forge hoods

[FieryFurnace]

I'm working on getting a shop put in the barn. Lord willing, concrete and all in a 14'x27' area.

I'm hoping to put a 4'x4' home made forge in. I'm, of course, going to need a hood. The question is, design?

I made this one for my forge trailer. Just to try to funnel a little smoke up....



It works pretty good, but I need something that works REALLY good inside my shop.

I've seen several side draft hoods that don't obstruct view or space while forging. How well do these works??? Do you have to have some sort of exhaust fan to suck out the smoke? (I've got a huge squirrel cage blower....man would it get the smoke out....hehe probably suck out the coal! LOL Really though, would something like that work?) A side draft hood would be a lot easier becuase if I go straight up, I'm going to have to go through a second story floor. However, if I go out the side, it's just out the side and straight up the side of the barn. (Of course having spacer brackets to keep the pipe off the wood.) It would also save on elbows when I buy piping.

Ok and what about top draft hoods? How big do they need to be? How close to the fire pot? (12"x12" fire pot) How tall does the hood need to be? (Like from the bottom to the top where the piping is.) What size piping?

I've drawn up some rough designs that I will eventually post for suggestions. Right now I've drawn a 4'x4' forge with a 3'x3' hood centered over the fire pot. The hood is 12" measuring from the base to the top where the piping starts. But I have no clue if this is right. The shop will be sheltered from the wind.

Pictures...Thoughts???
Thanks!

[Rob Browne]

Side draft that go out through your wall and up the outside is the way to go. Make sure you have the horizontal part from your forge to your chimney a bit lower outside. A couple of holes in the bottom and all water will just fall out the bottom. I think there was a thread a while ago showing Hofi's school set up where he had a whole rack of these along his wall.

[Tri Moon Forge]

After researching chimneys for blacksmithing, I found that you need a pipe that goes above the roof peak by at least 4 feet for optimal draft. The diameter of the pipe should also be at least 10" and the topper is twice the diameter of the pipe. So if you are using a 10" pipe the cone topper should be 20" above the end of the pipe.

As for your hood a side draft would be a good choice as it allows for large pieces to be heated without to many clearance issues. Another thing is to use good quality Blacksmithing coke for minimal smoke and fumes from your fire.

[Spears]

Hello Dave,

Post a sketch with some dimensions of what you're looking for as far as a hood. I don't use charcoal but I have seen some pictures. It seems like these things are hard for people to find. I work for a company that makes commercial insulated ducting. Stainless steel inner wall and galvanized outer. I'm the one who programs the laser to cut the hard to make shapes in the flat position before it gets rolled or folded. Just the negative shape cut-outs generate enough scrap to sink a battle ship. Amazingly, some rather large size pieces. Scrap stainless .035 thick is what I can buy for 70 cents a lb. Even if a hood weighed 20lbs that's still only $14 material cost. I would like to see if I could fold one of these out of one piece. If I can't, I'll make it in sections with tabs and spot weld it together. There is a guy in Alabama who makes and sells hoods, but much like any black smithing equipment, it's "for sale" not "on sale". No, I'm not looking for money, if you look on this website you'll find out I gave away a treadle hammer. I just genuinely support my fellow blacksmiths and I truly like a challenge. Pictures or sketches with dimensions please..... Spears.

[eric sprado]

If you go to Beautiful Iron http://www.beautifuliron.com/ they have a great article on chimneys. My hood is almost two feet above my forge and works fine,BUT: Here is a nice trick: I have a five gallon bucket with both ends gone that I put over my fire just as it is starting. This directs smoke right up in to chimney. Once the smoke quits,your chimney has warmed up and draws fine. My chimney extends about 2 feet above roofline. Do check out the article on chimneys. It is very informative. Eric Sprado

[Rob Browne]

Check out this thread. It refers to a blueprint by Hofi but you will get the idea.

[FieryFurnace]

Here is the forge I drew out.....don't know if I'll be able to build that right off, but I have a smaller portable set up I can use until I get it built.



There are some of the drawings. They are all to scale and self explanitory!



Thoughts???
Dave

[Rob Browne]

Use the side draft otherwise you will be banging your head on the hood or it will be in the way of you seeing your work.

Cheers

[unkle spike]

I have used both, and given the choice Side Draft is the best choice hands down. I have purchased 12" galvanized round ducting pipe at Home Depot with the swivel elbows. It is pretty cheap. I just had to replace my lower outside elbow, it rotted out after 5 years, the soot collected in the bottom and I didn't know it. The elbow was around $9 and they have straights in 6 foot sections I believe. You would need a heavier piece adjacent to the fire, but you are a good scrounger and should be able to come up with something. The swivel elbows have sections you can rotate to just about any angle, and I would say you would want two 45 degrees to give the slope in your drawings.

[Don A]

I happened to steal the pictures of Hofi's forges:



When I ever build a more permenant shop, this is what I'll go with.

I particularly like not having to cut through the roof.

[FieryFurnace]

I'll go with you on not liking to cut the roof....we fabricated both the roofing flange and the indoor box when we installed our woodstove! I don't care to do that again at all!

Those pictures of Hofi's is exactly what I want.....how do you get it to draft that good? Is it a special design shape or somthing? I've seen some drawings of the upright ones that are side draft and they have a "smoke shelf" inside to create a circular motion which helps draw better. I've got a friend who has a side draft that stands upright and it doesn't draw AT ALL! Must not have the smoke shelf. We are going to be storing antique furniture in the upper level of our barn, so I need an efficant sucction to get rid of the vast majority of smoke. Are there diagrams somewhere of these type side drafts? I've found plenty for the upright side draft hoods, but haven't found any for these.

Thanks,
Thoughts???
Dave

[Mainely,Bob]

Just a thought on smoke control.Don`t know what you plan on using for fuel but as suggested in a previous post most of the smoke is generated at start up.Once the fire is going the heat rising thru the chimney will cause the draft needed to draw the smoke/fumes out.

As suggested in another post you could use a temp fix to control the smoke during start up.I believe the fellow suggested a metal 5 gallon container which surrounded the fire to direct the smoke up to an overhead hood.
If you plan on using a design like the side draft Hofi stack then it would be fairly easy to add an extra section that hinged out over the fire to direct start up smoke up thru the stack and once the draft took hold you could just flip it up out of the way.
An alternative approach is to do as a friend does and just use some balled up newspaper in the back of the stack.He places the paper,preps the forge fire and then lites the paper in the stack first to start the stack drafting.Once he gets some air moving up the stack then he lights the forge fire and the forge smoke follows.
His is a brick forge and has no smoke shelf inside.He does have an "eyebrow"(his term) of metal that attaches to the front of the brick to help direct the smoke.

Yet another way to deal with any smoke/fumes that escape is to put an exhaust fan in the wall next to the forge.If things get out of hand and a little smoky then just flip on the fan and it`ll work at the forge just like it does in the kitchen.This is especially important for folks like me who use the smoke alarm as an oven timer. :blink:

[ThomasPowers]

I used an overhead system before and even with a 1/3 hp fan assist it didn't do a great job. I have also used side draft systems at other smithies.

I'm planning to go with a side draft in my new shop extension. Left the two purlins near the peak spaced enough to run the pipe between then and it's a lot easier cutting the circle where there is a gap in the sheetmetal roof already. Helps that there is no wood in the structure save for 4 utility poles holding the roof up.

I lucked out at the local Habitat for Humanity Re-Store and picked up two 10" dia, 10' long spiral seamed ventilation ducts for $4 a piece and also a couple of pieces of stainless pipe to make the fire side stuff from.

The shop is coming together and all the piles of scrounged materials are shrinking much to my spouse's delight!

[pkrankow]

The height of the stack is the key, taller is better. Priming it with a wad of burning newspaper may help if it won't start on its own, it will continue drafting all on its own.
Phil

[FieryFurnace]

Ok well I definately want to go with the side draft like in the drawing. The only problem is a big sliding door on the barn.....looks like I'm going to have to make some really big strap hinges...LOL

I did a brief search on the internet to see if I could find piping....ha.....the internet search said "what is 12 inch stove pipe!"

Spears:

If you are offering your help here, that's great! I don't look for free-bees but if one falls in my lap (other than materials/shipping) I'm not one to dump it off! LOL
Shipping would be a handsomely round sum though!
I can get sheet steel at 25 cents per pound here but I can't get piping that cheep. I can get it at 30 cents a pound (not stainless) but we are talking 1/4 wall......hmmmm 20 ft of 1/4 wall....uhhhh no! LOL Crain please!?


Dave

[eric sprado]

Why in the World would you need 1/4" wall? The Spiro ducting that was mentioned a couple of replies back is incredibly strong! Comes in 10' sections and is easily handled. I'm somewhere around 200years old(give or take-but that's how I feel sometimes) and I recently put up a joint in my new shop..After seeing the pictures I wish I would have gone with a side draft exhaust...
Look up sheet metal supply shops in Yellow pages and ask about the spiroducting. Home Despot type places don't usually carry it..

[CTBlacksmith]

I recently built my shop and i put in a hood instead of a side draft. I had aluminum coil stock for siding that i pop riveted together to make a 3x2x15 hood. I only had 6 inch stove pipe at the time so i put it in and it didn't work at all. The other day i was at the scrap yard and i found a 6 or 7 foot piece of 10 inch SS pipe that was cheap enough. I bought it and it was installed in less than 2 hours. I have absolutely no smoke in my shop at all with the hood and chimney. I like the hood because i can but large pieces in the forge and not have a side draft right next to the fire. I think i have the hood about 18 inches above the forge and it gives me plenty of space to see the work and keeps the hood out of the way. I guess i just contradicted what everyone else said but the hood works for me and i like it.

[Spears]

Hello Dave,

The exterior exhaust pipe itself will be better constructed from the light weight galvanized stuff available from the common stores. The hood you decide on which may take some fire exposure on and off, I could help with some stainless sheet .035 thick (about 1/32"). I used that on an outdoor wood burner exhaust and as hot as I got it, it only changed color a bit. I can cut and fold that to be economical as far as a hood. Piping made out of that stuff gets heavy and expensive. You're about 3hrs north of me if you run into a road block in getting a hood you need and decide you could drive my way cheaper. As far as you're tire hammer, I have on hand some 1/4" plate steel. I have a range of circles from 8" to 20" diameter. I have rectangles in the range of 8" to 15" at 60" long. Shipping anything these days could be hell compared to driving even with the price of gas. All I would ask is you trade me some of that soap and lip balm stuff you folks make (my wife likes all that) if traveling turns out to be your cheaper option. I'm just south of Huntsville. I'm stocked pretty well on 1/4" iron plate right now. Regards, Spears.

[FieryFurnace]

Ehhh well I was joking about 1/4 wall for the exhaust pipe!

Spears:

Which "Huntsville are you in? We are heading to a craft fair in Dahlonega Ga., mid April. (I think 16th-18th) I'll have to double check our route to see if we'll be close in! Would it be possible to collect the stainless before then?

I am going to need some more plate for my tire hammer because of the mistake I made in getting 3/8ths instead of half. So if I welded 1/4inch on top of the 3/8ths, that would give me a pretty good base.
Like I said though I can get plate all day long up here pretty cheep. However, stainless is selling about like gold here, so if I could at least pick up some stainless from you that would be great. I would have to get some measurements to see how long of a box I would need. I know that the forge will be 1ft from the wall, the fire pot 1ft from the edge of the forge, and then at least a foot out the side of the barn....probably more! I think a 12"x12"x5' box would be safe. Then with the angle on the inside to help catch the smoke. I don't know about that thickness right where the fire is though........I might case it in some thin plate for six inches or so just to be on the safe side.

Thanks,
Thoughts???
Dave

[Spears]

Hello Dave,

I’m here in Huntsville Alabama which may be out of your way but in either case I have a summary of my dumpster diving options. I guess you’re looking for a 12”x12” square 5ft long closed on one end with a 10” or 12” hole next to the closed end with a 30 degree angle cut opposite side the hole is on. The 30 degree angle will bring the bottom lip back just under 7” calculated.

I can get my hands on:

.025 thick aluminized (that stuff is a bit thicker than the thin stuff you buy from Home Depot but may not last through the years and takes spot welding or screws for fabrication). .035 thick stainless. (cost more and harder to fabricate but will outlast most all) .075 thick galvanized (easy to fabricate extremely durable and cheaper) This stuff welds solid but ugly and the first time you get it real hot or weld on it you need ventilation) I built my tumbler out of that stuff and that is probably the best bet.

If you decide to make the trip I need to know if you can cut the hole and weld the individual pieces or if you want it completed. The stainless is scrap I have to pay for and having that made would be $40. The thicker .075 galvanized $30. That’s about as good as I can do because I have to pay for certain labor and equipment and some materials I don’t have in my personal workshop. I hope this gives you some economical options and have fun in Georgia. I’ve been to Dahlonega twice and I really enjoy it. Regards, Spears.

[FieryFurnace]

ALABAMA????????????????

Aww man! That will be about 3 hours out of the way! I thought you were talking about Huntsville Tn. which would have been near on our way.

So that's not going to work out! I suppose I'm going to have fabricate the box out of sheet steel. I do appreciate the offer though!

Dave

[Phil H]

I have a 2ft diameter forge that I made a hood for by joining two 5gal. oil drums end-to-end and taking a large scallop out of the bottom one. When fitted it sits on the rim at the back of the forge. It has a 6" stainless steel flue 6ft long, and once it starts drawing it does an excellent job of taking the fumes back and away (no more headaches). Having it set back gives more room over the fire. The bottom drum has now rusted away, and I have the materials (tumble dryer drums) to make a new hood out of shiny stainless steel. Bling meets blacksmithing!

[thecelticforge]

If you are thinking on priming a metal chimney, this product http://www.drawcollar.com/ is supposed to work wonderfully. The guy told me he was working on one for ceramic but I finished mine before he finished his.

[Spears]

That's alright Dave. Sometimes the work is slow and the waste materials are extreme. We throw away quite a lot of useful stuff around hear. I try to help my fellow metal workers when I can. It took me 10+ years to move to a place and build a work shop and I didn't get a whole lot of help. I can't always get the stuff for free, but even at the scrap price some of our materials are a decent value. Just drop me a message if you come up dry on any certain materials. I may or may not be able to help. It just depends on what the factory has going on at the time. Regards, Spears.

[Dave Leppo]

I use a side-draft similar to the Hoffi design, but made with 14"pipe going thru the wall, into 12" vertical chimney. I also use a hood extension attached to this, directly over the forge which is a piece of the 14" pipe split in half.

Also, I have an exhaust fan going out thru the wall above all this to take out anything that might escape. I don't always run this, but if you put large odd-shapes in the forge, they can divert smoke away from the chimney. I think you mentioned having a squirrel-cage fan you could use for this.

I use coal, which gives quite nasty fumes. If you only ever use charcoal, you can probably forego the exhaust fan. But the fan is also good for getting rid of other smoke or fumes from the building, (such as forging hot steel on a wooden anvil). The forge fire isn't the only source of fumes.

I just added a squirrel-cage furnace fan - blowing out - to the area where I do the most grinding, to help with "dust collection". Grinding swarf and dust are nasty to breathe, too.

"Too much of everything is just enough" in this case IMHO.