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Super-Charged Side Draft Forge

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I built the original side draft forge in 1992 out of left over steel from a few odd jobs and used it mercilessly for a few years, but after building my propane forges it fell by the wayside and ended up spending the last 6 or so years living outside on its back. That is until I built my new shop and finally made room for it. In it's previous life it had a fire pot made out of 3/8" plate and a salvaged blower off of a gas heater connected to a dimmer switch, which worked just fine, but recently a friend of mine gave me a newly rebuilt giant electric Champion blower with a new variable speed motor that he had "laying around", and I also managed to score a Centaur forge cast iron fire pot from another friend (for a chunk of change). I first torched out the old fire pot and installed the "new" one, but I ran into a problem with the blower. It put out WAY too much air even at it's lowest speed. The solution was to use any extra air from the blower to force the smoke up the chimney. So I plumbed the blower into a home made T-fitting with one side of the T feeding the fire pot and the other side being diverted all the way up to the center of the chimney to the point at which it narrows (where I figured that the air blast would induce the most draft). I also cut the tube that carries the extra air into the back of the chimney so that the fire will help to pre- heat the chimney air blast. With that all done I whipped up a set of sliding air gates to independently control the firepot air and the chimney blast, and then conected the controls to the front of the forge to a set of control levers. I added a third lever that connects to the clinker breaker on the firepot so that I don't have to reach under the table to rattle the clinker breaker lever. Some of the pictures were taken with the forge laying down so that you can see the plumbing. It works amazingly well!! I don't have to do a thing to get the draft started, just turn on the blower. Absolutely no smoke escapes, even on startup, which is nice when working with the doors closed and the A/C on when its 110 outside. I must admit that it is nice having a coal forge inside again!







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I like the good clean welding. I know I am new here-but, I keep getting the impression that any kind of welding is the ignored step-child- unless the welding is done with a hammer.Those welds look complete with appropriate height- just something I do. I can be outside a building and just can't help but studying any welds that might be around-railings,lamp-posts,high pressure pipe, etc.jet

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Yep, I agree, racer, I too noticed the good looking welds. In what I read from Jose, I think he knows a thing or two about welding...

Goog looking forge, by the way; it seems very efficient.

May I suggest a little modification? I know that Yamaha, for one, has found that inducing air into an exhaust was helping the hot gases complete their combustion and eliminate some more pollution. Maybe you could divert a little of your air going up through the pipe; this little air stream would point upward and toward the center of the chimney. The extra oxygen is supposed to complete the burning process. In a time when global warming is on every lips, I think it would be wise to do what we can to reduce our environmental footprint.

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Thanks for all of the interest!!

Donnie, the air conditioner does a fine job of keeping the temp in the shop just low enough that all of the water doesn't boil out of the slack tub by it self!

HWooldridge, thanks! I put quite a bit of thought into it. Anything worth doing is worth doing well I guess.

racer3j, It sound as though you and I share the same curse... I can't pass by a weld without studying it, I have been welding for near 18 years and finaly found an exelent way of making looking at welds pay (at my day job I am an Instructor of Welding Technology for the local college)

Abenakis, the exess air from the blower is already being introduced dead center into the base of the chimney and does seem to help to thin out the thich smoke from startup. I have attached another pic of the forge with a line drawn on it indicating where the top of chimney air dump pipe is, and if you look in the opening in the front of the forge you will see the air tube. Also, another shot of the plumbing taken from the left side of the forge.



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Yes indeed very nice setup. I for one will chime in on welding for shop equipment. If it needs cut with a plasma and migged ( or gas welded ), I do it. The airgate has solved all my issues with variable speed on a blower motor. Run the blower top speed and just control the blast. Very nice looking setup you have there.

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Jose-Nice forge. My forge also uses a large blower (in the next room to reduce noise) and the waste air blows up the flue. Mine is piped through a box with a butterfly valve in it so as air is increased to the firepot air is decreased to the flue pipe. In the picture you can just see the edge of the air pipe inside the forge hood.


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Skunkriv: And as the temperature of the burned gas is augmented by more air being sent to the burning coal, the speed of those gas is also increased so less air is needed to help it go through the chimney; at the same time, the higher the heat, the more complete the combustion so less oxygen is needed to complete the process while exhausting. Very neat.
(please be indulgent with my english; here is the only place I can practice it!)

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Nice work Jose.

The design is a linear inducer just like a Reil EZ burner.

If, instead of introducing the primary air (air from the blower) above the smoke entrance, you introduce it below the smoke entrance it'd finish combustion for a close to zero emission stack.

The induction would increase as well and on far less blower air because it would be an "ejector type inducer like a Side Arm burner. Heck it WOULD be a Side Arm burner.


Edited by Frosty
Syntax because SOME things should make sense.
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nice job Jose but it is an ''overkill''
With this size of blower I run 5 forges in my school and smithy with very good result
very cheap and much less work. see BP 1048 ''SIDE DRAFT CHIMNEY''
In our days we must think also how to save energy when it is not needed!!!!!!!!!

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Frosty, in your design, isn't there a possibility that the difference in air density could act as a wall against the much warmer gases? Maybe not if the pipe comes out at the back of the chimney; as long as it doen't create disturbance that would increase the 'wall effect'. What do you think?

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Mr. Hofi,
You are right about the blower being overkill. There is absolutely no way that I could use the amount of air that it is capable of moving, but it is what I have, and it was a gift from the 86 year old bladesmith that comes over to work in my smithy every weekend (and has taught me an immesurable ammount of tricks). He took the blower and had it fitted with a brand new variable speed motor, speed controller, and fan blade, then gave it to me as a gift to put on this forge. So I adapted. I have found that I only use it on full speed to start the draft, then turn it almost all the way down. Even at its lowest setting it provides enough for a beautiful fire. The big thing to me is that the man that gave it to me is happy every time he sees the forge being used. Attached are some photos of the old fire pot/blower assembly, and the new fire pot in it's new home.
PS. you might recognize the fire poker in the picture. Thank you for the time that you put into making the power hammer techniques videos, they are outstanding!

The old blower was a 90 cfm that came off of a furnace, if I recall correctly, and it produced more than enough air. I cut the air inlet tube to the chimney through the back wall of the stack so that it would be exposed to the heat from the fire. I did this in the hope of pre-heating the air blast to, hopefully, help reduce the effects of adding cold air to a system that relies on hot air rising to make it work.





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Thank You for taking the time and effort to share your talent in the blacksmithing craft with us.
From what I could see in the background, you have a nice shop.
I feel you have always been a great asset to I Forge Iron.
I have learned some very interesting consepts from this post! In fact, it is very timely because I am building a new forge configuration similuar to Hofi's that he has in his school. I think I am on the right track.
Ref: http://www.iforgeiron.com/blueprints/blueprints-1000/bp1048-.php

Edited by Ted T
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