Forges 101

[Mikey98118]

I think helium takes more pressure than Freon to compress. My guess

is that cylinder wall thikness has to do with the amount of gas party balloon cylinders store; not much is what I figure.

[ThomasPowers]

I think pressure=pressure; but at some point freon will go liquid and so easy to store a lot of it under a reasonable pressure. Helium, well if you are directly compressing it and getting a liquid I sure hope you are on the other side of the state from me (and I'm right on the border!)

[Frosty]

If you can compress helium into liquid directly you're a star in my book! 

I could be wrong but even on the metallic hydrogen core of Jupiter helium is still a gas.

Frosty The Lucky.

[Mikey98118]

I concur with both of you guys . What I'm supposing is that these light walled helium canisters, probably contain no more than four bars of pressure. Helium isn't a cheap gas to produce, and never was. Remember the 'good old days' of heliarc? I do; before nitrogen/argon welding mixtures, TIG welding was an empty daydream for younger weldors; these days a weldor merely needs to be darn good, to get the job; back in the fifties it was a sinecure for life long employees, during their waning years on the job. So, how much gas do we expect to find in a party consumable?

[JHCC]

1 hour ago, Mikey98118 said:

 So, how much gas do we expect to find in a party consumable?

According to the Balloon Time website, their standard tank contains 8.9 ft³ and their jumbo tank contains 14.9 ft³. 

(On a side note, they also say that on account of the current state of the worldwide helium supply, they use a 80/20 mix of helium and air, sufficient to keep a balloon floating for 5-7 hours.)

(Also, if you're not going to use one for a forge, they make great slack tubs.)

[Mikey98118]

8.9 cubic feet isn't much volume. "... on account of the current state of the worldwide helium supply" sounds more friendly than "in order to make more profit." Not that I'm complaining. Party balloons mean a plentiful supply of perfect shells for miniature forges.

[ThomasPowers]

Now *Hydrogen* we have a lot of and would make for much more exciting party balloons!

[CalebB]

Ok SO.

I just realized that I had a chimney flue to use as my forge but I have the problem of converting it into my forge and how to put in the burners/exhaust.

[ThomasPowers]

Details please: Chimney flue could be anything from square tile to flexible stainless pipe.  A picture would be good.

[Mikey98118]

NO! Chimneys cannot be shared by more than one appliance.

[Square Nail]

On pretty much an unrelated topic, I have read somewhere that you shouldn't expose your forges to freezing temps. With temperatures here routinely dropping below zero for a month at a time with lows to -20 or lower, will this hurt the ceramic blanket or refractory? My shop is for the most part unheated!

[Mikey98118]

I don't think so; it would probably be a good idea to keep the flame low, untill the forge comes up to room temerarature, before running wide open, but  I'm not aware of any special problems...

[Frosty]

No, cold doesn't bother forge liners unless you let it get wet and freeze. Freezing water expanding will break up anything it can get into. To be safe do as Mike suggests warm it up slowly if it's really cold. Put a light bulb in it if it's wet so it can dry thoroughly then warm it up slowly.

Frosty The Lucky.

[Mikey98118]

I never used a door on a tube forge, in the past. But after seeing a few made by guys on this group, I would recommend them on most forges, now. Just about any enclosure you can dream up for the exhaust opening, to pass work through (including baffle walls), can also be worked into a door arrangement; this allows better access to the forge for oversize pieces, and for making repairs. That constitutes valuable added abilities for limited additional work; a bargain any time you can get it.

Obviously, if it is such a potential asset on a tube, or "D" shaped forge, it must be considered mandatory on a box forge. A manufacturer may not use them because of structural considerations; some others may include poorly made doors on their forges for monetary considerations. Properly made, and insulated latching doors on front, one side and back of a box forge, is only reasonable for a forge you are building for yourself.

[Mberghorn]

So I have a question for all of you who have experience using castable refractory. Do you put some sort of a mold in the burner holes in the blanket to keep the refractory out of there or do you just cast the whole thing and then cut the burner holes in the refractory layer after it's all set up? I'm up to that part on the two forges I'm working on and I want to know what works best for you guys before I commit to mixing. Thanks for the help!

[Mikey98118]

That is a good question. Castable needs to be confined in some kind of form until it green cures, but that doesn't necessarily need to be a mold. You could rigidize the ceramic blanket in place and only use an inner form, such as Sonotube, or plastic pipe. On the other hand, you can reverse the process; building the inner face in a mold; flame cure it; wrap the insulation around it, with twine to keep it its diameter restricted. Heat will cut the twine, allowing the blanket to expand in the shell. But then, rigidizing the blanket gets harder to do. On the other hand, a superior hot face can be taken out of the insulation and wrapped with new insulation every couple of years. It all comes down to what you want most and what you are willing to give up for it.

[John in Oly, WA]

I've never tried to cut cast-o-lite 30. I just cut the ceramic blanket back from around the burner tube hole enough so the cast-o-lite 30 would form out to the shell. Then made a cone at 12:1 and put it around a tube the same diameter as my burner mixing tube so then when I packed in the cast-o-lite 30 it formed my flare for my burner right in the liner of my forge.

[Irondragon Forge ClayWorks]

I use a simple kitchen funnel to form the cone flare.

[Frosty]

I used the horn of an old fire extinguisher as a form for the burner ports, it was close enough.

The first time I used sonotube that nested with a 3/4" gap and rammed the refractory in. I used a sacrificial hole saw to make the burner port after it green set. Once it was fully set I peeled it, wrapped it with Kaowool, cut the burner port in the blanket and used newspaper and tape to make it small enough to slip into the shell. Lined up the ports and lit a charcoal briquette fire in it.

It was easier than it sounds and turned out nicer than hand plastering a hard refractory for the flame face. It's more limited for shapes though. It's a balance.

Frosty The Lucky.

[Mberghorn]

Awesome, thanks for all the great input guys!

I've already rigidized my blanket and fired it to set the rigidizer (pictures in Burners 101) so now I just need to pour my cast-o-lite. I saw before someone mentioned using cardboard with the corrugations pulled out as an inner mold so I have that sitting inside the forge now just waiting on whatever I put in the burner ports to keep them clear.

13 hours ago, John in Oly, WA said:

I've never tried to cut cast-o-lite 30. I just cut the ceramic blanket back from around the burner tube hole enough so the cast-o-lite 30 would form out to the shell. Then made a cone at 12:1 and put it around a tube the same diameter as my burner mixing tube so then when I packed in the cast-o-lite 30 it formed my flare for my burner right in the liner of my forge.

That's what I was thinking of doing too, I'm just at a loss for what to use as materials. I don't have a wood lathe so forming the cone out of wood is out (my whittling skills are less than exemplary). I do like Frosty's idea of the fire extinguisher nozzle, though. I can definitely make that work!

12 hours ago, Frosty said:

I used the horn of an old fire extinguisher as a form for the burner ports, it was close enough.

That's what I was curious about. Is 'close enough' going to be "good enough" to work without having to fool with it too much.

[ThomasPowers]

Do you have a drill press?  You should be able to use it to turn a cone.

[Frosty]

If the taper of the form is 1:12 , 12% or less it's good enough. More taper induces disruptive turbulence and degrades burner performance.

A drill press works fine as a vertical lathe but do NOT put much side pressure on the chuck a drill press quill does NOT have thrust bearings and you can wear them right out.

If you clamp a block of wood on the table and drill oh say a 1/4" hole in it. Then use a long 1/4" lag bolt with the heat ground off as a mandrel you can clamp the block of wood you're making the form from with a couple washers and nuts. Place the unthreaded end in the hole in the wood, a drop of grease helps a lot. Chuck the other end in the drill and use files with LIGHT pressure.

Make and use an angle gauge to get the taper right.

Easy peasy.

Frosty The Lucky.

[John in Oly, WA]

I'd do the wood block turning, or the smaller spout part (I assume) of a large plastic funnel as Mberghorn suggested, or just scrounge around for whatever might work. Sheet metal or heavy card stock formed into a cone and then duct taped to hold it's shape? It's just a mold piece doesn't have to be terribly durable; just has to hold up to casting the refractory.

[Mberghorn]

On 6/7/2017 at 12:29 PM, Frosty said:

 

I do have a drill press. The only reason that I hadn't used it as a vertical wood lathe is because I didn't know how to clamp the wood in the chuck but after reading this I think I can take a pretty good whack at it now. 

Also, good idea on the angle gauge.

[ThomasPowers]

I'd split off the corners of the chunk to make is semi round and then chuck it in the chuck and use a farriers rasp *gently* to make the cylinder and then turn it down with a Lathe skew chisel or the rasp and finally sand to final surface  finish and then paint it to make it release easily (and still use a release agent on it...)