[TheForge] No More Smokin' Hoods

Thu May 1 16:15:25 EDT 2008

Hmmm,  Andy's insults are less vociferous than normal.  I think I'm
being complimented!

I think the apparatus Andy refers to goes back several years to when I
had a coal forge in my garage shop.  I could only have a 6" flue, so
brought it down to the fire much as Peter recounts, and my experience
was similar - an incredible draw.  To control where the pipe was with
respect to the fire, I developed a ball-joint for the middle of the
flue.  This was two SS bowls, with holes in the bottom,  fastened
together and to pipes on either side somehow.  Frankly I don't recall
the details, but it enabled me to move the end of the flue anywhere I
wanted.

I gave this up because I live in suburbia, and now only use a gas forge.

I think simpler devices than a ball joint would work as well, but may
be more prone to leakage, reducing the draft somewhat.

This experience convinced me that folks who think a 10" or 12" flue is
essential are simply wrong.  No doubt there's an optimum diameter,
depending on the sort of fire you're making, but 6" worked fine for
me.

Bruce
NJ

On Tue, Apr 29, 2008 at 12:51 PM, Ron Childers <munlaw2 at hcsmail.com> wrote:
> We have a slightly smaller pipe (12") suspended on cables and counter
>  weights inside a larger pipe. We let it down close when starting the fire
>  and lift it up when it starts drawing. the stack is 3' higher than the
>  highest point on the roof. Works fine.... Ron C
>
>
>  -----Original Message-----
>  From: theforge-bounces at mailman.qth.net
>  [mailto:theforge-bounces at mailman.qth.net] On Behalf Of Andrew Vida
>  Sent: Tuesday, April 29, 2008 12:35 PM
>  To: Blacksmithing List Sponsored by ABANA
>
> Subject: Re: [TheForge] No More Smokin' Hoods
>
>
>
> I will note that the reason for this is because the sudden transition
>  from open air to the stack is what causes the right pressure drop.  If
>  you have a large hood that tapers to the stack opening, guess what: all
>  that air is being corralled into the same place and no drop in pressure
>  and therefore no flow...  Bernoulli 101. :)
>
>  You could probably get a little better performance if you replaced that
>  8" flue with 10 or even 12.  It should suck mo' bettah.
>
>  Bruce Freeman had a very interesting contraption set up at his forge.  I
>  will leave it to him to disclose or not, but I think the basic idea was
>  really good.  Almost fabulous, but if I go that far I'll never see the
>  end of his big head, and it's ugly enough at its current size.  No same
>  person would want MORE of that.  No insane person would either, for that
>  matter.
>
>  Trust me.
>
>  Peter Hirst wrote:
>  > Had an AHA! moment in the shop  today.  Since I got the forge up and
>  running over the winter, my special custom-designed open hood has failed
>  miserably.  It covers the entire area of the forge (2x2) and is only about
>  18" above the fire.  It tapers beautifully to an 8" adapter and is topped by
>  12 feet of 8" pipe with no cap.  Works beautifully on paper.  In the shop,
>  hardly at all.  Some smoke stays under the hood, and some even goes up the
>  stack, but mostly it just billows and swirls and spills out, even when the
>  pipe itself seems to be  drawing well.     I have noticed several times that
>  at the joint where the hood meets the pipe, it draws like crazy, and even
>  with a  roar when anything flaming is placed near that spot.  Even then,
>  smoke is going the wrong way at the edge of the hood. A lot of air goes up
>  that pipe, but it doesn't take much smoke with it. SO today, when I couldnt
>  stand it any more, out of sheer desperation I took a spare 4' section of 8"
>  pipe and inserted
>   it up under the hood at the joint into the existing 8".  That put the lower
>  end, with about a 30 degree angle at the opening, just a couple inches over
>  the fire..  As soon as I connected it, I had a winner.  The fire literally
>  roared into the 8" opening, sucking smoke from at least a 12" radius around
>  it. It may just have been because I was paying closer attention, but the
>  fire seemed to burn hotter, cleaner, and more efficiently.  Things were
>  suddenly so much better that just for grins, I got a nice clean, hot, deep
>  open coke fire going and dumped a few fat shovels full of green coal  on it.
>  No problemo.  All that thick, sickly yellow smoke -- and I mean all of it --
>  disappeared like a wisp into the stack.
>  >
>  > So now my entire hood and vent system consists of just 16 feet of 8" pipe
>  with  a 30 degree bevel at the bottom.  No side draft, no hood, no expansion
>  chamber, smoke shelf, step down, step up, 12 " flue,  nothing.  Just 16 feet
>  of pipe.   It doesn't interfere visually (in fact I can see the work better
>  than with smoke escaping from under the hood) or mechanically with the fire
>  or the work,  and if it ever does need it for a particular piece, I can
>  either swing it a few inches in any direction or remove it temporarily and
>  rely on the hood.  I was on the verge of ripping out the whole thing and
>  building a side draft with a 12 inch flue from scratch,  and investing in
>  about 12 or 16 feet more of 12" duct for the portable rig for shows.  Now
>  I'm all set with the shop, and for the portable rig,  think I'll just go
>  with the 8" pipe set about 4" over the fire, just like the shop, or maybe
>  resting right on the hearth with the end cut at 45 degrees.  .
>  >
>  > Life just got a whole lot simpler.
>  >
>  > Keziah
>  > _______________________________________________
>  > Manage membership or unsubscribe at:
>  > http://mailman.qth.net/mailman/listinfo/theforge
>  > theforge mail list group photo site is
>  > http://www.photoaccess.com
>  > Login:  blacksmithblacksmith at hotmail.com
>  > password:  anvil
>  > ___________
>  >
>  >
>  >
>
>  --
>
>         -Andy V.
>
>  no .sig
>  go .fig
>  _______________________________________________
>  Manage membership or unsubscribe at:
>  http://mailman.qth.net/mailman/listinfo/theforge
>  theforge mail list group photo site is
>  http://www.photoaccess.com
>  Login:  blacksmithblacksmith at hotmail.com
>  password:  anvil
>  ___________
>
>
>
>  _______________________________________________
>  Manage membership or unsubscribe at:
>  http://mailman.qth.net/mailman/listinfo/theforge
>  theforge mail list group photo site is
>  http://www.photoaccess.com
>  Login:  blacksmithblacksmith at hotmail.com
>  password:  anvil
>  ___________
>
>
>

-- 
Bruce
NJ