Burners 101

[Mikey98118]

Gas jet friction

I used to call MIG contact tips and the gas tubes they're threaded into accelerator assemblies, to make a point; namely that they will accelerate gas molecules far better than a hole drilled in the wall of a pipe can. it stands to reason that a longer jet will accelerate gas more than a short jet--within reason. The first practical limit we run into is over-acceleration. Yup; you can accelerate the gas up to the point that some of it is out racing the induced air it needs to burn; resulting in--of all things-reducing flames!

The second limit is do to friction. Smaller NA burners require smaller gas orifices. But friction doen't just add up; it multiples with a reduction in orifice diameter, pass a certain point. If you put a MIG contact tip between your lips and blow, you won't notice much difference between one meant for .030" welding wire and  .035" wire. Both of their orifice sizes are several thousandths larger diameters than their call-out sizes.

The smallest MIG tip is a .023" call-out size; but its actual orifice size is 0.031" which is just a little large for a 1/2" burner size with most burners. Not too large, but not just right either. Recently I found 1/8" OD stainless steel capillary tube with 0.027" orifice diameters, which is only one thousandths of an inch smaller than what I think would make an ideal gas jet for 1/2" burners.

For gas jets on 3/8" burners I use SS capillary tubes with 0.020" orifices. I still remember how much force it took to blow air through  one inch of that tube; about the same as it takes to blow air through twelve inches of tube with an orifice diameter of 0.027"; seven thousandths of an inch reduction in diameter makes that much increase in friction in these small diameters.

Friction can also be your friend. Because friction is so great at 0.020" ID, I could use fine sandpaper to fine tune the perfect gas jet for 3/8" burners by shortening them a few thousandths of an inch at a time.

 

[671jungle]

2 hours ago, Mikey98118 said:

Gas jet friction

Very helpful write up! Thank you

My 3/8" uses a .020" orifice dispensing tip wedged in a .025 mig tip per your tips in previous writings. It works like a dream. So much so that I am considering using three 3/8" burners for my small forge.

[Mikey98118]

Ah, but were are the photos? We live for photos; hunger for them...

It is much more encouraging for newbies to see the magic flame coming out of your home built burners than any of mine.

[671jungle]

2nd pic looking down intake.

3/4" mikey intake - tapered 1/2" spacer - to tapered 3/8" barrel.

3rd pic looking up into nozzle.

3/4" nozzle - tapered 1/2" spacer- 3/8" barrel.

4th pic 20ish psi choked up but runs fine and lean with open choke.

5th pic 1-2 psi. Doesn't backfire until barely 1psi and hot.

This build was a lot easier than I thought other than the hours of filing to get everything press fit together. With proper tools or better matched up O.D. to I.D. which is available online, it would be a lot easier. Aside from the build itself, proper stable jet alignment and length are the only other things to get right. I also sprayed some clear coat paint(kydex) down the intake to smooth out the handfiling work. 

Thanks y'all

[Kandar]

14 hours ago, Mikey98118 said:

The first practical limit we run into is over-acceleration. Yup; you can accelerate the gas up to the point that some of it is out racing the induced air it needs to burn; resulting in--of all things-reducing flames

I noticed this happening with my burners before.   You can actually smell the propane  dumping out of the forge if i drop a choke slide wide open.

I ended up using a much larger gas jet.  Im using 0.035s with an  unmodified bore. I only run at 4 to 6psi usually with the step nozzle pulled back to 1 1/4.  It gets hot faster than ever before and more importantly the burner is no longer fussy.  It just runs well.  As long as i can optionally eliminate any dragons breath on command im happy.

[Mikey98118]

There is a lot to take in there; you gave more than I bargained for! First of all; YUP; that's the magic flame all right, which means that every thing you have to say about your burner is important for other builders to hear.

Also, I like how you used a larger air chamber on the burner, to ease construction problems, which tend to mount up with small burners; very practical of you 

8 hours ago, Kandar said:

  As long as i can optionally eliminate any dragons breath on command im happy.

You have it exactly right, Kandar. Everything "burner" is all about flame control. And, everything "forge" is all about heat control

[Mikey98118]

Materials lists for miniature gas tubes and jets for miniature burners

1/8” nipples actually have .405” outside diameters; that starts becoming overlarge for gas pipes as burner sizes drop below 1/2” so smaller MIG tips in smaller gas  tubes becomes the obvious next step to take. Smaller MIG tips with 10-24 thread can fit into actual 1/4” outside diameter tubing with 0.180” inside diameters. The reduction in tip and tube sizes serve small burners better.

 

 0.250” outside diameter by 0.180” inside diameter seamless tubing has .035” thick wall that will except 10-24 internal thread, and 1/4-32 outside thread at the gas tubes other end; you can buy it in #316 stainless steel ($2.87 and shipping for one foot length): Onlinemetals.com  

 

0.250” X 0.180” #304 stainless steel tube $2.41 and shipping for one foot length): Onlinemetals.com     

 

Or you can buy it in DOM mild steel tube ($2.95 and shipping for one foot length):  Onlinemetals.com    

 

 MK Products 621-0001 series MIG contact tips are used in their Cobra® MX (262, 266), Cobramatic®, Cobra® System III, Cobra® MX Fronius MIG guns; they are 1-1/2” long, including threaded section; they thread into a 12-24 tapped holes. The shorter MK 621-0393 series MIG tips also thread into 10-24 threaded holes for .030” and .035”

 

Lincoln also makes spray-arc contact tips that are compatible with MK Products; they are 1/4” diameter, and use 12-24 thread, are 1-1/2” long including threaded section; and are called PX-621-001 for .035 wires (.044” orifice); PX-621-003 for .045/3/64” wires (.060” orifice); PX-621-076 for .030 wires (.040” orifice); PX-621-0325 for .030 wires (.036” orifice).  

 

Lincoln also makes compatible short-arc contact tips in PX-621 ; they use 12-24 thread, are 1-3/4” long including threaded section; and are called PX-621-002 for .035 wires (.044” orifice); PX-621-077 for .030 wires (.040” orifice); PX621-0286 for .045/3/64”  wires (.060” orifice).

    There isn't enough thickness in the recommended tube to run internal and external thread in the same areas; nor do you need it. Internal thread at one end of the tube can hold the small MIG tips, while external thread at the tube's other end can screw into hose barbs or other gas fittings, including a needle valve (or even a pipe cap that you drill and thread with an internal hole to match the gas tube thread with) to create a smaller version of the standard gas assemblies I've recommended for twenty years. The external thread can be extended for most of the gas tube’s length, simply stopping short of the internal thread for the MIG tip to use the Gas tube on a miniature linear burner's reducer fitting.

    These materials and tools allow you to create miniature gas tubes and, with the addition of capillary tube in the MIG tips, miniature gas jets. Why should you care? Aside from keeping these parts in keeping with the smaller burners they will power, smaller diameter gas tubes create less turbulence in  the gas stream as it passes into the MIG tip, allowing a shorter gas jet to do the same job as a much longer tube made from a larger pipe.

 

Caution: Gasket seal, or thread-locker will make machine thread gas tight; don’t forget it, even on pipe thread.

 

    Finally, for 3/8" and smaller burners a short piece of capillary tube inside one of the longer MIG contact tips (1-1/2") can, when desirable, become both gas jet and gas tube in itself; doing so forces you to carefully position the air openings, as the accelerator cannot be re-positioned to find the sweet spot. For instance, you would do best to use the standard configuration in a 3/8" tube burner, while you would be better off extending the external thread for linear burners, and use the capillary tube in a long MIG tip threaded directly into the original fitting when re-purposing an air/propane canister torch into a high power burner.

[Mikey98118]

Homemade parts vice

If you don’t have a vice, you  can clamp two pieces of two-by-four wood together and drill a hole between them about the same diameter as the burner’s mixing tube; if the hole is a little smaller than the mixing tube, your make shift clamp will still work, allowing you to conveniently position burner parts on a table, so that you can sit in a chair to do your drilling, cutting and sanding with reasonable safety.

[D.Rotblatt]

On 2/28/2019 at 10:06 AM, 671jungle said:

4th pic 20ish psi choked up but runs fine and lean with open choke.

I've got a few Mickey burners, so I have a question about the jet placement since your burner is working so well.  Looking at the 4th pic, I don't even see the jet and the choke is most of the way up.  Is it all the way back aligned roughly with the rear of the air openings?  I always thought the jet should be further forward, just before the front side of the air openings.  So my questions is; is this a function of the small size of the burner?  How does it work with the jet further forward?

thanks

[671jungle]

1 hour ago, D.Rotblatt said:

I don't even see the jet and the choke is most of the way up.  Is it all the way back aligned roughly with the rear of the air openings?  I always thought the jet should be further forward, just before the front side of the air openings

This is similar with the beveled choke so far up acting like the start of the throat. However the jet does like to be further back. I wonder if the much larger air chamber has something to do with it. Also the jet is pretty long. Trimming it back may allow it to be placed closer to the throat. I made another to play with. With some tweaks. The next one will have shorter slots further back on the chamber. Don't mind the galvy, it's gonna have a bath. 

[Frosty]

Jungle: I wince every time I see your supply tube sticking so darned far out of the burner! I understand you need enough to adjust but in the last pic you could advance the jet through the burner and part way across the forge! This makes it just WAY harder to keep everything aligned.

Frosty The Lucky.

[671jungle]

5 minutes ago, Frosty said:

This makes it just WAY harder to keep everything aligned.

Yes it does! Since I didnt know exactly what i was doing I made it a bit long (way too long)! The final burners will have same dimensions all round and a different jet setup. There will be three 3/8" burners in that half a helium tank forge. The copper tubing as a jet connected straight to the gas is tough to get accurate as one piece. I was thinking of employing your Frosty T jet setup as it is threaded solid into the head of the burner eliminating the mechanical stress and use hoses to connect. Any tips? 

 

1 hour ago, Frosty said:

the last pic you could advance the jet through the burner and part way across the forge!

This made me chuckle.

[D.Rotblatt]

2 hours ago, 671jungle said:

However the jet does like to be further back. I wonder if the much larger air chamber has something to do with it.

Putting so close to the rear may restrict/slow the gas or air flow.  The whole point of using the tapered MIG tip is to accelerate the gas speed which, I believe, then pulls air along with it.  Perhaps your larger air chamber is allowing too much air in...maybe slimmer slots and only 3 instead of 4.  You could try that on your next and always make them bigger if you like to tinker.  Just a thought, it's working as is, so if it ain't broken...

[Frosty]

1 hour ago, 671jungle said:

Any tips? 

If you still want a slide adjustment you can't do it the way I did. How about just shortening the tubing so only . . . (whatever distance you might have to adjust the jet) length is sticking out. Then put a 90* elbow fitting on it so you can have your hose hanging straight down instead of levering against the fittings? 

16 minutes ago, D.Rotblatt said:

Just a thought, it's working as is, so if it ain't broken...

Tinker?       

Thank you SIR! I rarely get as delicious a straight line as that one handed to me that way. It's a DOOOOOZY!

Seriously I had my response to Jungle written and edited, but scrolling down to hit submit I saw your reply and had to stop till the laughter slowed enough to type. I've still had to edit this 4 times.

Frosty The Lucky.

[Mikey98118]

Over the years on this forum I've learned not to argue with success; any burner that can make the magic flame already is a success. The guy has nowhere to go but up from here, and he is doing it with a design that is bound to be easier for others to build than mine, so all I've got to say is "bravo"! I hope he keeps on experimenting.

[Frosty]

I don't have anything to add to his results but I believe I can assist with the build itself.

I'm loving seeing so many guys experimenting with burners and seeing some really fresh ideas. 

Frosty The Lucky.

[Mikey98118]

Yeah; the last two years have been a wonder; I had given up after waiting so long, but now they really rock! 

[Frosty]

I think it just took a few people making the things and having to correct mistakes publicly then they started playing with their own ideas. I'm just hoping someone comes up with something easier to make than the T. Retiring the design would put a big grin on my face.

Frosty The Lucky.

[Mikey98118]

There will me no grin that way; if someone had come up such a design last year, you would spill be answering "T" burner questions into our nineties.

On 3/4/2019 at 5:44 PM, D.Rotblatt said:

However the jet does like to be further back. I wonder if the much larger air chamber has something to do with it. 

Yup; you have probably hit the nail on the head. Normally, we are all looking for maximum air inducement. But that coin has two sides; it can also be used to lesson air inducement. With some of the burner designs coming on the scene nowadays, we may be looking at the opposite sides of quite a few coins; an embarrassment of riches none of us would have considered likely twenty years back

[671jungle]

 

On 3/4/2019 at 7:11 PM, Frosty said:

If you still want a slide adjustment you can't do it the way I did. How about just shortening the tubing

Once it is in the sweet spot adjustments shouldn't be needed?

I think I have found a stable way to secure the jet but doesn't leave room for adjusting. 

It just so happens the 1/4" flare unit slides snuggly into 1/2" pipe, which then slides snuggly into the end of the 3/4" chamber. .

On 3/4/2019 at 6:44 PM, D.Rotblatt said:

Putting so close to the rear may restrict/slow the gas or air flow.

I made another 3/8" with the same dimensions as the first 2 except for a shorter air chamber with shorter and narrower slots. It still needs beveling and such so haven't tested.

 

9 hours ago, Mikey98118 said:

Normally, we are all looking for maximum air inducement. But that coin has two sides; it can also be used to lesson air inducement.

 I am trying for maximum induction that could be controlled by the choke but not so much that the extra air is useless. I guess there wouldn't be a flame if it was that lean. But I figured I'd get rid of dead space/length.

Thanks for the input everyone! 

I feel an addiction setting in.

[Another FrankenBurner]

5 minutes ago, 671jungle said:

I am trying for maximum induction that could be controlled by the choke but not so much that the extra air is useless

If you induce that much extra, so long as proper mixing is happening, it's time for a bigger jet.  

6 minutes ago, 671jungle said:

I feel an addiction setting in.

There is a reason that Burners 101 is at 59 pages.  Welcome to the club.  Hi, my name is Curtis, and I have a problem.

 

You could try the split bushing method of holding the 1/4 inch accelerator.  It seems to work well for the burners which use it.

[Frosty]

1 hour ago, 671jungle said:

Once it is in the sweet spot adjustments shouldn't be needed?

I think I have found a stable way to secure the jet but doesn't leave room for adjusting. 

It just so happens the 1/4" flare unit slides snuggly into 1/2" pipe, which then slides snuggly into the end of the 3/4" chamber. .

Once you have the fuel air mix tuned you don't need to change it. PSI changes just turn the heat up or down, induction remains the same. 

If you can center the flare nut in 1/2" pipe securely then use set screws to secure the 1/2" pipe in the burner tube. You can lose all that plumbing hanging off the burner! 1, (ONE ONLY!) 90* fitting so the propane hose hangs down rather than sticking straight out and you're golden. Just close the choke when you shut it down will prevent chimney effect burning the hose.

SWEET Brother you're there!

Frosty The Lucky.

[Mikey98118]

5 hours ago, 671jungle said:

I am trying for maximum induction that could be controlled by the choke but not so much that the extra air is useless.

Not only do "circumstance alter cases," but none of us is immune frp, the influence of others. When I started out, people whined about all of the controls on my burners, so that I fell into the habit of changing design characteristics to down play how much impact their chokes had on the flame. Between your burners and Another Frankeburner's, it looks like it may be time to rethink that habit of thought

[671jungle]

Thanks for the help and encouragement along the way. This pet project means a lot to me. Mike, Frosty and others have been a huge contribution. Also the new ideas from AnotherFrankenBurner keep interest fresh while projects are on hold.

Latest design seems to be a success. Shorter chamber and intake slots allows jet to be closer to throat reducing wind interference. Thanks D. Rottblat!

It like it's siblings is smooth throughout the psi range (1-25).

 

 

[Mikey98118]

Well done

Of course, if a guy really wanted to break new ground, be would use the construction aese of this design to try a 1/4" burner...

Oh, that's low; you bad old Mikey dog! What point could there possibly be in such a burner; well I had previously thought the answer to that would be "none"...but, looking at your burner, and remembering what I now about burner flames, tapered flame retention nozzles, and propylene fuel, the three factors could be combined to make a very handy air/fuel torch.