North State

My First Attempt (Picture Heavy)

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Heard the rubber mallet one also! My roomate in college was known for saying "...and what he doesn't tear up, he looks on!" Refering to me! Anyhow. Fun times! 

Much appreciation to your grandfather! I have tons of respect for our great military! I am a civil servant on a marine base in eastern NC. Those Devil Dogs are tough!

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Just a quick update video. There is a lawnmower blade in one end and a piece of half inch no name solid stock in the other. Since I am so unfamiliar as to how the forge responds to heat and how the metal reacts, I just stuck a couple pieces of junk metal in to see how they take heat. I ran the forge for about 5-10 minutes at around 20-30lb pressure on the regulator. Both pieces of metal got cherry farily easily and fairly quick. I only have one burner in. The only time I tried two didnt turn out as smoothly as with one. Im going to have to study on it some more. Probably have to put throttle valves in and gag one so it doesnt steal all the fuel from the second burner.

Take aways:

1. I still have a ton to learn.

2. The neighbors are going to hate all the racket associated with forging.

3. It was enormous fun!

How does the flame shape look to yall? Is there any thing else I need to consider? I am going to look up some pf that reflective paint to coat the inside with also.

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Good Morning,

Welcome to the Trap Line.

The Forge is not hot enough. There should be some 'Baby's Breathe' coming out of the Forge. Maybe you took your picture before the fire-box heated up. More Gas!!

Neil

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Flame shape and color look decent to me from what I could see.  Assuming that's a 3/4" burner, as long as your forge chamber isn't much larger than 350 cubic inches in volume you should be in good shape.

If those are heavy clay firebricks in your opening they will be a bit of a heat sink, but it shouldn't be much of an issue if that's the only place you are using them.

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Ok Swedefiddle, youre right about the time I had it going. Less than 15-20minutes. As for the 'babys-breath' can you tell me more about this? Honestly, this is the first time I have heard of it.

Buzzkill, yes its a 3/4" nipple that flares out with a 3/4" to 1" bell reducer. I want to grind out the threads on the 1" side. I think that will refine the flame shape even more. I haven't calculated the volume of the fire box, but I cant see it being 350 or more cu. in.  Also, yes they are firebricks in the opening. I was trying to trap as much heat in as possible. And, boy, do the get HOT! A lot of what i am trying to figure out is how long would it take to get the firebox up to temp. And the fuel balance between two burners.

Mikey, I was really happy withthe flame. Like I said, I generally followed the instructions on the video that i posted when I started this thread. I have read a lot of burner threads that were not as successful as mine turned out.

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Hey Buzzkill, I have been brewing on your last reply. I did the math and with a radius of 3" and a total lenght of 19", if my figures are correct, I am looking at like 537 or so cu.in. I didnt figure 6" round opening was too large, but does the 19" deep firebox put me over size for an efficient rig? And what is the relationship between regulator setting/number of burners/fuel consumption/internal heat roduction? I still have the sleeve for a second burner. I can appreciate how far I've come, however there is plenty for me to learn as I tune the old girl.

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It's unlikely that you will be able to reach and maintain forge welding heat with one 3/4" burner with that much volume.

As for the 19" deep forge chamber I have to ask what you are doing that requires you to heat up that much material at one time.  If you are doing long twists or something like that it makes sense.  If you are forging knives, swords, fire pokers, bottle openers, steak turners, etc. you'll be unnecessarily heating up steel which can also degrade/weaken the steel with excessive heats.   In general most of us can't work more than about 6 inches of stock by hand hammer per heat anyway, so spending more money on fuel to heat extra material can be both a financial waste and affect the quality of your finished product.  But to answer your question more directly, yes, I think that does put you over size for an efficient rig for hobby or small item smithing.

You should think of regulator settings merely as data points for your specific rig rather than to try to apply any hard and fast rules.  In other words keep a record of the psi when you have the forge running the way that you want it so you can easily return to that spot.   The pressure needed for a certain temperature in my forge with my burner is probably different than you would need.

The more burners of a given diameter you are running and the higher the pressure, the faster you will go through fuel.  Heat produced is a function of the amount of fuel burned properly in a given amount of time.  Ideally we would want all of the combustion to happen inside the forge and have only exhaust gases leaving it.  Normally though there is some flame outside the forge openings which we refer to as "dragon's breath."  That is combustion happening outside the forge and for the purposes of heating stock is wasted fuel.

If efficiency is what you are after then you want to go as small as you realistically can for a forge chamber and still be able to accomplish what you want to do.  I know that's a bit vague, but the attitude of "better to have it and not need it" will just cost a lot of extra money over time in this case.

Just for reference sake my propane forges have been between about 9 inches and 12 inches deep. In almost every case where I've had an issue with the size of my forge compared to the stock I wanted to work, it was the width or height of the forge or the opening rather than the length (depth) that was the problem.Your mileage may vary.

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It's generally cheaper to have a forge sized for your normal work and to build another just for working larger items.  Would you buy a dumptruck that gets 3 miles to the gallon for your daily driver because you may want to buy a load of gravel a couple of times a year?

I once needed to box fold some 3/8" plate several feet in length. So I dug a trench forge in my backyard to heat a section that long to make the bends. (Fire tray for a 15th century ship replica.) Filled it back in when I was done, ready for the next time I'd need it.

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Buzzkill thats some good advice. Being that I am a big novice, I just did things arbitrarily. Having zero experience to go on, I figured a firebox diameter of at least 6" would accomodate what I want to do. I just took the air compressor tank and used it at the length it was manufactured. 

Mr. Powers, I totally agree with the dump truck analogy. I know a novice painter need not focus much beyond primary colors, but I wanted to be able to grow into things somewhat before having to build another one. I was thinking along those lines when my good friend offered me an old compressor tabk to use early on. It is 20 gallons! Twice as big as mine! I would be even more on a fools erand! 

To answer both of you guys, I dont have an exact "thing" I am setting out to forge. I have been facinated by metal working, specifically blacksmithing for as long as I can remember. So my intentions were to start out small and heat some metal of varying compositions merely to see how they respond to the heat. Then once I have expored that, I want to try my hand at forging functional things (in no particular order) increasing in diffuculty... Tongs, bottle openers, steak turners, knives. 

I definitely dont think I want to undertake swords. So I wont be needing that dump truck! 

As for the size, I am exploring options on reducing the size. I think I could farily easily, cut the shell with a cutting wheel, then use a masonary bit to trim the refractory. I will have to move my hinges and latches, but hey, I'm becoming used to modification!

 

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Another option would be to cut just the very end off and make a baffle wall from insulating fire bricks or castable refractory (with a pass-through for long stock).  Place that inside your forge chamber to reduce the length and therefore the volume. That way you can remove the baffle when/if needed for larger projects in the future.  However, you'll have to pay attention to your chamber volume since you'll probably need to add that second burner once you exceed 350 cubic inches by much.

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Buzzkill, I actually wondered if I could fill in part of it and accomplish the same purpose... I have all the firebrick I want, but i was concerned about them being a heat-sync and still robbing heat from the firebox itself. 

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Insulating firebrick is a different animal.  These are lightweight and somewhat fragile.  They also tend to crack/crumble with repeated heat cycles.  However, if they are not structural in your forge and they don't see much mechanical abuse then the cracks aren't much of an issue.  I cut mine to shape with a dull hacksaw blade.  If you start with a sharp one it will be dull in short order anyway.  Unfortunately they are significantly more expensive than the heavy clay firebricks that are used for fireplaces or similar applications.

Heavy clay based firebricks like you showed in your forge's front opening earlier in the thread are indeed heat sinks and are much harder to cut, but they can take more abuse. You could still use those for a baffle wall (assuming they are rated to handle 2300 degrees F or more), but you should coat the side that will be exposed to the flame with an IR reflective coating like Plistex or Matrikote.  They will still absorb more heat than an insulating firebrick would, but it's not as bad as if you had a major portion of your forge built with them.

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Ok cool i have an infinite supply of regular firebrick and about 4 insulating firebricks that are about 4"×8"×15". I should be able to work out some sort of plan with those.

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8 hours ago, North State said:

if I could fill in part of it and accomplish the same purpose

This may be a dumb comment and I'm sure this's what you meant, but you only need a wall with a small opening at the bottom for stock to pass through, you don't have to fill it in completely. 

DanR

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11 hours ago, D.Rotblatt said:

you don't have to fill it in completely. 

DanR

I was actually thinking of adding a semi-circle "wedge" to make sort of a flat "floor" to yhe insode of it...

But I have some insulating firebrick that i am going to try first.

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Hi North State,

Do you mean something like this?

Forge_Raised_IFB_Floor1.thumb.jpg.6e0dccb1e662cd79fdf953798775cf0e.jpg

This worked well for me.

I used Insulating Fire Brick (IFB) and coated it with a Colloidal Silica/Zircopax slurry to give the IFB surface some protection.

It worked really well for me.

Tink!

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I like the flexibility of reducing the volume of the forge to save fuel, or to let it get hotter for forge welding.

This looks plenty hot enough! :)

Forge_Raised_Floor_Even_Heat.thumb.jpg.60d8f88e5b3848b90e082212765a9f6a.jpg

Good luck,

Tink!

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Tim, that looks great! Is that with one burner? If so, what is the size? 3/4"? Also, about how much run time does it take to get your forge that hot?

 

Nevermind about the size and number of burners, I zoomed in on your first picture and I think youre using a ribbon burner. Correct? Anyhow, how long does it take to get get to temp with it?

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Hi NS,

The burner is a single 3/4" AMAL gas injector with 8 inches of black iron pipe feeding into the Plenum chamber of my DIY Ribbon Burner.

The Burner is normally aspirated with 27 x 5.5mm holes drilled into the Insulating Fire Brick (IFB) that makes up the burner face.

As a hobbyist I wanted a Propane forge that was quick to heat up and economical to use. 

I decided to try the technique suggested by Dan Rotblatt, so instead of using a cast refractory lining inside the forge, I used a Zirconium Silicate / Colloidal Silica slurry to coat the rigidised ceramic wool.  This forms a layer only a few mm thick on top of the wool, which is then hardened by the Ribbon burner.

It gives me a lining that is not as strong as a cast refractory, but is easy to patch if I do crack it, but crucially has very low thermal mass.

I didn't want a forge to use all day, every day, but one I could turn on and off whenever I wanted to do some metal bashing.

So to answer your question, it was up to welding temp in about 5 mins, and is very responsive to turning the gas up & down between bashings.

I will probably sort out an Idle Bypass circuit at some stage, to make it more economical and easier to turn down between heats.

Anyway I hope this helps.

Tink!

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Sounds good, Tink. I intend to do the bypass circuit for that reason as well. I have some pipe fitting to do to arange my two venturi burners first.

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North State, I'm loving this thread.  I'm even more of noobie than you are as I haven't even begun to build a forge yet (target date is next spring). 

Referencing back to an early part of this thread, specifically on the "phobic" vs "philic" discussion, one of my high school teachers put it this way:  "Phobic" is like any other "phobe" as "phobes" aren't "for" anything.  "Philic", on the other hand, while not a complete acronym, the "ILI" can be thought of in terms of "I Like It." 

We had one fella that confused "philic" with another word (replace the first "i" with "a" and add an extra "l") and well, a certain degree of teenage boy humor ensued.  The explanation and the word confusion has always made that stick with me.

Good times.

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EDL, thats hilarious! Yeah i was aware of the difference, but it seemed that Google wasnt so much. Anyhow, I have recieved a GOB (eastern North Carolina term) of great tips and advice. I like to feel like I have really stretched the more experienced member's knowledge more than their patience! Dobt wait til then to begin accumulating materials to build your rig! Good luck and if you need any help, IFI is the right place!

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