Just before I build my first forge, I need to make sure I have this right

[Ethan Yap]

I've been doing research and I think I'm ready, but some information sources have gotten lost. There are 3 things I need to confirm before I get down to it

1. There is an ideal height of forge (distance between burner mouth and floor). I learned this about a month ago, but I can't find the source post to find out exactly what it is. IIRC it was about 1 foot?

2. I was told by Gameco Artisan Supplies that their set of two 1/2" burners will be suitable for a 1 cubic foot internal volume forge. But I just found a (3 year old) post yesterday that says a 3/4" burner should heat only 350 cubic inches for forge welding. I don't expect to be forge welding for quite some time, and I haven't been able to find data on if this set up will get hot enough for non-welding forging. I did kinda sorta anticipate this problem and I have 3 fire bricks (and 1 more that my pieces will sit on while heating) that I plan to just kind of leave in the forge to take up space. Is that a viable band aid?

3. Can I treat Plibrico Plicast 31 the same way as standard satanite? I can't reasonably get satanite in my country and this was the closest substitute. It's a castable refractory is all I know for sure. Should I just mix it with water until it achieves the oatmeal-like consistency and apply it like any cement?

[JHCC]

7 minutes ago, Ethan Yap said:

There is an ideal height of forge (distance between burner mouth and floor).

Depends on the size of the burner, the shape of the forge, and the angle between the burner and the floor. Without knowing that, we can't answer your question.

If you haven't yet, please READ THIS NOW!!!

[Latticino]

21 minutes ago, Ethan Yap said:

3/4" burner should heat only 350 cubic inches for forge welding

This rule of thumb is for a well insulated (say 2" of high temperature insulating material with a k-value equivalent to high temperature ceramic blanket) forge with an efficient burner.  The Gameco burner appears to be the latter, but you have given no details on how you plan on insulating your forge.  However, one cubic foot is the equivalent of 1,728 cubic inches.  That is a very large forge.  Are you certain they meant one cubic foot of internal volume?  Hopefully you are not planning on building that large of a gas forge, as the typical newbie gas forge mistake is to build it too large.

51 minutes ago, Ethan Yap said:

I have 3 fire bricks

Are these fire bricks insulating , or hard bricks?  The rules of thumb for forge volume to burner capacity, in my opinion, have more to do with the associated forge outside surface area and door size than actual interior volume.  There is also a minimum amount of interior volume that each burner needs to fully develop combustion as well, but that is a bit harder to predict.  Adding insulating bricks to the inside of a forge will decrease the volume of the chamber, but the bricks will be prone to cracking and damage over time (and it doesn't change the forge surface area or door configuration).  Adding hard bricks to the forge interior will add thermal mass, which will make your forge heat up and cool down significantly slower, but they will last longer than soft brick provided they are not thermally cycled too abruptly (but you have the same issue with forge surface and doors).  You will need to be careful that you don't provide any thermal paths "through" the hard firebrick to the forge exterior (all sides of the hard brick should be insulated as close as possibly to the balance of the forge walls IMHO).

As far as I'm concerned, a good door design will improve forge performance better than putting additional bricks inside to reduce volume.  Unfortunately making an effective and efficient door is one of the most difficult parts of forge design.

[Ethan Yap]

[Unnecessary quote removed. You don't need to quote when you're answering the immediately preceding comment.]

Thanks for the reply!

It's going to be 2" all round of ceramic blanket, sealed by 1/4-1/2 of refractory cement. I know the forge needs to be at least 8" wide by 12" long for the size of work we (I'm not the only one using it) plan to do. It's not super advanced I don't think, but it's pretty large. I might be able to get away with 8" on all sides (Edit: still 1' long , I messed up. So 8x8x12). The height is because I read somewhere on this forum that a forge ought to be taller than it is wide because the burner needs a certain amount of space in front of it to properly form a flame envelope. Something along those lines. 

I'm pretty sure they're hard bricks. The options I was given were SK34, SK36, SK38, and Insulating. When I tried to confirm the SKxx were hard, the reply was (paraphrasing) "all fire bricks are made of very hard material". I'm not sure if it's the standard of English in my country, or lack of product knowledge, but they're are specifically  a refractory company so...

The bricks will not be part of the forge. They'll just be sitting in there to prevent the flame from impinging directly on the refractory. The forge will most likely be cycled once a day, tops, which I think is pretty standard.

Ah, speaking of doors, I forgot. We plan to make our own doors, which will be the same as the forge walls, but as a separate piece. Steel, ceramic blanket, sealed with refractory. The door on the back will be closed 90% of the time (that's right, right? I don't need an exhaust hole on both ends, only the front?). We'll also have another rear door with a hole in it so we can heat the middle part of longer pieces.

1 hour ago, JHCC said:

Depends on the size of the burner, the shape of the forge, and the angle between the burner and the floor. Without knowing that, we can't answer your question.

If you haven't yet, please READ THIS NOW!!!

That was actually the first thing I read haha

[Then please put your location in your profile and reread the section on the Quote feature.]

The burners are 1/2". They are the Gameco burners I mentioned. This is the link to the page since I'm not sure what other dimensions affect the ideal height. It's a rectangular forge, so the burner will be perpendicular to the floor

[Commercial link removed]

[Latticino]

Ethan,

Don't feel that you need to quote my whole post if you are directly following it.

Not going to go into a great deal of research, but looking at the Gameco link you furnished, I saw only the recommended forge size for a single 1/2" burner.  Doing the math quickly for that, I come out with a recommended forge size for that burner of 0.125 cubic feet (215 cubic inches), which seem reasonable from my experience.  I find it very hard to believe that they are recommending two of these burners as being adequate for 1 cubic foot of forge volume (at least to get up to any kind of acceptable heat), but I suppose it is possible.

One of the big problems with using gas forges is that they aren't as versatile as solid fuel forges.  For efficient gas forging you will often find you need several different forge body configurations to allow forging of different stock and end products.  A forge for heat treating armor plate is very different from a bladesmithing forge.  Many of us try to design our first gas forge to be able to do too many different things, and it results in a forge that doesn't do any of the above well (and is usually too large as well).

[JHCC]

One advantage of starting out with solid fuel is that you get a feel for the kinds of projects that you are (or want to be) working on. If you move to gas, then you can design your forge on the basis of that experience, rather than on a guess or the recommendation of someone with different priorities or circumstances.

[Ethan Yap]

6 hours ago, Latticino said:

I find it very hard to believe that they are recommending two of these burners as being adequate for 1 cubic foot of forge volume (at least to get up to any kind of acceptable heat), but I suppose it is possible.

 

I was pretty specific, but knowing what I know now 3 months later, POL doesn't refer to a single size of fitting but a standard, so maybe I shouldn't be taking what he says as the gospel truth

I wanted to start out with coal, but we had problems with ventilation and smoke and dust. Recently we've upgraded the system though, so maybe a coal forge will appear soon. It's indoors since this country doesn't have enough land to do anything outdoors, where you can't stack land use on top of itself. Already everyone involved is paying an exorbitant amount for the use of space. Regardless, I'll talk to the guy about reducing the size, or making our own burners to supplement

 

[WayneCoeArtistBlacksmith]

Let me know if I can help you.  I prefer e-mails.

Wayne

[Ethan Yap]

Thanks man, will do! I'll probably know if something's gone wrong by tonight (it's 0830 now), but I've got huge amounts of excess material so I can screw up many times before there's a real problem

[Irondragon Forge ClayWorks]

So where in the world are you located?

[Frosty]

Ethan: The reason you don't understand what the manufacturer is telling you or what folks trying to help you here are saying is you haven't done any of the homework. When you say "I read somewhere here that. . . " means you didn't understand what that person was talking about.

The rules of thumb that say one well tuned 3/4" burner will reliably bring a 300-350 cubic inch forge to welding temperature are pretty well established as accurate. You are proposing using two 1/2" burners to heat a 8" x 8" x 12" forge. Did you to the basic arithmetic that tells you how much burner that will require?

Do you know how to calculate volume? Did they teach you how in school? 

We're not trying to discourage you or get you to give up but you don't know enough to build a forge. Honest Ethan you aren't even close to knowing what to order let alone making a successful build. If you just order stuff you'll be spending money for a poor return. You want to get your money's worth and this isn't going to do it for you. 

Frosty The Lucky.

[Mikey98118]

There are several accounts of how to build a forge. If you don't want to spend the time reading up enough to understand what you are doing, Larry ZoelerForge will show you how to build a forge his way. Ron Reil's forge pages will show you how to build a forge his way. Wayne has a website showing you how to build a forge his way. You can buy an old copy of Gas Burners for Forges, Furnaces, & Kilns, learn how to do it my way and then sell the book back to someone else. Or you can download a copy from a pirate site and put up with their games. Anyone of these paths will end with you owning a good forge at a good price; choose...or don't.

[Latticino]

12 hours ago, Ethan Yap said:

we had problems with ventilation

Please note that adequate ventilation is just as important with a gas forge as a solid fuel forge.  Possibly even more so as the combustion byproducts are harder to sense and more insidious (not to mention the potential for a gas leak ruining your day).  Hopefully your new system solves this, but this can be a major safety concern.  At bare minimum I would strongly recommend that you get a good CO monitor and install it in your forging space.

[Ethan Yap]

The problem was because of optical smoke detectors. The ventilation system could handle pretty much all waste gases and particles, problem is that visible particles like smoke would trigger the fire suppression system. The new system will be able to get right up close to a potential coal forge so no smoke escapes

[Frosty]

Smoke isn't what can kill you and others in the building, you NEED "CO" detector / alarms if you're going to burn gas. CO stands for "Carbon Monoxide."

Frosty The Lucky.

[Ethan Yap]

17 hours ago, Frosty said:

You haven't done any of the homework. When you say "I read somewhere here that. . . " means you didn't understand what that person was talking about.

Hey. come on, that's not fair. I've read almost the whole textbook, but skipped one chapter and only because I had an answer key. I'm only asking now because I didn't make or understand the answer key, since it's just a list of multiple choice answers. Now I did intentionally skip the chapter, which was wrong I'll admit. But having one question on one topic does not imply that I didn't read all the other chapters. Besides, the conversation with Gameco was "Is this suitable for a 1 cubic foot *internal* volume?" "Yes". I saw no reason to doubt that answer, until I coincidentally came across conflicting information. I say again, I intentionally skipped that information before because I already 'knew' the answer.

You're right that I didn't understand the thing about ideal flame length. That's why I went looking for it again, and failing that, I asked about it.

Yes I know how to calculate volume. If I didn't see the numbers clearly not tallying, I wouldn't have thought to ask the question. I had one guy tell me "these burners are enough for 1 cubic foot" and then everyone else saying "these burners are about enough for a 0.2 cubic foot forge". And  that's why I'm here to clarify.

Anyway, I more or less finished building the outer shell out of sheet metal a few hours ago. After all the insulation goes in, the internal dimensions will be 8x6x12", for 576 cubic inches. There will be a 101.25 cubic inch fire brick in there to rest pieces on, and 3 more to shrink the volume as needed, down to 171 cubic inches. But based on your recommendations, I doubt I'll ever need all 4 at once, so with 3 bricks, the volume will be 272.25 cubic inches

 

2 hours ago, Frosty said:

Smoke isn't what can kill you and others in the building, you NEED "CO" detector / alarms if you're going to burn gas. CO stands for "Carbon Monoxide."

I understand. The place is properly ventilated and always has been. The problem was smoke detectors, not toxic gases. It was essentially a technicality. Now we're able to avoid the detectors. Besides, the owner (well, tenant, but a level closer to the owner than me) said he will handle the logistics. Edit: For future convenience, you don't need to explain any technical chemical terms. I have actually done my homework, and I have *some* background in that sort of thing anyway

[(M)]

I know what youre saying, but a 30 minute skim throught forges 101 would solve all your questions.  Or most of them.  

As to the refractory, it should be a castable refractory good to ~3000.  I looked at the data for Plibrico Plicast 31 and it should do the trick, but next time posting some data for us would help.  Live and learn.  

I started my time here by asking some really dumb and demmanding questions, bbut ive been learning.  Not saying yours are dumb questions, but you can read forges 101 and possibly "construction of a gas forge" which documents my build to make your life easier.  Enjoy the learning and make a great forge! Who'd a thought you could make a forge better than any you can buy for ~$200! 

Best of luck!  Keep us posted

(M)

[Ethan Yap]

38 minutes ago, (M) said:

I know what youre saying, but a 30 minute skim throught forges 101 would solve all your questions.  Or most of them.  

I probably read the flame length thing in one of the 101 threads, since those make up probably 90% of my reading on this forum. But the search function didn't turn anything up, and I don't want to look through the haystack again, for a needle that someone already told me doesn't exist

I really wish I could have posted data, but I'm here because I couldn't find any. I have a safety sheet, but no instructions of any kind. I'll just pray it works the same as the regular cement I'm used to, with the exception of needing to be dried out and 'baked'

As I admitted to Frosty, I did skip over the burner to cubic inch ratio stuff. I only take issue with how he assumes that means I didn't read at all.

43 minutes ago, (M) said:

Who'd a thought you could make a forge better than any you can buy for ~$200! 

Ah, i so wish I lived in America  I would have had my forge up and running 6 years ago if I did (yes I knew nothing about gas forges just 3 months ago. I wanted coal)

[ThomasPowers]

The search built into these forums is a "known bad one".  You may have much better luck using your browser's search and including iforgeiron.com as one of the search term.   I just googled:   flame length iforgeiron.com     and saw several promising hits.

 

[Frosty]

Take issue all you'd like, your own posts show you didn't read the material. The burner to volume ratio is discussed often. Flame length isn't discussed because it's unimportant. The closest thing to discussing flame length is in regards to dragon's breath, why it's not a good thing to have very much and what the flame type means.

The only discussion of flame out of the burner is in regards to reading it to determine the fuel air ratio being burned and how to adjust it. Flame length can be an indicator in extremus but it's not usually significant enough to be a stand alone topic.

These are discussed repeatedly in Burners 101.

The most successful forge builds are discussed repeatedly in Forges 101, including where to download or buy proven GOOD forge designs with directions . Burner to volume ratios, placement and orientation along with the reasons are also discussed a repeatedly.

You ask questions that show virtually zero knowledge or understanding of such oft discussed topics can only lead a person to one conclusion. Either you didn't read the material at all or your reading comprehension is poor. You MIGHT consider reading the sections mentioned with a pencil and paper at hand so you can take notes. That is NOT a snide comment, it's a basic research practice. I use graph paper so I can make detailed sketches of devices I don't understand, I also note page and authors so I can look further if necessary. 

I only call it like I see it. Making excuses won't alter my opinion. Taking issue with my opinion doesn't mean much to me. To alter my opinions you have to actually SHOW me I'm wrong or there's a better one for me to adopt. I cherish people who point out my mistakes, they're very valuable to me. 

Frosty The Lucky.

[(M)]

2 hours ago, Ethan Yap said:

I really wish I could have posted data, but I'm here because I couldn't find any

Lol i just googled plibro pilcast 31 and got the temp rating.  Google is our best friend! As long as what you have is a castable refractory it should work(with the temp rating i saw).  

For curing and construction, see my thread.  People answered all my questions at least.  

Again pls pls read forges 101 fairly thoroughly.  It will give you the background info we all need for these things.  .  You will learn loads.  

Happy forging

(M)

[Mikey98118]

 

Since I'm the one who keeps harping on about the importance of building a forge with the flame angled away from heating stocks (round forges) or with the ceiling far enough from the floor (square forges) to keep the flame from impinging on heating stock, I can answer your question about flame lengths; since different burners make different flame lengths and since flame lengths also vary by how far the burner is turned up, there can be no pat answer; it is a judgement call on the builder's part.

 

Since most people find little reason to turn a burner on full blast, the flame for a box forge can be measured for length at a maximum of 20 PSI gas pressure and that can be used for a good height measurement in box forges. You want the length to be at least two-inches beyond secondary flames. No practical forge can avoid tertiary flames, so construct and tune your forge's burner well enough to avoid making them.

[Ethan Yap]

21 hours ago, ThomasPowers said:

The search built into these forums is a "known bad one".  You may have much better luck using your browser's search and including iforgeiron.com as one of the search term.   I just googled:   flame length iforgeiron.com     and saw several promising hits.

Yeah I tried that before, tried it again and still can't find that post. Frosty says it's not important though, so that's good enough for me

 

20 hours ago, Frosty said:

I only call it like I see it. Making excuses won't alter my opinion. Taking issue with my opinion doesn't mean much to me. To alter my opinions you have to actually SHOW me I'm wrong or there's a better one for me to adopt. I cherish people who point out my mistakes, they're very valuable to me. 

Fair enough then. That already makes you better than 99% of the internet. Anyway, my question's been answered and I'm not here to flatter or argue so I'll just thank you for all the information you've posted on this forum and be on my way

 

18 hours ago, (M) said:

Lol i just googled plibro pilcast 31 and got the temp rating.  Google is our best friend! As long as what you have is a castable refractory it should work(with the temp rating i saw).  

Oh yeah I've read a lot about refractories and how to cast/trowel them on here and elsewhere, but it's all about satanite, kiln washes, zirconia, ITC-100, and how to rigidise ceramic wool. I just needed to check if Plicast behaves the same way. I'd already checked the temp rating, just needed to know it can be mixed the same way as satanite etc. Thanks for the info!

 

16 hours ago, Mikey98118 said:

Since most people find little reason to turn a burner on full blast, the flame for a box forge can be measured for length at a maximum of 20 PSI gas pressure and that can be used for a good height measurement in box forges. You want the length to be at least two-inches beyond secondary flames. No practical forge can avoid tertiary flames, so construct and tune your forge's burner well enough to avoid making them.

Thanks! I was having trouble with that because there's been a delay in the propane delivery. My boss (not really, the tenant I mentioned earlier) is trying to sort it out. I'd planned to do as you say, measure the flame, but since the gas didn't (and hasn't) arrived, I'm just going to have to estimate the length

[Idk]

2 hours ago, Ethan Yap said:

I'd planned to do as you say, measure the flame, but since the gas didn't (and hasn't) arrived, I'm just going to have to estimate the length

Patience Grasshopper, patience.

Suppose to be 1 step forward, not 2 steps backwards.

Better safe that sorry.