Jump to content
I Forge Iron

Forges 101


Mikey98118

Recommended Posts

  • Replies 1.7k
  • Created
  • Last Reply

Top Posters In This Topic

Hang time

Naturally aspirated burners have large turn-down ranges. So, it would seem that a wide selection of burner sizes isn’t needed. But effectiveness is about more than how well fuel burns.

There’s another factor to control; that’s equipment atmosphere. it’s easy to see what goes wrong when heating equipment receives too much or too little flame. It is harder to appreciate what goes right with superb control of its exhaust path. That's because efficiency involves balancing two disparate combustion issues; they are flame and exhaust speeds. Fast flames burn hot, but a fast exhaust wastes heat.

    The reason burners, whenever feasible, are aimed on a tangent, is to cause their combustion gasses to swirl around equipment interiors; creating a longer distance from burner flame to exhaust opening. A longer exhaust path increases the amount of "hang time” for heat from combusted gases to be deposited on equipment interiors. That seems obvious doesn't it?

    What isn't so clear is that most of that increased time isn't gained by the hot gases running a little farther at a given velocity; it’s provided through a considerable drop in velocity over that added distance.

    Small flames decelerate faster than large flames. The smaller flames of a pair of 1/2" burners will drop velocity faster than a single 3/4" burner in a five-gallon forge or casting furnace, greatly increasing efficiency; because they can be turned up faster/hotter without creating a tongue of fire out the exhaust port. But, what about people who want to build a two-gallon knife maker's forge, or furnace? They will need two 3/8" burners to do the same trick. Someone who wants to forge hand tools in a one-gallon paint-can or three Lb. coffee-can forge is going to need two 1/4" burners to run it with maximum proficiency; these same figures hold true in casting furnaces. The law of diminishing returns makes maximum fuel savings a lessor issue in miniature equipment, but time savings and portability remain significant advantages.

 

Of course, the king of deceleration is the multiple port flame nozzle; a familiar example of which are ribbon burners. So which is better? I think that decision comes down to which extra effort we want to make to acheive the  desired end.

 

Link to comment
Share on other sites

Updating Forges

Here is a subject worthy of its own thread, but treading close to controversy. We don't really want to discuss the downside of commercial products on IFI,, nor to advocate others too strongly. Nevertheless, you need some understanding. to avoid making a useless purchase. Frosty has recently addressed this issue on another thread, and  I hope he will post his remarks here too. In the meantime, what forge would I recommend purchasing with a view to updating?

 the most forge you can buy in a moderate  price range is a Diamondback. They are adequate and long lasting. If you want any wow-factor for the same money you, you'll have to put in a lot of sweat equity, and learning time, to build your own forge. However, this forge only needs one update; its burner, which is adequate to work with, and can easily be replaced with a hotter design, with almost now down-time to do the installation. I don't claim this forge is your only choice; just the simplest and surest update.

Link to comment
Share on other sites

   On the other hand, The single burner Devil Forges from DFS give a lot of bang for the buck, but need some immediate improvements before even being heated; they need to be seal coated for safety, and the brick floor should be replaced with a high alumina kiln shelf or Kast-O-lite 30 refractory for added efficiency. I don't believe their larger forges are a good deal in any sense, as another $100 would buy a Diamondback. 
 

Link to comment
Share on other sites

After around 20 years and a number of relinings; I finally replaced my dual burner propane forge burners. The old ones were battered enough that I could no longer get them tweaked for a decent burn: welds had broken, set screws were rusted in place, etc. (It's done a lot of travelling and camping and overall ridden hard and put away wet!)  A friend gifted me with two of the first 3/4" T burners they had made and that fit the burner ports on my forge exactly. 

 Last weekend I had done the gas plumbing modifications to use the new burners on Saturday and on Sunday we were working on adjusting the burners from their starting configuration.  I haven't finished dialing them in but WHAT A MASSIVE CHANGE even the partially adjusted burners made.  Evidently I had gotten used to a slow degradation in performance over the years and the new T burners; wow! We had to turn the regulator way down to keep that forge to a manageable heat.

So updating a forge can really improve performance and efficiency.

Link to comment
Share on other sites

Exactly; the very part that most forge purchasers are trying to avoid building, ends up being the most valuable update. Yet, even economical Devil forge burners will give an old forge newfound zing. I find assumptions to be my biggest stumbling block, when it comes to progress :)

Link to comment
Share on other sites

As far as I could follow the information (twenty years back), the Aussies started playing around with homemade burners before the founding of the Net. Others, including Frosty have been at it over thirty years. I've been at it for twenty years. The result is lots of "better burner" designs. BUT, most forge manufacturers are still using grand pappy's burners; these are the burners that are so very much in need of changing out.

Link to comment
Share on other sites

Mine were originally built at a SOFA gas forge building workshop in Ohio; I was running the blown burner I made in their first workshop under the supervision of Hans Peot and didn't get around to using the second NA one till I had to choose one to use while waiting for the rest of the shop to arrive when I moved to New Mexico in Jan of 2004.  I chose the NA one as my new place had a dearth of outside electricity and I have been using it steadily for the past 16 years.   Should have upgraded years ago!

Link to comment
Share on other sites

On 6/6/2020 at 1:20 AM, D.Rotblatt said:

Flux? 20 mile team borax at your market in the laundry section.  

D, I have not been able to find Borax at Walmart of Kroger in Huntsville Al. I don't figure there is a big pandemic panic buying or Borax so I wonder if they pulled it from the store.

Link to comment
Share on other sites

Have you tried ordering it online at their website for in store pickup?  Wally world lists a 65 ounce box for under US$5.

It seems like once the local stores left town; the variety at Wally World went down and now I have to order in a lot of things I used to buy off the shelf. (Or go to one 50 miles away; they stock different items based on location.)

Link to comment
Share on other sites

If you have to buy online how about buying commercial welding flux? No, not "forge welding" flux they're crazy expensive and charge nuts expensive S&H. Hit a welding supply and look on the torch welding and brazing supply shelves, read the ingredients on the can. I haven't seen one list "anhydrous borax" just borax I'm pretty sure REAL fluxes are all anhydrous and see no need to say so. Anyway, look for Borax, Boric acid and if you like Iron powder or iron oxide. 

The local Weldaire carries 5-6 brands on the shelf ranging from $20-$35/lb. shipping included. I've been using Peterson's Blue, the one without iron oxide in it. 

If you took metal shop class in Jr. high / middle school, one of these is the powder you dipped your warmed brazing rod in. It just melts, no  foam, just melts and spreads out. I've used Swan and Black Magic, Peterson's works as well and is WAY less expensive. 

I have not seen any containing flourspar like the OLD Easy Weld, Swan, etc. etc. fluxes, the stuff is very toxic so I'm pretty sure it's no longer legal or desirable in home applications. 

Oh, I still buy laundry borax for the laundry and dishwasher. Works a treat. 

Frosty The Lucky.

Link to comment
Share on other sites

I spent some time reading all the cans of flux at the local WeldAire when I bought my Peterson's blue and not one varied beyond iron oxide. They list: brazing silver brazing, before listing any kind of welding. 

I've used it welding silicon bronze and it behaves just like the powdered brazing flux I used in jr. high. 

Same stuff.

Frosty The Lucky.

Link to comment
Share on other sites

19 hours ago, Frosty said:

hey list: brazing silver brazing, before listing any kind of welding. 

Silver brazing fluxes are designed to work at much lower temperatures than hard brazing fluxes; there are even temperature ranges meant for different filler alloys; some are activated at lower temperatures than others. Black silver braze flux is meant for a higher range than most; almost.

Link to comment
Share on other sites

Interesting, I'll have to go read my can of flux. I searched Peterson fluxes and they don't show nor list the stuff in the yellow can or list silver brazing. 

Heck, I use Stay Silver to silver solder/braze with anyway. Maybe they discontinued the particular formula I have, it's only about 15 years old though. I'll try to remember to look next time I'm in the shop.

Frosty The Lucky.

Link to comment
Share on other sites

A helpful tip for anyone interested in finding what is in an industrial (or commercial, or household, or other) chemical: search for the SDS.  You should be looking at them anyways for the products you use.  There can be some obfuscation or omissions of the content and ratios of ingredients to protect trade secrets, but you can usually figure out what the active parts are.  This can give you a starting point when trying to home brew.  It will also help you understand whether certain chemicals are even safe enough to consider in your mix.  Stay Silv Black has Potassium fluoborate 20 - 40%, 
Potassium tetraborate  20 - 40%, &
Potassium difluorodihydroxyborate <20%, for example. The fluorine in these compounds is both effective AND dangerous! Educate yourself on the hazards of chemicals that you buy or make, or find someone qualified to educate you if you don't understand a particular hazard. 

Most of the fluxes I just looked at were a boric acid/borax mix. Others included or substituted fluoride compounds into this base. I even found two that had silica, and one that had a mix of oxides in addition to the active parts. Sodium carbonate was the base of one high temp flux, with boric acid rounding out the mix on that one. You may even learn about compatibility with your refractory (very much a "maybe" from an SDS, but I did come across some good "do not use with" information). 

Bottom line is this: flux isn't glue, but an aid. If you use and like borax or borax plus boric acid, then carry on. If the water boiling off from borax bothers you, then buy a commercial one (with NO fluorine compounds!).  Either way, check out the SDS, and know what it is that you are using and how to use it safely.

*Note: There are specific specialty cases where using the fluorine containing fluxes is warranted, but never for general smithing. The best control of a hazard is elimination or avoidance of the hazard. Don't risk your life and health over convenience or ignorance! 

Edited by Chris Williams
Added a statement on compatibility.
Link to comment
Share on other sites

Well said Chris, I frequently check the product's MSDS (Material Safety Data Sheet) for the same reason it specifically lists ingredients by their hazard and reportable quantity. I'll check the SDS and see what they say soonest. Okay, back SDS is a shortened term for the same thing. (Safety Data Sheet.) Search either and get both. 

You're absolutely right Chris. Like so much in life YOUR safety is YOUR responsibility as is the safety of visitors to YOUR shop. Buyer Beware has a frighteningly literal meaning so do your Due Diligence. 

Frosty The Lucky.

Link to comment
Share on other sites

  • 3 weeks later...

Fine tuning the forge

Judging and fine-tuning burner performance completely can only be done while running it in its intended equipment, and only after finish coatings and a front baffle plate or brick wall for an adjustable exhaust opening is added, along with an adjustable secondary air choke being installed on the burner port. These additions are needed in order to raise internal temperatures high enough to better judge flame performance. Sounds backward, doesn't it? But the thing is that the best evaluation only comes in equipment that has been turned into a “radiant oven.”

The burner is merely an "engkne" of the forge; if performance only revolved around the burner, most of what we've learned about constructing heating equipment would be "gilding the lily"; it’s not.

 

Clear back while still writing Gas Burners, I raised the temperatures in a five-gallon forge from light orange to lemon yellow, merely by painting its refractory with high-emissive coating it from from the stuff that came out of the jar to colloidal grade particles, by simple water separation. I A few weeks later lemon yellow jumped up to yellow white by stopping all secondary air from entering the burner port; this has been further refined for other burner designs by the addition of a variable secondary air choke on the burner port. It has been stated that good burner performance requires a delicate dance of several factors; ditto for the equipment it heats. Variable baffle walls came afterward, with a change from yellow-white, to straight white heat, all with the same burner design, The less burner you have "under the hood" the more these improvements will do for you.

Link to comment
Share on other sites

  • 2 weeks later...

Three versus four

It is never good to see  four screws holding burners in a forge's burner portal; or good to see four screws holding the gas tube in the burner itself. Why then, is it so common?

I figure its is the lack of shop class or trade jobs in the computer generation. Anyone who ever ran a lathe knows why they common with three jaw chucks, and you have to mount the four jaw variety for special projects. Three jaw chucks automatically center the part. I think guys just find it easier to divide circles in half, and then half's in two. But anyone who ever took a shop class knows that the secret to good math, is to avoid it whenever possible :rolleyes:

So, speaking of secrets, what is the secret to dividing a circle (or tube) in thirds, and sixths without doing the math? Hex head bolts down at your local hardware store.

Link to comment
Share on other sites

A piece of string and ink pen works well. wrap it around the circle and mark where it meets then fold it using the mark as the anchor point. 2 folds =4 equal parts or 4 points. 3 folds = hex. 

Another easy method is with dividers or compass.

Frosty The Lucky.

Link to comment
Share on other sites

22 hours ago, Frosty said:

Another easy method is with dividers or compass.

I started out by using a compass, but the smaller the burner the more important accuracy becomes; then,  compass work gets to be a lot of time checking and rechecking.

 

21 hours ago, Irondragon ForgeClay Works said:

I usually eyeball it.

On small parts, the easy way has a nasty habit of turning into the hard way :)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...