Propane Forge Build Questions

[Mikey98118]

Position #1 is top-dead-center facing down. As Frosty noted, this position is usually a matter of personal preference.

Position #2 is incorrect. The line should be facing down toward the near edge of the floor.

Position #3 is also incorrect. The line should be facing down toward the far edge of the floor. In either position, the flame is intended to impinge on the floor; not at the junction of floor and wall.

Position #4 is the one I advise these days; especially with "D" shaped forge interiors--but only if you plan to use Kast-O-lite 30 as your flame face.

The reason why the first three positions became popular in forges was that each of them caused the flame to impinge on the forge floor, which is protected far better against heat than the forge wall is. If you only use Plistix 900, or some other seal coating over the ceramic blanket insulation, then you need to at least keep the flame from impinging on it.

If you draw a line where you intend the top surface of the floor to end up, then the advantages and drawbacks of each position will become plain to you.

[Bodhi]

Thank you all for all the input.

I am thinking to position my burners so that I get a little bit of a hot spot.

I have made a little drawing of what I plan my forge to look like, so I hope this helps you all get a better idea of what I should do. 

I drew two different positions for the burners, but am thinking to do position one in this drawing to get a hot spot.

Does position one look good to you all? 

Would you recommend tweaking anything?

Thanks again for the help!

[Mikey98118]

No; but that isn't because position one is wrong--not if you want a hot spot.

I would aim the burner so that the flame misses the parts, most of the time. This is because I design forges to primarily work as incandescent ovens. I avoid hot spots; that isn't to say that my way is the only way, or that you're wrong if you don't agree. To have a hot spot or not is a personal choice.

[Frosty]

Mike and I differ a bit on this point. We both build reverberatory forges, the flame heats the liner which radiates IR to the work. The flame does very little direct heating of the work it's just not efficient nor thorough. 

I do however like a little differentiation in the forge temperature. Not so much a hot spot but definitely a hotter zone.

Your burner port is too high, lower it about 1/3 of the as sketched distance to the floor and angle it to impinge a little closer to the right side as shown. The hot spot will widen to a larger area what I consider a zone and the flame will travel in a strong swirl. Placing the work in the center of the floor, enough flame will pass over it to maintain the direction of flow. The incandescent forge liner will heat the work evenly. The energy radiated into the work and out the doorways will be replenished by the flame, the strong swirl will flow over the top and back down to the burner ports heating the entire liner. Make sense?

As drawn now maybe 1/3 of the flame will flow backwards from the desired direction causing turbulence of the not good kind. Placing a piece in the center will make the turbulence worse and the forge in general will lose effectiveness but burn the same amount of fuel.

My preference is not better, I just like it like that, it works well for me.

Frosty The Lucky.

 

[Mikey98118]

Go with Frosty's advice, because I avoid the whole issue; therefore, he is the expert on this.

[Frosty]

WHAT!? No discussion of the various merits? I just can't count on you for any fun today can I. <sniff>

Frosty The Lucky.

[Mikey98118]

Ah, but it's Sunday; time to behave. You can count on me to slither out from under my rock, and hiss away with abandon tomorrow

[Frosty]

Right you are and MOTHER'S day too! Give your better half my best please.

I'll just hang till then. Well, out weather's been nice and it's greening up so we're going sight seeing, then to dinner and back to hang out. 

HAPPY MOTHER' DAY  to all applicable members and spouses.

Frosty the Lucky.

[Mikey98118]

The weather has been very fine in Seattle this spring; just one more glorious day "in the neighborhood" after another. The very few rainy days have been welcomed by us gardeners

[Frosty]

Been beautiful here too, it's greening up at an explosive rate, we had good snow cover and plenty of rain and sunny days so the forest is happy. We drove into Anchorage, spent a couple hours driving up the Eagle River valley for the views only to find the visitor center at the end didn't have space to park even a small RV so we drove back down. Then into Anchorage proper for dinner at Olive Garden and on home. It was glorious, sunny with just enough broken high cumulus to make the sky pretty. 

Frosty The Lucky.

[The Jeff]

Not trying to derail the conversation but I'm preparing to build another forge soon.

Would there be an advantage to an oval, over the D shape. 

[Latticino]

Either shape will work quite well for heating stock.  The big difference is the flat floor.  For some projects that can be an advantage, in others a curved floor will help you lift flat stock.  Personally I like a flat floor.  Certainly easy to cast in place.

[Mikey98118]

Since it works so well with upturned bottom position ribbon burners, is so much easier to construct, and works so well as a shop forge, a "D" shape is the logical choice. I still prefer an oval. There's this rumor that I'm maybe a little sick. You should pay it no mind; honest

[Frosty]

A flat floor has it's advantages but I find myself using bits of broken fire brick to get projects up off the floor so they can absorb IR from all sides. An oval forge has the advantage of being able to lay work at an angle and provide the same space. It also has the advantage of curved surfaces being lenses focusing the IR to a degree.

Frosty The Lucky.

[Mikey98118]

Even when I built tunnel forges, they all had flat floors. Chile Forge only makes oval forges, yet their interiors are box shaped. The little oval forge I will be rebuilding this summer, shall have a modified flat floor; that is, mostly flat, but curved on both sides for good atmospheric flow (swirl). Its one of the reasons I want to use an oval shell; to have my cake and eat it too

[Frosty]

My oldest successful propane forge is cylindrical without a flat floor. It was my first though and was sized for my first successful T burner, a 1" T in a 700 cu/in forge. It worked fine except for getting coated with old borax and various stuff that melted when it came to heat. At one point it was so bad I'd just scoop a little to flux welds. It's still collecting dust in the shop and the original T is on a shelf. 

I've made them with flat floors since though. My latest tinker's thoughts were to try corrugating the floor in the direction of flow to increase the available radiating surface under the work. I just haven't come up with a need for a new forge so it's still on the drawing board.

Frosty The lucky.

[Bodhi]

Ok, so I got the burners holders installed (I went with frosty's advice) and laid 2" of super wool, then rigidized and lastly cast my kast o light on top of that.

My question now is what is the best way to cure my kast o light? I am hoping that I can do it with just my ventiri burners because I don't have a good oven or much electricity. I have already allowed it to set by mixing it, applying it and then letting it sit in 100% humidity for 24 hours. I have read around that it is best to heat it up in incrementally 100f per hour, should I try doing that with my burners (I don't think I will have much accuracy)? 

Anyways what is your guy's recommendations for how I should cure my kast o light?

[Frosty]

24 hrs. at 100% humidity is good but curing it longer increases strength and heat tolerance.

It water cures the only reason to raise the temp gradually is to make sure no moisture is trapped between the hard refractory and forge shell. Kastolite is formulated to HOT patch furnaces, as a trowel on or gunnite application. Once you've gotten it above 230f for an hour or two and driven off any trapped moisture it's good to go to work.

The old incremental heat cure methods were necessary for older refractories that required a dry time and firing like a brick. The newer ones tend to be water setting.

My recommendation is, once the Kastolite is applied, seal your forge in a large plastic bag with a couple dripping wet towels in it and leave it in a shady spot till you can't stand it anymore. 7 days is about all the time that significantly improves the refractory. However seeing as you probably aren't lining a commercial furnace that's going to be ripping HOT for month on end we don't need max strength and temp limits. One or two wet days is plenty.

Frosty The Lucky.

[Mikey98118]

Don't forget to drill  one or two small (1/8" or so)holes in the bottom of your forge shell, to allow steam and re-condensed water to exit more easily, during firing. Frosty is right. Kast-O-lite 30 is much easier to deal with than the old standard refractories.

[Hefty]

On 5/22/2023 at 7:32 AM, Frosty said:

My recommendation is, once the Kastolite is applied, seal your forge in a large plastic bag with a couple dripping wet towels in it and leave it in a shady spot till you can't stand it anymore.

Sorry if this seems like a stupid question, but am I correct in thinking the towels don't have to be in contact with the kastolite, just generating the humidity in the bag?

[Frosty]

No they don't, I cured one in a closed plastic tote with a few inches of water in it. You could go so far as to submerge it completely and it'd only make it stronger. 100% humidity is all it wants.

The calcite binders in Kastolite behave just like concrete made with portland cement, you can follow the same rules for mixing, set and cure.

Frosty The Lucky.

[Bodhi]

Alright, so I have finished lining my forge with kast-o-light and painted it with itc-100. I put one of my doors on and am at this point trying to test my burners in the forge.

So, I tested my burners out side of the forge and they looked like they had been working well. I then put them in the forge and tried to fire it up. The burners would not hold a flame, they would cough and light up for a second and go out. When I tried lighting them with more pressure it looked like they were blowing themselves out and at lower pressure it would light up for a second and go out.

These are the plans that I followed to make my burners (they are T style venturi burners): https://youtu.be/SAP8Xho_I6w

 

 

These are all the parts I used:
1x1x3/4 Tee -

3/4 x 6 Nipple -

3/4 Merchant Couple -

3/8 Flare x 1/4 MPT -

1/4 Flare x 1/8 MPT Union -

1/4 Flare Swivel -

1/4 Flare x 1/4 FPT Elbow -

Mig Tip (0.030) -

If that link gets taken down, basically what I did was drilled and tapped the reducer T and screwed the 1/4 Flare x 1/8 MPT Union into that and then tapped the 1/4 Flare x 1/8 MPT Union and screwed the mig tip into that, then put the nipple onto the T and put the 1/4 Flare Swivel onto the 1/4 Flare x 1/8 MPT Union, put the 1/4 Flare x 1/4 FPT Elbow on that and the 3/8 Flare x 1/4 MPT on that. 

What you end up with is that you hook your propane up to the 3/8 Flare x 1/4 MPT which connects to the 1/4 Flare x 1/4 FPT Elbow which connects to the 1/4 Flare Swive, which connects to the 1/4 Flare x 1/8 MPT Union, which connects to the Mig Tip inside of the T that is connected to the nipple.

I hope I did an okay job explaining that, the video make it much simpler to understand since you can see everything.

And I attached some pictures of the burners inside the forge, so I hope that helps.

Anyways do any of you know why my burners are not working and/or how to fix them?

Thank you so much in advance 

[Mikey98118]

I mostly like your choices, but the MIG contact tips look like they are positioned off center to the mixing tube; you will probably need to bend them into better alignment at some point.

I assume that the brick you are employing as a forge floor, is of the semi-insulating variety, and won't be to much of a heat sink...

[Frosty]

Use a 0.035" mig tip, trim it back so it's about 1/2 way across the air intake ports of the T.

Pull the burners farther out of the forge the coupler should NOT be inside the forge it should be just inside the liner.

The difference in how your burners work outside as opposed to inside is exactly why I recommend NOT tuning them outside the forge.

The guy in the video does a nice job of building a T burner except for using too small a mig tip and having it too close to the end of the mixing tube. 

If you really want to use a 0.030" mig tip use a 3/4" x 3/4" T so it doesn't induce too much combustion air.

You've done a good job of making the burner you just followed someone else's plans.

Frosty The Lucky.

[Bodhi]

Mikey:

Good spot, I will make sure to straighten the mig tips out and yes the brick is light weight insulating fire brick coated in itc-100.

Frosty:

I might try switching out the T first because I don't think that I want to be pushing more fuel. From what I have read my to burners in this forge should be plenty of heat and I want to be as efficient as possible. Does that seem like a good idea?

Do you think it will be okay if I just cut the end off of my mig tips and then maybe clean up the edge a little with some fine sand paper?

Lastly, I will definitely try pulling me burners further out of the forge.

Thank you all for the advise, you guys are so generous with your knowledge.