack easier than others?
Are some more sensitive to "overwatering" than others?
Our club bought and installed at least a dozen firepots from a
certain company and about half of them have cracked. Some are as old
as 6 or 7 years and some are as new as 3 or 3 years old. None of them
are in everyday service. Most are used by trainees.
For reference, the firepot I am using in my shop has been there since
1986 and shows no signs of any problems. (Different mfr'r).
None of the firepots I describe are used to burn coke as a regualar
diet.
Pete Stanaitis
----------------------
Chilla
the melting phase. A dirty casting, may have too much porosity, if it's
a remelt as opposed to a smelt may also cause this problem.
Usually if you find a bad product you tell the company that manufactured
it and give them a chance to rectify the situation. If the products are
still crap, you go with a good producer.
Pure iron is difficult to get these days, so the firepots that are
cracking may not be iron at all.
I was thinking that with the alloys available today, you could feasibly
construct a firepot, but you would have to select the right alloy in
plate form. Plate is less likely to crack than a casting.
Regards Charles
Prometheus
<charles...@optushome.com.au> wrote:
> From a casting point of view, casting these objects can be screwed in
>the melting phase. A dirty casting, may have too much porosity, if it's
>a remelt as opposed to a smelt may also cause this problem.
>
>Usually if you find a bad product you tell the company that manufactured
>it and give them a chance to rectify the situation. If the products are
>still crap, you go with a good producer.
>
>Pure iron is difficult to get these days, so the firepots that are
>cracking may not be iron at all.
>
>I was thinking that with the alloys available today, you could feasibly
>construct a firepot, but you would have to select the right alloy in
>plate form. Plate is less likely to crack than a casting.
(Sorry to cause your thread to drift, Pete- I'm afraid I have no
information about the original question)
I had asked about this once before, but it didn't come to much. Since
you mention using plate, I figure it might be worth asking what it is
you're envisioning- the firepots I've seen have been more or less
universally round. While it's certainly possible to roll sheet metal,
rolling heavy plate might be asking for cracks in the forming process.
A better bet might be to find a tubing offcut at a steel supplier,
assuming that a suitable alloy could be found, and weld or bolt a
plate to the bottom.
I've been trying to get my head around the coal forge, and still am
coming up with a reasonably large blank spot in my mind. The basic
trouble I'm having is this- if you're burning coal or coke on a metal
plate at a temperature high enough to burn up steel, what keeps it
from simply burning through the bottom? Obviously, it works in
practice, it's the theory I'm having trouble with. I've been wanting
to go ahead with making a coal forge to use this summer, but until
I've got at least a working idea of how the forge body acts to keep
itself from burning up, I'm pretty hesitant (I just can't see a
situation where burning coke and hot steel falling on the concrete
floor in my little forge building would be very fun!)
As an alternate design, anyone have any thoughts or preferences
relating to side-blown coal forges? Because of the issue I mentioned
above, I've been thinking that I might make a coal forge with a
full-length manifold that can deliver air from one or both sides, with
black pipe tuyeres that can be closed off as needed by sliding plates
in or out from the ends (so that the fire size can be adjusted as
needed). The thought here is that I would then be able to line the
bottom with castable refractory or sand covered with fire bricks, and
thus have a replacable forge lining. I've never seen one of these in
actual use, but I know they used to use a similar setup in the old
days, and I'm wondering if it was an inherantly flawed design that was
abandoned, or if the bottom-blown forges are simply more portable
and/or convenient.
Or what about simply having capped iron pipes coming up through the
bottom refractory and fire brick, with some holes drilled in the end
to allow the air to move through? While I'm sure these would get
dirty, a T-junction for the air delivery and a nipple and cap on the
bottom end would allow the pipe to be opened and cleaned out with a
poker and wire brush. The nice thing about this, in my mind, would be
that if any part of the assembly cracked or otherwise became damaged,
it could be replaced with a trip to the local hardware store- the down
side, of course, is that it would be less than ideal to try and clean
those pipes out when they're hot.
Chilla
Certainly there are firepots that are round, but they come in different
shapes also, and some quite angular... I'll see if I can find an image
for you... wait a tick... take a squiz at these :-
<http://www.villagesmith.com.au/html/VS_forge.htm>
<http://www.blksmth.com/my_portable_forge.htm>
Vulcan firepots :-
<http://www.centaurforge.com/prodinfo.asp?number=CENTVULCAN>
<http://www.centaurforge.com/prodinfo.asp?number=14FIREBOWL>
<http://www.centaurforge.com/prodinfo.asp?number=CENTVULCANDP>
<http://www.blksmth.com/mild_steel_firepot.htm> They suggest mild steel
for this one, but maybe there's a better alloy
A firepot doesn't have to be made out of metal elemental or otherwise.
I have this big-ass blower, that was used to power a note in a cathedral
pipe organ... can hardly lift the bugger...
<http://members.optushome.com.au/charlesanderson/img/blower.jpg>, and I
was thinking that if I constructed a frame with removable angled hard
fire bricks, this would make a very powerful solid fuel forge.
-----------
Firepots are usually pure iron, which has a ludicrous melt point, so
this is usually why they don't melt through. I made a half pipe sword
forge that I recently extended the sides with 16 gauge hot roll. I only
intend to burn charcoal in it, so it should last a while... the pipe
section is 1/4 inch. The tru iron is a 1 " pipe with holes drilled
along the length and an end cap in place.
------------
If you are going to build your own coal forge, then you could buy a
firepot from one of the links above, or you could go the ceramic, or
fire brick route.
As to side blast or bottom blast, I'm trying to figure out why people
would prefer to use the bottom blast over the side blast. Especially
when you take clinkers into account. Logically the problem of clinkers
would be less with a side blast, so why do people still use bottom
blast... anyone?
Regards Charles from Oz
P.S. I had a win today, found a fast way to forge weld spring with
L6... works a treat :-)
spaco
usually cast iron; maybe some are cast steel, but no idea what alloy.
A properly maintained coal fire has a layer of coke all around the
sides. It is constantly being made from green coal, then chipped into
the heating zone as needed to react with the atmospheric oxygen from the
blast. This coke layer acts to keep the temp of the firepot down.
Remmember that you are constantly blowing cold air into the firepot, and
this also acts to keep the firepot below the temperature of the hot zone
of the fire. Yes, we do sometimes see a dim "glow" on the firepot.
Yes, I see firepots that are round, but most people I know use
rectangular firepots, the deeper the better.
Refractory won't last long in the bottom of a forge because it will
mix with the clinker and be eaten up. Many of the little "rivet"
forges and some of the large table type forges did/do use refractory
cement, but not right in the "pot" area. It keeps the hot fire from
affecting the table area. But most people I know don't bother with it.
On my forge at home, I have added 2 inches of firebricks on my forge
table, more to add depth to the firepot than anything else.
The reason that most coal forges end up being bottom blast is the the
clinker breaker does a good job of keeping the fuel from falling through
while still allowing good air flow. You want the incoming air to be as
far from the work as possible so all the oxygen in it is used up before
the hot gases get to the work (to minimize oxidation). Also, since the
blast and cleanout are also at the bottom, it makes cleaning out the
forge without loosing the fire the easiest. Remember that clinker,
which is melted ashes, obeys the laws of gravity and falls straight
down. That puts them right close to the clinker breaker where they can
congeal quickly (with a short "blower off" time) to be either pulled out
in chunks or crushed by the poker and/or clinker breaker and sent down
to the cleanout.
You DON'T want multiple tuyeres. You want to be able to control the
fire's size and shape as you go and, with the single tuyere that forms
at the clinker breaker, you have just what you need.
And you don't need or want a large blower. You'll just be turning
it 'way down to use it. I'll bet that most 50 watt blowers will work
fine. You are only providing oxygen to the fuel, not blowing coke
around. See what some other people are using and go from there.
If you must build your own, I'd strongly consider stainless steel.
Cast firepots for coal seem to often be about 3/8" thick. Firepots
designed for continuous coke bueing are usually 1/2" thick or more.
That's because coke doesn't "coke up" and therefore stays loose in the
firepot allowing more heat to get to the edges. And, from my
occassional use of commercial coke, it appears to have a higher heat
value, creating additional heat, stress and oxidation problems with
longevity.
Not that you can't invent your own design, but the old timers spent
their whole lives figuring out the system we generally use today.
We built a side draft forge some years ago here with a specific purpose
of aggregating iron bloom. We had to do it that way to keep from
loosing the small pieces of bloom that we were forge welding together.
(They wanted to crumble). So there's an application for a special
shaped fire. And I am sure there are more. But for a general
blacksmith, who never knows what's coming in the door next, the bottom
blast works well.
Pete Stanaitis
--------------------
Chilla
becoming a relic, cast iron could be the next best thing. The other
good thing about iron is it's an element, and takes a looooooong time to
rust away.
I intend to have a large firepot, naturally I will adjust the air flow
and have the fire bricks replaceable, as it will be using charcoal I
think the bricks will have a long life. Or if I decide to go to coke,
could have a few more options, and its always good to have the ability
to use more air, for other purposes.
I was thinking bottom blast just for convenience, and as discussed
clinker wont be a problem for me, but an ash dump is a pretty neat idea.
Regards Charles
Prometheus
wrote:
>I never knew that firepots were made of "pure iron". I think they are
>usually cast iron; maybe some are cast steel, but no idea what alloy.
>A properly maintained coal fire has a layer of coke all around the
>sides. It is constantly being made from green coal, then chipped into
>the heating zone as needed to react with the atmospheric oxygen from the
>blast. This coke layer acts to keep the temp of the firepot down.
>Remmember that you are constantly blowing cold air into the firepot, and
>this also acts to keep the firepot below the temperature of the hot zone
>of the fire. Yes, we do sometimes see a dim "glow" on the firepot.
Okay, I think I see that- and I'll admit to having had my gas forge
glowing a time or two, but in that case, it was on the top where
nothing was likely to fall through.
> Yes, I see firepots that are round, but most people I know use
>rectangular firepots, the deeper the better.
That's good news, actually. It's far easier for me to make a
trapezoidal box than it is to try and find a useful round pipe. When
you say "the deeper the better," is there a functional limit to how
deep the pot should be? As I'll be fabricating the thing, it can be
as deep as I want it to be, really.
> The reason that most coal forges end up being bottom blast is the the
>clinker breaker does a good job of keeping the fuel from falling through
>while still allowing good air flow. You want the incoming air to be as
>far from the work as possible so all the oxygen in it is used up before
>the hot gases get to the work (to minimize oxidation). Also, since the
>blast and cleanout are also at the bottom, it makes cleaning out the
>forge without loosing the fire the easiest. Remember that clinker,
>which is melted ashes, obeys the laws of gravity and falls straight
>down. That puts them right close to the clinker breaker where they can
>congeal quickly (with a short "blower off" time) to be either pulled out
>in chunks or crushed by the poker and/or clinker breaker and sent down
>to the cleanout.
> You DON'T want multiple tuyeres. You want to be able to control the
>fire's size and shape as you go and, with the single tuyere that forms
>at the clinker breaker, you have just what you need.
The shape and size of the fire is what I had in mind with the multiple
tuyeres- I guess what I was thinking is that even though I've never
done it, and may never get around to it, having multiple tuyeres might
allow me to make a long, thin fire for working on something like a
sword. I don't know that I personally would have any use for
something like that- but I've found that the first question everyone
asks me when I say "Blacksmith" is "can you make a sword?"
> And you don't need or want a large blower. You'll just be turning
>it 'way down to use it. I'll bet that most 50 watt blowers will work
>fine. You are only providing oxygen to the fuel, not blowing coke
>around. See what some other people are using and go from there.
> If you must build your own, I'd strongly consider stainless steel.
>Cast firepots for coal seem to often be about 3/8" thick. Firepots
>designed for continuous coke bueing are usually 1/2" thick or more.
>That's because coke doesn't "coke up" and therefore stays loose in the
>firepot allowing more heat to get to the edges. And, from my
>occassional use of commercial coke, it appears to have a higher heat
>value, creating additional heat, stress and oxidation problems with
>longevity.
It's not so much that I *must* build my own as that I build anything I
can for myself, as part of the hobby. I've found I just plain like
working with tools I made myself, and even when they're not quite as
attractive as a machine made item, I usually make the effort to make
sure that the basic design and material quality meets or exceeds the
commerically availible stuff.
So, on that note, Stainless steel is always an option for me- what I
can realistically expect to be able to cut, form and weld is 7ga
(3/16") 304 Stainless. Any gut feeling on whether or not this would
be thick enough to make a reasonable fire pot?
> Not that you can't invent your own design, but the old timers spent
>their whole lives figuring out the system we generally use today.
Agreed- the problem that I'm running up against is a lack of
experience with the various designs. Basically, what I've been trying
to figure out is what design it is that I actually want and need, and
whether or not using modern materials makes more or less sense than
the old cast iron. Cast iron can be awesome when it's good, but the
stuff in my budget range is often full of voids and small cracks, and
it can't be easily repaired if it breaks.
Prometheus
<charles...@optushome.com.au> wrote:
>They should be made from pure iron, I suppose that as pure iron is
>becoming a relic, cast iron could be the next best thing. The other
>good thing about iron is it's an element, and takes a looooooong time to
>rust away.
I'm not sure if I follow this- by "pure iron", I assume you mean iron
with little or no carbon content, like the old wrought iron. Cast
iron has a very high carbon content. Wouldn't they be near opposite
ends of the spectrum, and not first and second best?
If low carbon is desirable, I wonder if 1008 steel would be a good
choice?
Trevor Jones
I got my doubts that firepots were ever made of "pure iron".
More likely they were made of whatever was available that day, to go
in the cupola or crucible on the day they were running that pattern.
Make the new pots out of mild steel plate, and get down to business,
if you are set on making new pots.
Have you tried welding the cracked ones?
Try to get the users to build the fire a little higher in the pot,
rather than right down in it, and it the pots won't take as bad a
beating, either.
Stainless, in high heat, sucks! It warps and burns, and the chome
burning leaves a vile taste in my mouth when I am around it being
welded. If you could get the users to make the fire up high, it would
work, as would plain old mild steel sheet.
The pots in the forges I used in the past were rectangular or square.
The guys that I wa hanging with, all were keeping their eye out for
deeper and larger firepots. :-)
The rule of thumb that was taught to me, was that you should be able
to lay a bar straight across the lips of the table (say, 3 inches or so
above the flat deck of the forge) and heat that bar there. We were using
small (for commercial use anyway) forges with pots 10-12 inches across
the top, and 6 inches or so deep.
Saw a write-up about the use of a piece of pipe, with rows of holes
drilled in it, for use on a side blast forge. You removed enough bolts
to build the fire length you needed for the particular job, and could
fish the whole thing out og the bottom of the forge when you did not
need it. Good for long work.
Cheers
Trev
spaco
ones that many of us use today.
Remember what started this thread, however. trevor makes a real good
point about having the users "build their fire higher in the pot". This
means, of course, that you KEEP the fire higher in the firepot. Many
people, and even many who should know better, fail to properly feed the
fire by pushing coke in from the sides.
Pete Stanaitis
--------------------------
Chilla
Prometheus wrote:
> On Wed, 02 Apr 2008 11:29:20 +1100, Chilla
> <charles...@optushome.com.au> wrote:
>
>
>>They should be made from pure iron, I suppose that as pure iron is
>>becoming a relic, cast iron could be the next best thing. The other
>>good thing about iron is it's an element, and takes a looooooong time to
>>rust away.
>
>
> I'm not sure if I follow this- by "pure iron", I assume you mean iron
> with little or no carbon content, like the old wrought iron. Cast
> iron has a very high carbon content. Wouldn't they be near opposite
> ends of the spectrum, and not first and second best?
>
> If low carbon is desirable, I wonder if 1008 steel would be a good
> choice?
Absolutely. I was thinking that the cast iron would still have more
properties closer the iron, but you're probably correct, and pure iron
is the better product... I agree.
Maybe 1008 would be the go, or a heat resistant alloy... maybe an exotic
alloy. I think the cheaper alternative should be pursued first.
Some of the links I provided earlier should be a good start for anyone
wanting to make their own firepot.
The other alternative to making a firepot that lasts forever would be to
make one that is disposable, cheap and easy to make. There are several
options with this route. Maybe make it out of a castable refractory,
that sits in a metal housing. You'd have to make a mould that was
pretty spot on, but moulds are an easy thing to make.
Regards Charles
Chilla
> It's not so much that I *must* build my own as that I build anything I
> can for myself, as part of the hobby. I've found I just plain like
> working with tools I made myself, and even when they're not quite as
> attractive as a machine made item, I usually make the effort to make
> sure that the basic design and material quality meets or exceeds the
> commerically availible stuff.
>
> So, on that note, Stainless steel is always an option for me- what I
> can realistically expect to be able to cut, form and weld is 7ga
> (3/16") 304 Stainless. Any gut feeling on whether or not this would
> be thick enough to make a reasonable fire pot?
I prefer to build my own tools too, you can customise them for what you
do, and if it breaks you know how to fix it. It just makes good sense
(imo).
There is stainless and "there is" stainless. For example I needed some
flares for some burners I was making for some friends. I went to the
local steel store (which really isn't that local), and told them what I
wanted and what it was in for.
"Ah, I think I've got some left over stainless used for exhaust pipes,
that should do the trick, and it's just an end piece so I'll give you a
discount."
"BING"
He was absolutely correct, the burners are used to melt brass and bronze
inside a crucible furnace (actually a multi use device
<http://members.optushome.com.au/charlesanderson/img/FFART.jpg>), so the
temperatures far exceed that of a forge. Absolutely no wear at all,
discolouring yes, but wear no.
304 stainless depending on whether it is 304, 304L or 304H, can
determine it's resistance to heat. You can heat these to 1120 Celsius,
above this may cause issue. If you do heat these alloys above 860
Celsius, you must not drop water onto the hot alloy, otherwise you will
crack it.
Regards Charles
Carl West
> The other alternative to making a firepot that lasts forever would be to
> make one that is disposable, cheap and easy to make. There are several
> options with this route.
One of our forges has a firepot made from the bottom half of a
single-use helium tank.
The table is a sheet of 16ga mild dropped into an angle iron frame.
There's a hole just larger than the diameter of the helium tank. I
turned the edge of the firepot out into a 1/4" flange and it sets
nicely in the table. It gets used 12-20 hours a week and lasts about 6
months before burning through just below the top edge. Cost? the time to
make the pot. We pick them up at the recycling center. A freon can works
too. When the pot burns out, you can use the top half of the tank for
the replacement.
--
Carl West
http://prospecthillforge.com : The Blacksmithing Classroom
Reduce. Reuse. Recover. Refurbish. Repair. Repurpose. Recycle.
Chilla
Carl West wrote:
> One of our forges has a firepot made from the bottom half of a
> single-use helium tank.
>
> The table is a sheet of 16ga mild dropped into an angle iron frame.
> There's a hole just larger than the diameter of the helium tank. I
> turned the edge of the firepot out into a 1/4" flange and it sets
> nicely in the table. It gets used 12-20 hours a week and lasts about 6
> months before burning through just below the top edge. Cost? the time to
> make the pot. We pick them up at the recycling center. A freon can works
> too. When the pot burns out, you can use the top half of the tank for
> the replacement.
If you wanted that to last a little longer, you could mix up furnace
cement with perlite, and build up the inner surface of that tank bottom.
It wouldn't cost too much to do and maybe last three times as long (if
not more).
Regards Charles
paul_bi...@excite.com
As a couple have mentioned here, have you considered building your
own? I have seen a great set of instructions on building a firepot
that was shown in the book "A Blacksmith's Primer" by Randy McDaniel.
Not only is the book a great resource for the firepot, it's a great
resource for teaching beginners and intermediates as well. From your
comments, it sounds like it would fit right in with the folks who are
using these firepots. As I recall, the instructions were VERY clear,
and used straight forward techniques to build the pots. Also, the book
is still available.
Hope this helps,
Paul
Carl West
Hmmm... how tough is that stuff?
Much of the use is by students, and I can't expect them to give it the
same care I would.
The problem only happens around the top edge. I've made this recent one
a little shallower than the last (~4"), we'll see if that changes anything.
The last one died prematurely because a chunk of iron melt-welded itself
into half the grate and directed the fire to one side, which burned
through in short order.
New rule: no small chunks of metal are to be left on the forge table.
Too easy to get them into the coal and into the fire.
Chilla
> Hmmm... how tough is that stuff?
> Much of the use is by students, and I can't expect them to give it the
> same care I would.
>
> The problem only happens around the top edge. I've made this recent one
> a little shallower than the last (~4"), we'll see if that changes anything.
>
> The last one died prematurely because a chunk of iron melt-welded itself
> into half the grate and directed the fire to one side, which burned
> through in short order.
>
> New rule: no small chunks of metal are to be left on the forge table.
> Too easy to get them into the coal and into the fire.
Give it a try, some cements can be chalky, the black stuff seems to be
good though. The grey stuff is pretty good too and is easier for me to
get in Australia.
The perlite makes it light.
Regards Charles