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

Aren't those Arduino's amazing little uC? So many things to do with them.

I'm very impressed with your build - GREAT job.

Ken H>
 
Outstanding forge...makes my blown propane tank forge look like a Yugo sitting next to a Chevy ;0
 
YES! I accept your build as a gift. You'll have to chip in for the shipping to my place, though. PM sent.


:p

Well done, bud. You do need to address the additional venting issue. It sounds like you are working on it.... I know it must be exhausting but forge on, my friend.
 
we were doing some brainstorming on the subject yesterday and my bosses suggestion was to create a sort of an overpressure valve... something very very sensitive with an exhaust flapper valve on the top... the thought was that it would stay closed if there was enough venting for the exhaust, but if there became an overpressure situation, it would open on it's own to whatever amount of venting it needed... still kicking that idea around through the back of my head... my thought was more of a traditional 3 hole vent, same style as what would be commonly found on an older stove... with the adjustment plate and everything... that way it would be easy to control it if the need arised... choke it down just a bit if it didn't want to maintain temperature with the controller...
 
gotmike said:
we were doing some brainstorming on the subject yesterday and my bosses suggestion was to create a sort of an overpressure valve... something very very sensitive with an exhaust flapper valve on the top... the thought was that it would stay closed if there was enough venting for the exhaust, but if there became an overpressure situation, it would open on it's own to whatever amount of venting it needed... still kicking that idea around through the back of my head... my thought was more of a traditional 3 hole vent, same style as what would be commonly found on an older stove... with the adjustment plate and everything... that way it would be easy to control it if the need arised... choke it down just a bit if it didn't want to maintain temperature with the controller...
Click to expand...

First, I like the look of the forge. Reminds me of an old bank vault door and some sort of rocket system... The arduino idea is neat, though I personally find a simple PID more than enough control for something as raw as a gas forge. Arduino could be helpful on a HT oven setup though. And I see what you're shooting for. I hope it works out for you.

Take the below for what it is. Moderately educated advice. There are forge gurus on here that can be more specific or throw me out with the bath water...
In my experience I personally think of it more as flow, fluid dynamics style, than pressure. You can have a blower kicking hard and build pressure with no gas at all, way lean. Same thing with too much gas. If it isn't burning, it isn't burning. With too much gas and not enough blower, you can be way rich with zero pressure... You'd likely see it burn once it reaches the open atmosphere and picks up enough oxygen to fully combust.

Propane forges (especially horizontal) are more about air/fuel ratio and heat migration than raw pressure. You want enough flow to support a clean enough burn to reach to reach a target condition inside the forge. And sometimes you might want it rich and sometimes lean... Sometimes spot heat and sometimes a spread. Just depends. Relying on some sort of flapper to do the balancing job seems more complicated than need be. Some things just need to be watched by eye, and adjusted manually. I just don't think you can automate the entire process with this.

I am certainly rooting for you to succeed though. I'd be in line to copy the design!

-Eric
 
Eric took the words out of my mouth - A forge doesn't run on internal chamber pressure. Actually, the lower the chamber pressure the better it runs.

I would have to look it up again, but a while back I did the calculations, and IIRC, the exhaust surface area needed to be at least 10 times the burner nozzle input surface area. So with two 1" burners you need two 4" ports to run on high. You only need about half that when running low for HT, which is why many people block the rear port with some firebricks when doing HT.

Your vent idea is half way there....just get rid of the flapper valve. My best suggestion if you want a dedicated chimney would be to build in a 3-4" round or oval chimney vent on the top center and make a refractory plug for it that aligns with the liner.. When not using the muffle, place the plug in and the forge runs just as it is now. When the muffle is installed, remove the plug and the chamber has a vent. Because the burners are running at a very low burn for HT ( when you would use a muffle), that would be more than sufficient.

As I said earlier, the simplest solution would just be to modify the back end of the muffle pipe to allow venting.



One temptation when you have the ability to do very complex work ( as you clearly can) is that every job becomes complex. A forge is an insulated box with a fire in it. That can be tidied up to make it attractive, propane used for fuel, PID control added to run the flames, blowers added to control the air, etc......but in the end it is still an insulated box with a fire inside.
 
very very true on that last line... i've been trying to reign my imagination in when it comes to the complicated part of this all... i had grand ideas of putting a fan on it with a PWM controller for infinitely variable fuel air mixes, but it was far simpler to find a convection oven, 3 speed fan, and put it on a 3 position switch... then i can dial the needle valves up and down as needed depending on the air i have pumping in... i have a ways to go before i get the controller up and running... (and with the way that side of technology is going i can have the whole arduino setup together for around $150 and be cheaper than most quality PID's on ebay) so i'll deal with the muffle and other things at that point... for now i like playing with high carbon steel and getting better with my grinds... this at least gets me back into the game and away from using a torch to do backyard heat treats... I do like the simplicity of making a modified muffle and just running with it... seeing as how it's only going to be holding a flat piece of steel, i don't need as much volume inside as i currently have... so cutting down a section and closing it back up with flat plate would not be hard at all... and saves me from another modification to the forge this far into the build...
 
finally recovering from my neck surgery... got to do a little more work on the forge... even been heating random pieces of mild steel... just to play around with it... now to get the thermocouple hooked in so that i can at least read what the internal temps are... then to work on the automation...

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installed a barbecue igniter system into the burner tubes, makes it much much easier to light the thing...
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the sparker comes in right above the tip for the fuel, so it ignites quickly
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my ebay fan control switch temporarily located... 15psi fuel wide open, and high speed and it will get very very hot very quickly...
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my adjustable fuel regulator and gauge...
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my fire brick cut and fitted into the floating stainless shelf
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