[TheForge] Gun Burners (AKA fan blown)

[Ben Barrett]

Well I'm borrowing a 3/4" T-rex to fire my first (home-built) forge.
I'm not sure of the internal volume (but I guesstimate ~500 in^3), and
I'm running off a crappy BBQ regulator at present (but have a better,
higher-pressure one ready to be hosed up).  The forge roof is a
half-round with kaowool, coated with ITC-100 and also the ITC
finish-layer (296A topcoat), and the table (which I welded to hold a
dozen soft bricks) has one layer of softbrick holding up the insulated
half-round, between which the burner tip is injected, sealed with some
spare kaowool.  I usually kept one end closed off with soft brick,
read on below...

It was a joy to see this intial setup get me to forging temperatures,
and within 20 minutes the whole inside is glowing (IR3 helps for
examination, I took some digital photos through the lens too :) and I
can heat up pieces really quickly right in front of the burner.

I have been reading about these [venturi] naturally aspirated burners
here on TheForge, even though I already have a laundry list of tweaks
to improve performance.... well this weekend (along with selling my
first couple smithed pieces, small hooks) I was heating some pieces
from both ends, and after reading about needing *enough* ventilation
in these things, and wadding up little bits of starter paper which had
nto burnt and tossing them into the forge, I had a great AHAH:
With both ends of the forge OPEN, the wadded-up bits of paper burned
really violently & quickly, and made a large yellow flame, compared to
when one side was clased-off -- the "ahah" is that the forge is now
getting enough air, right?  Or is my flame too oxidizing if a wad of
newspaper burns that quickly?  I am running about 14psi, fwiw.

Well I need to make more tongs and hardy tools, and do the right
regulator... I think I will take out one wall of bricks, and
experiment with spiraling my flame more... I get dragons breath but it
seems unavoidable... I like the idea of venting most of the heat away
from the ends of the pieces I'm heating up, it is a pain to quench so
often (relative to working coal or coke).

I'd like to find a good high-temp thermometer, but a friend suggested
using some cheap disposable indicators to get started (they melt at
certain temps, I think)... feedback?  Really curious about the correct
amount of air/ventilation.  :)

thanks y'all!

ben



On 4/29/07, Jerry Frost <frosty at customcpu.com> wrote:
> Chuck, Robert:
>
> I'm surprised you can't get more than 2,200f from Rex
> burners. What size are they, how many are they and what
> is the volume are you heating?
>
> I figure Robert's is around 2,714 cu/in which would
> take 7 or 8, 3/4" burners or 3-4, 1" burners. They'll
> actually heat more volume but the rule of thumb of:
> "one, 3/4" burner for every 350 cu/in." is pretty sure
> to melt steel if you let it.
>
> My 1" "T" jet will melt steel if I turn it up too high,
> I don't see why a better burner wouldn't perform at
> least as well.
>
> Maybe the issue is altitude, humidity or something I
> haven't run across?
>
> The soak time is whatever it takes.
>
> Frosty
> -------------------------------
> If it ain't forged
> it ain't real.
> Wrought iron is.
> The FrostWorks
>
> Meadow Lakes, AK.
>
> http://www.artmetalradio.com/
...