My experimental forge/ heat-treat oven build (WIP)

[gotmike]

Haven't been on in a while, bought a new house, started a new job, and just generally been so busy i haven't been able to even think about making a knife... but my boss knew i was into making knives, and i mentioned making a forge to further my abilities... he offered to help... so we've been doing some work, gathering supplies from scrap bins, drawing things out in cad, and just generally bouncing ideas off each other to get this thing going... started out with fiberfrax ceramic insulation from out big heat treating oven (could easily fit two school buses in there.) I was able to gather large amounts of "lightly used" insulation for free. also had access to both stainless and carbon steel pipe of just about any size you can think. the stainless would have cost me scrap prices, so i went for a carbon steel body, with stainless burner tubes, and a stainless shelf and muffle inside. On top of all of that i'm building an Arduino based controller system that should be able to allow me very very precise control of both air and fuel, with almost infinite programmability and upgradability. I'm finally to the point of having a working set of forced air burners in a very very well insulated forge. And now for the pic's

the face piece that will have threaded holes to support a muffle to be sealed against the back wall with the thermocouple inside.

here's the face of the forge... may have to cut a secondary vent in the top of the front door to allow for better exhaust... but that will only be after further testing.

and here's the general layout of the forge body.

 

[gotmike]

here's the pic after i cut in the burner tubes... drew them up on cad and marked them with tangent lines to cut and weld in place so that they would go into the body of the forge even with the face of the insulation

 

[gotmike]

here's with the front handle in place, and the burners themselves set into the burner tubes

found an old grill base that i made some pieces of 10 gauge to put the forge onto to get it up and off the ground and moveable

the layers of insulation and the stainless "chicken wire" used to stiffen it

 

[gotmike]

the mocked up forced air tubes (flexable exhaust) and gas feed piping

more mockup
[IMGhttps://scontent-sea1-1.xx.fbcdn.net/hphotos-xfp1/v/t1.0-9/10338315_10206074853128610_6528994702478119114_n.jpg?oh=cd1a98f66a2bfe9bd1192ea0f4fc7fae&oe=56653D5D[/IMG]

 

[gotmike]

i have a dual squirrel cage fan setup mounted below with a custom built charge air chamber feeding the burners.

backing up a bit... was test firing the system to bake the 2000 degree ceramic paint on the inside of the forge body

this was all with only one burner going, though both were blowing air

made a beautiful swirl out the front

 

[gotmike]

and finally here's it firing after putting the refractory cement on top of the ceramic insulation

on high, manually adjusted for high heat, don't have the thermocouple in yet, this was just a trial burn but it got the 4" stainless piece of channel inside glowing red in under 5 mins and after about 10 mins it was bright red

after running for 20 mins i turned it down to low and let it bake for a bit... before i turned it down i wanted to see how much heat was transferring out of the forge... and it was warm, but still easy to rest my hand on the outside for an exteded time

after shutting it down i let it cool for 5 mins, and it was still glowing quite well inside... put in a wooden stir stick and it almost immediately light on fire..

 

[Jemblade]

Me likey...:thumbup:

 

[Teppojutsu]

Very nice, looks very pro
was the stainless channel just to protect the forge bottom from flux?
awesome work

 

[tattooedfreak]

Nice build, how much does it weigh? In the picture of the paint bake, it looks as if your burner tubes are inside the forge, how far in do they go?

 

[Stacy E. Apelt - Bladesmith]

Mike, Really a nice build.

Sadly, you won't be able to run it with the muffle as it is built now. You need more exhaust port surface area than input area to start with for normal running. With the muffle installed you have a choked forge....which will not run. The gas exhaust has to have somewhere to go.

With your welding skills, here is one option:
Take the muffle you now have and make a cut 6" in from the end. Cut straight down 75% of the way. Now cut in from the end to remove that cut piece. This will leave a projecting tongue. With that tongue resting on the back port, it should allow the exhaust gasses to escape. If there looks like enough clearance for the gasses, good. Weld a circular plug in the back end of the tube to close off the muffle. I hope that makes sense. You can stick the TC in from the front of the muffle.

The alternate method is to add a "chimney port".

 

[BareKnuckles]

Very nicely built!

BTW... How do I find a job where my new boss chips in and helps with my hobby?

Sounds like you're on a winner there!

 

[Ken H>]

Boy, that's a good looking forge - I like the idea of a blown forge. I plan to change to blown on my forge someday anyway. That really looks good.

Stacy - Thanks for the tip on needing room for the gas to exhaust. When I get around to mod'ing my forge I might not have thought about that part.

Ken H>

 

[gotmike]

my thoughts were to cut an extra venting door in the top middle of the front facing door... all the insulation mounted to the front door is on stainless mounting tabs so it's relatively easy to remove and modify to that end... there are a series of ports drilled in at a 45 degree angle into the front face piece to add extra venting around the muffle as it is, but i didn't figure it would be enough, though mathematically the space around the muffle and the added ports equals out to the same surface area venting as the inlet to the burner tubes... (CAD is a wonderful thing...) but i wasn't sure with one being forced air volume coming in, and static exhaust venting if the one would overwhelm the other... but it's just steel... it's all easy to modify... thanks for the tips stacy...

 

[HSC ///]

wow, you have some fabrication skills!
i'm curious how many hours you put in?

regards

 

[gotmike]

it was all an hour or two here or there for the last 2 months. probably a good 20 or 30 hours. and about $200... should top out at about $350 with the controller all set up and everything. it will have a fire eye sensor to ensure flame, just to keep from getting an explosive atmosphere, speed control for the fan, a stepper motor to control each needle valve, and a thermocouple. the whole thing's going to be on a lockout valve (manual over electric) so that i have to manually start the process, turn the gas on, hit the little ignitor, and start the program. from there it will be self controlled. i've already got a PID algorithm that was written for an arduino operating system... and i've built a 14" x 14" junction box with a modified computer power source to run the whole thing. The face will have a keypad input with a 2 row LCD display (all part of the arduino starter kit from amazon) and i'll have a large red emergency stop button on the side to shut the whole thing down. so there's still a lot of work to do, just to work out the little kinks... but once i get it all up and running i should be able to set it to run just about anything i could want to run...

 

[gotmike]

tatoodfreak... the burner tubes go in just to where the insulation would eventually cover. we drew it out on autocad and turned it into a paper template to cut and set the depth. we also drew out the holes for them to fit and made a template for that... you can see in the pic above with the bare insulation the tubes just create openings in the insulation in the top left of the burn chamber. but they are flush with the inside line of insulation. just to increase the swirl effect inside. that's also the reason for the floating shelf inside. i can set fire brick on it and place a knife blade on that, or use it as a guide for putting the muffle in, but i can still get good airflow around the bottom of it. keeps the turbulence down inside.

 

[Drew Riley]

That's a mighty impressive looking build. If your knives are half as nice, you'll be doing well.

 

[Daniel Fairly Knives]

That's a work of art!

 

[PCL]

That really looks cool, my last gas forge was from an old helium bottle. Was it just me or from the first outside pic it looked big enough to forge cars in, lol.

 

[gotmike]

the pics can be deceiving... lol... the finished inside diameter is about 9" and it's 18" deep after insulation... so it's big... but not that big... it's also very very well insulated....