[TheForge] propane forge

Sun Sep 1 13:54:01 2002

As has been pointed out already, propane or any fuel for that matter has X
btus per unit, all you can effect is efficiency. When it's reduced to the
basics, there's no difference between a gun and naturally aspirated burner.
There are pros and cons to each but not as far as burn efficiency is
concerned, either type, properly set up and operated will yield a proper
burn.

A naturally aspirated burner is a non-mechanical blower using a flamable gas
or liquid as primary pressure. We use two basic types of amplifier, linear
and jet ejector.

A linear amplifier is what we get on naturally aspirated commercial forges
and can be identified easily by looking up the bore. With choke plates,
flame holders, etc. removed you can look straight through to daylight. A
commercially built linear amplifier designed for propane/air will produce
around a 19:1 amplification.

A jet ejector is basically the same as a linear but the air intake is at 90*
to the bore and jet (the intake on a linear is in line with the bore and jet
. . .linear.) For reasons I don't undedrstand a jet ejector is around 30%
more efficient yielding around 29:1. The "mongo" burners are jet ejectors.

Those of us who build our own burners have some trouble holding commercial
tolerances <grin> so a home made linear amplifier is harder to get tuned as
19:1 max efficiency is pretty close to the 17.5:1 for a neutral propane/air
burn. It's much easier to build and tune a jet ejector with it's much higher
efficiency. You have wider tolerances to play with.

A gun burner is easier to build and much easier to tune but you have to buy
a blower and electricity, it takes up more room and is heavier. A naturally
aspirated burner can be made for $10-15 and doesn't need electricity but
takes more precision to build and is harder to tune. I spent $9.00 on the
one I'm using now and it melts steel easily but I spent a day tinkering with
it tuning.

Does it really matter if you prefer a gun (blown) or naturally aspirated
burner? There's been much heat generated on this list in the past on this
topic but it's still the same old Chevy vs. Ford debate. Both work just
fine, both have pros and cons and it's still a matter of taste and need.
What matters is how you feel and what you need.

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

Meadow Lakes, AK.

----- Original Message -----
From: "Lynn Emrich" <[email protected]>
To: <[email protected]>
Sent: Saturday, August 31, 2002 3:01 PM
Subject: Re: [TheForge] propane forge

> I'm not sure why someone would choose a naturally
> aspirated over a blown forge. The blower reduces the
> gas usage quite a bit.
> Also, I don't see a good reason to make a small intake
> for the gas. I use a 1/4" pipe supply. I suppose that
> the high pressure would jet the gas more into the
> forge but the larger opening would seem to mix the gas
> before it enters the forge body.
> Jay has been on this mail list for several years and
> his pressure regular costs less than I paid at the gas
> company.
> BTW, my guage broke over a year ago and I haven't
> gotten around to replaceing it so I guess it's not
> really necessary for me.
> Lynn
> http://www.geocities.com/theatre_weapons/index.html
>
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