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I Forge Iron

Propane can forge design questions


Fallon

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I've got an old brake drum coal forge a friend made decades ago & was handed down. I've used it a bit, enough to know some of it's many limitations & am looking to finally complete my first propane forge. I've got an old propane tank shell I've started building & a pile of other supplies. Started things a year or 2 ago but other stuff put this project on hold. I've read through the forums a lot over the past few years & have the general process down, but still have a few questions. Probably making a run to the local Ferrier/blacksmith supply tomorrow or in the next week to grab some missing parts. I should probably just toss together a quick & dirty first try to see what works & what questions are actually relevant. But unfortunately my brain needs to over-engineer everything on the first try, usually focusing on a bunch of constraints that don't end up being relevant.

Stuff I have on hand

  • Propane can, grinder, welder, scrap pipe to make a mount for the burners
  • Lots of 8# 1" ceramic blanket
  • A stash of soft & hard fire bricks
  • 2 Black Beauty burners (3/4" OD)
  • A 55lbs box of Kast-O-Lite 30 (hopefully still good after a year or 2 on the shelf, box didn't seem hard, but haven't opened it up to check)
  • 100lbs propane cylinder, POL fitting, high pressure regulator, gauge & hose
  • Stove paint

Stuff I'm missing

  • Ridgidizer
  • Probably several fittings & some copper to go between the burners & propane hose
  • Pristix/Metricote

Any particular angle or offset I should go for on mounting the burners at? Consensus seems to be mounting them at an angle for a swirl & more even heat rather than vertically with hot spots, more scale & chimney issues.

Is the hole through the blanket & refectory just a straight hole slightly bigger than the burner or does it need to be tapered in a particular manner?

Should I be going for a relatively flat floor building up the bottom with some wool before applying the Kast-O-Lite, or leaving it more circular/oval & not building it up as much? Should I use the Kast-O-Lite as the floor of the forge or plan on sticking one of the hard fire bricks on top of it?

I have the front of the can tack welded on for alignment while I weld on some brackets to bolt things back together. Should I just leave the front off & use some of the soft or hard fire bricks to close off the front of the forge for now until I figure out what works best? If I attach the front of the tank back on, any particular size or shape I should be shooting for to retain heat, minimize back pressure & maximize access?

I cut a hole in the back & had been planning on plugging it with a fire brick. But I realized that hole was centered & isn't likely to match up with the wool + castable height. May not even be the right size for the fire brick (cut it a year or 2 ago). Fire brick for the back going to be a decent start?

I don't have any Kiln wash at the moment. Would it be fine to just use the forge with the Kast-O-Lite for now & add that in later? Local Ferrier/blacksmith supply only has ITC-100 I think.

Do I need to fire the ridgidizer for the first 1" of wool, then install, ridgidize & fire the 2nd 1" layer of wool or can I fire both layers at once?

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Not bad, you have most of what you need and are asking before you make things permanent! 

Rigidizer is easy, check with plastics or fiberglass suppliers for "Hydrophilic," colloidal silica, "fumed silica" is more of a description of the manufacturing process than a Type so don't hang on whether it is or is not fumed. Hydrophilic IS important you want the type that mixes easily with water. This IS important.

You mix it with clean fresh water in a spritzer bottle. Butter the ceramic blanket with clean fresh water (Butter it) and spritz the silica on. A little food coloring in the solution makes it easy to see it so you apply it evenly.

Firing it with a Bernzomatic torch or firing off a burner for a short time fuses the silica to the fibers making them less likely to break off and drift around in your breathable air. AND as the name implies makes the blanket more rigid which improves everything.

I prefer a flat floor but it is a matter of preference. Have you attended club meetings and used propane forges so you have an idea of what works for you and you like? If possible it's a really good idea because the choices are all yours to make. Hmmm?

I am NOT a fan of hinged doors on forges, when you open a HOT forge that incandescent door liner is facing out hitting YOU with intense IR radiation in addition to the IR being radiated from the forge interior.

Sliding thermal baffle doorways only open as far as YOU need them at the time and the HOT face is never pointed at YOU. Regardless of what you do heat exiting this type forge will heat the steel tank and cause warping. It may not be bad enough to effect anything but if you have hinges connected to the tank it'll almost certainly become a problem sooner than later. Make sense?

One good option is a track connected under the openings you can slide fire brick on edge. This allows you to move them open or closed in the position and degree you wish. They should NOT come in contact with the forge body so exhaust gasses can escape through the gap and disperse. A good portion of the HOT exhaust gasses will contact the steel track and possibly warp it.

This is why my personal preference is a porch level with the floor of the forge and extending 9"+ from the doorway. and one brick width from the rear (pass through) opening at the other end. Yeah, this makes the foot print more than a foot longer but the benefits tend to out weigh the downside. A porch lets you rest long stock you're heating without having to come up with a helper on the stand or floor. It provides an ideal heat proof shield to the surface the forge is standing on and provides an ideal surface to slide the thermal baffles. Exhaust gasses can blow on the porch, so what, it's fire brick or cast refractory? Hmmm?

What kind of IFBs (Insulating Fire Brick AKA light brick) do you have? If you've had them for a while there's a good chance they're the old style and not rated to survive a propane forge environment, the high temps or mostly the rapid thermal cycling. A propane forge will go from ambient room temperature to mid 2,000s if you get the burners right up to 2,600-2,700f. If I don't pay attention my home made burners will melt steel. They eat the old style IFBs in one or two sessions I don't need IFB crumbs. 

I HIGHLY recommend Morgan Thermal Ceramics K-28 IFBs they are the new kid on the market and have a sustained working max temp of 2,800f, remain ard at temp and are fairly resistant to caustics. (Molten forge welding fluxes)

Do NOT use ITC-100 it's a good product just NOT for propane forges. It's intended to prevent glazes, pottery ceramics, etc. from sticking to kiln furniture, it stays friable so it rubs off. Plistex or Matrikote fire hard like a coffee mug are high alumina and are rated for a sustained temp in excess of 3,000f. Not much in excess of 3,000f but a little. 

 Aligning your burners is a matter of preference all mine are vertical down but my forges are rectangular "box" shaped and the chaotic turbulence evens the heat well enough for my needs. NARB doesn't suffer chimney effects because the T inducers are horizontal while the burner flames are vertical down. 

Anyway, angling single nozzle burners in a cylindrical of D shaped forge imparts a strong swirl which keeps the flame inside the forge longer to transfer more energy to the liner which is a good thing. Forges are a "reverberatory" furnace meaning the flame doesn't heat the stock directly as it's primary functio, the flame heats the forge liner which re-radiates the energy as IR radiation which heats your work. So aiming the burners at the work directly is NOT an advantage, it doesn't generally hurt but it doesn't help.

Drilling the holes for the burner ports through the ceramic blanket can just be straight holes a little larger than the burner tube but remember to make them enough larger to apply a coat of Kastolite and kiln wash. After rigidizing them of course.;) However making them into an expanding cone lets them be the burner flare and it's from refractory and will last a lot longer than whatever you use for a steel or stainless steel burner flare. 

I'm sure there's more but as you can see I tend to be long winded so I'll give everybody a break, we can talk about other things in another post.

Frosty The Lucky.

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I will only add that, Your burners were a reinterpretation of my original burner design as a commercial product, done by a very competent smith. I have never handled one of them, but they are probably quite good enough--IF, and only IF, you follow through with his instructions for their use

Mikey

Why would I be so particular about this? Because I can see that their mixture flow will be significantly different than Mikey burners are. So, if you attempt to mix and match directions that I have laid out in the Burners 101 thread, with his burners, you are practically guaranteed to have disappointing results. My advice is to stay the course; always follow what the burner's designer has to say about his product.

And good luck to you.

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