Vortex forge

[Ted Ewert]

My old forge was starting to fall apart so it gave me the opportunity to build a new one with an idea I'd been thinking about. Nothing particularly different in concept here except the "ribbon burner" part. Instead of a cast burner I used 5 ceramic tubes. They are 3/8" ID, and 1/2" OD. Good up to 3k degrees F. These are more than sufficient to provide as much heat as I need.

I used a small propane tank for the outer shell. The combustion area is 1" thick Kast-o-lite which is 5.25" in diameter by 9" long. This size is ideal for the type of work I do. 

I cast some doors for the front and back. The back doors have an exhaust port and can be opened for long pieces. The doors are all 2" thick and also made from Kast-o-lite. 

My goal was to make an energy efficient, well insulated forge where the majority of combustion takes place inside the forge and the resulting heat is retained. This forge achieves those goals to a large extent while still being functional and flexible.

I also made a video of the build for anyone who is interested: https://www.youtube.com/watch?v=67Yl7_g3KO4&t=15s

[Latticino]

Interesting idea.  Just be really careful to keep those tubes from physical or thermal shock.  You don't want your air gas mixture poring into your shop if that happens.  I would be tempted to put a wire mesh cage around them, at least.

[Ted Ewert]

The tubes were designed for high temperature applications like this and are quite strong. Nevertheless, the manifold is bolted to the outer case and no physical load is placed on the tubes. 

I did discover that the tubes need to be recessed somewhat into the liner. If the tube is fully exposed in the combustion chamber it will heat up and cause premature ignition of the gas. This did not cause blowback into the manifold, but I didn't like the idea of gas burning in the tube. Pulling them back solved that. 

[Latticino]

I've used similar high fired ceramic tubes in the past.  They are certainly designed for the temperature, but will still crack if exposed to thermal shock (rapid changes in temperature) or mechanical load (stock flipping off the anvil or getting launched from a hot cut and flying across the room).  Just be careful is all I'm saying.

I assume you have bubble-tight mortar joints between your steel manifold and the four tubes also?  You certainly don't want a leak there either.

[Ted Ewert]

Caution noted. Yes, the tubes are fully sealed at the manifold. While in operation the tubes barely get warm.

I have found that the fewer tubes, or holes, used corresponds to greater fuel efficiency. I'm sure that 4 tubes would have been sufficient in my case. 

Once the forge gets up to temperature I turn the gas way down. I can accurately judge the mixture by watching to see if any flame is coming out through the door opening.  I crank it down until the flame just dissappears. That's just right for most forging. 

There's a balance between the number of tubes, size and air velocity. When the forge gets really hot, and the gas gets turned down, there still has to be enough velocity to prevent blowback. I was a bit concerned with going up to 3/8 but it works fine. With fewer tubes you can get away with a larger diameter hole. 

[Stonetar]

I know this post is getting old enough to where it's starting to consider retirement but I was curious if you might have some pictures of this thing running? 

[Buzzkill]

He showed it running briefly around 1:09:40 in the video link given in his first post.

[Ted Ewert]

17 hours ago, Stonetar said:

I know this post is getting old enough to where it's starting to consider retirement but I was curious if you might have some pictures of this thing running? 

I took a couple of pics to show the flame path. The first one is on start up. The input ports are about in line with the crack in the shell. The blue is where the flame is igniting. 

The second is the forge after its warmed up a bit. At that point you can't see the flame anymore. 

One note, I removed the rear tube so there are now 4 tubes feeding the chamber. That's plenty for me. The rear of the chamber stays a little cooler which I prefer. 

I've had to recast the chamber once since I first built it. Otherwise it's been a great forge.