1st 7 gal Propane Tank Forge Build

[Calkidd]

My first post everyone. I am a little late in the knife making game at...*cough*... 50. However, then again it's never too late. I want to get started in a hobby that I can do when I retire along with woodworking I do now.  In the meantime I plan on making knives for my coworkers that retire. 

Right now I am building my first forge from a 7 gal propane tank. I'll end up using 2 inches of ceramic insulation and Kast-o-lite 30 for the floor. I was going to use a fire half brick, but this forum showed me its better with a floor casted in.   Coupled with 2 venturi Frosty burners.

The burners were a challenge since it made my brain hurt reading how to properly set up the angle. Using info Mikey98118 provided I think I got it some what close. I went 2" from TDC, but I probably could have maybe gone 2¼-2½" to get a tiny bit more angle towards the edge of the floor. Also instead of shoving Koawool in the gaps of the venturi and the holder I have some 2" washers I would drill out to 1" and weld them on the burner holders, actually then how would I remove the venturi burner?   

Question; on the stainless steel end of the burner, a 3/4" x 1" reducer, would it help or make the flame more efficient if I ground down the threads and smoothed out the bell?

I am debating to make the back, I had cut off, a door so I can access the inside to replace the consumables. I would weld a strip of flat stock for the door to seat against the body.

Also,  I am figuring out a design to make the legs, or carriage as Mikey would say, and a handle on the top. I am thinking rebar for the handle, we'll see. 

In the photos I have tacked welded the holders on. Well, I am going to have to cut them out so I can cut the holes in the insulation.  Of course the long pipes are just for fitment purposes.

Thanks for reading through my drivel.

Bryan

[Irondragon Forge ClayWorks]

I wouldn't weld the washers to the burner holder, but let them slide up & down on the burner to close off the air gap if needed. With my forge the burner needs some secondary air to preform at it's best.

[Calkidd]

Thanks for the insight.  I see the flaw in my idea. I sometimes over think it and look for being more aesthetic rather than function. 

[Mikey98118]

7 hours ago, Calkidd said:

actually then how would I remove the venturi burner?   

Place the washers on the burner's mixing tubes; they work on the forge, but are part of the burners.

You either need to include brazed nuts on the washers, so that you can keep them in place at various heights above the top end of the pipes (that are trapping the burners in place), or else use wood slivers to hold them in position on the burners.

[Frosty]

Welcome aboard Bryan, glad to have you. Pretty good job o the forge for not picking a set of proven plans and following them. Most guys who try to modify other folks plans make more mistakes than improvements. I don't see any mistakes, not really. Things I'd do differently to be sure but that doesn't make them mistakes.

I tune my burners so they don't need secondary air but I have practice, it's just different, not wrong. As mentioned using a set screw on the washers so you can adjust secondary air intake is all the tweak they need. Mounted on the burner that is. 

Your feet don't need to be nearly that complicated. How about a couple lengths of SQ. tubing welded parallel the length of the tank. (forge shell) The distance between is up to you and isn't too important as long as it holds the bottom of the shell off the table or whatever you use as a stand. I like them as close to 8"-9" apart as is practical. I make them and similar things from a pile of old broken wind master road sign stands. You know the kind that fold up, 4 legs and a telescoping post? 

They're made from square tubing that telescopes smoothly. I use the larger (receiver) tubing for the parallels welded to the forge shell. Then I use shorter pieces of the smaller tubing to make sliding fire brick holders. A little angle iron across the ends and the fire brick will lay securely right on the tubing. These are "porches" and let you lay long pieces in the forge without having to hold them. You can also lay them at an angle and reduce how much more stock gets heated than you want. The inserts only reach half way but you can extend them out enough to lay maybe 2 more fire bricks for an extended porch. Your door baffles rest directly on the porch or the inserts as works for you.

Why half way? You DO want a doorway at both ends don't you? It'll let you heat the center of long stock or evenly heat long pieces by passing it back and forth through the forge. Two extendable porches, two doorways makes a darned versatile forge.

These aren't HOW to do it, just some ideas for you.

Frosty The Lucky.

 

[Mikey98118]

3 minutes ago, Frosty said:

I tune my burners so they don't need secondary air but I have practice, it's just different, not wrong. As mentioned using a set screw on the washers so you can adjust secondary air intake is all the tweak they need. Mounted on the burner that is. 

And I find his burners capable of creating perfect flames. However, he can't control the quality of burners made and tuned by others, any more than I can with Mikey burners. If your burners turn out perfect, great. If not, washers help. But in that case, the washers can be used to shut out all secondary air.

[Calkidd]

3 hours ago, Frosty said:

Welcome aboard Bryan, glad to have you. Pretty good job o the forge for not picking a set of proven plans and following them. Most guys who try to modify other folks plans make more mistakes than improvements. I don't see any mistakes, not really.

Thanks Frosty, yeah I have been researching the best I can and taking from others who have built a propane tank forge along with information I got from here, especially burner alignment. Mikey98118 helped with that.  I honestly don't know if I have made any mistakes, but well see once it is up and running

3 hours ago, Frosty said:

I tune my burners so they don't need secondary air but I have practice, it's just different, not wrong. As mentioned using a set screw on the washers so you can adjust secondary air intake is all the tweak they need. Mounted on the burner that is. 

I am using your design and printed out your instructions hoping to build them as well as I can. I have HF (Vulcan) MIG tips and found out they are metric, but I have metric taps.

3 hours ago, Frosty said:

How about a couple lengths of SQ. tubing welded parallel the length of the tank. (forge shell) The distance between is up to you and isn't too important as long as it holds the bottom of the shell off the table or whatever you use as a stand. I like them as close to 8"-9" apart as is practical.

Exactly, once again really thinking in to it too much, its not furniture its a tool.  But yes I have settled on 3/4 or 1" square tubing.

3 hours ago, Frosty said:

They're made from square tubing that telescopes smoothly. I use the larger (receiver) tubing for the parallels welded to the forge shell. Then I use shorter pieces of the smaller tubing to make sliding fire brick holders. A little angle iron across the ends and the fire brick will lay securely right on the tubing. These are "porches" and let you lay long pieces in the forge without having to hold them. You can also lay them at an angle and reduce how much more stock gets heated than you want. The inserts only reach half way but you can extend them out enough to lay maybe 2 more fire bricks for an extended porch. Your door baffles rest directly on the porch or the inserts as works for you.

I am going to have to read this a few more times. I am not sure what you're saying.  However, you gave me an idea to use angle iron attached to opening where I have the 3/8 plate along the edges of the opening.  I don't have a "porch" installed yet, because I am figuring out how big to make the porch. The opening is 7"x5", therefore I was thinking extending the porch out to about 6".  I have plenty of 3/8 plate so I can make it a big as necessary. 

 

3 hours ago, Frosty said:

Why half way? You DO want a doorway at both ends don't you? It'll let you heat the center of long stock or evenly heat long pieces by passing it back and forth through the forge. Two extendable porches, two doorways makes a darned versatile forge.

I have an opening at the back, again this is a design I have seen around, and thought this was standard.  I was under the impression if I had another opening as big as the front, the forge would be inefficient.  However, just like you said I can add a brick on the back to shut the opening.

2 hours ago, Mikey98118 said:

However, he can't control the quality of burners made and tuned by others

Bingo! I will need to do more research how to tune these burners.  I know one of the important aspects is the distance in relation to the tip of the gas jet (MIG tip) to the entrance of the air in the T plumbing.  Taking my experience in porting cylinder heads, I may try to radius the bottom edge of the T to aid in the smoother flow of air.  Additionally, I came across a propane tank build where they installed a draft on the ends of the T, kind of like the photo I have attached ( I can't find the exact thread), but this other builder put a rod between two ends so the draft moved together on both ends of the T.

------------------

Frosty, I asked this earlier, but what are your thoughts smoothing out the threads on the burner end?  Will that help with a better flame?  I know from working in the automotive machining industry, smoothing out the intake ports to allow the air to flow smoother keeping down the turbulence.

 

Frosty and Mikey98118 thank you for taking the time to post on my thread with your suggestions.  They will always be welcomed.

[Frosty]

When I said I tune mine so they don't need secondary air bear in mind I've been making T burners for a good 30 years now and can pretty much eyeball them. I tried to make the directions as clear as I could if they're not I'm around to help out. 

The telescoping tubing porch mount, forge stand is a combination of things I've done. I've laid angle iron parallel lengthwise as a cylindrical forge stand rather than legs for years. The telescoping porch mount is shown in my too large shop forge pic below. Do NOT build a forge this silly big one half is more than I usually use and with all 4 burners running 6 guys can heat work without getting in each other's way too badly.

This is the back of the forge but shows the porch, the 2" angle iron is to connect the insert tubing and keep the fire brick from falling off the end/ You can see the ends of the insert tubing under the angle iron. I can slide the porch straight out and either place more brick or just let one brick support the end as a helper.

I made a tong rack on the other side coming off the angle iron so I can keep the tongs I expect to use where I'll need them. The rack holds the tongs well below the porch so dragon's breath (flame exiting the doorways) from heating them up. You have to be careful to remember to reach down and grab tongs by the reins. I promise you are NOT going to grab the bits a second time! I don't have any in the pic but I close the working section as much or little as I like with firebrick on edge on the porch.

I found cutting the threads out of the flare or turning the inside of the T into a smooth curve made no measurable improvement, if fact smoothing  the flare ID seemed to reduce performance. I didn't actually test it though so I could be wrong. I only tried it a couple times and moved on, I wouldn't be too surprised if someone didn't come up with something worth doing on that track.

These aren't like a ported and polished intake manifold, I think the threads actually reduce friction through Bernoulli effect. As the flow is forced to move over a thread it causes a low pressure contact layer which greatly reduces friction like flowing over a wing. A series of threads might cause the entire threaded section to be a low pressure/friction zone increasing induction over all. I do NOT KNOW that, it's a personal hypothesis based on observation, I'll gladly welcome better observations, measurements, etc. I'd LOVE to really know why internal threads perform better than a smoothed ID.

A T burner that requires choke plates to make a neutral flame was built incorrectly, typically it has too small a jet. It's easy though if you make it induce way too much air you can just choke the intake ports until the flame is right. I much prefer to increase the amount of fuel till they balance. I run 0.035 mig contact tip at typically lower psi. meaning I'm putting more flammable mix per second in the chamber at a lower velocity so it stays longer to transfer energy to the liner.

Once tuned to a neutral flame the induction curve is pretty flat it only leans out a little bit as you increase the psi to the max that'll support a stable flame. I was frankly shocked when I discovered a T inducer just screwed into a NARB produced a stable flame over the full range of my old 0-20psi regulator, screw it out till there is no pressure on the diaphragm or all the way in till the screw bottom against the stop. From tiny little flames to a serious conflagration and it burns smoothly. 

The burners with choke plates you show are "side arm" type burners, they have half as much air port and if they need a choke plate are probably running a 0.025" jet diameter or about 1/3 the BTU output and around 2x the flame velocity. Less heat for a shorter time. Hmmm?

Frosty The Lucky.

 

 

 

[Calkidd]

 

Day off and got a little bit done. Welded on some legs for the forge. I had some extra ¾ x 1 ½ square tubing. I like the the simplistic but yet effective design. 

Got both burners built. At first I was getting a crazy whistle and chugging plus it wouldn't ignite very well. I cut an ⅛ off the tip and viola. I think I am good and may or may not need to trim more off the tip. 

Frosty,  how much taking off the tip makes a difference? Are we talking few thousands or tenths? I mean if I file the tip is that enough to fine tune?

I would assume if it was lean placing my hand or fingers over the air inlet would clean up the flame. Thus meaning too much tip was cut. Wish I had a lathe. I could make different lengths and just test.  Then again I do not have any sealer (tape or dope) on the burner tube. I don't think there is enough force to pull air from around the threads and cause a lean issue.

Some photos of today progress. 

[Irondragon Forge ClayWorks]

I wouldn't mess with the burner any more, until you have the forge finished. Then fine tune it with the burner mounted in the forge. There is a big difference in the burner running in the open and forge.

[Calkidd]

I am starting to install the insulation. Shout out to Frosty for the help with my questions. 

I was waiting to install the burner holders, but if I need to fire the ridigizer I guess I'll need to. 

Question; should I go ahead and weld on the back and then feed and install the second 1" layer of wool via the inlet? Or install all layers, assemble and fire it all at once?

I would assume this is necessary in order to fire the ridigizer for the first layer.

[Calkidd]

I went ahead and welded everything on and installed the second layer of wool and ridigized.  

The first layer I fire with one burner because the second one was blowing itself out. Once I replaced the trimmed gas jet (MIG tip) it lit.

After the second layer I fired it up. Holy cow does this thing heat up fast. It went bright orange in less than a minute at 6lbs of pressure.

Next is Kast-o-lite 30. I bought 10 lbs, hopefully that will be able to coat the interior and pour a floor. 

[Frosty]

Rather than "pour" the floor if you cut a strip of ceramic blanket the width you'd like and feather the edges to make a smooth transition into the cylindrical walls, rigidize it in place. You can cover it with KOL with the rest of the forge. This will give you a nice flat floor that's more well insulated and hold the carrying weight of the forge down a little bit.

Looking good so far. 

Frosty The Lucky.

[Mikey98118]

BTW, the high orange color in your forge, at this stage, means that you are right on track so far. After using a finish layer of heat reflective coating, your forge should come up to lemon yellow incandescence.

[Iswhatitis]

In my opinion it is best to have it both ways. Cast in the floor with kastolite, but make the floor /walls large enough to where you can fit a hard fire brick on top of your floor as a sacrificial floor. My forge is a 20# propane tank for the body like yours and that is how I did it. I am glad I did it this way because my fire brick floor now has a skin of scale on it that softens and becomes sticky when the forge is on which is fine but  I know at some point I can just change the hard fbrick to a fresh one and get a brand new floor. I used kastolite as well which is said to be more resistant to flux than most refractory  and I plan to weld in my forge in the future but keep in mind that resistant isn’t the same thing as flux proof. My hard fire brick floor is really there for the flux so that it doesn’t start messing up my kastolite floor. 
 

btw I had enough itc-100 left to put on the hard fire brick floor plus another hard fire brick for a future swap out which I think helps the efficiency of the forge floor a bit but it definitely isn’t necessary. The itc-100 was really purchased  just for coating the whole inside of the refractory to increase the efficiency. I bought a 1/4 pint which wasn’t too pricy and was enough to coat the whole thing.

 

note: when I say hard fire brick I am talking about the ones that are normal size but much thinner, I think about 3/4” but I’d have to look. This way it doesn’t take up much room in the forge.

[Frosty]

Half thick brick is called, "Split brick." The surface of yours is getting gummy at heat most likely because it's beginning to break down. Once it reaches vitrifying temperature, somewhat below it's rated max prolonged exposure temp, the silicates in the brick begin fusing, I don't know what happens to the iron oxides that make them "fire" bricks. Anyway as the silicates fuse they begin to consolidate reducing it's insulating properties, the silicates push to the hottest area. The surface and make it gummy sticky at forging temps. Forge scale gets mixed in forming a weird pavement like stuff that is a PITA to live with.

The split brick on the floor of my WAY TOO large shop forge runs about half way through the brick but I can place work to either side and avoid it. Every once in a while I'd scoop as much out as I could and replace it with bentonite, cheap clay kitty liter is bentonite and works but it's still a PITA.

My newer less too large forges lined with Kast-o-lite and kiln washed with Plistex don't form the gummy goo. Welding flux does but scraps out easily enough. 

A prime sacrificial floor is Kiln shelf. It can be expensive but is impervious to borax based fluxes or abrasive erosion at welding temps. 

There are hundreds if not thousands of posts on this very subject in the Forges 101 section.

Frosty The Lucky.

[Calkidd]

I have lined the interior with KOL-30. It took a about 9 lbs to coat the forge at probably ¼ thick. I didn't want to reduce my interior space. I need to coat it with Plistex now. I just need to get off my rear and get it ordered.

The picture makes it seem it's choked down towards the back, but it's not.  

[Mikey98118]

Good job so far. Plistex would make a nice finish. You may want to consider a movable internal baffle, so that one burner can be shut down, and only one-half the internal area heated for small jobs. Your wallet will thank you.

[Iswhatitis]

On 12/4/2021 at 2:09 PM, Frosty said:

Anyway as the silicates fuse they begin to consolidate reducing it's insulating properties

You are talking about the very hard type of brick that isn’t called “insulating fire brick” but just “fire brick” right? Because that is what I have as a throwaway floor. It is just sitting on top of the kastolite. I’m just making sure I am understanding what you are saying.

I actually just swapped it out for a fresh one with a coat of itc-100 today. Then I realized I had failed hard heat treating a hammer earlier. I had it glowing just barely and my oil wasn’t quite hot enough yet and of course my tank decides to run out of gas so I took the pluming torch I use to light my forge and was trying to add a bit more heat to the  last little flame coming out of my t burners by shooting it into the front of the forge at the hammer head, it was kind of ridiculous and probably looked seriously weird but Once the burners went totally out I grabbed the head which was probably 50-100 degrees too cool and dunked it in the oil and hoped for the best. 
I went and got more propane and then hot drift tempered it to straw, cooled it, and tryed it against some cold mild and it just felt too soft so I will heat treat it again using water this time. 

btw: are you supposed to have your water warmed up to a certain temp before quenching like you do with oil?

[ThomasPowers]

Oil is heated to lower it's viscosity.  Heating water doesn't lower it's viscosity to a noticeable amount.  The problem using water is it's boiling cause leidenfrost issues.  I would not encourage those!  If your alloy will take it; brine is a better quenchant, don't preheat it.

If I don't know how the alloy will react; I will start with warm oil and if that doesn't harden enough; then go to the water based quenchants: water, brine, blood, etc...

[JHCC]

Do a file test on any piece that you attempt to harden. If the file doesn't skate, don't bother tempering.