Propane Forge Build Questions

[Bodhi]

Hey everyone,

I am a beginner blacksmith, I have forged a few things like knives etc. with others guidance. I have recently taken a more serious interest in blacksmithing and am planning to build myself a propane forge. I have done a ton of research online on this forum, others, as well as youtube and more. I am pretty sure that I know what I want to do, but I wanted to post my plan here in case any of you have suggestions on how to do it better, or tips and tricks for some aspect or otherwise have some advice. 

Before I get into my plan I am going to tell you all what I am planning to be blacksmithing. I plan on just doing a variety of simple projects to get started and see what I like. I am thinking of things like knives, hooks, tongs, fire strikers, utensils, bracelets and simple tools. 

So now for the plan: I am going to use an old 20lb propane tank as the shell (I will make sure to fully clean it out before I cut into it). Then I will put in two layers of 1” kaowool all around with more on the bottom to make a tray that will hold an insulating fire brick (this is so that I can replace the brick when it gets worn through and so I have a flat floor to set my work). I will then spray the kaowool with rigidizer (buttering it first). Next, I will coat all the kaowool with 1/8in of selenite (maybe a little more) and apply ITC 100 to that (again buttering first). Lastly, I will insert my fire brick floor and coat that with ITC 100 as well.

I am going to use a venturi burner (the 100k medium one from atlas knife) that I am thinking of installing on the side just above half way up the tank angled slightly downwards. I am hoping that this will allow me to get up to forge welding temps if I want.

Please feel free to offer any advice on any part of my plan, but here are the things that I am not sure about: I am planning to make some doors for this, what size opening am I going to want? Do I need to have it closed up enough to get a back pressure for the burner? What is the best orientation for my burner, to get a good swirl,turbulence and even heating? 

This is the list of all the supplies that I am going to get and where i am getting them from:

Propane tank: I already have

Kaowool: Hightemptools Inswool 1" (from Hightemptools)

Rigidizer: Colloidal Silica Rigidizer - Coating for Refractory Ceramic Fiber Products - 1 Quart (from Amazon)

Satanite: MR VOLCANO Refractory Satanite 10 Pounds for Ceramic Blanket Lining 3200  Degree Mortar (from Amazon)

ITC 100: Mr Volcano ITC-100HT (1 Pint) (from Amazon)

Fire brick: In store

Venturi burner: Atlas Custom Burners 100K medium Burner (from atlasknife)

I will post pictures when I get the supplies and start building if you all want.

Thank you all so much for your generosity with your time and knowledge.

 

[Frosty]

Welcome aboard Bodhi, glad to have you. I have a couple questions for clarification purposes and one "suggestion." I'm not familiar with the burner you wish to use, the 100k designation isn't enough info. I'm more used to matching burner tube ID to forge volume, not many well tuned naturally aspirated burners perform significantly differently. 

What is the expected finished volume of your forge? Please don't list the dimensions of the tank I don't do basic math. And what's the tube diameter of the burner not counting the flare dia. if it has one?

Lastly pick a better refractory, Satanite is furnace mortar, it is formulated to cement brick together in a furnace of fireplace it is NOT up to surviving long in a propane forge. Burning propane is very chemically active and tends to dissolve mortars and cements. I highly recommend Kast-olite 30, available in small quantities from the Iforge store if it's in stock. 

Is the Itc-100 a dry pint or premixed? Last time I priced kiln washes I decided I didn't want to spend the same money and shipping for the water in the can. The actual product dry makes quite a bit more kiln wash for use.

Frosty The Lucky.

[Bodhi]

Hey Frosty,

Thank you for the quick reply! 

This is the information that atlas knife provides on there website were I am thinking to buy it from: 100k burner produces 105k BTU @ 20 PSI, 6″ burner tube length, 1.050″ outside diameter, Stainless steel and brass construction. All fittings are custom made, steel 3/8″ flare 45° fitting. Thant is all I know if you go to atlas knife and search Atlas Custom Burners you can find the listing petty easily.

I am expecting the finish volume to be about 450 cubic inches.

Ok, thanks for letting me know about the refractory I will try and get it here.

I think the ITC-100 is dry, it says to mix 2 parts of the ITC with 1 part water.

I hope I answered all your questions,

Thanks again for the help!

[Frosty]

It was just a matter of timing, I turned my comp on and your post was the first thing to pop up and it's in my wheelhouse. 

Okay, I've seen those burners I'd look for something else IF I didn't want to build one.

450 cu/in wants more than one 3/4" NA burner if you want welding heat though two 3/4" burners is a bit over gunned. However it's pretty easy to turn the psi down and impossible to turn it high enough to get more than a burner can produce.

A pair of 3/4" T burners is a nice level of too much for the volume and they are easy to build with a minimum of shop tools and skills. 

ITC-100 has changed significantly since I bought a can so I don't know what my application method is worth now. I mixed it about the consistency of thick latex paint and brushed it on. This is the same basic ratio I use for Plistex-900.

Give a shout if you have more questions.

Frosty The Lucky.

[Bodhi]

Ok, I was initially leaning towards buying a burner, but I will look back into building one. Just off hand what do you think of the burner that red beard ops shows how to make for $21 (it is a frosty T design)? Maybe I will make two of those?

Also do you have any thoughts on any of this: I am planning to make some doors for this, what size opening am I going to want? Do I need to have it closed up enough to get a back pressure for the burner? What is the best orientation for my burner, to get a good swirl/turbulence and even heating? 

[Frosty]

No idea what a red beard ops burner looks like, all I found in a search were ads to become a patreon supporter so I could look at the pictures. I have no idea what he's peddling. 

My directions for a T burner are in the gas forge section of Iforge. If you decide to build one or two let me know there is ONE change that makes them easier to make.

Just so you know, I don't spend any time surfing the web for burner designs and avoid people selling "Frosty" T burners, most are too tempting for me to call out on their page as being junk made by someone who doesn't know how burners work.

Frosty The Lucky.

[Mikey98118]

1 hour ago, Frosty said:

450 cu/in wants more than one 3/4" NA burner if you want welding heat though two 3/4" burners is a bit over gunned. However it's pretty easy to turn the psi down and impossible to turn it high enough to get more than a burner can produce.

It is worse than that, I think. The information they provide suggest 1/2" burners; not 3/4". Although, I would choose two 1/2" equally spaced burners over a single 3/4" burner to heat a 20 lb. propane cylinder forge in any case.

As to the burner design; it looked competent, but I saw no GOOD reason for the photo to be so dark. Sailor take warning...

[Frosty]

Three 1/2" burners would be dandy in that forge. Four would be better though. 

Frosty The Lucky.

[Mikey98118]

What I think would be better in that forge, would be a slice taken out of the cylinder lengthwise (say about 3" wide), to turn it into an oval shape. I just don't see the point of large tunnel forges, unless they are to do double duty as casting furnaces.

Of course, what is considered large or small is disputed endlessly. However, once we pay the fuel bill a few times, there is likely to be more consensus on the matter; kind of late by then, though

[Frosty]

Too late Mike? I forget, how many propane forge do you have around about now?

I like feathering the edges of a piece or two of Kaowool to build up a flat floor in a cylindrical forge. It's easier than cutting and welding a tank.

Frosty The Lucky.

[Irondragon Forge ClayWorks]

On 4/15/2023 at 10:19 AM, Bodhi said:

with 1/8in of selenite (maybe a little more)

I think that will be too thin. When we built our forge from a 20 lb propane tank we put in 2 coats of Satanite for a total of about 1/2 inch. Also found out Satanite is a heat sink although strong so we added another layer of Bubble Alumina, which gave us about 350 Cu in. If we build another or rebuild this one, I would go with Kast-O_Lite 30 instead of Satanite.

20 pound propane tank forge in progress - Gas Forges - I Forge Iron

[Frosty]

You're using the bubble alumina as a kiln wash aren't you? I'll bet it will prolong the lifespan of the Satanite quite a bit.

Frosty The Lucky.

[Mikey98118]

2 hours ago, Frosty said:

Too late Mike? I forget, how many propane forge do you have around about now?

Just one at the moment; and that one purchased as a source for parts. My little garage would be bursting at the seams if I kept this equipment. All hose forges, casting furnaces, assorted burners, and the special heating bench have been given good homes over the years. And every tool to come will be passed on, the same way.

 

2 hours ago, Frosty said:

It's easier than cutting and welding a tank.

Agreed; it is easier.

[Frosty]

Yeah, I have more room than is good for me and I still have trouble walking around. 

I'm almost afraid to look once my leg heals enough to dig a path to the door. I toddled down earlier today to scatter ash and speed it melting. Snow falling off the roof is piled a couple feet deep against the walls and the drainage has probably 4' pile from the plow guy we hired when I broke my leg. The floor is going to have a couple few inches of water on it soon. <sigh>

Frosty The Lucky.

[Mikey98118]

What did you do to your leg, to get it broken? Skying?

[Frosty]

I took up Curling last October and Feb 5th we were picking up after the games. I was bending down at the knees to pickup one of the hacks and my right foot went sideways. I went down like wet laundry. I thought I'd sprained it badly, I saw it twist sideways but the ER pronounce 2 non-displaced fractures one of the fibular platform and the other right through the tibia "knob". 

No cast, surgery, pins, plates, etc. Just stay off it and wear the articulated brace till they say I can stop. <sigh>

It's cleared for partial weight bearing so if it hurts back off till it stops. I call that the HeeHaw method, "Doc it hurts when I do this!" and Doc say, "Then DON'T do that!"

I ended my season early and curling is so much fun! <sigh>

Frosty The Lucky.

[Latticino]

Frosty,

Only you could elevate curling to a contact sport .  Hope you get better soon.

[Mikey98118]

Speaking of which, how are you doing, Latticino?

[Latticino]

Mike,

Pretty good aside from my knees starting to fail, my memory apparently going to the devil, and still having to work instead of retire and get to indulge in my hobbies full time.  Why, do you know something I don't?

[Mikey98118]

No; just wishing you well (think that will work?). Anyway, I always intended to interact with you so much more than it has worked out (good intentions and other rubbish). As to what I know; its that these smashups, don't get us off the hook for all standard junk that everybody must go through.

I survived two major strokes, and can walk and talk, and even write (sorta). nevertheless old age's Teflon days happen just as though I needed them to prove some point. "Hill" What hill? I don't remember any hill!"

[Frosty]

Thanks Latticino, I'm healing up about as expected, maybe a little faster than doc guessed. If I'm going to continue curling like it's hokey I need more protective gear than a bicycle helmet. 

Hill Mike? Is that the hump thing behind us?

Frosty The Lucky.

 

[Mikey98118]

4 minutes ago, Frosty said:

s that the hump thing behind us?

You can turn your neck around enough to look behind you? Radical; that went about thirty years back

The wife's car has a back up camera, so she can still parallel park; super cool

[Frosty]

You DON'T watch your back trail? 

We have a back up camera in the SUV and I still use the mirrors. The one in the RV is instead of a rear view. It came with side mirrors only and Deb was not pleased. I just wish it wasn't a TV screen in the dash. It shows a nice view, just not up THAT hill.

I like my Mother's attitude about age, she VOWED to never be middle aged she was going straight from young to old. She turned old in her early 80s. It's become a family tradition from my generation on. I'm skipping middle age and may be creeping up on, grizzled white haired old coot-ness in a couple few decades before I make up  my mind.

Frosty The Lucky.

[Bodhi]

Okay,

I have finished the shell and am now ready to install my burner holders. This is what the forge looks like now.

I am wondering where you all think I should put my burners (I am using two 3/4" ventiri burners). I am going to put at least 2" of super wool (it performs essentially the same as koa wool but is supposed to be less toxic), 1/3" of kast o light and then itc 100 with a insulating fire brick floor. So the inner chamber will end up being essentially D shaped.

 From looking through the burners 101 thread and others it seems like their are four main positions people recommend:

1- placing the burner at the top of the forge angling straight down (this is to purposefully create a hot spot)

2- placing the burner at around 2 O'clock angling the far bottom corner

3- placing the burner at around 2 O'clock angling straight across (so that the burner is level)

4- placing the burner at around 4 O'clock angling upwards as much as possible

I attached an image below with the burner positions drawn and labeled.

So my question is: what are the different advantages and draw backs  of each of these positions and what would you all recommend that I go with?

[Frosty]

What's missing from your pics is the flame face line of the liner. Referencing burner alignment to the shell isn't too useful.

At least sketch your forge. 

However if you bear in mind this is a poor guestimate if educated. You can create differential temperature zones with all orientations but 3&4 and with those to a lesser extent.

I prefer having a hot zone but that's me and my style at the anvil. 

If I had to choose I'd select position 3 and aim the burner at the floor centered approximately 1/3 from the transition from floor to wall.

As sketched 3&4 are virtually identical as they both develop a strong tornadic flow and as neither would produce an impingement zone on the floor or close wall there is no hot zone to speak of.

2 is apparently aimed at the junction of floor and wall a corner in a D shaped chamber this is a BAD thing. It generates back pressure which inhibit burner performance and the flow of flame is generally chaotic, more so than the vertical down of 1.

Doesn't that raise more questions than it answers? I'll be able to be clearer with a better idea of what you're making. No I don't draw in your liner, flame face, mounts, etc. I only comment on and make suggestions for what you provide.

Frosty The Lucky.