I've decided to build a gas forge

[KPeacock]

This weekend I headed down to Mike Blue's place to take in a bit of information regarding metalsmithing. First of all, Mike is a great guy that was more than willing to answer all of my questions and point me in the right direction. Secondly, Mike introduced me to the world of gas forges. It didn't take me long to realize that this is the way to go for consistancy in welding.

 

I'm in the planning stages of building my own small gas forge. I'm debating whether to go with a forced ait setup or a venturi set-up. I gather there are pros and cons both ways. Portability isn't an issue as my truck is wired for 120V power and can easily support the draw of a shop vac or other blower. I have a shop-vac that is already configured to be a hand held blower. It seems like this would be the way to go, but I am intrigued with the simplicity of the venturi type burners.

 

Mike offered to sell me one of the burners that he made and I declined. I'd like to at least try to make it work myself before I buy the real thing. I get a bit of satisfaction out of the fabricating side of things.

 

I presume that the forced air burners use less propane, but I do not know this to be the case. I also think that they would be a bit more adjustable via globe valve on the air supply. For the fuel side of them, I'm picturing a variable pressure regulator and also some sort of gas valve.

 

I just looked through the forum for about an hour and a half or so, but I have to get at least a little bit of work done. Feel free to comment and let me know what you think one way or the other. I undertand if you don't want to take the time to comment as this has been covered before I'm sure. I'll continue to dig through the archives for the next few days before I begin assembling my parts.

 

Thanks,

[Christopher Price]

First off, Mike is a world-class gentleman, and you're richer for spending considerable time with him.

 

My impression, having used both, is that it's much harder to get a welding heat in a venturi forge. They must be built properly, run at the right pressures, and maintained well. Forced-air is idiotproof, and in my shop, that's a hard requirement.

 

I offer my furnace-building thread for your enjoyment, just ignore all the oil-related stuff... http://www.bladesmithsforum.com/index.php?showtopic=10400

 

Also, here are some pics of how i plumbed it:

 

Blower

 

Air gate, then propane inlet (gas is a 3-valve system... the tank valve, a red hat regulator, and then the ball valve shown in the pic)

 

Forge body (ignore the oil pipe welded to the tuyere)

 

 

Good luck!

[KPeacock]

That looks pretty similar to what I'm thinking of. From what I've gathered reading through posts here and elsewhere, is that this forced air type of setup is no dependant upon orifice size. it is more dependant on pressure delivered via pressure reducing valve. What do you have your PRV set to and what is the final opening size where your propane is mixed in with that forced air?

 

BTW, nice video. I feel bad for it, but I got a healthy chuckle out of it. I'd like to pretend I've never been in a similar situation, but I've gone from a beard to side-burns on more than one occasion.

[Christopher Price]

I don't have a gauge on my regulator... it's all by eye. I crack it open enough that I get adequate gas flow with the ball valve opened about 1/3 of the way, then tweak them both to where I'm able to run right up to the riches I want with the ball valve wide open, and can choke back there instead of fiddling with the regulator. In long sessions, over 1/2 hour, I'll have to crack the regulator open a little bit more as the tank cools and runs lower (using 5 gal propane tanks).

 

The air pipe is 1 inch inner diameter, from the main air gate (PVC one you see in the pic) all the way into the forge. The brass fitting for gas is 1/4 inch I think, but it just shoots propane into the airstream and has a foot or so to mix before entering the forge and igniting. Keeping the air gate half-open (vs. wide open) increases turbulence, so it almost burns better at a lower air setting than full-blast.

[KPeacock]

I believe I'll try both methods. As soon as I got back from Mike's shop I started cutting, tapping, welding...etc. I cobbled a venturi style burner up in about 30 minutes only to find that my propane tank was nearly empty. I'll be filling both tanks in the enxt day or so and I'll test it out. I think I'll also test out the forced air set-up as well. Depending on how the tests go, I'll pick one or the other. I think I'm leaning towards the forced air at this point, but I don;t have any good reason for this. All of Mike's stuff is venturi style and it sure seems to work out just fine for him and the guys working in his shop. Heck, with the equipment he's got in there one of the guys manage to weld and draw out a billet a few times over and have working pattern welded stock in a few hours. I'm anticipating a few weeks of work to get to that point.

 

I'm hoping that I'll have things a bit more set in my mind by the time the weekend rolls around. Thanks for your input and advice.

[KPeacock]

perhaps this has been covered before, but wouldn't a weed burner work just fine for a gas forge? You can get them cheap at 20 bucks a piece. most of then havea flow control valve on them as well. I'm thinking something similar to this.

 

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=91033

[Christopher Price]

perhaps this has been covered before, but wouldn't a weed burner work just fine for a gas forge? You can get them cheap at 20 bucks a piece. most of then havea flow control valve on them as well. I'm thinking something similar to this.

 

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=91033

 

 

It's been done, but with far less control than a proper venturi tip.

 

 

As for the welding, I didn't say you couldn't do it with venturi, but it's not as easy. A forced-air forge will do it even when you don't know what you're doing. And eat up more fuel. And be noisier. But, it works.

[cdent]

If you were influenced for the better by your visit to Dr. Blue's shop, why not follow his lead and advise. Whatever happens, it won't be a bad start, then down the road build the whole forge package to fit your taste/style.

 

Good luck with the build, Craig

[KPeacock]

It's been done, but with far less control than a proper venturi tip.

 

 

As for the welding, I didn't say you couldn't do it with venturi, but it's not as easy. A forced-air forge will do it even when you don't know what you're doing. And eat up more fuel. And be noisier. But, it works.

 

You've just sold me. Considereing my somewhat less than vast experience i nthis field, I'm going for simple and effective. My concern is with the welding itself. I got some GREAT procedural advice while down at Mike's place over the weekend. Now I just need a way to get the steel to that temperature in a more controlled manner. I don;t mind burning through a lot of propane to do it. I still have the charcoal for the heat and beat process.

 

It looks like I'll be stopping by the hardware store on the way home to get a few more fittings. and random parts.

 

thanks for the input,

[Mike Blue]

I'm glad you had a good time and thanks for the kind words.

 

A couple more pennies then...

 

The fire you saw running was two 1 inch venturis into a formerly blown hard castible forge. The guys you were watching didn't have too much trouble (given their levels of experience) getting things to weld up. Greg worked on three separate billets and Steve did one of his own and then fiddled with a couple billets he'd patterned and took them down closer to final forging dimensions. Either way, you need to think about working patterns at or near welding heat regardless.

 

I think, without having measured actual consumption, that I burn less LP than when I was using a blower. But that's a consummable that's lost in the middle of all the costs of doing this anyhow.

 

One of my very good friends tapped a venturi burner into a pipe and then blew air down the pipe. Sort of a combined unit. That went into a forge that was a couple inches of cerowool on the top and hard brick on the bottom. Not only did it routinely produce great welded product but it is the quietest forge of it's size that I've ever heard. We can stand next to it and have a decent conversation instead of looking like a couple old smiths yelling at each other. My next evolution will be one like it. Haven't got to it yet because the one's I have are working fine. Earmuffs and plugs soak up a lot of the unsafe sound, and I can talk to myself, or sing, without scaring anyone when it's noisier.

 

I think you're on the right track. Really, you won't be convinced until you do it for yourself, and that's the smith's path, truly.

[KPeacock]

I hadn't considered the possibilities of a hybrid burner. I've got a venturi style unit put together that needs a bit of testing and fine tuning. I might just as well try a hybrid set-up after I get it working. Before I start buying parts just to have them i want to get a few ideas tested out and then weld them up into the finished product. Ultimately, the amount of gas it consumes isn't a real big factor in the design. I'm looking for simple and effective with consistant results. I recognize that a fair bit of the consistancy rests firmly on my shoulders. I'm clearly not in a position to claim that i have the skill set to weld with consistancy, so I'd like to get the equipment set up to eliminate as many problems as possible.

 

If nothing else, I get to do some tinkering and fabricating. This will give me some time to toss ideas around in my head before I just grab a hammer and start smashing hot steel. I'm at the point where i can view this as a fairly safe hobby, but i can see how this could rapidly spiral into addiction.

[Alan Longmire]

I'm at the point where i can view this as a fairly safe hobby, but i can see how this could rapidly spiral into addiction.

 

I hate to break this to you, but it's too late. You're hooked already, and were gone beyond return from the minute you set foot in Mike's shop. You're one of us now. BWAAAAHAhahahahahaha!!!!

[Doug Lester]

I, of course, haven't seen Mr Blue's rig but I'd recommend a needle valve on the gas line (note: this does not replace the shut-off valve) for fine adjustments. I have to open my valve a little when the forge is cold and then cut it down a bit when it gets up to full temp. I haven't done any measurements as to how many hours of burning that I get out of my forge with the blown burner but I do believe the it uses the gas at a lower rate.

 

Doug Lester

[Mike Blue]

I hate to break this to you, but it's too late. You're hooked already, and were gone beyond return from the minute you set foot in Mike's shop. You're one of us now. BWAAAAHAhahahahahaha!!!!

 

You should have seen the look on his face change. He hung around on the finishing side of the shop for a bit, but then once the firelight got in his eye and a little smoking flux up his nose, gone, gone, gone. You know how it is when they are just glowing after watching for five or six hours. LOL.

 

Thanks for the reminder about the needle valve Doug. I think I mentioned it, but it's a necessary little thing that could easily be overlooked.

[KPeacock]

I licked out on a site visit today. I'm a mechanical/civil engineer that does building inspection all over the midwest. Today I was out to a large construction company in St. Cloud and they do a lot work in the undergound piping side of things. The shop foreman told me I could take whatever I wanted to out of teh scrap bin. They are all cut off pipes, scrap plate steel...etc. I got some random pieces of plate to use as ends of my (not yet built) gas forge. I alos picked up a couple pieces of thick walled steel pipe. One piece is 8" diameter but about 16" give or take a bit in length. I didn't put a tape on it. The other piece is 6" diamter by 12" length . I plan to use 2, one in thick layers of kaowool along ith some castable refractory and hard firebrick at the base. The insulated pipes should have an interior volume of about 200in^3 for the larger pipe. The 6" pipe will only have a 2" diameter opening with 2" of insulation. this seems a bit small to me, but would probably work grat for smaller blades. Any thoughts on which one to start with?

 

My inkling is to set the larger pipe up with a forced air burner and get that operational. then I can tinker with the smaller one and a venturi style burner.

 

I'm not sure how to guess at what size blower will be adequate. Will a hairdryer supply enough air? I can use an electric leaf blower, but that seems like overkill and I have a hunch I'll be chiking it way down with a valve to reduce flow. ideas or comments?

 

I plan on putting the forced air burner together tonight. I I don't see any reason why I wouldn't be able to assemble it. I do not have the small needle valve. I'll make an attempt to get it running right using a gate valve for the air supply and a variable pressure regulator for the fuel side. When I get a chance to stop by the welding supply shop I'll order a valve.

[cwilliams]

Sounds like you are on your way to getting a nice forge built. I will go ahead if you dont mind tell you the direction I went with forges, I started with about a 12 piece of pipe layed sideways with firebrick as a base and two layers of Kwool and 2 venturi burners and easily got welding heats and was very pleased with it last year for my damascus forge even though it needed two tanks (40lbers) in parallel to keep a single tank from freezing up.

Fast forward to this year, I have made a Fogg vertical forge and I can run this off just one tank and it has never froze up and gets much hotter.

Now having both styles of forges I really like the Fogg forge and would only ever use it if doing damascus work.

Dont get me wrong I love my horizontal forge and for General purpose work its my go to forge, you cant beat setting down on the floor forge what you want heated but for damascus give me a vertical forge.

PS Forgot to mention it takes my horizontal forge 30mins to heat up to forge welding temps. It only takes my Fogg forge 5 mins.

Hope this helps.

Chris

[cwilliams]

Forgot to mention I got my blower from surplus center.

Below is a thread of my forge with pic of the blower if interested.

http://www.bladesmithsforum.com/index.php?showtopic=11477

[Doug Lester]

You're going to need a blower that will deliver at least 60cfm. If you go above that, you can adjust it with the gate or ball valve on the line behind the inlet for the gas. If you can't find a needle valve locally, try elliscustomknifeworks.com. Darrel has saved several of us by stocking some of the harder to find parts.

 

Doug Lester

Edited November 19, 2008 by Doug Lester

[KPeacock]

Without the needle valve, I was able to produce and maintain a flame and vary it's coloration a little bit. There MAY be pics of this if I can figure out how to post them. If they don't show up, I'm sorry. This was produced at about 5psi running through a 1/8" inlet hole. I decided to try it with a hairdryer as the blower. I had my doubt regarding the flow rate of the dryer, but this was all done on the lowest setting and seemed to be enough. I had the gate valve on the air supply mostly closed.

 

This is built to duplicate a forced air burner I saw online a Indian georges knives. The only difference with his and mine is the fact that Mine has a 12" mixing tube where his is 6." I can't imagine this would change performance much.

 

This is a picture of the flame itself...

Here is the layout...

Here are the bits and pieces that will become the forge...

Edited November 19, 2008 by KPeacock

[PMARTINKNIVES]

I'm glad you had a good time and thanks for the kind words.

 

A couple more pennies then...

 

The fire you saw running was two 1 inch venturis into a formerly blown hard castible forge. The guys you were watching didn't have too much trouble (given their levels of experience) getting things to weld up. Greg worked on three separate billets and Steve did one of his own and then fiddled with a couple billets he'd patterned and took them down closer to final forging dimensions. Either way, you need to think about working patterns at or near welding heat regardless.

 

I think, without having measured actual consumption, that I burn less LP than when I was using a blower. But that's a consummable that's lost in the middle of all the costs of doing this anyhow.

 

One of my very good friends tapped a venturi burner into a pipe and then blew air down the pipe. Sort of a combined unit. That went into a forge that was a couple inches of cerowool on the top and hard brick on the bottom. Not only did it routinely produce great welded product but it is the quietest forge of it's size that I've ever heard. We can stand next to it and have a decent conversation instead of looking like a couple old smiths yelling at each other. My next evolution will be one like it. Haven't got to it yet because the one's I have are working fine. Earmuffs and plugs soak up a lot of the unsafe sound, and I can talk to myself, or sing, without scaring anyone when it's noisier.

 

I think you're on the right track. Really, you won't be convinced until you do it for yourself, and that's the smith's path, truly.

 

 

Kind words, nice guy??, he must have caught you at a rare moment for you to give up all that info-----free?

Are we talking about the same Mike Blue?

JUST KIDDING Mike is a great guy, very knowledgable and a good friend to boot. Sounds like your guys had a great time, wish I could have been there!

Peter

[KPeacock]

Sweet fancy Moses. I just called to get a price on kaowool and was a bit shocked. I was expecting a price somewhat similar to standard insulation. Maybe double the cost or so. After hearing the local price I elected to bid on some through ebay and just buy my castable refractory and bricks through the local retailer. I plan to use 2" thick layers of kaowool for both forges. Have any of you tried using an adobe type of liner?

 

I'm guessing that this is not as effective as athe kaowool. but it seems like it would work well enough. Any thoughts and comments on this? one wouldn't have to worry about flux damaging the liner :-D

[Christopher Price]

I'll repeat something that was told to me not long ago... nothing insulates like "nothing". That is, a material that has lots of air for its volume is an ideal insulator. Castables, adobe, and hard bricks just don't have that quality. They're tough, and will contain and refract heat, but at an enormous cost of heating that material first before they start benefiting the forge chamber. And, they're heavy. And stay away from soils... they tend to turn to slag quickly. DAMHIK.

 

Kaowool with a satanite wash (less than 1/8 inch thick) has worked very well for me, for several forges. My improvements have been shell and plumbing related... the material itself does the trick for me. See my "hell's crock pot" thread... a cold start to a crucible of liquid bronze in 6 minutes. I know others use other coatings, ITC among them, but I just haven't bothered. When I get a flux-hole, I just patch with furnace cement and get on with my day.

[KPeacock]

If it works for the crock pot, it should work for me. Thanks

[KPeacock]

I'm starting to think beyond the basics of making ym forge. I have most of the materials gathered. I still have to obtain the firebricks and the castable refractory. Once I have those pieces, I'll begin welding parts together. I want to have my bricks before welding so that i can cut doors and weld shelves in locations that allow the firebrick to be easily positioned. I've been thinking a bit about flux runoff.

 

It is my understanding that this fulx is bad for the kaowool. The solution to this is to use a castable refractory to protect the kaowool. What happens to this flux after repeated use of the forge? I doubt it disappears or evaporates. Could one build a drain system of sorts to drain this liquid off? I'm envisioning a slightly dished floor in the forge that drains into a 1/4" hol that is plumbed out the bottom of the forge. It seems to me that this would work, but would likely clog up. Could this drain then be drilled out to re-open it, or would teh cooled flux be too hard?

 

Alternatively. if the base of the forge cavity was slightly concave and sloped towards the open end it stands to reason that the flux would run right out the front of the forge and into/onto whatever device i weld up to collect it. Have any of you attempted to fabricate a similar feature? Any input or thoughts are appreciated. I'd like to make my first gas forge as user friendly as possible. My second forge is also in the design phase.

 

I have constructed one forced air burner that works well and I plan to use on my first forge. I also have two venturi style burners that "work" one appears to be usable as is. the other makes an impressive flame, but has served it's purpose as a learning tool. It is not useful as is. It will take a bit more trial and error to get it dialed in. I do not have a lathe to make the parts as I want to, so I do a lot of welding. it's much harder to adjust a welded joint than unscrew a threaded joint.

[Christopher Price]

Your flux ideas sound cool, and I would love to see one that actually works well. Most of us throw a hard firebrick in there, or some castable, let it build up for a while, and eventually re-line it. Such is the life of a bladesmith.