[TheForge] Re: reducing fuel costs by improving forge efficiency.

Mon Aug 2 11:50:15 EDT 2004

Those measurements are about right. I basically made the thickness the same as
the fire bricks to keep things somewhat smooth. So it's nowhere near the size
of your forge, but it suits my purpose pretty well. And I'm using 3/4" burners.

When I mentioned the lamp base, that's with the lamp, candlestick, etc.,
attached. So I end up with a 3-D size that just won't fit through a 4.5 X 7
inch opening. With the ends swung up, I get an 8" height in the center.

The castable isn't hard to mold, just a lot more work than rolling out a Kaowool
blanket. The stuff is fluid until dry, not too different than concrete. There
are a bunch of pictures on my website, but basically the ends of the shell are
dammed up. Then I had to stick in a couple pipes for the burner openings and
wrap wax paper to be able to take them out later. I may have been able to drill
the holes, but didn't want to take the chance that it didn't work. Looking
back, the refractory is easy enough to carve that I think drilling would be
better.

I used a piece of Sonotube for the interior mold. This had to have cutouts for
the burner tubes. Before putting this in I filled up 2 1/2" in the bottom of
the shell. Then put the Sonotube in place and clamp to keep it from floating.
Then fill the shell the rest of the way. You've also got to work fast because
it sets pretty quickly. But somewow it stays fluid enough to float a Sonotube.

When all that is done, it takes a few days to dry and then you've got to ramp up
the heat slowly to cure it.

Like I said, it wasn't difficult, just time-consuming. Castable is a lot cheaper
than Kaowool, though. But the Kaowool would have taken me all of maybe 10
minutes to put in place, vs many hours of prep and days of waiting.

I don't know if I need the SS angle to hold it in. This was just another of
those "better safe than sorry" things. The castable seems to stick pretty well.
But is it enough to support its weight?

So when this ceiling does fall apart, if it does, I would just Kaowool it. But
if building another forge, I would stick with the tank shape and use the SS
angles to hold the blanket in. Maybe go with a bigger tank, or maybe with a
rolled sheet. I don't have a roller and couldn't find anyone to roll me a top
for anything less than $100.

As for fixing the blanket to a flat surface, I think even SS would corrode over
time in that heat. My old burner's SS flare corroded pretty badly. I wonder if
you could push some rod half-way through the blanket horizontally and attach the
ends to your frame? Considerably less heat at that point.

I haven't noticed any warping at all. And half the shell stays cold because of
the back wall. I angle the burners inwards, maybe 10 - 15 deg. That keeps the
dragon's breath pretty well down. I also have a blower that feeds in the back
of the forge, with the air directed under the forge, towards the front, and
then re-directed up across the front. I get no dragon's breath that way at all.
Only the IR radiation, once the inside of the forge gets hot. No that I'm in
the new shop, I may switch to a simple fan blowing down from the ceiling. If it
doesn't interfere with the burner operation, then that would help keep my feet
warm in the winter.

--Marc

Quoting Ralph Sproul <brhlbsmt at mcttelecom.com>:

>         Marc,  Am I correct in saying the 12" tank with 2 1/2 inches of
> insulating material leaves a 7" finished forge?   If so I see why you get
> the decent heat.
>         What size are the burners in this forge - 3/4?
>
>         What are you talking about heating a lamp base with the lid ends up?
> Does it not heat well laying down?.......or is this a three legged colonial
> lighting fixture base your talking about?
>
>         I'm curious as to what made the castable hard to mold to shape?  The
> mix is too watery and settles? or the insulation had to be affixed to the
> lid somehow? or does it just stick to the metal and you have a finished lid?
> Is there any need for stainless holding brackets at the edges?  I've never
> worked with this material so I was asking. You seem to indicate you'd go to
> Kaowool next round...........would that be blanket your thinking of? or the
> M board?
>         I find the blanket much cheaper than the board.  The board does have
> the ability to hold in a flat plane - but I'm dissappointed in the
> replacement costs when I drop something and it flips up and hits the board
> breaking it.  I have found the folded stainless edge components to have held
> up well in the lid after five years of use.  This is also mostly because
> I've kept the bricks under them so the direct flame travel is not on them
> all the time.  I"ve wondered how the Kaowool blanket in a domed lid would
> work out.  If you had stainless edges to support the arc of the blanket, and
> the blanket was coated with a reflective glaze - it would certainly be
> cheaper than the M board. (about 1/3)
>         The best option would be if you could fasten the blanket in a flat
> lid somehow to stay up and not fall in.  I wonder how stainless bolts and
> washers would hold up to the intense heat of the center of the ceiling
> panel.  Right around the burners, the ceiling gets intensely hot in my
> forge.  Thoughts on how to keep the blanket up and flat could leed to the
> cheapest option for a ceiling.  A blanket would dent or the coating might
> get broken, but it would be very easily repairable.........the M board is
> all done when it breaks and falls.  You only get to use it in smaller forges
> as replacement insulation then.
>         I'm actually thinking of making a smaller forge to accomadate the
> three half sheets of broken M board I've got since running these two units.
> Mostly I've been careful of not breaking the board, but workshops tend to
> have folks who don't pay attention to it as much.
>
>         One thing I question is how a domed lid would hold up for staying
> straight.  I had to go to 1/4 x 2 x 2 angle iron to get my lid to stay
> straight under the rising heat and not create "a curved shape" while
> operating and coming off the bricks on the end.  By this I mean the lid does
> distort and move, and the lighter angle iron I tried earlier, tended to
> curve into a shape like a rocking chair runner (not as drastic, but about
> 3/16 to 1/4" up on the ends - allowing the gasses to pass by the stainless
> full time).  I found the heavier angle iron and slotted holes for the
> fasteners worked well and allowed for the movement during operation and
> cooling.
>         Does your domed lid stay straight? or does it warp up with
> temperature?  This is another consideration in designing a floating lid.
>
>         Your sliding rear wall is a neat idea.......... I've not used one in
> my forge as the burners seem to generate so much heat I don't need to
> contain it when doing 6-8 pieces at once.  The scale build up is tolerable -
> but this could improve things.  I find the forge's "dragon breath" to be
> much less when half the pressure heads out the rear opening.........it makes
> for less heat transfer into longer parts, and less flame to singe your arms.
> I've found laying a brick flat midway of the forge allows the flame travel
> to go to the rear and still contain some of the heat for parts that don't
> pass thru.  I also use broken bricks as insulation to control the heat into
> less of the part for bending a tight radius.
>
>         I'm real curious as to the best idea for a lid shape and fasteners
> that will work with the Kaowool blanket used flat.
>         For some reason, I'm not enthused about clamped bricks.  Paul had
> run support rods thru bricks he'd put into his frame - it was a lot of work
> on drilling, aligning, etc.
>
>         Frosty's suggestion of bringing the burners in from the side is a
> good one, as it keeps the lid less complicated.  Side burners would be easy
> to mount.
>
> Ralph
>
>
>
> ----- Original Message -----
> From: "Marc Godbout" <marc at ironringforge.com>
> To: "Sponsored by ABANA" <theforge at mailman.qth.net>
> Sent: Sunday, August 01, 2004 9:53 PM
> Subject: Re: [TheForge] Re: reducing fuel costs by improving forge
> efficiency.
>
>
> > Hi, Ralph. I did use a tank. I cut the ends off of a 30lb propane
> > cylinder, then cut the cylinder in half lengthwise. The two half were
> > welded end-to-end to get my 18" length. I was going to try a bigger tank
> > and not have to weld, but these are wider than what I was going for. The
> > 30lb is the same diameter as a 20lb - 12". The next higher sizes start
> > at 14".
> >
> > I find the hinged front and back very useful for wider things like lamp
> > bases. It's much quicker than jacking up the roof and re-arranging
> > bricks.
> >
> > The castable insulating refractory seems to be holding out real well. No
> > falling rock yet :-). I also embedded some SS needles in the mix. It's
> > supposed to help hold things together when cracks happen.
> >
> > If I were to do it again, I would probably use Kaowool for the roof
> > insulation. The castable was a pain to mold. I would think the
> > flexibility, compared with the M-board, would make it withstand the
> > falling-pole problem. Maybe. But the simple cut-and-stuff would seem to
> > be a simple way to insulate.
> >
> > The weight isn't bad at all. I think the roof, without the burners, was
> > 35 lbs. That's 18"L X 12"wide (outside dimension), with 2" - 2 1/2"
> > insulation thickness. The bigger tanks would have been a bit heavier, as
> > they're 14" wide and the shell is thicker.
> >
> > As for getting a smaller insides, I've got a sliding rear wall with a
> > "mousehole" cutout for long stock. This back wall is carved to match the
> > arched ceiling. If I ever want to move the side walls in, I think I
> > would just add a brick inside, instead. But I haven't ever tried that,
> > and I'm not so sure why I would need to. The way the burners are mounted
> > I get a decent enough spot heat.
> >
> > --Marc
> >
> > On Sun, 2004-08-01 at 18:58, Ralph Sproul wrote:
> > >     Hi Frosty,  These considerations on how to build a forge
> "top/ceiling"
> > > were my
> > > head scratchers as well.  I opted for the Kaowool M board as it is
> > > hard/rigid
> > .
> > .
> > .
> > >      However, I see the picture on Marc Godbout's page of a domed roof
> with
> > > castable refractory as an insulation and it makes sense to me.  It
> appears
> > > he used a tank of sorts - and made his ends hinge up for more room to
> stand
> > > something in his forge. BUT when the lid is considered as a unit, it can
> be
> > > sealed
> > > around it's perimeter.
> > >     I think I'd leave these ends closed or welded on the domed tank
> > > approach - be it a tank or a barrel with ends - and thus
> > > solve the "sealing the ends" problem when moving in the bricks.
> > >
> > --
> > Marc Godbout
> > http://www.ironringforge.com
> >
> > New England Blacksmiths Membership Director
> > http://www.newenglandblacksmiths.org
> >
> >
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