andgott Posted April 1, 2010 Share Posted April 1, 2010 I decided that I needed a gas forge for my small work- I CAN do it in the big coal forge, but I've been working with some really small pieces recently, and they burn up in a matter of seconds in the coal fire if I'm not careful... I figured a propane forge would allow me to control the temps a little better! All I need is a really small forge- At first, I was looking at plans for a 'one brick' forge- Really, that's plenty big for me. And, I am not worried about getting it up to welding temps, I have no plans to use this forge for welding- If I need to weld, I can use the coal forge. I mentioned that I was planning on putting together a gas forge while I was in the shop today- And was given this- Well, I was given a rusty, half-painted thing that looks like this now, anyway. I hit it with a wire cup brush, then painted it with the uber-cool metallic bronze high heat paint. The hard part is done for me already. Ok- So now I need to line it. I have refractory cement to do so with- It was free as well- So that's what I plan to use. I was thinking that i'd make a nice, thick lining, so I've got a relatively small chamber, in the interests of efficiency. The tank is 8 1/2" in Diameter, 12" deep, and has a 6" hole cut in the front. I was thinking that a 6" dia chamber would be MORE than enough for my needs. When I go to line it- I was thinking about doing it in 2 'pours'- First, standing it on end, and filling the back of the forge, letting this dry, then inserting a 'plug' into the center of the forge to form the chamber, then pouring the rest. I've never worked with refractory, though- So I dont know how or if this will work... Input?? Also- the interior is a bit rusty, as you can see... How clean do I need to get it before lining?? And- For the burner. The holes are there for 2 burners, but I think that I only need one for my use. I'm wondering how using a torch burner like the one brick forge uses would work? Or am I better off making a burner? I've never done that- But I ain't skeered (not too much, anyway!)... I just wonder which would be more efficient. Anything else I'm not thinking of here? Thanks! -Andrew Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted April 1, 2010 Share Posted April 1, 2010 Thick refractory decreases efficiency as it's a heat hog till it comes up to temp. Can you line it with something insulative and then cast the refractory? Quote Link to comment Share on other sites More sharing options...
andgott Posted April 1, 2010 Author Share Posted April 1, 2010 I could easily do that- Is something like Kaowool appropriate for this? How would I go about doing that- Just lay the Kaowool in place then pour the refractory right on to it?? I would actually PREFER that approach, as in addition to being more efficient it would be lighter, too... Quote Link to comment Share on other sites More sharing options...
pkrankow Posted April 1, 2010 Share Posted April 1, 2010 You may want to make the hard shell separate, then fit it in the cavity left by the kaowool. Others have successfully used concrete forming tubes for this task. Certain sizes nest together leaving a nice gap that you can pack the refractory into. You may end up needing to peel one tube off or out to get a full cure before firing. You can use newspaper to control the wool as you slip the shell in. Whatever paper gets trapped will charcoal and burn away slowly over time. If you put the hard product onto the wool directly you may compress the wool and reduce its effectiveness. Phil Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted April 1, 2010 Share Posted April 1, 2010 So you may need to work out some standoffs for the cast refractory over the kaowool. The one I am currently building will have a soft firebrick liner and then rammable refractory as I am building a welding forge. Quote Link to comment Share on other sites More sharing options...
andgott Posted April 4, 2010 Author Share Posted April 4, 2010 Here is what I'm going to try. First, Line the inside w/ Kawool- About 3" or so. Then, make an insert out of the refractory, using a mold... This is the plug for the mold- That is the forge chamber, I'll put this inside a 6" cylinder, then pour the refractory around that. Once it's cured, I'll remove it from the outer mold, then burn away the foam, hopefully leaving me with a nice, one piece liner. I cast some test pieces with the cement yesterday to make sure that they were 'tough' enough to hold together if cast in the thickness that I'm planning on using them, and they seem to be OK. Next, we've got the burners to work on. The interior volume of this forge is pretty small- Just about 60 cubic inches- so I really don't need much of a burner! I think I'm going to try a torch. If that isn't enough, I'll probably try something like the Mini sidearm burner on the zoeller forge page. -Andrew Quote Link to comment Share on other sites More sharing options...
JNewman Posted April 4, 2010 Share Posted April 4, 2010 That should work well, a former employer of mine had moulds that the shop apprentice would cast foam forms out of. These foam forms were used at a steel mill to make curved refractory tubes that molten steel was poured through for continuous casting. They do exactly what you are planning to do, cast the refractory around the foam and then they burn out what they cannot dig out. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted April 4, 2010 Share Posted April 4, 2010 Consider bumping your volume up to 150 or so cu inch and using a single 3/4 inch burner of your choice. Anything over 2 inches of wool is not getting much benefit for the price of the wool. Your shell is plenty large for that. Also consider having a separate dense firebrick for a floor so you can change it if necessary. Phil Quote Link to comment Share on other sites More sharing options...
arftist Posted April 4, 2010 Share Posted April 4, 2010 My only input is to suggest a small back door, even if it is only 2 or 3 inches in diameter. I can't count the number of times I've needed to heat the center of a long bar. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted April 4, 2010 Share Posted April 4, 2010 I'll second Arftist's comment! You can plug the door with a scrap of leftover wool just fine till you need it, but I find the opening is used more than not in my forge. Just remember the plug with be very hot if the forge is lit and you knock it out! Phil Quote Link to comment Share on other sites More sharing options...
LouieIV Posted April 22, 2010 Share Posted April 22, 2010 Thick refractory decreases efficiency as it's a heat hog till it comes up to temp. Can you line it with something insulative and then cast the refractory? Perhaps I'm wrong, but wouldn't that make it more efficient for a long session of forging, because doesn't it hold the temp better once it gets up to heat? So that when you use an idler valve your forge stays hotter while idling. I'm brand new to this and don't even have a forge built yet, just trying to understand. -LouieIV :) Quote Link to comment Share on other sites More sharing options...
pkrankow Posted April 22, 2010 Share Posted April 22, 2010 Perhaps I'm wrong, but wouldn't that make it more efficient for a long session of forging, because doesn't it hold the temp better once it gets up to heat? So that when you use an idler valve your forge stays hotter while idling. I'm brand new to this and don't even have a forge built yet, just trying to understand. -LouieIV both are right, but for different time frames. For short work, say 1 hour or so, wool insulation with or without a coating is best, it will heat up to temperature very quickly. Finding a way to omit the brick floor is also a good idea in this time frame, but use of fluxes almost requires a brick on the floor. For half day work having that brick on the floor is fine with all wool insulation. Having a castable, rammable, or plastic for the inside 1 inch and an inch of wool would probably work fine. Having a quick heat-up is key, but near instant is not required. For all day work, durability is now more of an issue. The half day sets would work fine, but the bare or coated wool would take damage from use and "carelessness" from bumping the sides. Having a thicker hard layer becomes less of a problem, and may aid reheat time by storing a quantity of energy to return. This benefit is not useful if your heat up time is a significant portion of your day, but if the day is long then it may be helpful. For multi-day work, hard refractories become the only cost effective choice, heat up time becomes moot as a process that runs for 30+ days is not going to be hampered by a preheat time measured in hours. This is my opinion, you are welcome to form your own. Phil Quote Link to comment Share on other sites More sharing options...
andgott Posted April 22, 2010 Author Share Posted April 22, 2010 Makes perfect sense to me, Phil... Most of my forging sessions are a few hours long, so I will plan accordingly. I think that I'm going to skip the castable lining, though- and just use kaowool. I'll probably end up with about 3" or so in there. I know that thickness is overkill, but I got a really good deal on a whole roll (25') of the stuff, and I've only used about a foot of it in my micro forge, so I've got PLENTY of it on hand to use! I'll be lining it with plistex 900, just like the micro forge, and I plan to use a fire brick on the floor to protect it from my clumsiness I've got MOST of the burner parts on hand now, I've just got to get it put together. -Andrew Quote Link to comment Share on other sites More sharing options...
pkrankow Posted April 22, 2010 Share Posted April 22, 2010 3 is overkill, 2 is good, but that is up to you. If you reuse fired kaowool, wear extra protection...the stuff is more itchy than fiberglass. Before its fired it is not nearly as bad. Losses from radiation are worse than conduction through 2 inches of wool. Phil Quote Link to comment Share on other sites More sharing options...
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