[TheForge] photos under "inexpensive recuperative forge"

[Jerry Frost]

No sweat Mike.

I recall your concern for the burner nozzle from the 
last discussion and thought I'd addressed it but may 
not have. I get distracted so easily any more. <grin>

Today for instance, I've been plugging away on my shop 
for about three summers now and today when I went out I 
spent probably an hour and couldn't come up with a 
single thing to do except start hanging the skin on it. 
Talk about a distraction! <grin>

Anyway, a burner in an induction circulation 
recuperative wall furnace (man is that a clumsy mouth 
full!) is no more vulnerable to excess heat than a 
single wall furnace. The nozzle, flare, etc. doesn't 
extend into the gap so it has the outer wall for 
protection. In fact, temps in the gap will be well less 
than in the furnace chamber so nozzle life should be 
significantly better.

If the burner port in the outer furnace wall is made 
with a 1:12 taper, if you use a flare at all, then the 
burner tube can be mounted to the exterior shell with a 
pipe flange and there is so little heat effect as to be 
nonexistant.

Here's another plus to add to the list of reasons to go 
to all the hassle of making a double wall forge. In 
addition to greater heat and fuel economy, 
recirculating the exhaust gasses will eliminate any 
excess oxy in the forge chamber. This means we can run 
the burner closer to a neutral air/fuel ratio and 
maintain a carburizing environment.

So, here's my list of plusses. Recirculating exhaust 
(semi-burnt air/fuel) through a gap in a double wall 
furnace rather than exhausting it directly out of the 
furnace:

#1 Keeps fire in the chamber longer for greater BTU 
exchange. (Economy)

#2 Fire heats both sides of the inner wall so the 
absolute temp in the furnace chamber is higher. 
(Efficiency)

#3 Fire temperature in the gap is lower than normal 
forge temp so there is less heat loss through outer 
liner and shell. (Economy)

#4 Excess oxy and fuel is consumed completely allowing 
leaner mixture to the burner without creating an 
oxidizing environment in the forge chamber. (Economy)

    4a. More neutral air fuel mix to the burner means 
less CO and other noxious exhaust products. (Health & 
Safety)

    4b. Reduced dragon's breath. (Comfort & Safety)

#5 Greatly extended burner life. (Economy)

#6 Last (That's occured to me anyway) but not least; 
much quieter operation. The gap is a natural and 
integral muffler. (Comfort, Health & Safety)

The real downside of building a forge like this is the 
extra hassle but seeing as I build double lined forges 
anyway, what's the big deal about putting some space 
between them. <grin>

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

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Michael" <michael.a.porter at comcast.net>


> Frosty,
> OK, we will call induction method one, and the other 
> three can move down the
> desirability scale. I had forgotten induction, 
> although you had gone into it
> thoroughly last summer. It is hard to believe this 
> conversation is a year
> old! I didn't like induction at the time, because of 
> the probable increased
> heat gain in the burner, but that is because I'd 
> forgotten about cast
> refractory burner nozzle/mixing chambers. It wouldn't 
> be so bad; becoming
> vague, if the fuzziness also applied to "my most 
> embarrassing moments."
> Alas, they still come back in full Technicolor (and 
> then some >:-)))
> Mikey
>