ES0NE

Burner to cubic inch relationship

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I have built a 3/4" t burner. Pictures to come. I was going to make the chamber inside my forge 250 cubic inches. Is this cavity too small.? Tank measures 10" diameter x 12" long. 

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It is naturally aspirated. I just didn't think that making the chamber bigger than the work I will be doing in it made sense. I'll get some pictures in the morning. 

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Greetings ES.                                          Yep a Frosty moment is about to happen. Make room for the master.. Oh by the way glad to have ya.. Frosty will finish this statment.. LOL

Forge on and make beautiful things

Jim

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Sure, no problem if it isn't closed up too much. The only problem you might run into is melting the liner out faster than normal. Mike's right, you can turn it down at the regulator quite a bit. If you get it tuned well it'll bring 300-350 cu/in to welding temp.

How did you line your forge?

Frosty The Lucky.

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Here are some pictures of the Bruner and the potential donor tank. Also, pictures of the front door opening and work rest I will be applying to whatever vessel I decide on. 

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:wub: burner......

Tank is 10" by 12" long. Build bigger? I have not collected all refractory material yet. I have 1.5" thick material in a roll and bricks. That's why I am here. Looking to iron out the details with the best advice I can get. 

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I also didn't know what to do with the burner cone. I didn't feel like flaring my own custom cone so I turned the threads out of the ID of a concentric reducer made from stainless. Is this going to work or is it too much of a transition from tube to flare for the flame? I am also currently looking for a gas regulator and hose set up is there anything particular that I should be looking for?

I wish i could light it and just find out for myself but I figured I needed to understand a little bit more about the exact regulator that I need before lighting it up for safety reasons among others. Please keep in mind that I am new to Gas Forges. 

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I wouldn't be surprised to see that flare work out pretty well; if not, it will be simple for you to try different sidameters of tube in it to find the ideal size; then you could just cut two or three of these "inserts" since the flame wear is all internal; this would allow you to stay with tha very nice screw on flare.

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Not bad at all. You can't mount the burner that deep in the forge it'll just burn up. Pull it back till just the tip of the flare (whatever you end up with) is just poking into the liner. That burner should handle that volume just fine. Remember the number that counts is the inside volume and shape. Those tanks have been making fine forges with that size burner for a hundred years.

I much MUCH prefer using 1" 8lb. ceramic blanket refractory it rolls with fewer wrinkles so there is less disruption of the flame path inside. The flame contact layer is a wear item, it WILL burn out eventually though the right kiln wash might make it brick tough. I'm still thinking about that one.

I'd put the gauge between the regulator and the burner, that's where you'll adjust pressure. Putting it there means you'll have to adjust the regulator and then go look and repeat till you have what you want. My progression is tank, regulator 1/4 turn ball valve, gauge line to the forge. This puts the gauge right next to your hand when you adjust.

The 1/4 turn ball valve is the emergency shut off, you can shut the gas off with a thrown rag where turning off the tank valve can take several seconds. That doesn't sound so bad and most of the time it doesn't matter however there are times when instantly isn't fast enough. Here's hoping you never find out.

Buy your propane hardware, reg, gauges, hoses, ball valve, etc. at the local propane supplier. They have a showroom at the office and keep parts on the shelf. One thing for sure you do NOT have to worry about them selling you something that's not propane rated.

Oh yeah NO teflon tape or thread sealers!!! Teflon and propane do not play well together, dangerously so. Sure you can buy past thread sealer for propane but you're using tapered threads and bras fittings. Assemble it, crack the propane and take soapy water to it. If it doesn't start bubbling don't worry about it unless you take it apart and reassemble it.

Frosty The Lucky.

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You did a lovely job welding things together, look forward to seeing the finished forge.  If the burner doesn't work well, no biggey, just build a new one.  Your fab skills are first rate, lets get you some experience. Welcome aboard.

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Esone, I've seen few folks who can weld that pretty.  Nice job.

 

Frosty, I don't want to hijack this thread, but you said earlier that a 3/4 burner should be able to handle about 350 inches.  I am contemplating re-purposing a worn out compressor tank.  The tank itself is heavy, in good condition, and didn't cost me anything to haul it off.  However, the cylinder portion is 12 x 20 not counting the domed ends.  I anticipated needing 2, 3/4" burners for the whole thing with the thought I might be able to just use one for smaller things.  However, if I pack the ends and use 2" around the inside of the cylinder, I still have about 1000 in3 not including fire brick for the floor.  This brings me to my primary question:  do multiple burners require additional insulation/refractory?  And secondly, should I just add additional insulation/refractory inside to lesson the volume to about 350 in3 per burner?

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Welcome aboard Zap, glad to have you. If you'll put your general location in the header you might be surprised how many Iforge members live within visiting distance.

The ratio of one each well tuned 3/4" burner per 300-350 cu/in holds pretty steady. A 1,000cu/in chamber wants 3 ea. 3/4" burners.

What you'll run into though isn't the volume making you use more burners it's a fire brick floor, even split bricks hog fuel. I've learned a bunch since recommending them go with high alumina kiln shelf instead, it's superior on all counts.

Multiple burners don't NEED more insulation but another inch can't hurt and it will reduce the volume significantly say to about 6" That leaves a long narrow chamber so it's not going to heat evenly without multiple burners anyway.

Hey WAIT A MINUTE! I just ran the dimensions of your compressor tank across my calculator watch and I don't get anything like 1,000cu/in. Are you calculating the volume after subtracting the liner thickness? Seriously, 12"dia. x 20" with 2" of Kaowool says 600cu'in. Just pack the ends so they're not domed inside.

Two 3/4" burners evenly spaced aligned tangentally should do the trick.

Frosty The Lucky.

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Frosty, 450 BTU per cubic inch keeps coming to mind (IF I remember correctly). Until I can locate my notes I do not recall any specific type burner being mentioned for the 450, so I will default to your numbers and your burners.

 

Edit: A search produced the following

From the Ron Reil site.
1. You will need at least 450 BTUs per cubic inch of forge chamber volume if your forge is going to be able to forge-weld. Some would argue for a figure as high as 540 BTUs per cubic inch.

Earlier discussion of IForgeIron

 

Another reference

450 BTUs per cubic inch (For the 3/4" diameter Reil or EZ burners only) *Do not use these rules for the Mongo series of burners*

 

From a gas forge builders site:

The rule of thumb for side arm burners to forge volume is: (1) 3/4" side arm burner for every 350 cu/in of interior forge space if you are wanting to achieve forge welding temperatures. Note: these figures are for a properly insulated forge.

 

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"450 BTUs per cubic inch (For the 3/4" diameter Reil or EZ burners only) *Do not use these rules for the Mongo series of burners."

Wow; that takes me back! Ron added this comment after I started showing him my early burner series (Mini Mongo, Nano Mongo, etc.), because they seemed about twenty percent hotter than the old burner designs, but my burners are easily turned down, and so this exception to the rule does more to confuse than help newbies.

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Scrambler, Reaching back: Posted December 18, 2015 (grin)

Lots of stuff in the IFI archive. One reason we suggest you pack a lunch and a cold drink. 

 

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Hi, I'm new to this site.

 

I've been running a 3/4 Mikey style burner in a brick pile forge for about 3 years. I'm in the process of building another 3/4 burner with smaller air ports, from info that I got from this thread, just to see if I can tell a difference. I've been running a .030 mig tip orifice with good results. I'm at 5,200'

 

Can anyone elaborate a bit on the sizing of the orifice? I'm going to be helping my friend (offgrid) with a forge that he will be running at high altitude , 9,800'.  A commercial burner manufacturer who uses .035 mig tips in their standard 3/4 burners recommended  to him that he would put an even larger orifice in that burner for high altitude. I have read both this thread, and the forge 101 thread and have not gleaned any info on how the orifice size is determined and how thinner air might effect this. Is orifice size just done by trial and error? Wouldn't a larger orifice result in a slower velocity, for a given amount of propane, and result in less air being pulled into the burner? I'm thinking that we will be wanting to pull more of the thinner air into the burner.

Great thread!

Victor

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On 6/18/2016 at 11:01 PM, Frosty said:

Welcome aboard Zap, glad to have you. If you'll put your general location in the header you might be surprised how many Iforge members live within visiting distance.

The ratio of one each well tuned 3/4" burner per 300-350 cu/in holds pretty steady. A 1,000cu/in chamber wants 3 ea. 3/4" burners.

I’m just starting out building my own forge and was curious how you calculated the volume to be 600 cu.in.  If 2” of kaowool lined the entire inside of the tank, wouldn’t it be 8” diameter, so 4” radius and 20” length?  It comes out to 1004.8cu.in. for me. 

Am I missing something?

I ask because I have a 12”x25” air compressor tank I’m planning to use, but was planning on cutting down to 12”x20” due to the volume. 

Thanks in advance!

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I think that Frosty just made a simple math error. Lets review the formulas first.

Cylindrical volume is V=A×h

Area of a circle is A=3.14×r^2

Circumference of a circle is C=3.14×2r 

Frosty simply used Circumference in his calculations instead of area to calculate volume. I'm not easily able to remember the difference myself so it's easy enough to mess up. Just as a side note, if you add a bottom plate to your tank it will decrease the volume and make it easier to grab multiple pieces out from your forge.  With a bottom it will also be much easier to achieve the cubic inches needed to not use lots of propane (added burners).  Just my two cents. I'm looking to build another gas forge this spring myself.  Let me know if I'm wrong but it's all good either way.

-KB

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On 6/16/2017 at 11:17 AM, bluesman7 said:

Can anyone elaborate a bit on the sizing of the orifice? I'm going to be helping my friend (offgrid) with a forge that he will be running at high altitude , 9,800'. 

In general, the smaller the tip size the more forcefully the gas column is inducing air. The more forceful the gas column the more air it entrains. So, heck no a larger gas orifice isn't going to provide more air, to a offset air thinning at elevated altitude; it will provide more gas and LESS air!!!

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I am building a forge from a sand blaster tank.  The diameter is 12" and the long flat part of the cylinder is 18".  It is 24" cone to cone.  I plan on putting 2" of inswool inside which should be roughly 1450 cu in. Would 1 burner be enough?  Still in the air on a multi port(ribbon) or not.  I have about 4 lbs extra kast o lite 30.  Would that be enough kast o lite to make a ribbon burner. Thank you in advance for any help

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Yes, No or Maybe depending on how large a burner you are considering, the type and how hot you need the forge to get.

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I have built a forced air burner from plans that I found on the internet.  It is a 1.5 inch t I have a .30 Mig tip bringing my propane in I have an 1.5 inch x 8 inch nipple that reduces down to 1 in with an elbow that will bring a 1 in into the forge with a inch to inch and a half reducer as a flare.   Currently I have a hair dryer as my forced air source until I can find a squirrel cage blower reasonably priced. I have fired it up and it seems to burn like the others that I've seen in videos

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