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Hofi side draft question


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Hi! I'm still kind of a newbie at this, I started forging this summer, outside, and now winter is approaching and I am thinking about setting up shop indoors.

I've got an old barn at my disposal, that actually was used as a blacksmiths shop some 50 years ago, but my grandfather removed the chimney and everything else to use it to store his cars.

It would be nice to have a chimney but since it was removed several years ago that is not an option, so I was thinking about the side-draft chimney and looked at Hofis blueprints.

There's a bit of draft from the windows, and also from the door, could this be a problem or is it just a good thing?

Also, I have got the square tunnel, what bothers me is the pipes he uses, I can get my hands on 6inch pipes but anything bigger than that seems to be pretty hard to find here in Sweden, atleast at a decent price. Will the side draft work with such a small pipe or do I need a wider one? 

The barn is roughly 6x5m, so 30m2, almost 100squarefeet If I am correct. 

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Turns out that this square tunnel that my friend had was rusted all the way through, with big holes in it.. that wont work!
But I was thinking, could you put and old oil barrel through the wall to act as a tunnel? With the tunnel horizontal, couldn't you just attach a 90degree pipe-bend-thingy to the bottom?

I'm guessing the part through the wall doesn't have to be square, or does it?
And perhaps an oil barrel is too big in diameter, I don't really know.. 
 

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I believe he used square because that's what he had cheap and it's easy to put out the wall.  Airflow is better in round pipe of the same area.  I myself used 10" round spiral seamed duct because that is what I had cheap; US$4 per 10' length at a ReStore that was getting ready to move.  As my walls are sheet metal and I had a large round hole in it already I just stuck a piece of pipe up at 75 deg angle and got to forging.

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Edited by ThomasPowers
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I built my side draft from sheet metal off an old washing machine and sheet metal screws. Instead of buying a collar I cut several tabs on the top side and folded them up into the chimney pipe which is (for now) a five foot long piece of six inch air conditioning round duct. If I ever finally finish my new shop I'll get a bigger stack even though I really haven't had issue with what I have simply because the forge is going to be a little bigger.

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  • 1 month later...

I'm doing the same thing. Made my square horizontal duct with the sheetmetal from an old furnace. I now wonder how to protect the metal from rusting since it is not galvanized. I can paint the outside. but was wondering about the inside. Could paint that too but will it stick after a while? would i need high temperature paint? Not trying to hijack thread butmaybe sebastian will have similar situation with his new box.

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I didn't paint mine. I just used it as it was with the factory paint. I have lost much of the paint off the side ride next to the fire and a little down the length on the fire side. If I was to decide to paint it I would definitely use the high temp spray paint or try some kind of epoxy paint. I'm not gonna worry about it because I'm workin on a new side draft using some 1/4" thick roughly 8" pipe I found recently.

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