[TheForge] burner adjustment

Fri May 3 21:21:02 2002

Hi Andy:

Sorry for the slow response but I have a long commute and only check E-mail
on my weekends.

Anyway. What you describe is exactly why I no longer parrot the jet
placement ratio as it's presented in the papers I have from various
manufacturers. After I discovered the placement ratio I was giving didn't
work very well I looked into it a bit further and there are so many
variables involved I just started moving it around till it burned well.

For conversation's sake this is the ratio I was given. The jet should be the
bore radius before the bore. Using this ratio for a 1" bore the jet would be
1/2" in front of the bore.

However, even making inducers as alike as I can the jet position which works
the best varies quite a bit. I've also found that varying the diameter of
the jet will change it's optimum position. SO FAR I've found that the larger
the jet diameter the further into the throat it needs to be.

As I mentioned earlier I prefer a smaller jet diameter running at higher
pressure to aid air/fuel mixing. This puts my jets closer to the "factory"
recommended placement and increases the need to choke for a neutral burn.

I personally like an inducer I have to choke for a few reasons:

First adjustability. In Alaska I get to experience some pretty wildly
varying temperatures and humidities. The colder the air the denser and dryer
it is requiring more choke.

Second it puts the inducer under a vacuum aiding air/fuel mixing.

Third it's a stronger drawing inducer and as I manifold to multiple burners
per inducer this really helps.

Last and least important I kind of get a kick out of hearing them roar.
<grin>

Recently I've had enough spare time to start playing around with inducers
again and have refined some of the inducer hardware, especially for the
jets. I use all-thread lamp rod for the rigid gas supply in the inducer
itself, it's handy as it's 1/8" - 27, IPT which is straight rather than
tapered pipe thread. You need a 1/8" pipe tap to chase plumbing fittings and
need to exercise some care as the tapered tap will tap the hole oversized
and make the lamp rod sloppy. If you can find the 1/8" IPT tap by all means
get it as it'll save time.

After fitting the lamp rod to the inducer body the next little challenge is
fitting a jet to it. I used to weld a 1/4"-28 nut to the end and grind it
smooth but wasn't happy with how hard it is to align properly. Now I simply
use a 1/8" mpt - 1/8" compression coupler chased and tapped for 1/4" - 28 on
the compression side. I'd use 1/8" fpt - 1/8" compression couplers if I
could find them. I use the shortest mig tips I can find for the jets
themselves and drill them to size.

One of my recent experiments was to use a 1" cross, bushing one end to
chased 1/8" pipe on a 1" x 8" tube with an unmodified 0.045" mig tip as the
jet. The jet placement was a good 1/2" down the throat and it draws poorly
but provided a nice neutral burn from 25psi to lower than my gage reads
without choking. Unfortunately it doesn't draw strongly enough to be stable
if there's a breeze blowing. It also doesn't burn outside the forge but this
is okay with me.

I picked up a pack of 0.035" mig tips and will start sizing them probably
tomorrow. I would've been doing it today but had to put an alternator in the
wife's Bronco and I don't want to overload my weekend schedule. <grin> Oh
okay, I'm still ankle deep in mud in my present tarp tent "smithy". <sigh>

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

----- Original Message -----
From: "Gladish Family" <[email protected]>
To: "Theforge@Mailman. Qth. Net" <[email protected]>
Sent: Monday, April 29, 2002 9:00 PM
Subject: [TheForge] burner adjustment

> So, I went to the shop and built a venturi burner.
> Playing with it mounted in a vise I found that I could get a good flame
and
> it would hold it as long as it was neutral, but that the closer to the
> venturi I moved the orifice, the more I had to choke it. To my eye, the
> quality of the flame was similar, but is there an advantage to moving the
> jet closer or farther away from the tube?
> BTW, thanks for all the great discussion and tips, Frosty et. al!
> Andy
>
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