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Those with one burner gas forges with doors


bigb

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How much of an opening do you find you need to keep it running smoothly? I am working on my doors and I know I'll never be able to close them all the way due to exhaust needs and I am planning to cut a small hole to act as exhaust relief and for viewing as well. I realize this can be quite variable but looking for a starting point. My forge has a 3/4" Z burner and is between 325 and 350 cubic inches. Would a 2 or 3 square inch opening be sufficient? I can start small and increase if necessary.

My design uses hinges instead of sliders. It is nearly finished and I will post pics tomorrow.

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Fire up the forge without a door and slowly close the opening till it starts effecting the burner performance and make the opening a little larger to account for work and drag around the work.

An adjustable door is a good way to go.

Frosty The Lucky.

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Thanks for the good replies, Frosty I thought of that last night after I posted and that is exactly what I'll do, take the doors off and do some trial runs with stacked fire brick. I decided to give the hinged doors a try since I didn't want to be fumbling around with sliding bricks and stacking bricks. If this works I think it will be faster and easier. If it doesn't work then I'll get out the grinder and do something different. I did a lot of Googling and didn't find anything like this so I said why not give it a try?

20170115_140808.jpg

20170115_140751.jpg

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Some food for thought, in the Forges 101 sticky post #6 Mikey talks about a moveable barrier to allow exhaust gasses to rise out and up while the barrier, with it's reflective coating, reflects radiant heat back into the forge to help avoid a cold spot. I have an idea to cut only a very small viewing hole in the doors, then control the exhaust by leaving them ajar. I believe this will create what Mikey is talking about. What do you guys think?

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  • 2 weeks later...

"I believe the rule of thumb is 7 times burner area needed for exhaust due to expansion of gases.  So pi * r^2 * 7 = pi * 3/8^2 * 7 =  3 sq inches.  A 2 inch square hole would be 4 square inches, and would be enough by that reckoning...  -- Dave "

If any of us stop for a minute to contemplate what is glaringly obvious to anyone who used a burner or torch of any kind ever... the lack of PSI or orifice size of a gas jet shows these numbers to be irrelevant; since without them we don't have a clue about how fast, and therefore how much exhaust is being generated, do we!?! A mathematical formula not only needs to be right; it also needs to be completely and correctly applied to a given problem, or it is worse than useless.

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