Gas forge progress

[newbieforge]

Just thought I'd share some recent progress I've made on my gas forge.

It is a 4-burner forge, modelled after Ron Reil's 4-burner forge. See http://ronreil.abana.org/design1.shtml for more info.

Forge Body
The body is a 24" segment cut from a 100# propane cylinder, which I got for free. The inner diameter of the cylinder is 14.5", and I've lined it with 2 layers of 1" kaowool type ceramic cloth insulation. That leaves the forge interior with a 10.5" inner diameter. All interior surfaces are brushed with ITC-100.

The forge floor is made from four 2" thick insulating kiln bricks. These bricks are nice and light, and good insulators, but are too weak to work as a forge floor. Every single one is cracked in multiple places. But they still get the job done, and I'll replace them when they have reduced to a pile of brick crumbs.

Burners
The burners are Reil style 3/4" burners, with tunable chokes. The parts for the burners were purchased new, and cost around $15-20 each to build. (Just a bit more than the optimistic $5 that some online sources claim it costs to make these.) The most expensive parts of the forge are the brass and copper hardware for the gas lines. These were also purchased new.

Stand
The stand is welded and bolted from 1"x1" angle irons. The stand footprint is about 18" by 18".

Embarrassingly, I started The Gas Forge Project more than a year ago, and got it to 80-90% completion in about 2 months. It was working around this time last year, in the sense that I could light up the burners, and get pieces of metal to red or orange heat. However, it was lacking some important features: front door, back wall, and workpiece holder. Without the front door and back wall, it was possible to heat metal, but it was very inefficient because most of the heat was being wasted.

Finally, this past week, I made the time to finish up these loose ends. Here are the results.

Just after lighting the front 2 burners:


I'd like to point out the frame holding the fire brick door in place, with the forged scrolls. The scrolls are free hand shaped with hammer and bending fork, out of 1/4" square stock. It was a fun opportunity to use the forge to build the forge. It was also my first blacksmith project that ended up serving some kind of useful purpose... which is why I'm pointing it out. :)

The fire bricks that form the door can be moved and adjusted as needed. Originally I was going to build a metal door with a fixed size opening and kaowool liner, but the fire bricks are a much easier and much more flexible and future proof solution, in my opinion.

The sliding work holder rack is made from 1/2" round, and it slides into two 24" long pipe nipples welded to the angle iron frame.

The newly made back wall:


This is made from 1 layer of 1" kaowool, tied to a piece of expanded metal with stainless steel wire. The expanded metal is tack welded to legs made from 3/8" square stock. The expanded metal has a square hole near the bottom. If one day I need to heat long pieces of metal, then I can poke a hole in the kaowool to pass through.

Heating some 3/4" rebar:


Gas valves and supply to burners:


It is hard to see in the picture, but there is an idle circuit controlled by the ball valve with the black handle. Closing the valve reduces the pressure to the burners to about 1-2 psi (depending on the main pressure of course) which keeps the forge interior hot while consuming almost no gas. When heating metal, I can close the idle valve right before taking the work piece out of the forge. When the workpiece goes back in, I can open the valve again for instant heat.

At the manifold with the four yellow ball valves going to each burner, there is a 4-port junction. The top port is plugged, but soon I'll install a second pressure gauge there, to be able to monitor the gas pressure at the burners. It will also allow tuning the idle circuit better to save more gas.

The forge, in its temporary home on my work bench:


Practicing shaping some tongs:


Overall Notes
The forge body is too long at 24". I found that I only use the front 10-12" and since putting on the door and back wall, I have never used more than the front 2 burners. If I were to build another one, it would be shorter, maybe 16-18" max, with only 2 burners. With the movable back wall, however, the excessive length is not really a problem; it just makes the forge harder to move around.

The burners seem to work ok, but I don't know if they can bring the forge to welding temperature. The hottest I have seen it is very bright orange or yellow.

One of my next welding projects will be to make a dedicated stand on wheels for the forge, to free up my metal work bench, and to make the forge less of a lug to move around.

Overall I'm pretty happy with this thing. It only took 10 times longer to make than I thought it would. I finally feel like I will be doing some actual forging this winter, instead of making and collecting the tools needed for forging.

Comments and criticisms welcomed!

All the best
Markus

[vihalvor]

im envious of it !! :D

[setlab]

Nice looking forge, I really like the front brick holders.

Not too long ago I got an old air compressor about that size I intend to make a gas forge out of so this has deffinatlygiven me some good ideas. Your back wall is interesting, keep us posted on how effecient it runs with just two burners.

[Frosty]

Looks good Markus. Ron came up with a great idea in the moveable back wall. The rule of thumb for burner number or size is, one each 3/4" linear burner per 300 cu/in to reliably get welding heat.

A linear burner is an induction device with the air intake port(s) in line (the linear part of the name) with the tube and jet. Ron's spent a LOT of time perfecting his burner design and it's a good solid one to use. So, with an inside diameter of 10.5" each burner is only going to be able to bring about 3.5" length to welding heat.

Not so much eh? You can reduce the ID or increase the number of size of your burners. A 1" burner has 2x the output of a 3/4" burner, the trickiest part of doubling burner size is getting the gas jet right. I use mig contact tips, 0.035" for my 3/4" and 0.045 for the 1" so as a departure point figure the burner tube and the jet dia. will be similar proportions.

All in all it's a very nice job you've done, Ron would be pleased, especially if you didn't pester him with a lot of questions.

Frosty The Lucky.

[newbieforge]

vihalvor, thank you!

setlab, the brick holders on the front are working really well. Having tried the bricks, I would not consider using a fixed size front opening on this forge. The flexibility to reduce the opening to the minimum required for a particular work piece is great, because it maximizes how much heat the forge retains in the interior.

[newbieforge]

Frosty,

Thank you for the constructive advice.

Clearly, my forge is slightly underpowered given the volume I am expecting to heat.

Based on what you are telling me, I am working on a 1" burner. When it's done, I'll replace one of the 2 front burners with it. That should give the equivalent of three 3/4" burners for the front 10" of the forge, putting it in the ballpark of one 3/4" burner per 300 cubic inches.

In fact, I think Mr. Reil should not even know of my existence. His information is very thorough, and so I found no need to contact him with questions. Furthermore, other people have documented how they build their own Reil burners (for example: http://metalcast.boorman.us/reil_1.html) so all I had to do was read the instructions and do the work. The hardest part was getting to the plumbing store to get the parts! :)

All the best
Markus