[TheForge] Re: Gas forges (burner adjustments)

Wed May 8 19:35:06 2002

Hi Ike:

I don't remember if I replied to your post but don't think so. Also I
normally wouldn't be getting back till thursday or friday night but I have
an infection in a toe and being diabetic have to take it pretty seriously so
I'm hanging out, keeping off my feet, taking my antibiotics and checking
E-mail.

You have a huge forge, close enough to 4,700 cu/in as makes no difference.
To reliably get welding heat in a naturally aspirated propane forge the rule
of thumb is 1 ea. 3/4" burner per 300-350 cu/in. In your forge this would be
13-16 ea. 3/4" burners. A 1" burner has twice the output of a 3/4" burner
but you'd still need 7-8 of them.

My advice at this point is make a smaller forge unless you REALLY need the
volume. Even if you do need the space I'd make a couple forges rather than
try using one so large. If I needed one 19" long for heat treating blades
I'd make it about 4-5" dia. and manifold a number of 1/2" burner nozzles to
it from a couple 1" Jet Ejector type inducers. Then build a 12" dia. 12" or
so long forge for scrolls and other large volume things.

It's been my experience I can't hand work more than a few inches of stock at
a time unless it's a twist, scroll, etc. Most of the time my 6" dia x 12"
forge with 4" x 6" openings at either end works just fine till I bend
something then I can't get it back in. <sigh>

One reason blown (gun burner) forges boast low gas supply pressure is
because of the diameter of the supply line. The larger the supply line, the
less pressure you need to supply the same amount of fuel. Gun burners are
easy to make and tune but tend to be more expensive to build and are tied to
a power source. Naturally aspirated burners are cheap, I have less than
$9.00 in my latest and it'll melt steel in my little forge but they're
harder to get tuned.

I'm presently working on a forge based on Ralph Sproul's new design. It's a
departure from the clamshell design. There is a fixed refractory table with
fire brick sidewalls and a refractory lid. The lid is mounted to a jack and
can be raised or lowered as needed. The sidewalls can be moved in or out and
up or down as needed.

What I'm doing is using 2 1/2" of the ends of a 55gl. drum for table and
lid. I've rammed up the table but am still working on burner placement for
the lid. I'm EXPERIMENTING with home made insulating refractory for the
backer. It's made up from perlite and fireclay without waterglass, furnace
cement or any of the other possible ingredients. The part meeting the fire
directly is rammed up using a 4,000f high phosphate refractory that is
unfortunately unavailable anymore. I'm going to ram up sidewalls in the same
manner.

I'm going to form the final burner nozzle flares from the 4,000f rammable
refractory so they won't burn off. As people are getting burner efficiency
up they're finding they can't keep nozzles on them and refractory is much
cheaper than jet or rocket engine alloys would be. <grin>

The basic chamber is going to be 8" x 8" x 8" with 4 ea. 3/4" burner nozzles
on a 6" square pattern, driven through a manifold by a 1" jet ejector type
inducer. Okay, that's easy enough but the trick is going to be the outer
burner nozzles.

I want to put the outer 4 burner nozzles 16" apart, 45* off the main/inner
burners. The trick is going to be valving them so I can use them in whatever
combination I need. If I can pull it off I can have a forge chamber as small
as 6" x 6" x 2" h. to as tall as 20" without remounting the jack, expand it
to 18" x 18" up to 20" h., make it 6" w. x 18" l. up to 20" h. or any
combination in between.

That's probably enough rambling for now. <grin>

Frosty
------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Sunday, May 05, 2002 12:11 PM
Subject: [TheForge] Re: Gas forges (burner adjustments)

>
> I know that I have been a lurker and Haven't posted anything in a while
but
> here goes.
>
> I have used an old home made propane forge that is 19" long and 13" dia.
with
> 2 atmosphere burners. It was originally made for making long blades. It
has a
> number 60 dill hole in the tips. I can't get to welding temp but I can get
my
> heat up and keep stuff workable i.e. 10 1/2" square HR stock in it at one
> time. I usually am set at about 10 psi at start and drop to 5-6 psi after
it
> warms up.  I have had very few problems with it and I like it as a base
> forge. I have seen blower assisted gas forges that can almost melt steel
in
> it and use about 2-3 psi on it. I have seen those forge weld all day long
and
> after the day was done they replace the fire brick and continue to work.
>   I have also seen small 8" long and about 8" dia. atmosphere forge heat
s-5
> and s-7 stock up to heat and put into a 25# little giant and forge them
down
> to punches and other tools.
>
> I have not cleaned my tips in my forge for about a year. I have not had
any
> problems with it except for my tips that come through the kaowool.  I
ended
> up drilling a hole and putting a screw in and the tip of the screw melted
off
> in about 20 hours of burning.
>
> A lot of us here in AZ use propane due to pollution problems here. Most of
> the forges are blower assisted types. I think that the style came from
> someone putting a drawing in a blacksmith newsletter. I have a copy of the
> drawing in a book published by the AABA from stuff published by ABANA
chapter
> newsletters.
>
> I use a 10x15 tent frame with silver tarps for my roof to keep the sun off
of
> me. No walls in the summer. Work at night if possible.
>
> I am a hobbyist blacksmith.
>
> Later Ike
> Pan's Forge
> But it is dry heat.
> _______________________________________________
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  [email protected]
> password:  anvil
> ___________
>
>