FW: [TheForge] Burner angle

Kathy keporter at comcast.net
Thu Jul 19 21:26:32 EDT 2007 

Pete,
Yes, a pottery supply store like Seattle Pottery Supply (they ship)..
Mikey

-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net]
On Behalf Of Peter Fels And Phoebe Palmer
Sent: Wednesday, July 18, 2007 10:37 PM
To: Sponsored by ABANA
Subject: Re: FW: [TheForge] Burner angle

Hi Mikey;
"Ceramic saggers" sound like a potter's supply is the place to 
check. No shortage of flesh saggers.
Has a junk stainless assembly all ready to weld save trimming the 
last part...it cut too easily...it was chromed brass!...no 
stainless substitute in sight....Damn...some days...pf

Kathy wrote:
> Pete,
> If you wish to use a ceramic material to protect fiber blanket from an upward
> directed flame, than I would suggest looking into ceramic saggers, which are
> pretty inexpensive, replaceable, and are an easy way to obtain a curved
surface.
> I have long been considering building a furnace this way.
> Mikey
> 
> -----Original Message-----
> From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net]
> On Behalf Of Jerry Frost
> Sent: Wednesday, July 18, 2007 11:10 AM
> To: artgawk at thegrid.net; Sponsored by ABANA
> Subject: Re: FW: [TheForge] Burner angle
> 
> 
> From: "Peter Fels And Phoebe Palmer" 
> <artgawk at thegrid.net>
> 
> 
> 
> 
> 
>>  aww Mikey; Guess i'll cancel my plans to picket in 
>> front of your shop then.
>>
> 
> Geeze Pete. Does that mean you're not picking me up on 
> the way? I had my sign made and everything. Oh well I 
> guess I'll drink the beer I had packed. <sigh>
> 
> 
> 
>> The reason i brought it up is that, prior to your 
>> excellent book, many naturally aspirated forges have 
>> had difficulty making a high welding heat. Many 
>> smiths have gone for blown forges for that reason.
>> I've read recommendations that owners of cool forges 
>> ( hey, cool forge dude) carefully polish the inside 
>> of their burners, fool with venturi placement and so 
>> on, all to gain some bit more flow.
>> So it always seemed to me that facing up from below 
>> would be a bit more efficient...one can always choke 
>> it down if it's too much.
>> In a related consideration, many forges pull the 
>> exhaust off the top, where the hottest gases hang 
>> out, spewing extra  BTUs
>>
> 
> I don't know how many decades commercial forge builders 
> used really poor linear inducers for their burners. 
> Most wouldn't reach welding heat at all unless you used 
> a really agressive flux. The result being the myth that 
> a naturally aspirated burner couldn't reach welding 
> heat. I wouldn't go so far as to say it lead to selling 
> more expensive gun burner forges but . . .
> 
> Anyway, the truth is a burner is nothing more than a 
> system for introducing a flamable material and air in a 
> metered ratio, mixing them and delivering them to the 
> desired location. Both gun (blown) and naturally 
> aspirated burners deliver air under pressure, that 
> result is the same either way. A gun has the advantage 
> of delivering it in a more robust manner and is less 
> sensitive to outside conditions like open or closed 
> forge doors, etc. A naturally aspirated burner will 
> usually need to be adjusted for changing conditions of 
> smaller degree.
> 
> In either case the effects of natural convection are so 
> slight as to be a zero effect variable. This isn't 
> necessarily true with the commercially produced forge 
> burners as most are made to barely do the job. They 
> simply do not have any reserve to overcome any level of 
> adverse conditions. In this case convection may indeed 
> effect performance to a noticeable extent.
> 
> 
> 
>>
>> The test, while very interesting, isn't all that 
>> relevant because you don't have 2000* of hot gas 
>> pushing up from below.
>>
> 
> 
> Actually that test illustrates the only effect 
> convection has in a forge. The burner is introducing 
> air and fuel into the forge chamber under pressure, 
> combustion causes them to expand but they're already 
> moving in one direction; towards the exhaust port 
> whether that is a dedicated port as in a melting 
> furnace or an open door like most forges. Force seeks 
> the route of least resistance; Always.
> 
> 
>>> 2. "The greater heat of the top of the forge would 
>>> cook the burner faster."
>>>
>>> The minuet the burner is shut down, interior gases 
>>> can enter the burner through
>>> buoyancy; this is called the "chimney effect," and 
>>> is prevented by closing the
>>> burner's choke completely during shutdown. While 
>>> running, the burner prevents
>>> the forge gases from entering. Refrigeration effect 
>>> from the expanding fuel gas
>>> is sufficient to keep the burner from overheating do 
>>> to conduction and
>>> convection gain from the forge body and nearby 
>>> exhaust gas. These rules apply
>>> equally to top mounted burners (the overwhelmingly 
>>> dominant mounting choice),
>>> whether they are placed at vertical down (90°) for 
>>> spot heating, or 3” down from
>>> top dead center (on a 14" diameter forge) to create 
>>> a swirl.
>>>
> 
> As Mike says so well, the only time convection is a 
> problem for a downward aiming burner is on shut down 
> when gasses super heated in the forge will rise through 
> the burner. This can burn up your gas hose but is 
> unlikely to actually damage the burner itself. Shutting 
> the choke completely or just stuffing a piece of 
> Kaowool (or whatever) into the intake eliminates this 
> potential problem.
> 
>>> Finally, why is vertical down the dominate choice 
>>> even for swirl effect? Because
>>> portable  forges use ceramic fiber for most of the 
>>> interior insulation, and
>>> placing a burner at the forge's top allows it to be 
>>> aimed directly at the
>>> firebrick or kiln shelf slab on the forge's bottom. 
>>> Should you decide to use
>>> Kastolite 3000 insulating refractory for the forge's 
>>> interior, instead of
>>> insulating fiber and a kiln shelf floor, than the 
>>> burner placement can be
>>> changed to whatever you find most convenient. Also, 
>>> solid refractory is a much
>>> better choice for multiple use forge/furnaces, or 
>>> for a forge employed in billet
>>> heating. A typical five gallon cylinder with a two 
>>> inch thick Kastolite 3000
>>> refractory lining will still be portable 
>>> (approximately 65 lb.) On the other
>>> hand the same forge built with ceramic fiber and a 
>>> kiln shelf floor can be
>>> lifted comfortably with two fingers; it's all a 
>>> question of what features you
>>> find most convenient.
>>>
> 
>> Perhaps a burner target  area of kastolite ( thanks 
>> for the reference) or kiln shelf would solve that.
>> Speaking of that, i got an old carbide kiln shelf i 
>> cut up for a floor, very durable.
>> Thanks Mikey...your answers are informed, considered 
>> and help a bunch!....pf
> 
>> Mikey
>>
> 
> Careful consideration of the target material is 
> important and a small argument in favor of tangential 
> burner placement. A flame hitting something on a 
> tangent spreads the heat over a greater area so the 
> target material stays at a lower absolute temperature.
> 
> Frosty
> -------------------------------
> If it ain't forged
> it ain't real.
> Wrought iron is.
> The FrostWorks
> 
> Meadow Lakes, AK.
> 
> http://www.artmetalradio.com/
> 
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