[TheForge] Sidearm burners

[Jerry Frost]

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

Meadow Lakes, AK.

http://www.artmetalradio.com/


From: "Steve Smith" <sos at alum.mit.edu>


>
>
> I'm responding to Frosty's comments, but welcome 
> replies from all.
>
> I'm still messing with burners in a very slow 
> fashion. I've made maybe a dozen Reil burners and 
> have been very happy with their performance. I make 
> the jet out of 1/8" brass pipe, aligned with the axis 
> of the burner, jet hole drilled in the brass end cap.
>
> I was pretty interested in sidearm burners when they 
> were first discussed. I followed in Frosty's 
> footsteps and experimented with a 4 way pipe fitting 
> instead of a sidearm. It was ok, but not as good as 
> the Reil burners, which I chalked up to not having a 
> smooth transition to the 3/4" body.
>

More likely you're trying to use the same size jet 
orifice as you do for one of Ron's. Try stepping it 
down about 30%, a jet ejector type burner is about a 
30% more efficient inducer. Alignment is still 
critical, no change there.

There isn't a significant difference in the transition 
from a Bell reducer to a nipple than there is a "T" or 
Cross to a nipple.

> Then I saw that Larry Zoeller had added a sidearm 
> 'kit' (all you have to do is tighten things up). I 
> bought one of these. It came with a tapered mig tip 
> for the gas jet, pretty nice setup and for not much 
> more than the fittings would have cost me. I recently 
> compared the performance of this sidearm burner to a 
> Reil burner. Both are 3/4" body with Larry's 
> stainless flares on the end. I measured with a 
> thermocouple, both in the same, single burner forge.
>
> The sidearm was almost as good as the Reil burner. 
> Final temp was maybe 100 degrees lower. This makes me 
> think that the sidearm is just an easy way to put the 
> same burner together, and less impressed with the mig 
> tip. Sounds like this isn't correct--what am I doing 
> wrong?
>

If both are properly tuned there will be no significant 
difference in performance, a neutral burn is ging to 
put out the same BTUs for the same amount of fuel. 
Tuning a sidearm requires taking into account the 
single air intake and how it deflects the propane jet. 
You need to offset the jet slightly to make up for the 
single air intake.

> I'm at maybe 300' above sea level, neither burner has 
> a choke. Pictures could be done if important to the 
> plot.
>
> Thanks,
> Steve
>

A little (recent) history may be in order:

The "sidearm" configuration for a jet ejector was 
Robert Grauman's innovation. The summer of 98 or 99 
Robert and his wife were visiting Alaska and stayed 
with us for a few days. Deb and I were in the middle of 
building the house and I didn't have much of my 
smithing stuff unpacked. Certainly not the propane 
forge, we had heaps and piles of wood so that's what I 
was using for the little smithing I needed to do while 
building.

Anyway I described the "T" jet without making sketches 
and Robert misinterpreted the description. The first 
time I saw a picture I nearly E-mailed a correction but 
reading further realized he'd made it work just fine so 
I filed it in my "learn something every day" file. One 
of Robert's casting buddies made a 1 1/4" bore sidearm 
and melts up to 25lbs. of iron at a time with it.

Another good example of well tuned sidearm burners is 
Ralph Sproul's variable volume forge. 
http://www.bearhillblacksmith.com/

Ron's criticism of the sidearm was about it's off 
center flame. This is easy enough to correct by 
tweeking the mig tip towards the air intake a LITTLE 
till the flame centers properly. It's a minor thing.

Then there's the whole mig tip for the jet thing. I'd 
given up on making a linear inducer to my satisfaction. 
Oh, I'd made a couple but they took more tinkering than 
I liked to get tuned properly so I tried a jet ejector. 
The first "T" jet. I suppose I should call it a "T" 
intake but what the hey. If I'd been smarter I would've 
gone ahead and spent the time to hunt down a pipe cross 
but having a lathe I just used a pipe "T".

What I knew from the general information I have on 
inducers is; a jet ejector will be about a 30% better 
inducer than a linear but I'm not good enough at math 
to calculate the ratios. So instead of going to all the 
headaches of drilling a bunch of pipe caps till I got 
it right, I drilled and tapped one, 1/4"-28 and bought 
a handfull of mig tips. that's when I learned a brass 
cap isn't thick enough for a mig tip to thread into 
securely so I found a brass fitting with 1/8" FPT to 
something with a hole smaller than I needed for a 
1/4"-28 tap and chased it out.

So, I spent about an hour lighting it up and changing 
mig tips till I got my first "T" jet tuned to my 
satisfaction and called it good. I still have a little 
baggie with half a dozen different mig tips. The one 
that worked was a 0.045" Miller mig tip in a 1 1/4" x 1 
1/4" x 1" pipe "T" and I'm still using it some 12 years 
later.

Having met with acceptible success for such little 
hassle I haven't bothered to replace it with a better 
one. I have made half a dozen since and fine tuned the 
"design". I've shortened the mig tip considerably to 
move the introduction of the gas jet higher in the 
intake's cross section. This improves induction 
considerably so a simple 1" x 1" x 1" pipe "T" works 
quite a bit better. This is how I made the burner for 
Rich Fizzell, host of the first (now) annual ArtMetal 
Shindig.

What I didn't realize when I started using the mig tips 
for jets was just what a genius I was. I thought I was 
doing it the easy way and it wasn't until Mike Porter 
straightened me out that I realized I was using the mig 
tips for something else entirely. <grin>

What Mikey uses the mig tips for is an "accelerator". 
Basically the same thing as the nozzle on a hose. It 
"conditions" the propane into a laminar stream which 
performs much better as it enters the burner's 
induction zone. Being a smooth conical stream (rather 
than the turbulent vortex a simple drilled hole causes) 
the propane expands smoothly and enters the the throat 
of the tube uniformly. All this increases both the 
device's induction and disperses the propane uniformly 
in the intake air column. It also allows a natural 
vortex to form in the burner tube which enhances 
mixing.

Here I thought I was being expedient (lazy) and all 
along I'd come up with a simple solution for a complex 
problem. <grin>

So, there is a good reason for using mig tips though 
they don't have to be full length. I've found 9/16" 
works just as well as full length and I'm sure shorter 
will work as well though I don't know how short is too 
short. I haven't had much time to experiment this 
winter like I'd planned.

It doesn't matter much which configuration you choose 
for a naturally aspirated burner, tuning it is what 
counts. Some (jet ejectors) are easier to tune by their 
nature but once tuned there won't be any difference in 
heat output.

Tuning is where gun (blown) burners really shine, 
they're easy as adjusting the gas valve till you like 
the fire. You have to retune every time you turn it up 
or down but it's still very easy. Building a gun burner 
is pretty easy if a lot more expensive. You simply 
plumb a blower's output through at least 1 90* turn 
with a gas fitting either in the elbow or just in front 
of it. Attach it to your forge as you like and begin 
tuning.

A properly tuned naturally aspirated burner on the 
other hand needs no further fiddling. The intake air is 
induced in a direct ratio with the propane. Turn up the 
propane psi and the air induction rises with it. The 
only time you might need to choke a properly tuned 
naturally aspirated burner is for lighting. I simply 
put a palm over one of the intakes on my "T" jet and it 
lights right off. It'll light anyway but it sometimes 
blows the newspaper out of the forge before it lights. 
Like THAT'S a big problem. <grin>

I haven't put an electronic igniter in it though one is 
on the board for my next forge.

Frosty