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Venturi Burner Help


Royal

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Hello everyone!

So we (me and my father) just tried to make one of Jarom Rush's Venturi burners (instructional video series) for our first forge (of Zoeller's design). However, I am having a few problems:

1. We couldn't find any 1 1/4" to 3/4" reducers, so we put an additional piece to decrease to the appropriate size. I assume that by deviating from the original design, we messed something up.

2. We have no adjustable PSI regulator. The one we tried to use seemed far too low for the torch to do anything; do I even need a PSI regulator?

3. When we light the flame, it doesn't seem...right. In other words, it either will not light unless we keep the flame to it, or if we turn the PSI's down the flame is too weak.

Here is the video of the forge in action without the weak PSI regulator, though you should bear in mind that this is just a quickly thrown-together pile of firebricks in a frame to test the burner. If you don't want to watch Jarom's thing, I put a list of all the parts' dimensions below the video.

IMG_1074.MOV

PARTS LIST:

Orifice hole: #57 (0.043")

Nozzle: 8" length of  3/4" black iron pipe. (We cut off an extra inch afterwards because we read some forums and thought it would help :P)

Reducers: 1 1/4" to 1" bell reducer, followed by a 1" to 3/4" adapter

- 1/4" street elbow

- 1/4" union

- 1/4" brass plug (drilled for the orifice)

Is the #57 orifice too large, or should I go with the 0.035" MIG tip?

 

I'd appreciate any feedback or fixes. I want to make this work so I can make a leaf spring karambit soon!

~ Royal

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Quick response to some of your questions:

  1. Yes you do need a regulator.  Trying to tune a gas forge without one is like trying to drive a car without a gas pedal.  Something like this one: https://www.amazon.com/Bayou-Classic-Adjustible-Regulator-Assembely/dp/B007PS0938/ref=sr_1_16?s=lawn-garden&ie=UTF8&qid=1500384766&sr=1-16&keywords=regulator (though I haven't used this particular model a 0-30 psi regulator is what you are looking for, not a standard barbeque grille regulator).  The needle valve that Jerome appears to use (haven't watched the video closely) is a barely adequate alternative to a real regulator.  In any event I strongly recommend that you add a 1/4 turn gas rated ball valve to the gas train to allow you to shut the system down quickly.
  2. The 0.043 orifice seems large to me, but that is specific to the type of burner designed.  What size does Jerome recommend?
  3. Position of the orifice in the assembly is critical.  It needs to not only be centered, but also in exactly the correct position relative to the small side of your pipe reducer.  By not using the design standard reducer you can't have it in the position the designer has developed, so will have to experiment with that location.  From your video it looks like you have too much propane and too little air to maintain a decent flame at the outlet of your burner.  Typically the solution for this is to move the orifice tip towards the burner outlet, decrease the orifice diameter, and increase the gas pressure.  Needless to say only modify one thing at a time and check the operation afterwards.  Tuning a burner is a slow iterative process.  Ideally, to have a well functioning forge you should have a burner that will keep a flame at the burner outlet at propane gas pressures varying between 5 and 25 psi.
  4. Jerome uses another reducer (actually an increaser) as a flare for his burner.  Didn't see one in your parts list.  This will make a huge difference to the gas/air mixture flow rate at your burner outlet and consequently the ability to retain a flame at the right location.  I believe that he uses stainless steel reducers at that location and I would recommend you source the same.  Plumbing supply stores, not standard hardware or big box stores are a better source for these more unusual parts.
  5. I know you said the forge is just thrown together pile of firebricks, but they have such a great thermal mass that you will likely never see forging temperatures out of that.  Not sure what you plan on building eventually, but lose those hard firebricks.
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Welcome aboard Royal, glad to have you.

I haven't built a linear burner in a long darn time and stopped drilling holes in pipes for jets before then. It's just too difficult and demanding a type for my taste. If I'm going to put that much work into a burner I'm building a Porter. 

I haven't watched the videos so I can't comment.

The major problem I see right off is using a bushing reducer to make up the 3/4" mixing tube to the 1 1/4" x 1" bell reducer. The change in diameter needs to be smooth and the abrupt and downright rough nature of a "bushing" reducer causes disruptive turbulence and inhibits intake air induction. 

Latticino's advice is solid as well. Especially about the gas regulator and 1/4 turn shut off valve. Be SURE they are rated for propane. 

Please take a look through the gas forge and gas burner sections of Iforge, there are a number of burner designs that are easier to build and work well. They're something to think about if you can't find the correct Bell reducer.

Next time please just attach photos, that was a crazy lot of bandwidth just to get a look at the flame. Videos are rarely any help trouble shooting and tuning burners. The angle is good, we can see what the flame looks like in the forge. Once we get you a little farther along we'll ask for a couple different angles to see other details but for now this is good. Just please no more videos. ;)

Frosty The Lucky.

 

 

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Update:

OK! So, I followed your advice (matched Jarom's torch exactly, got a PSI regulator, played with the air tuning, etc.) and it works now!! Here are the changes:

  1. Found the correct bell reducer at Lowe's in galvanized (that's a bad idea, I know, but we will make sure it doesn't get hot)
  2. Replaced the pipe nipple to full 8" length
  3. Got a 0-20 PSI regulator (It's weaker than recommended, but it works)
  4. Drilled holes in the bell reducer to allow greater airflow. We noticed that when we blew air into the forge with a copper tube, it got WAY hotter.

As a result, the torch heated the metal to a yellow color, which I think is forge-welding temperature(?), and made it really easy to work with. The bricks do take some time to heat up, but after 10-ish minutes at 10-15 PSI they turn to a bright cherry-red color. Now that this is solved, we will remove the top layer of bricks, drill a hole in the two remaining roof bricks, and weld the nipple to a piece of metal to go across the top and finish the frame.

Thank you so much for the help and feedback!

~ Royal

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Galvy is okay on the intake end, just plug it with some Kaowool or maybe fiberglass to prevent the chimney effect from over heating it and it won't burn the zinc off. Or you can soak it in vinegar till the galvy is cleaned off.

Good to hear it's working better. You may need to drill a smaller jet I started using mig contact tips because I got tired of redrilling the jets.

Frosty The Lucky.

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On 7/19/2017 at 9:57 AM, Royal said:
  • Found the correct bell reducer at Lowe's in galvanized (that's a bad idea, I know, but we will make sure it doesn't get hot)
  • Replaced the pipe nipple to full 8" length

Not really; in fact zinc coating. which is what "galvanized" usually means these days, is a good idea: unless the part is getting very hot. In that case, the coating can be stripped with a few hours in a pan of vinegar, or burned away in a charcoal grill. It is important not to say "no" to a source of threaded pipe fittings, in the face of ever shrinking sources.

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I was going to agree Mike, I thought about the thing when I first watched him but wasn't going to say anything. Then I read your response. You know I read every thing you post. Yes? Gotta keep an eye on you, no telling what you'll come up with next. ;)

Frosty The Lucky.

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It's easy to tell that, Frosty.

I will most likely post something quite obvious; bottom line is, the obvious frequently turns out to be the key factor to unlocking progress.

Progress = exchanging Formula 1 burners and forges for properly hopped-up family rides.

Personal progress = sneaking up on Frosty a bunch of times, and coaxing lots of people down to the deep end of the pool :)

Nirvana = getting someone so excited about a new idea that he can't rest until he can jump all over it :D

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Hmmmm and I thought Nirvana was a fluffy lobster souffle. Or was that the place that served them? 

The obvious is easy to overlook you've seen it so many times you take it for granted and miss the significance. Of course it just might be misplaced. 

Progress = changing your mind about what you think you know.

Frosty The Lucky.

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Not ALL of it surely. It's something I've told people since I discovered it myself, I learn as much teaching others, maybe more than they do. Good questions are things to be cherished, they make you think about why you do things the way you do or you can't explain. What could be better than having my mistakes pointed out and making me think about the whys of my thinking. 

Frosty The Lucky.

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  • 2 weeks later...

Another Update:

Well, the forge is now fully functional. After welding the nipple to a cross-piece on top of the forge (dropped down enough to remain flush with the inside of the bricks), I noticed that it wasn't burning as hot or efficient as I wanted, so we raised the orifice in the bell housing. As a result, I can get forge-welding temps at about 20PSI within 2-3 minutes of putting it in the forge. Besides that, it takes ~10 minutes at 10-15 PSI to get the burner warmed up, and the bricks to turn sunburst yellow. If the zinc coating on the housing is burning off, then I guess I'm lucky the garage door is always open with the forge out front :). I plan on making a coupe-coupe machete with a bit of leaf spring from a Jeep in the near future.

Thank you so much for the help and feedback!

~Royal

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Preview attachment IMG_1223.JPG

 
 
Yep! One thing that isn't in the picture is a small circle directly beneath the flame where the propane cools it down...but it's kinda too late to change that I guess. It also turns out that it takes a lot more energy to move leaf spring metal than I thought, so I scrapped the coupe coupe idea...maybe I'll make a karambit from a wrench, who knows? 
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