Thanks Mikey!

That is the sort of answer I was expecting/hoping to hear but I figure you would have the knowledge and experience to confirm or refute.

Just in time for upcoming holiday tinkering. A small forge in an Australian summer will be a huge blessing!

Cheers,

Jono.

Jono,

I hear you loud and clear, mate. It was the desire to avoid standing in front of something like a blast furnace that started me on this journey, in the late nineties. The last job I had before the little woman retired me was with a metal artist. He had built a fan-blown natural gas forge that heated up a large commercial building to the point that we had to open the truck door in the dead of winter--ugh!

What are you employing for a burner?

I've made a few smaller burners using 3d printer nozzles and some 9mm dia. tube, based on Trevor84's "pocket rocket" 1/4" design, which is partly based on your own designs and a few others.

I've had them for a year or so and had already made another small cast forge interior that I was going to try them in but it has become a more complex build and I think it will be a longer-term project with ceramic wool and a more fabricated outer shell, so I wanted to try this option as a faster solution.

I thought that you might need some advice on how to employ a commercial propane torch-head properly, but It sounds like you are right on track. Any photos of your burners? We love photos

Here's one of them. Oh, and the mix tube of the other one in the second photo. Not sure if you recall, Mikey, but this was the one I mentioned a while back, either in "burners 101" or AHB's 3D printed burner head thread, where I accidentally twisted the ribs between the air intakes when trying to thread the back end and made them parallelogram shaped. I didn't end up noticing a difference in performance.

So, I turned down a piece of hex bar, soldered a short section of (I think) 1/4" copper tube into the back end with a flare/compression nut on it to connect to the regulator hose, and made a double threaded front end, M6 interior thread for the 3d printer nozzle and M10 exterior thread for the mixing tube to screw on to. I also made a little lock nut so I can dial in the position of the mix tube and lock it there:

The short one on the left is the one I accidentally twisted (this is twisted most of the way back):

My jumble of tube sizes to get a stepped nozzle. I will use a small grub screw when it is mounted in a forge:

And a shot of the flame:

Cheers,

Jono.

The burner flames in the photos are both seen to be reducing, because of their green tinge; yet, they have a nice shape, and the secondary flame envelope is quite short...I would say that you might try shortening the amount of overhang in the flame retention nozzle, past the end of the burner's mixing tube. If that does not improve the flame color, than "if it ain't seriously broke, don't fix it."

Yes, I remember the discussion of "the accidental twist." Thanks for sharing your photos; they always help others to come up with new ideas.

                          What do you think about the new Diamondback forge line?

Since there have been major changes in the construction of Diamondback forges, it would be nice to here an evaluation of them from anyone who has purchased one of the new models; especially if they had previously owned or used one of the old models.

  Aside from the change from ceramic board to ceramic wool, I don't expect to hear about any other significant differences, but we never know, do we? As to the different insulation; yes it is a down grade. However, it is far more than matched by the reduction in prices, allowing many more beginners to buy a dependable gas forge, and upgrade back to ceramic board, later on.

I would only be concerned if purchasers did not consider the rest of the forge construction, to be as solid as the old models.

Or, maybe it would work better to hear an evaluation

                                                  Avoid overheating your torch-head

It is popular to use small propane torches in two-brick and coffee-can forges; as an introductory move to metal work, this makes since. However, when more heat is desired, propane canisters are often replaced with propylene, and greater caution is required.

    Nearly all torch-heads that are rated for use with both propane and MAP gas (actually propylene fuel gas since 2008) have the same warning about not turning the torch flame down too far; to avoid overheating its flame tube. Increased fuel flow, induces added air. This air/gas mixture is all that cools the flame tube; which makes sense, once you realize that the incoming air is mixed with gas that has been greatly chilled by expansion from its liquid state (refrigeration effect).

    But, when the flame tube is placed in super-heated equipment, like a forge or furnace, overheating problems can increase; it’s something to keep in mind before cutting back your gas pressure to save fuel. The more its flame is reduced the less super-cooled gas/air mixture that is passing through the torch-head's flame tube, at any given time. But the heat retaining layers of insulation surrounding that tube, in the portal, will rapidly accumulate very high temperatures, despite the flame being turned down. So, it is prudent to keep the refrigeration effect from the incoming fuel/air mixture turned up high; especially during longer heating cycles.

    The safest plan is to locate the end of your flame tube just inside of the equipment’s steel shell, and create a slightly tapered (expanding) opening, with cast refractory, between the shell and the forge interior’s flame face.

    While fine for use in brazing out in the open air, take care if using propylene inside forges and casting furnaces; unless your burner is undersized, such confined spaces will get too hot for many refractory materials; propylene flame temperatures can easily melt a stainless-steel flame retention nozzle inside heating equipment. Refractory flame retention nozzles are a better idea than stainless steel with propylene fuel, unless the equipment is only going to be run, as a hand torch, out in the open air.

Note: Most commercial dual-fuel torch-heads have a thin wall stainless steel flame-tube, which ends in a bull-nose shape at its gas opening; this serves a similar purpose to what we call the mixing tube and flame retention nozzle on a propane burner.

The G LAXIA 4 amp angle grinder is the first small angle grinder that I've seen with this low an amperage rating, since Makita first marketed their 4" angle grinders about forty years ago; since then, every new model angle grinder has boasted more, and ever more power.

So, why would anyone want a wimpy little 4 amp grinder, anyway? To be able to cut steel parts, in reasonable safety! The joy of this deal is that this grinder only costs $27 on Amazon.com; it even has fair costumer reviews

Angle grinders are the faster tools for cutting the metal parts needed to build forges, and the air/fuel burners that heat them; while rotary tools (or die grinders) are more precise tools for cutting and shaping the small parts, which burners are made from. There is a lot of cross over between both kinds of work, and therefore between what tool does what task best. In the grand old tradition of "wanting our cake and eating it too," we like to find ways to extend the usefulness of both tools; I hardily agree

  The main obstacle for doing this easily is that rotary tools tend to have too little power (thus, we look to electric die grinders), and angle grinders mostly have way too much! One more reason to keep that grinder "under powered."

  So, by starting with a 4-amp grinder, and including a fan speed controller to its power cord (always avoid using the inbuilt speed control circuits on power tools, if you want them to last), You can safely use that grinder for all manner of metal cutting, and grinding tasks, which would otherwise be most unwise.

 Such as what, for instance? Such as mounting a small extension spindle and/or converter chuck, and using rotary accessories, in what will then amount to an angle head die grinder.

Electric motors, which are only rated for intermittent use are designed to be run for short periods. Of course, the higher a motor’s amperage, the hotter it gets. Power equipment that are rated for ever higher amperage, should have ever better cooling systems, to offset the load, rite?

  Of course, nobody wants a big heavy power tool, and manufacturers want their products to sell…thus, we now have 4 ½” angle grinders with 9.2 amp motors in them (one model boasts 12 amps); these would have been found in 9” angle grinders, back in the nineteen fifties. Has there been a magic upgrade in electric motor manufacturing since then? No; “compact” electric tools simply heat up fast, and need to be used intermittently; the higher the amperage rating for your little grinder the smaller its duty cycle (the amount of time it can be run, in any ten minute period); or else buy a big grinder to do the job.

  It's not a magic wand, Harry; it's just a power tool.

On 11/26/2024 at 2:32 PM, Mikey98118 said:

always avoid using the inbuilt speed control circuits on power tools, if you want them to last

Why would that be? Inbuilt speed control circuits on most power tools are tiny; they rapidly heat up, when engaged. The slower you run your tool the faster they heat up. Before you know it, your tool "makes magic smoke" and dies. Then, you must either throw the tool away, or replace that dead circuit with a length of wire, because very few foreign made tools have replacement parts available.

  Thereafter, you will need to mount a fan speed controller to the tool's power cord, to vary its speed; these have sturdy power circuits, which are designed to take the load. BTW, fan controllers work smoothly through their entire speed ranges; most miniature control circuits, built into power tools, do not.

On 11/15/2024 at 1:26 PM, Mikey98118 said:

Better yet, that refractory can be made pretty insulating with the addition of silica or high alumina spheres in its mixture

Mikey, would silica spheres be the same as "silica fume"? It keeps coming up when I'm searching for silica concrete additives.

No; fumed silica is what we use, in water, to make rigidizer (to spritz onto ceramic wool insulation). However fumed silica is also used as part of ceramic and refractory mixtures, because it melts-the first time, and only then-at very low temperatures.

Silica spheres where originally used to create voids in concrete bridge parts, and is now also used in hard refractories, to lighten, insulate, and make it resistant to cracking. These spheres are very thin, so when they melt into the refractory (during firing), they do not increase its silica content noticeably (that would lower its insulating abilities, and lower its maximum temperature rating), but they do a fine job of leaving behind loads of voids.

Did this cover your questions?

I remember back before the home our casting groups "discovered" Kast-O-30; they were using chicken wire in the hope that it would help keep our refractory together a little longer, after it started cracking. In those days, we all mixed Perlite into the refractory mix, to make insulating voids. So, the insulating, and lightening aspects of Kast-O-30 were no big deal to us, but its fracture resistance made it an instant hit

Egad! That should read "our home casting groups" and "Kast-O-lite 30"...

14 hours ago, Mikey98118 said:

No; fumed silica is what we use, in water, to make rigidizer (to spritz onto ceramic wool insulation).

That's right! I knew the term sounded familiar!

Searching for alumina spheres is giving more results, but how big should the spheres be? I'm seeing results from 1mm up to 12 (!) mm diameter!

(I've also found perlite much cheaper at one of our big box stores and will probably just use it, but I'm still curious about the alumina spheres)

Alumina spherules would be sweet! They have a much higher melting temperature than silica spherules but cost quite a bit more. Here at any rate. 1mm - 12mm is way too large for a component in refractory, at our scale anyway.

Frosty The Lucky. 

One millimeter spheres should be okay.

  Perlite is fine, but you will probably want to finish coat the flame face with Plistix, to smooth its surface. Remember that a smooth surface radiates heat back into the equipment interior far better than a rough surface can; that is the genius of Plistix.

Knocked this one together this afternoon with perlite and castable refractory:

I cast some step nozzle sized holes for my burners using some appropriately sized tube and I offset them from centre to induce some swirl.

I just need to twist them in the holes every hour or so to make sure the tubes don't set in the castable as it cures.

I rammed the mix in thoroughly and then vibrated it with an 'L' shaped piece of rod in my drill held against the edge.

The tin is 3 litres, from memory, so about 3/4 of a gallon. I think the tube that makes the forge interior is about 2 1/2" diameter. We'll see how well it all worked in a couple of days.

Cheers,

Jono.

7 hours ago, Hefty said:

Knocked this one together this afternoon with perlite and castable refractory:

I cast some step nozzle sized holes for my burners using some appropriately sized tube and I offset them from centre to induce some swirl.

I just need to twist them in the holes every hour or so to make sure the tubes don't set in the castable as it cures.

I rammed the mix in thoroughly and then vibrated it with an 'L' shaped piece of rod in my drill held against the edge.

The tin is 3 litres, from memory, so about 3/4 of a gallon. I think the tube that makes the forge interior is about 2 1/2" diameter. We'll see how well it all worked in a couple of days.

Cheers,

Jono.

Isn't it great what some vibration does to smooth out a refractory casting 

Sure is! The oiled PVC centre ended up being harder to remove than the burner nozzle cores, but apart from some tiny air bubbles she's almost shiny smooth inside!

I've got it sitting on a brick above some water in a plastic garbage bin to cure in 100% humidity for a day or so, then I'll slowly ramp up the temp of each burn until I see how hot I can get it. 

Cheers, 

Jono.

Ramp  the temperature up slowly, to begin with. Give time for whatever steam forms, to escape, rather than build up pressure. Just bring it up to red heat two or three times, before "going for it." I think you will be pleased with how well it works.

The Hyper Tough 20V Max Brushless Cordless Cut-Off Tool is just like a 3” 12V angle grinder, but with nearly double the power of 12V tools; it is available,  with a 1.5Ah Lithium-Ion battery and charger, from Walmart for $39.88.

Battery adapters that allow Milwaukee 18V, or DeWalt 20V batteries to energize Hyper Tough tools are available through Amazon.com. 

Working with castable refractory: Whatever castable refractory you use as a flame-face on the interior surfaces of your heating equipment, the finish product will turn out far smoother, if the casting is vibrated for a couple of minutes, after casting. Most refractories are packed in place, with a minimal amount of water, because excess water in the mixture weakens the final product. Vibration permits the refractory to move around like a liquid, filling in small voids, so that all surfaces end up smooth; this is especially helpful for castings with multiple internal holes, such as ribbon burner blocks.

Home casting enthusiasts used to make their own casting vibrators; they posted several different kinds, but that was a quarter century back; my old brain no longer remembers much about them.