Forge and Burner Design Page #1
(Note: This page is now broken into two pages, #1 and #2)

Golden Age Forge

Jump to page #2


I am about to forge-weld a Spontoon pipe-ax head.
(This excellent image was taken by my apprentice, Kevin Brown)

A New Addition to My Shop - Out of this world!
This is a 64 pound nickel-iron meteorite from Argentina that fell about 4000 years ago!

Contact me by phone: (208) 462-4028
Note: Due to spam problems I no longer post my e-mail address.

Warning!

I provide the following information as a service to the blacksmithing community. Although the designs I employ in building my burners and forges are safe and reliable in the way that I use them, the same may not be the case for you. You assume all risk in using this information, or any other information on my site. Other designs that I have posted here have been submitted by other smiths, and I have no experience with most of them. Use care and good sense in using any of these designs. Get help from a knowledgeable smith if you are new to this work. Don't take chances, because these tools can cause injury, blindness, or even death, if used improperly. Also, be sure you are in a well ventilated space (see the Nighthawk CO & explosive gas detector paragraph), or better yet, work outside. Additionally, never operate a forge that is connected directly to a propane tank located near a forge, or indoors. An emergency pressure valve release could instantly place you in the middle of a fireball. Follow all local codes regarding indoor use of propane. I believe indoor use of a propane tank violates code everywhere in North America, and most of Europe. A new concern has arisen with the introduction of the "Mongo Burner Series." Please read carefully all the information in the separate "Safety Warnings and Considerations" information which heads the "Mongo Burner Series" section. Thank you.

An additional item that should be of interest to you is obtaining an explosive gas/CO detector for your working space. Mark Manley, of "Manley Metal Works," Silverton, Oregon, provided a short piece of very important information in the Winter 2000 issue of "Hot Iron News" that I think needs to be passed on to a wider audience. There is a very reasonably priced digital read-out combination explosive gas and CO detector available in local hardware, building supply, and other stores. I was concerned about having a CO monitor in my shop, even though I have a very efficient induced draft hood in my shop. The detector is made by "Kidde Safety" and is called the "Nighthawk." I will not go into the specs for the instrument here, they are available on their web site, but I will say that it is a very finely designed and built instrument. It runs on 110 VAC, and has a 12 VDC back-up. It plugs directly into an outlet, or the transformer plug detaches for remote mounting up to 6' from the plug. You can easily check your CO level with a quick glance at the digital read-out, and if it detects any kind of flammable gas it will instantly sound an audible alarm, and the word "Gas" will show on the digital display. If it detects CO, it will sound a different audible alarm and display the PPM level. Also, you will know it's operating because the blinking decimal point in the digital read-out indicates it's operating and sampling the air in your shop.

I bought one of these instruments for my shop, and was so impressed with it that I went down and bought a second one for my home, which has natural gas heat, gas hot water, and a natural gas fireplace insert. I priced CO detectors on the McMaster-Carr web site, and they alone were $170, where this combination instrument is only $59 at my local Home Depot. Considering how deadly CO can be, this instrument is very inexpensive, well worth the investment, and it may well save your life. After Mark installed his "Nighthawk," he discovered that he had been exposing himself to CO levels of 30-160 PPM for a long time while running his forge! Thanks for the tip Mark.

Note: There has been a recall of Kidde Safety "Nighthawk" gas and CO detectors. This does not affect any detectors sold after the date that I posted the above information, however you may check your unit by going to http://www.cpsc.gov/cpscpub/prerel/prhtml99/99082.html.  


A Word About Obtaining My Help

I am no longer able to offer my support to help solve problems you may have with your burners or forge. I have reached the point that something has to give. Two to three hours a night answering questions has brought my metal working each evening of the week to a stand still. I will continue to update my blacksmithing pages, and will now also have the time to clean out all the outdated and conflicting information in my pages, however, I will no longer be able to troubleshoot your system. I still want to receive your e-mails if they do not pertain to forge or burner problems. If you build your burner to the design specs and information shown and discussed on my pages, including in the Troubleshooting Document and FAQ, your burner should work well. If it doesn't, then its not built correctly, and you will need to make some adjustments after looking through the available information. The best thing to look at when fine tuning your burner are the various flame images I have posted. If yours looks like these images, you have it right. Here are a few helpful links.

Note: If you e-mail me, please be sure your e-mail in "txt" (text) format, not html. I am now averaging two to three virused e-mails each time I download my e-mail, so I have to be very careful. If your e-mail is not in "txt" format I will most likely delete your e-mail without opening it in order to protect from possible virus infection. It's certainly sad that we have idiots in our society that feel they must cause such problems.

FAQ

Forge & Burner Troubleshooting Document

Some Often Asked Questions

EZ-Burner Construction

Rich To Lean Flame Image

1) T-Rex Flame Image - Ideal Neutral Flame

2) Side-arm Burner Flame Using Temporary Cast Iron Test Nozzle - Slightly Reducing Flame

3) Another Flame Image - Oxidizing Flame

The bottom three flame images give you views of burner flames adjusted to 1) neutral, 2) slightly reducing, and 3) strongly oxidizing. The burners have nothing to do with it, just the choke settings. All of these images could have been done with the T-Rex, or Side-arm burners. At your high end gas pressure, if you have achieved a flame similar to the oxidizing flame shown in the bottom image, #3, you will then have full control over the burner flame across the full pressure range. This will allow you to achieve oxidizing, neutral, or reducing, flames as needed by simply adjusting the choke. You will then have a properly functioning burner.


My Home Page, & Pages on This Site

The Full Site Map - Lists All Pages on This Site

newnew .gifVisit my newest page, my "New Home and Shop Page"newnew .gif

My Home Page

The Golden Age Forge Gallery

Why Build A Gas Forge?

Construction of the Freon Tank Mini-Forge

 So You Want to Forge a Sword

Ron's Fly-Press Page

Note: "The Best of Theforge" is a collection of posts to "theforege" covering a great many blacksmithing subjects. It is made up of three separate files that are all hot linked and indexed. If you want to know what Superquench is, or the composition of a railroad spike, this is were you will find it. I have a lot of work in these files, I hope you will find my time was well spent.

The Best of "Theforge" - a Zipped Download of All Three Files
-or-
The Best of Theforge - Vol 1

The Best of Theforge - Vol 2

The Best of Theforge - Vol 3



Subject Index for the Design Pages

(Small font indicates a subsection.)

Page #1

Safety Warnings

Explosive Gas/CO Detector

TWECO Tip Modification

The Reil & EZ Burners (These are the standard burners)

Flame Characteristics

-Proper Nozzle Placement in the Forge

The Mongo Burner Series

-Safety Warnings and Considerations for the Mongo Burners

-Burner Efficiency VS Economy

-The Mongo & Side-arm Burners

-Minimongo Burner

-Micromongo & Nanomongo Burners

-Nanomongo Burner

Forge Design Rules of Thumb

Page #2

Sources for Refractories, Burner Nozzles, & T-Rex Burners

-Sources for Refractories

-Obtaining Premade Burner Flares 

-The "T-Rex Burner"

-The "Shorty Burner"

Download the BTU Output Calculator

Will Gas Forges Weld?

How Hot Can These Burners Get?

Misc. Burner Chokes

Axial Burner Choke

Additional Burner Designs

-The Monster Burner

-Bienstock Burner

-Jay's Burner

-The Wasser Modification

Gas Forge Designs

-My Four Burner Forge

Some Additional Gas Forge Designs, 1 through 4

-Sandia Recuperative Forge Design

-Clamshell Forge

-Building a Large Gas Forge

Forge & Burner Design Links

Coal Forge Designs

Additional Coal Forge Designs & Brake Drum Forges

Blacksmithing Terminology

Closing


A Preface for All Burners on This Page
The "TWECO 14T Tip" Modification

Work by Michael Porter in Seattle has resulted in a powerful modification that I recommend you apply to any of the burner designs on my pages. Instead of simply drilling the desired jet hole in the burner tube, you can achieve far superior results by drilling and tapping the jet hole location to take a 1/4"x 28 threaded "TWECO 14T" copper tip, available at your local welding supply shop. There are a variety of these tips in various jet diameters and external configurations available. You should try to obtain the Tweco tip configuration that measures 1-1/2"x 1/4," and has a long tapering nozzle tip. With this arrangement you can easily experiment with various tip openings simply by switching them as desired. Once you determine which tip performs best for your particular application, then you should silver solder it into place to prevent any possible gas leakage past the threads. Because of the high temperatures that the jet tip may encounter, due to occasional chimney effects, you should not use any other lower temperature process, such as Teflon tape or soft lead solder. Another comment that applies if you are modifying the "Reil or EZ Burners" regards the bell diameter. The increased suction created by this tip modification will require that you increase the intake bell to a 2" diameter, or you will not get enough intake air to achieve a balanced burn.

An additional consideration that I need to mention, and which is covered in detail in the "Safety Warning" section at the top of the Mongo Burner information, regards UV radiation hazard. The Tweco tips increase the efficiency of the burners and their output temperature. In the Mongo burners the temperatures are up into the middle UV temperature color range, and it is possible to get "flash burns" from the light coming out of the forge. Be aware of this potential hazard with any burner you modify to use this tip. UV radiation is very damaging to eyes and skin.  


Propane Forge Burners

The Reil & EZ Burners

(Reil Burner Modification)

Be sure to read the FAQ that goes with this design also.

The burner design above is my modification to the well known "Aussie" burner, as designed by various smiths, some noted on the drawing. The "Reil Burner" is a superior burner in all respects. It will sustain a controlled flame with propane gas pressures of over 50 psi. The cost of building it averages about $5 US, and it is constructed of all "off the shelf" plumbing parts, available in any hardware store. The FAQ explains its construction, but is not a detailed step by step instruction sheet. It is a collection of suggestions and observations that will be of use if you decide to build one. This document also includes a section on tuning your burner.

Note: Brian Boorman has created an outstanding step by step pictorial web page showing the complete construction of a Reil Burner. If the line drawing linked above isn't enough information for you to work from, you may want to visit Brian's page. Go to http://metalcast.boorman.us and click the "Propane Burner" link. I want to thank Brian for his outstanding contribution to the metalworking community.

I have now included an additional "EZ-Burner" design that you may find much easier to build. It eliminates the difficulty of doing the flare in the nozzle, and also eliminates three of the drilled and tapped holes. I am not including a drawing for this modification, as it is not necessary, but I do have an image of the burner if you are interested. The "EZ-Burner" HTML document linked above should provide all the information you need to build this quick and easy burner. It should only require a couple of hours to complete it. I would like to include one additional note about galvanized pipe. By all means do use it for your burner. It will not get hot enough to bother the galvanizing over most of its length, and if it does, you are doing something wrong. Properly used, the burner should be cool enough to handle at all times, except for the 1" diameter nozzle piece at the end. The galvanizing will protect your burner from rust. If it does get hot enough at the end to burn off the coating, the tiny amount involved will not cause you any problems. Also, do not use any pipe joint compound in the 3/4" joint, it's just not necessary, or of any value.

I used four Reil burners on my 24" long cylindrical forge, but two or three are all that is necessary, and two will probably be enough in most cases. I live at an elevation of 2300 feet, and I can easily weld with only one burner running at 6 psi propane pressure. They are also being used successfully at over 7000 feet elevation, and they can weld easily at that elevation. If you would like to see more images of this forge, please go to my Forge and Foundry Page. Thank you.

Use of Natural Gas: You may use this burner for natural gas applications, but will have to increase the jet size in order to do so, and you will require 10-20 psi natural gas pressure. I know of at least two smiths currently using them with natural gas, but I do not know the jet diameters they are using. If you use this design for natural gas I would very much appreciate knowing your jet size, so I can add that information to this page so others may benefit from your work. Please contact me at (208) 462-4028. Thank you.

I was contacted by Ray Maiara concerning the use of natural gas. He is using natural gas at only 1/3 psi pressure, and has had to go to a very large "jet" size, about 1/8", and he is using a blower also, so this doesn't fit in the category of a venturi type burner. He has also gone to very large plumbing diameters, main feed of 1-1/2", and forge lead in of 3/4", to obtain as little restriction on the gas flow as possible. If you are considering the use of natural gas, contact your gas utility and ask them if they can provide you with a high pressure feed. My gas company will provide a high pressure tap off the household service, up to 80 psi, and there is no additional service to pay for, nor is there any charge for the work to install the high pressure tap. I do have to buy the additional regulator however. It is worth your time to check into, since this burner will function with natural gas if sufficient pressure is available, but again, you will have to experiment with the jet diameter to find the proper diameter, given your available pressure. You must have enough pressure for the venturi action to operate correctly to draw the air into the bell. Remember that natural gas will not provide as much heat as propane, so your forge may not be able to forge-weld. If you use a blower and large jet diamerter you will be able to forge-weld easily.

A properly adjusted gas forge will have an air/gas mixture that will create a neutral, or slightly reducing, environment inside the forge. This is necessary to prevent excessive oxidation and scaling of the metal. With my burner design, the forge environment should meet that requirement if you use a #57 or #58 jet diameter. I have found that my forge needs no choke or intake air controls, and runs with a slightly reducing atmosphere as desired. If you want a very simple and extremely efficient burner, use the modified Aussie design. If you build it with the Bordeaux modification you will have the greatest versatility for adding a blower, or intake air controls (choke), if you feel you need them later.

There are an unlimited variety of forge designs, almost as many designs as smiths, and most work well enough to do normal forging. Probably fewer are hot enough to forge weld, but that can usually be corrected with a little homework in proper forge design. However, every now and again a forge comes along that is truly unique and worth posting a picture of. The "Dragon Forge" by Wayne Coe is one of those forges. Here are two image links to his asthetically as well as functunally unique forge. Besides the obvious and beautifully forged dragon, notice the hinge system on the forge, allowing Wayne to open his forge like a clam-shell. I need to add that if you are interested in a "clam-shell" design, be aware that a vertical lifting upper half will not expose you to the searing heat of the interior of the forge like a hinged design will. Wayne does not open his forge far enough to expose himself to the intense IR, so it isn't an issue with him. And yes, those are twin 1" Rex burners Wayne is firing his forge with. No problem attaining forge welding heat with this forge.

Dragon Forge 1

Dragon Forge 2


Flame Characteristics

A lot of people ask about what a proper burner flame should look like. Thanks to Don Foreman, I now have an excellent image of a virtually perfect burner flame. The symmetry and zonation are as good as it gets. It is a an oxidizing flame. Your color intensities may not be quite as dramatic as in this image, but otherwise this is what you are attempting to achieve at your highest pressure setting, and which you can tune to neutral with the choke. Notice the perfect symmetry of the flame, which is an indication of a well centered jet, and the "jet-engine" like velocity the flame has. A flame that tends to burn to one side is an indication that the jet is not aligned correctly. You may click on the image for a larger view.


(Image courtesy of Don Foreman)

Rupert Wenig has provided an excellent sequence of six images of his Minimongo Burner showing the effects on the burner flame of opening the choke. I have combined them into one image. The images on the right were taken without flash to show the flame characteristics more clearly. This is a very instructional image, and should be extremely useful when you are tuning any kind of burner, not just the Mongo or Minimongo. You want to achieve a neutral flame as shown in the center image.  Note: The coupling that Rupert is using for his flared nozzle has been machined out to have a 1:12 internal rate of flare...it is not just a coupling. Being cast iron it would also melt in an actual forge or furnace application. This is for test purposes only. Use stainless steel.

T-Rex Flame Image - Ideal Neutral Flame

Side-arm Burner Flame Using Temporary Cast Iron Test Nozzle - Slightly Reducing Flame

Don's Flame Image - Oxidizing Flame

Note about burner nozzle placement in the forge: Your burner nozzle should not enter the innermost layer of Kaowool. To do so will cause the nozzle to overheat and quickly degrade, or melt all together. Using a sharp knife, cut an "X" through both layers of Kaowool in front of the burner port, and from the outside, force the burner nozzle into the forge while spreading the Kaowool with your fingers to allow the nozzle to squeeze in. Stop when your have fully penetrated the outer layer of Kaowool. Use some kind of tapered plug, I use a turned hardwood plug, and from the inside of the chamber, force it through the X into the burner nozzle while working the Kaowool with your fingers to allow the plug to seat home against and inside the inner lip of the nozzle. The plug will need to have a steeper taper than the 1:12 that is inside the nozzle. By leaving the plug in place when the forge is not in use, it will force the Kaowool to take a set, and soon the plug will no longer be necessary. The hole in the inner layer of Kaowool will continue the tapering opening of the nozzle, and the 1" setback from the chamber will prevent the nozzle from being destroyed prematurely.


The Mongo Burner Series


The 2-1/2" Diameter Mongo Burner

The Mongo Burner Series:
Mongo Burner = 2-1/2" diameter burner tube (Air starved)
Minimongo Burner = 1-1/4" diameter burner tube
Micromongo Burner = 3/4" diameter burner tube
Nanomongo Burner = 1/2" diameter burner tube

Safety Warnings & Considerations....a Must Read: The Side-arm burner has now been perfected and can be found at the bottom of this section. You are building and using this burner entirely at your own risk. If you don't wear eye protection, and you loose your eyesight due to the UV radiation that these burners can produce, then you are responsible for not reading and following the warnings, and must bear all consequences. I will not accept any liability for the stupidity of the builder and user of this device if he should injure himself with it by ignoring this warning. Please read the following e-mail I received. It will give you an idea of the temperatures these burners can achieve.

"At this point, my only observation is that the (Micromongo) burner is too hot for the current nozzle design. Don't get me wrong, the burners worked great. I could not get the burners to run quite right without Larry Zoeller's nozzles, but I did not try very long, as I had a job that I had to get done this weekend ( I was already behind because I could not get enough heat out of the Reil Burner ). After going down to the welding store to buy a shaded full face plate (a definite necessity), I got right to work. Things were going great until the burners went erratic. The problem was that the nozzles got yellow+++ hot and sagged over the end of the burner. The nozzles now look like a tuba run over by a semi. I can not wait to get some more nozzles from Mr. Zoeller so I can form up some type of ceramic nozzle and start experimenting with this burner. Great potential. Thx's for all the help.   Fred jyblood@nwi.net"

There are a few more items to address. It is apparent in our testing that these burners display a very wide range of behaviors depending on what jet diameter is employed. Also, we are now using the long tapering copper 14T Tweco tips for our jets, even on the Reil and EZ-Burners, which I strongly recommend you do also due to the greatly increased performance they afford. I suggest you experiment with various diameter orifice Tweco tips and settle on one that works best for your particular application. See the FAQ for a listing of nominal to actual orifice diameters for these tips. They are threaded, 1/4"x 28 thread, so you can easily switch them for experimentation. I may post a "recommended jet diameter" later on for each burner size, but presently I want to leave it open ended, even though the Mongo and Minimongo Burners both have jets called off in the information below which will provide a good starting point for you. Additionally, the tapered nozzle stainless steel flare operates at a much higher temperature, a red heat, on the Micromongo Burner than on the Reil or EZ Burners. This increased temperature will cause much more rapid degradation of the burner flare, even if its made of stainless steel. In fact I would say that stainless steel is your best option for metal nozzles, and even their life may be fairly short, although proper mounting of the nozzle 1" back into the Kaowool will greatly extend its life. I am getting more than three years out of a nozzle presently. You may want to consider casting your nozzle flare into the wall of your rammable refractory shell, if you have this kind of forge lining, thus eliminating the metal nozzle all together. This would be an easy task to perform, and may be the very best alternative for these high temperature burners. Another possibility is coating the nozzle, either stainless or black iron, with ITC # 213.  Have fun and be careful!

A Note about Economy vs. Efficiency:  There are numerous comments in my pages about "economy" and "efficiency." They do not mean the same thing. As I use these terms, the economy of a burner refers to how much its going to cost you to run it. The efficiency of a burner, in the way its used in my pages, refers to how much air it can draw in due to the  strength of the vacuum it creates in the intake bell or ports at a given gas pressure. There are only so many BTUs available in a pound of propane, and no matter what you do you can not get any more than that out. If two different designs of burners are both running with a totally neutral burn at 100% combustion, and maintaining two identical forge chambers at the same temperature, their economy will be identical. The Micromongo Burner can produce higher temperatures than the Reil Burner, but it uses more fuel to do this. If you lower the output of the Micromongo so that the temperature inside the forge chamber is the same as in an identical forge chamber heated with a Reil Burner, the fuel usage, or economy, should be the same. If they are not, then one or the other is not running at optimal tuning. So don't choose the Micromongo Burner because you think it will save you money, it won't. It will give you the ability to get the same economy as provided by the Reil Burner, but it will also allow you to reach higher temperatures than the Reil Burner can attain, but this will cost you more in fuel usage. There is just no free lunch. It is likely that overall you will spend more money on fuel with the Micromongo burner because you will probably want to use that extra heat range to run a hotter forge. You pay for what you get. Note: We were very surprised by the results of some recent side by side tests of the T-Rex and Reil burners. They both consumed about the same amount of fuel, yet the T-Rex was much hotter. We concluded that the mixing and fuel/air ratios in the T-Rex are superior, and provide a better burn, thus extracting more of the BTU heat value from the fuel than the Reil burner is capable of doing. The T-Rex is both more economical, and more efficient. It is more econimical because it can be run at a lower gas pressure, using less fuel, and obtain a comparable temperature in the chamber.

The only exception to the basic statements above may be when using a Mongo Series Burner, or one of the big Rex series burners, to run a melting furnace. If you are able to achieve a higher temperature in the furnace with a bigger burner, it will achieve the melt more quickly, which cuts the time available for heat to escape through the furnace walls and up the stack, thus wasting fewer BTUs. However, the higher temperature creates a greater thermal gradient across the thickness of the furnace wall, increasing the amount of heat loss in a given time, so there is a trade-off to consider. If the Furnace walls were made of 100% efficient insulation this relationship would not exist, and the burners would perform with equal economy, but perhaps not convenience. I point out these various relationships to show you that things are not as simple as they may sometimes appear. There are a lot of factors to take into account when discussing economy of a burner. For the most part, the smith operating the forge, and the quality of the forge, will be the most important factors in determining overall economy, not the burner. Think about running your burner to do a day's forging, without the benefit of a forge chamber, and you will understand my last comment.

The Mongo Burner & New Side-arm Burner

Note: For historical purposes, and to keep information available that may be of use to someone, I have not removed the drilled air intake hole Mongo burners from this page, nor the old Side-arm information shown several paragraphs below. The drilled hole ports are too small to provide the necessary intake air volume on the original Mongo burner, resulting in a very rich burn and high CO production...potentially dangerous. The original Side-arm burner design has also proven to be an inferior design if built as shown in this drawing, and I do not recommend it. There is now a far superior option available which turns the Side-arm burner into to a very fine burner by using an asymmetric T-fitting. If you enlarge the "intake" bell opening, as shown in the images linked a couple sentences below, the inlet "R" value will drop to a level to allow these burners to perform extremely well, especially if you use a Tweco 14T jet tip. Larry Zoeller has been experimenting with this concept and has provided some examples of high quality Side-arm burners. Check these out if you want a good example of these very easily and quickly made burners. Paul Pirtle has also been working on these burners and has produced an excellent Side-arm burner, shown with "axial" choke installed, which performs extremely well across the entire pressure range. He has since replaced the cast iron test nozzle with a stainless steel nozzle so that it will not melt in his forge chamber. Please do not use cast iron. The following are a few comments Paul sent me regarding his excellent Side-arm burner. I include it here because the jet orifice information may be of use to you.

"Yesterday I built two air choke assemblies, using a 1-1/4" short nipple with round choke plate, 1/4-20 all-thread, and a brazed T per your design. Tested both, they work perfectly to adjust flame to blue/green transition. Based on how far the choke needed to be closed I think I could run a larger than .035" orifice. I tested the .023 orifice again with choke, it runs fine but fussier than the .035. I am guessing it might be marginal to small for the 3/4" burner tube. A 1-1/4"x 1-1/4" x 3/4" cast iron T-fitting is necessary to provide the needed intake air flow volume for a 3/4" burner." (It may be possible to use a smaller bell on the top end of the fitting where the jet pipe enters, perhaps a 1" x 1-1/4" x 3/4" or even a 3/4" x 1-1/4" x 3/4" fitting.)

The original Mongo burner is a huge multi-purpose "Jet Ejector" burner. I was so impressed after I built one, even though it had a too short burner tube and no nozzle, that I felt it deserved a place on this page. I named it after "Mongo," the giant in "Blazing Saddles," because of its huge size.... 2-1/2" diameter bore! It is a different design of burner, having seven 1" diameter air holes in the barrel of the burner, and an axial 1/2" diameter internal jet tube, but it works quite well, except for not being able to get a fully balanced fuel/air mixture. It tends to run on the fuel rich side due to the small intake port area and resulting insufficient intake air volume. When I first tried test firing it I was unable to run it below 20 psi or it would become erratic and run extremely rough. I switched out the jet tube for one 1" longer, to get the jet just slightly downstream of the air intake openings. This made a huge difference. I can now run the pressure down to zero gage pressure, doesn't show on my gage at all, but it is probably about 1/10 psi, and it purrs away just beautifully at a very reduced output. This low end operating range is due to the 28:1 induction ratio of jet ejector burners, as compared with the 20:1 ratio for the linear inducer burner like the "Reil or EZ Burners." This burner has tremendous adjustability in its output, making it useful for kilns, but the possible CO dangers need to be considered and precautions taken. For forge use, I strongly recommend going to an asymetric Side-arm design as shown at the top of this section, and use of a flared nozzle.

The original Mongo burner design discussed in the paragraph above was sent to me by Richard Mize, in Kentucky, and I have to thank him very much for sharing it with us. He included some additional information and suggestions in his drawings which I too included in the packet of drawings. I did not build the refractory venturi throat, nor the bracket he suggests, at least not yet. I have simply run scans of Richard's hand drawings and posted them below for download. It is a zipped file containing 6 images, including an assembly drawing, text comment sheets, refractory venturi throat, mounting bracket, mounting suggestions, and a list of materials needed. I have reduced them in size to allow downloading to be faster, but all together they are still 264K in size. These are hand drawings with hand written notes. They were plenty good enough for me to produce a dandy burner, and I am sure they will work just as well for you. An alternative that I strongly recommend due to its small file size is the "pdf" Adobe Acrobat file I have available also. This is a single fine quality drawing, with fewer notes and comments, and it is a much smaller file. It should be plenty detailed to allow you to build the burner without problem. Click on the gif "preview file" to see a reduced size image of the "pdf" construction file. The preview image may be all you  will need to build this burner, but the text is pretty small for older eyes like mine. I do want to say that I strongly suggest the Side-arm burner discussed above, which is easier to build and produces a fully balanced fuel/air ratio, and no CO danger if adjusted correctly.

Alternate Side-arm Design: (Note: this is older information, but is preserved for its historical value. Please see the latest Side-arm information at the top of this section.) You can build this burner more easily if you substitute a large "T" fitting, see link, in place of the pipe coupling. The burner tube screws into one arm of the "T", and the reducer and jet tube into the other arm. The air intake is provided by the opening in the base of the "T" fitting. You will not need to drill the big air intake holes this way. Also, it can be easily choked using a butterfly choke design, or an axial choke design, which is placed in the "foot" of the "T". You will have to experiment to determine the proper length of axial jet tube in order to place the jet in the right location in relation to the incoming air. I have not tried these modifications to the burner design.  (Thanks goes to "Frosty" in Alaska for this suggestion, and the induction ratio information above.) Robert Grauman has built one he has named the "Side-arm Design," in the Minimongo diameter, and this is what he has to say. (Note: I strongly recommend using a 1/8" jet tube, instead of the 1/4" tube shown in the drawing.) "I used to have a choke plate in the air tube, but I found I was getting a neutral burn with the choke wide open, so I removed the choke, and am now running with the inlet wide open. This has simplified the burner considerably. I am using a #55 (0.052") jet at about 22 psi. The flame burns near neutral (I think), but it requires a flame holder on the end of the burner tube when the burner is not in the burner port of my crucible furnace. It burns quietly. If provoked, the flame will burn back in the burner tube, but I believe that the burner tube is too long. I will start experimenting in that area tomorrow. The burner seems to work best with the jet cantered on the air tube, but it is non-critical."

Please note that Robert uses the burner in a cast iron and aluminum melting furnace, not a forge. You will want to operate at much lower pressures for forge work. Note: From tests done by Michael, it appears the "Sidearm" design is not a good choice for the smaller Micromongo and Nanomongo burners. He was unable to achieve a stable flame over a range of gas pressures in his Sidearm Micromongo test burner.

Note: There is one important error in the Adobe Acrobat "pdf" file below. The jet opening should read "#52 = 0.0625" diameter", not #58. This is a very important difference.

Preview the Following "pdf" file as a Reduced Size "gif" Image

Download a Single Complete Design File in "pdf" Format (Recommended - 16K)

Download all Six Construction Drawings in Zipped "gif" Format (264K)

(Before considering the construction of any of the Mongo series of burners, please read the informationa about the Side-arm burners at the top of this section.)

If you don't have "Adobe Acrobat Reader" on your computer you may download it here, its free.

"Minimongo Burner": I received a communication from Rupert Wenig regarding a half scale version of the Mongo Burner that he is using to fire his cast iron melting furnace. His experimentation work is continuing, but here are his latest design modification details. He is getting good results with it using these parameters. See the cast iron test melt results below the following specs Rupert provided. For forge use, I strongly recommend going to an asymetric Side-arm design as shown at the top of this section, and use of a flared nozzle.

-Burner tube: black iron pipe, 1-1/4" diameter by 12" long
-Jet: #56 drill = 0.0465"diameter (You may need to experiment further to determine the optimum jet opening)
-Air induction holes: 13/16" diameter
-Additional changes in Rupert's own words:  "I also changed the pipe bushing to a standard easier to get one. As pipe bushings are not normally solid I made a plug to fit the inside of the bushing to give the fuel pipe more surface area to hold it straight. I then drilled a clearance hole through the plug and bushing and installed a set screw to clamp the fuel pipe in place. This allowed adjusting the position of the fuel jet. Another change I made for convenience was to thread the inside of the fuel pipe so that I could use the jets I had on hand."  "PS. There is no question that this burner is quieter than other burners I have tried."

Rupert's Cast Iron Melt Results Using the Minimongo Burner Without Flared Nozzle:
I did a cast iron melt with the Minimongo today. I ran the furnace for 1:12 hrs, melting 15# of cast iron while running the burner at 20 psi after a 2 min. warm up from a cold start-up. That equates to about 0.21 lb/min. From my logs the Monster burner melted 17 lb. in 1:13 hrs. This equates to 0.23 lb./min.

Unfortunately, the casting didn't turn out because I got impatient. I should have superheated the melt for another 2 or 3 min as the casting I poured was a very thin section (1/4"). I would say that this compares favorably (with the Monster burner) as the Minimongo has a #56 jet in it while the Monster burner had a #54 jet.  

Based on the latest information I am receiving, you will need to make a 1:12 tapered nozzle flare, for the Minimongo burner, and probably for the Mongo Burner as well, once it has been fully tuned.

Thanks to the work of Robert Grauman in "Sunny Alberta," we now have a very fine jpg drawing of the "Minimongo Burner" that Rupert has provided information for. You may click the link below to view the design drawing. This drawing incorporates all of Rupert's modifications to the full scale version, including some details he did not mention above. Thanks Robert.

Mongo Burner Half Scale Design Drawing 
Note: I strongly recommend using a 1/8" jet tube, instead of the 1/4" tube shown in the drawing. 

Choke Settings Image: The below linked image is a composite image of six images Rupert sent me of his Minimongo Burner, photographed at three different choke settings, rich, neutral, and lean. All the images were shot at a gas pressure setting of 10 psi. The images on the right were taken without flash to show the flame characteristics more clearly. This is a long needed set of images that are very helpful when attempting to tune any kind of burner for a neutral burn, not just the Mongo or Minimongo Burners. Note: The coupling that Rupert is using for his flared nozzle has been machined out to have a 1:12 internal rate of flare...it is not just a coupling.

Minimongo Showing Flame Under Different Choke Settings at 10 psi Gas Pressure

(Be sure you also look at the full output image)

Micromongo and Nanomongo Burner Designs: We now have good Micromongo and Nanomongo Burners in operation, and the development work is complete. Michael has performed virtually all the development work for this burner, while communicating and discussing possible alterations and modifications with me. I credit these burners to his tireless hours of modification and development. For the Micromongo Burner, Michael suggests starting with a #65 jet diameter. This appears to be a good jet diameter in his test burner, but we may modify this recommendation after the burner undergoes an extended period of "on the job" testing. Absolutely do use the 14T Tweco tips discussed above, and the movable tunable jet pipe modification shown in the Minimongo Burner design images. (Note: I strongly recommend using a 1/8" jet tube, instead of the 1/4" tube shown in the drawing.) 

Nanomongo Burner: I am posting an image of the prototype Nanomongo burner if you are interested in where we are going with this design. Michael came up with this version, and it has good operating characteristics. The burner is totally stable from zero psi gage (the needle was resting on the peg in both of my test jig gages), to 30 psi plus. In the image the burner is burning at a pressure of 10 psi, but due to the sunlight you are unable to detect any flame in the nozzle. The burner is 100% copper and brass, with a high chromium stainless steel nozzle. The interior of the nozzle is machined to a 1:12 taper, but it additionally has a "step" of about 1/8" where it meets the end of the burner tube to increase the diameter a quarter inch, the same as the normal flared nozzle does on other burners due to the 1/8" thickness of the burner tube wall. We found this "step" to be necessary due to the thin wall of the copper pipe. It turns out the "step" is a critical part of the flare's operational design. We have determined that the secondary set of smaller air intake holes toward the rear of the burner are not necessary, and will not be included in the next version. The entire air intake assembly will be shortened and simplified. It will also include a sliding sleeve choke, although the present version displays an apparently neutral burn across its entire operating range, at least as much as I can determine at this point. The four screws in the forward part of the intake are to precisely align the jet, and will be moved toward the rear and reduced to three in number in the next version. The jet orifice is a 0.023" diameter, 0.60 mm, Tweco tip, silver soldered on the end of a 1/8" brass jet tube. There is also a set screw in the back of the rear of the burner to lock the jet tube from forward or backward movement.

Michael determined that this burner had to be modified with a larger intake diameter, in order to draw in the necessary quantity of air to balance the gas volume. The burner tube diameter is 1/2," and bells out to 1" in the intake chamber. This burner will easily match the Micromongo burner, 3/4" burner tube, in its output. It is very impressive, especially its flawlessly smooth operating range of zero psi to 30 psi plus. My test jig gages would not allow me to test it at pressures exceeding this level. As Michael mentioned to me, in the upper pressure range you can actually feel the air suction with your hand at a distance of 8" from the burner! The venturi vacuum is very impressive.

My Personal Observations: I have finally had the opportunity to try out one of the Micromongo burners in a short but interesting test. It is a reasonably good burner. I experimented with the nozzle flare adjustment to achieve the lowest input pressure, while maintaining a stable flame, and the results were better than I had hoped. With only 3/4" of flare exposure, the burner was stable to pressures down to 1 psi, or even a little lower. I did not have my most accurate gage on the system, so I am not sure exactly how low it went, but the gage needle was almost riding on the peg. This was after only about 15 minutes of experimentation. There is a very critical interaction between the jet location, centering, and the flare location, and the jet tube was loose in the mounting so I was unable to perfect the adjustment to its finest degree. I think that it is entirely possible to get this burner to operate in a stable manor at gas pressures down into the ounces range. Its upper end range is a given, but the low end capability makes it a very special burner indeed. This low end operation range is of no consequence when the burner is used in a melting furnace, but in a forge the low end ability will be extremely useful for some operations. It is possible that when I switch the present jet to one that is larger it will change this low end performance. That is yet to be determined.   Parts breakdown image for the Micromongo   (Before considering the construction of any of the Mongo series of burners, please read the information about the Side-arm burners at the top of this section.)


*** Rules Of Thumb for Forge Design ***

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

If you want to design your own gas forge there are a few simple "rules of thumb" to keep in mind. These are not exact, and may not even result in a successful forge, but they are a starting place for designing your own propane forge system. There are a great many variables involved with any forge system, insulation "R" value, exhaust opening area, smoothness of burner penetrations, elevation, quality of forge and burner construction, jet diameter, tuning, etc., to name but a few. Any one of them can cause problems. To design forges using other burner types, use the BTU Calculator, along with the information in paragraph #1 below.**

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.

2. The "Reil Burner" will deliver about 135,000 BTUs at medium to higher gas pressures, and can be cranked up to almost 200,000 BTUs by raising the pressure to 20 psi or more. In the lower pressure range of from 1-6 psi, where I do most of my work, it will produce about 60,000 BTUs, or even a little less. Use the middle figure in any design calculations.

3. Shoot for a burner to volume ratio of 1:300 or less. Some smiths who are very knowledgeable would say a more conservative ratio of 1:250 would be safer and insure that your forge will be able to weld. To calculate how many  3/4" burners you will need just divide the total chamber volume of your forge, in cubic inches, by 250 or 300, and then round up. If you come out to a burner requirement of 2-1/3 burners, then you will need 3 burners for your planned forge volume. Always plan conservatively or you may end up with a forge that is too cold to forge-weld.**

It should be apparent that a 4' long by 2' diameter pipe forge will require far too many 3/4" burners to be practical. Keep your forge chamber as small as possible. If you can't build what you need with these burners you may need to look at the "Monster-Burner" as a possible alternative to heat your forge. I will not provide rules of thumb for them, so please don't ask. You can easily enough get a "propane jet diameter/BTU output table" and figure this information out yourself. These tables are available locally through your propane dealer or on the Net.

** The above information is assuming that you will build a well insulated forge, having at least 2" of Kaowool lining coated with ITC-100, not Satinite, on the interior surface of the chamber. A 3" lining of Kaowool would be even better, and would probably pay for itself in fuel savings over the long run. If you elect to use a rammable or pourable refractory, or bricks, you will have to address the lower insulation values associated with these materials. One option is a composite design, a pourable refractory shell for durability, inside a Kaowool shell for insulation value. These are more difficult to build but are long lasting and can work very well.

Continue to page #2


23 Nov 07

Golden Age Forge