Subject: side draft hood

From: [email-masked] (Vince Herod)
Date: Thu, 8 Aug 1996 16:56:42 -0500

Hello all,

Today's equipment question is about side draft hoods.  I am building one so
that I may use my forge and have the exhaust go out through a built in
system that is already in my shop.

The only picture I have to work from is the hood in Centaur's catalog.
Does anyone have any pointers for building this type of hood?  It seems
simple but that usually means it's not.  Are these good deminsions?  How
close to the firepot should the hood be placed?  Any tricks of the trade?

As always, many thanks!!!!!!!

Vince Herod
Spotted Dog Forge

******************************************************************************
Vincent Herod, Metal Shop Supervisor     Phone:(512) 471-0662
Performing Arts Center                   Fax:  (512) 471-3636
University of Texas at Austin            E-mail: [email-masked]
P.O. Box 7818,Austin, TX 78713-7818      Campus: PAC 2.208 E3300

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From: "Dr. Mark E. Williams" <[email-masked]>
Date: Fri, 9 Aug 1996 11:28:28 -0400

As I recall, an early Anvils Ring had an article on side draft forges. Pre
1990, but  I don't recall exact issue.

Maybe someone else could help.

Mark

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From: [email-masked]
Date: Fri, 09 Aug 1996 17:08:35 -0700

Anvil's Ring Volume 7 Number 1 the March 1979 issue has an excellent
plan for a side draft chimney.  I had a sheet metal one made to the
dimensions of the inside of the one shown, worked just as well.  I think
the bill was 100.00.  (or as he really said  "a hunnert bucks auta do it"
  The article was written by Dimitri Gerakeris, (who else?)
  Today, the same hood in sheet metal will doubtless be more expensive.
  By the way, don't scrimp on the "smoke shelf" part, it really makes
a lot of difference.
  Bob

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From: Michael Spencer <[email-masked]>
Date: Fri, 9 Aug 96 22:59:14 EDT

Bob ([email-masked]) wrote:
> dimensions of the inside of the one shown...

Yeah. This is what I use, too. With an approx. 13" round flue about
12' tall on top, it draws ok except when the wind comes across the
church across the street. Then the turbulence around my shop can make
it draw backwards for 2 or 3 seconds at a time. Made the first one out
of 16ga and it rusted out in about 10 or 12 years. The present one is
a notch or two heavier. If I wuz a little brighter, I'd use stainless
next time. :-)

Someone asked earlier about preheating air. On the previous hood, I
has a light sheet metal shell around the body of the thing and my
blower air intake connected to it -- a crude heat exchanger. Seemed to
improve the fire when the shop was hovering around mid-winter ambient
(say, 10 or 20 deg. F or colder) but I never did any accurate
measurements. (The new hood came out a tad bigger and I haven't taken
the time to refit the exchanger shell.)

- Mike
-- 
Michael Spencer
[email-masked]
URL: http://www.mit.edu:8001/people/mspencer/home.html
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From: [email-masked]
Date: Sat, 10 Aug 1996 16:48:07 -0700

Mike,
  What a terrific Idea!  My blower/forge would lend itself to a short,
3 foot chuck of stainless flex tube from the chimney down to the intake
for the blower.  Will try that, it makes sense.
  Also, I looked at my blower a little more closely this a.m. and it's 
a champion 400!  The gears are so pristine there is virtually no play
between a clockwise and counter clockwise wiggle, and it has a provision
to run it from a line shaft.  Two 6" diameter wheels, one fixed to the
shaft and an idler.  The casting for the extended shaft, bearings, grease
cup etc. seem to be stock, since they fit precisely and would work if
I had a lineshaft.  But the drive would have to be very slow, no more 
that a fraction of an r.p.m. or it would blow everything out of the 
pot.  There is a homemade airgate under the blower made from a piece of
tube and an old car piston.  The piston is bored dead center for a bolt
that runs out the back of the tube to a lever, it too would work, but
several years of idleness outside, have frozen it solid.  At least it 
froze in the full open position.  When I bought the forge, the pot was
on top, and there was a four inch tree growing up out the center hole.
It was a trick to get it home, but I am really happy with the find.
   Thanks for the tip about recycling heat, will try it this winter.
  Bob

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From: Jim McCarty <[email-masked]>
Date: Mon, 12 Aug 1996 08:47:09 -0500

> the time to refit the exchanger shell.)

Mike,
Perhaps your chimney isn't tall enough? My brother had this problem 
with his masonry forge. He added three feet to its height and it 
pretty much stopped. Seems like the rule of thumb is 2 feet higher 
than three feet away...
-- 
Jim McCarty
Father Helias Forge
Taos, MO
Editor Rural Missouri Magazine
Newsletter editor, Blacksmiths Association of Missouri

³Foolish consistencies are the hobgoblins of little minds³

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From: Michael Spencer <[email-masked]>
Date: Mon, 19 Aug 96 12:01:35 EDT

>>>  ...side draft chimney.  I had a sheet metal one made...
>>
>> it draw backwards for 2 or 3 seconds at a time.
>
>Mike,
>Perhaps your chimney isn't tall enough? My brother had this problem...

Likely so. But it's a funny configuration. My shop is a shed roof --
pitch about 1:5 -- with fasle walls at the ends to make it look like a
flat roofed building (except from the back). A hundred feet from one
end is a church maybe 50' or 60' high with a maybe 90' steeple. When
the wind blows from the church direction and over one of the false
walls, what happens around my shop is somewhat bizarre,
atmospheric-pressure-wise.  (When the wind is from the sea, I gotta
lash the cat to the swage block or he gets sucked up the flue from
clear across the room and the neighbors, accustomed to coal smoke,
complain about the odor of singed cathair.:-)

But yes, maybe an extra 3' or 6' would help. Or maybe not. But damn!
Those 13" glass-lined water tanks have gone out of style and I dunno
where I can get an extension! ;-)

- Mike

-- 
Michael Spencer               (902) 543-8375
[email-masked]
URL: http://www.mit.edu:8001/people/mspencer/home.html
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From: Ralph Snel <[email-masked]>
Date: Tue, 20 Aug 1996 9:46:05 METDST

> where I can get an extension! ;-)

That's a bit narrow, don't you think? I have a 2 ft ventilation shaft,
the kind they have in stables. Not side-draft though, but it sucks big
time :) (The top extends to above the highest part of the roof)

Ralph Snel
[email-masked]