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Recommendation on enclosing the back end of my Propane Forge


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Gents--I have contemplated enclosing the back end of my forge. It is made out of 12" diameter pipe with a Kaowool insulation. I have based this design after forges that were used in a Blacksmith class I took.

My initial intent was to use fire bricks for both the front and back and in the event it is necessary to get to the middle of a longer piece it could poke out the back. I would like to tap into the wealth of experience here and ask:

  • Should I close in the back (weld up a 1/4" thick plate) and place Kaowool to insulate?
  • Should I also do the same with the front--1/4" Plate welded with a sqaure opening and same insulation but hinged such that the whole front opens
  • Or, just use the brick concept and call it a day?

Here is a photo of the current state of the forge using the brick option:
17557.attach 17555.attach 17556.attach 17554.attach
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If it were me i'd make a lid for front and back with whatever dimensions of ports you think you need. If you want you can even make doors for those ports. Just to keep debris and dust out. The one thing though about those fire bricks though is you can adjust the ports front and back but realistically you can't hold all the heat in, nor do you want to choke the forge, so the ports won't hinder your heat. Nice looking forge!

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Avadon--thanks, I appreciate the advice, I had not thought of hinging the back but certainly could so and its just as easy to fab up two as it is one.

If I do put a sliding gate in the front and back, I am assuming I probably want to use something heavy like 1/2" or 3/8" plate given this piece would be not be insulated.

Again many thanks, the help is much appreciated.

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No need for the heavy plate for doors, insulate them and they'll be fine.

I don't like sliding doors, they almost always end up warping and jamming unless the tracks are so loose as to make the doors loose too.

Bricks as is works just fine too though there is always a chance of knocking them over and breaking them or scattering HOT pieces around. Still, they work just fine.

Avadon is right, you can't close a forge off completely, it has to breath. Exhaust has to escape to make room for the flame coming in.

Nice looking forge.


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Mike-hr: They are the light weight type and they cost me an arm and leg and first born and three hours to go get them half way across the state, I have to go get a towel now because I am crying all over the key board.......they do appear to disintegrate if you look at them sideways. And what is now the worse part of all, is that I was planning to use a higher temp brick as the base for inside. That $6 brick will last about as long as it takes to pull the first piece of steel out.

How come I didn't post that question on bricks earlier? Experience is a wonderful thing, it allows you to recognize a mistake when you make it again.

Oh well, this is my first Forge Rodeo..... and that's the excuse I'm sticking to.

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Yah I personally wouldn't bother on sliding type doors as really you'll always want a good amount of each port completely open at all times. Closing that sliding portion chokes your forge and decreases it's efficiency. I was thinking more of hinged flaps, not to control or choke down the port, but simply to close the ports off when not in use so no debris gets in there or someone decides to reach their hand in and poke at the ITC coated parts, etc. That's why I hinged the ports on my cayenne. Not necessary but in my small shop a lot of sparks go everywhere from the angle grinder and they get in everywhere. I didn't want them spraying in the forge or dust getting in there. I also didn't want anything to jam in or fall in there when I move it via uhaul/storage. So basically the doors just protect the fragile internals.

I know what you mean about the lightweight bricks. $$Spendy$$ The one advantage you have though with your type of forge you can do quite large/odd shaped items in it. Of course the drawback is your heating up a slightly bigger area then whats in my cayenne which has fireboard sides and bottom shelf. You may want to put a fiberboard in the bottom of yours to catch flux, and you may also want to coat the kaowool with ITC to increase the efficacy of the heating. I think they boast that it can do as much as 20-30% if I recall.

The neat thing though about where your at in the process is you can make your own end ports to whatever size you want. Just make a lid and then weld on a cross section piece of sq or rectangular channel (or make your own) and your good to go.

You can see my ports are flat rectangular..

But you could do whatever you think works best for you.


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Does coating the lightweight bricks improve their durability? I ordered 2 to use as doors.

Hard bricks can be had about anywhere that sells wood burning stoves for $3-$4 per. They are typically rated at 2200F for use in a stove. Cut them before firing them if you need to cut, as they get much MUCH harder after getting all glowy.


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Avadon--thank you for your words of wisdom, I too have a "dirty" shop at times mainly because of the angle grinder working on welds, that fine dust covers every thing in sight and the stuff you can not see but find five years from now. I would like to protect the interior I will probably do something like you have shown with your forge and when done for the day, either slide in a block or fab up a cover to make it some what tight for dirt and bugs.

I did coat the interior of one forge (I am making two) with Plistix 900, I believe it is the equivalent of ITC 100. I got the mix from a great source:

Burner Flares & Gas Forge Parts

Prankanow--I doubt the coating of the bricks would do any good, these things are so delicate if you look at them wrong they want to crumble, God forbid, if you were ever to drop one to the floor from a few feet up, might as well get a dust pan.

Thanks guys for your thought and advice.

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I used the classic 18kg propane can design. I closed up the back with 1mm sheet over a disc of fibrewool. I kept a hole in the middle for long stock as you describe - and close it with a pad of fibre and a brick.
Works well, will take an 18mm bar to forge heat in just 3 minutes, even when just lit. I'll upload a pic.
Looking at your pics you're using two burners ... here's something I've never read anywhere: I fitted twin burners with cocks so I can shut one down when I don't need a longer heat. The trouble is, the shut down one conducts so much heat back up the assembly it will melt the rubber supply hose (scary moment!). I have to keep both burners operating as it is the gas flow (with the gasoeus rapid expansion - latent heat etc) that keeps the burner assembly cool and stop the hoses getting hot. Could've saved mucking about fitting cocks.




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Dex ,, nice forge for a starter

Second ,,, GET RID OF THOSE FLEXIE HOSES & replace em with copper pipe

After that shutting down " a " burner wont be as much of a worry

Plan on coming back at least below the feet of forge with copper line , less chance of accidently knocking flex hose up against HOT forge

My 2 cents

Dale Russell

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How ever you close the back end remember that you still have to despose to the dragons's breath.

My solution was to leave a small port for stock pass through and built a chimney.
The result was that I could proportion the dragons breath between the two. With a curtain wall just before the chimney I able manupliate the hot and cooler zones
by partialy obstructing the three openings.

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  • 2 months later...


Nice to see you again:)

I fabricated a back cover for my 'venturi' forge using a piece of 1/8 plate with two hook tabs on the side. They engage lugs on either side of the forge body (one hook up and one down). I got the idea from my camper's dump tank connector. I lined the cover with KOAwool (high temp silicon adhesive) and a coating of Hercules 3000 degree refractory cement and it works like a charm - the forge gets hotter get their quicker! For long blades I have one cap with a slot cut in it to allow the blade to pass through. here's a photo of the slotted cap. The slotted tabs/lugs are designed to be quite snug but make the cap removeable with just a tap of a small hammer and a twist.

Here's a photoFinishedForge4.jpg

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