First forge - a couple of questions

[wbj]

Hi all - 

I built my first forge, and I'm looking for a little feedback.  I made the forge by cutting the bottom off of an old steel vacuum tank.  Mostly because I had it, and it had legs on it, and it already had a threaded hole in the bottom that I could attach an air pipe to.  I used a 5/8" cast iron drain cover to cover up the air pipe (is it really a tuyere if it's just a pipe?  seems pretentious!  ).  The air pipe itself is 1" inside diameter black pipe.

You can see the rest of the tank in the background - I thought I might cut the other end off and cut it in half to make a long trough with a horizontal tuyere in the future.

I lined the tank bottom with potters clay mixed with some sand.  I tried kitty litter first, but I mixed it too wet I guess.  After two weeks it still wasn't dry.  My wife (a potter) graciously donated some clay that was drying out to the cause.  It cracked some, but seemed to provide some insulation.  The paint on the bottom of the forge didn't burn off anyway.

I attached a shop vac to the pipe to act as a blower.  Note to self: Shop vacs blow WAY too much air, but they sure get the coal burning in a hurry!  I ended up turning on the vac for about 5 seconds at a time to get the coals going good.

The up-shot is that it all worked.  I was able to heat up steel very nicely and work with it.  I made a set of tongs and some J-hooks to hold some pulley wheels to make a sliding barn door.

Anyhow, I know I need a MUCH less powerful blower, or at least some kind of valve so that I can reduce the air flow dramatically.  I was wondering about the clay?  It's not very thick - perhaps an inch or so near the grate - mostly to sort of contain the coals over the grate.  It's probably a half inch thick around the outer edge.  I'm not sure it's necessary at all?  I've read that cast iron forges can suffer from thermal shock, but this is made of steel (mild steel probably).  It's about 1/8" thick steel.  Way thicker than my bbq grill that I burn the same coal in.  Granted, I'm not forcing air through that fire.

I've been using natural hardwood charcoal, because it's available at the local wal-mart.  I can get good blacksmith coal (bituminous?) but it's an hour away.  Would the clay be necessary with that due to higher heat?

Any other thoughts?  Is a round forge better/worse than a rectangular one?  What other changes might you make?

Thanks in advance for any feedback!

-wbj

[Frosty]

That's not a bad first forge at all. The sides are a little high it'll be hard to get long stock down into the sweet spot in the fire. Glenn has an excellent diagram of the zones in a fire, hopefully someone will link it here, I can't find anyDARNED thing on my comp. Its a TBI thing and OS (up?)grades on my comp. 

There are a couple issues that'll become issues as you progress. You'll need something more durable and smaller than a floor drain for an air grate. A series of say 3/8" or 1/2" round stock either bent into hairpins and tacked or lengths welded into a bar grate works very well. It should cover the tuyere opening and overlap some, it doesn't need to be fixed in the forge. A bar grate is much easier to clean than holes, you can just slide the pointy end of your fire rake along the gaps between bars and either knock clinker and debris through or pick it out. Easy peasy. Holes on the other hand require something that'll poke into them and means maybe another fire tool or not, whatever it's more hassle than just being able to drag the rake across it.  Make sense?

Oh yeah, a shop vac, leaf blower, blow drier, etc. make too much air for a small forge though the blow drier can be modified, or throttled with a valve. Charcoal especially requires little pressure. A blow drier angled so the air is only partially going in the tuyere is a good control method. You can pick up old blow driers at yard, garage, etc. sales for next to nothing. 

You really need a better tuyere than the existing fitting. I use exhaust pipe, a length of 3" semi exhaust pipe about 8" long is good, with a bolt flange for the vertical. I use hole saws frequently, the flange is a piece of sheet steel, (14ga. because I have it on hand) I cut a 4" dia. hole, then cut a 3" hole. I welded the exhaust pipe in the 3" hole and it makes an easy peasy bolt flange, pop rivets or better still sheet metal screws and it's attached. First though you need the horizontal air supply which is again exhaust pipe 2" dia. Again I drill the access with a 2" hole saw. This hole is positioned about 2" from the flange so the bulk of the vertical section is below the air supply to hold ash, clinker etc. that falls through the grate where it won't interfere with the air supply. Make sense? 

Back to the horizontal and vertical joint. The 2" hole in the vertical will accept the 2" pipe almost perfectly for welding. There are lots of ways to mark and cut the horizontal to match the vertical but I'm lazy and go the easy way. Once again Frosty breaks out the hole saw and drill press. Simply position the pilot drill of the 3" hole saw half an inch from the end and slowly drill through the 2" pipe. Near perfect match, certainly close enough to weld. Lastly being close to one end makes it easy to get a mig gun in to weld it up. Extend the 2" pipe about 1/4" into the 3" and it's really easy to weld. Don't worry about a good weld it only needs to be attached it can be leaky and ugly doesn't matter. 

I like the horizontal supply to extend past the forge table so I can put an elbow on it and get the blower above the fire so flammable gasses generated when you turn the blower off don't settle IN the blower because when you turn it back on it'll flash over causing POP (read small explosion) sometimes powerful enough to blast the fire out of the forge or light the blower up. Hmmmm?

The last bit for a tuyere is an ash dump My favorite is an exhaust flap cap like you see on semi stacks. They come in all sizes and clamp on, put it on the bottom of the tuyere, the counter weight should keep it closed, if not add a little weight. This will let you reach under the forge with whatever you have in hand and lift the counter weight and dump the ash. It also makes a fine safety valve, if you get a POP it just blows the ash dump valve open and empties it out for you. I like to keep a steel bucket under the ash dump, sometimes with a couple few inches of water in it if things are dry out.

You don't need to worry so much about popping with a charcoal fire but if you switch to coal it can be an issue.

Not that it matters but that tank wouldn't be mild steel it's under too much stress in use. Using clay to protect it from the fire is a good idea an inch is plenty. You're mostly distributing the heat more evenly and keeping the flame and oxy from direct contact. It'll preserve it significantly. Next time don't use so much water it only needs to be damp enough to pack hard with a mallet or whatever. About 3-4 pts. sand to 1 pt. clay is a good mix, the sand allows it to expand and shrink with temp changes without cracking. 

Coal isn't really hotter than charcoal but it's a denser fuel so you can have more fire in a smaller space and it can form a nice dome as it cokesonce you get the hang of managing it. A closed fire is like an insulated furnace it keeps the heat in a small space which is a good thing.

I think that's about it for now. You've done a good job on a first forge, Youtube is a good place to take buckets of salt with you if you want to learn things, it's mostly full of wrong and sometimes down right dangerous stuff. Ask us, we'll steer you straight.

Frosty The Lucky.

[Irondragon Forge ClayWorks]

Like Frosty said working longer stock will be a problem, I would cut notches on opposing sides to let the stock lay flat in the fire.

Glenn's diagram is in this thread, a good one to read.

https://www.iforgeiron.com/topic/30887-forges-and-fires/

 

 

[wbj]

Thanks Frosty & Irondragon - I'll definitely trim the sides down a bit.  I did find that even with a short piece of stock it was pretty much resting on the rim and angled down into the heat. The diagrams from Glenn you mentioned were very helpful.

Kinda wish I had I had found IFI before I started :), the JABOD idea looks better.  Still, I learned stuff making it and it does work.  It's very portable as well, so that's a plus.

[Buzzkill]

You found the site a lot earlier in your journey than a lot of us did.  If I had found it a couple years earlier I would have saved myself at least a couple hundred dollars and a whole load of frustration. Welcome to the addiction where we encourage users to experiment and use even more.

[Frosty]

Okay, I have been spouting a HUGE mistake! It was pointed out in this or another thread but I missed it so I was contacted on the side. Using an exhaust flap cap REQUIRES more weight on the counter or it'll hang open upside down. The weight as made can't hold it closed or it'd keep the cap open on a truck stack.

I made the first hinged ash dump before seeing them in the Heavy Duty scrap dumpster and scrounging a couple. I don't know why but those had weights tacked or spot welded to the counter weight and I ASSUMED they were all like that. I found them in almost all auto supplies and again ASSUMED they were weighted the same. However they can't be counter weighted enough to stay closed inverted or they'd stay open right side up and completely defeat the purpose of putting a rain cap on an exhaust stack.

Talk about not thinking! ARHHHH!!

So, in spite of my saying they work as is, for all these years I WAS WRONG! You must add to the counter weight to make them stay closed inverted. 

If you don't have a welder try taping a short bolt and nut to it and see if it's enough weight. When you find the size that works, drill a hole and put the bolt and nut on. Maybe a tire weight or two you can squeeze the clip closed with a big pair of pliers or on the anvil. Heck, they make stick on wheel weights for alloy wheels, it' not like the ash dump's going to get hot. Epoxy'd do it. 

 Frosty fesses to being really REALLY wrong!  I'm sure someone out there has given the flap cap, ash dump a try and discovered my embarrassingly obvious screw up but kept mum or maybe mentioned it but not loudly enough. WHEN I make mistakes please, PLEASE bring it up! Kick my cage a couple ties if necessary. 

Frosty The Lucky. 

[Irondragon Forge ClayWorks]

I thought I was wrong once, however my wife corrected me.

[Frosty]

Not enough zeros?

Frosty The Lucky. 

[Zeke Zabo]

How about using a beam clamp to attach a counter weight. They have a 1/4-20 threaded hole and a screw when you buy them at the local box store. I used one to fix/attach a missing fan blade when restoring my handle forge. They come in a bunch of sizes and have a ton of uses.

 

[Frosty]

Beam clamp? Uh . . .  Google google google. Ooooh I LIKE! If you can buy singletons that looks to be about as simple and easy a counter weight as there is.

Thanks Zeke!

Frosty The Lucky. 

[Zeke Zabo]

Sorry Frosty, should have posted a picture:

I've bought them by the case  (back when I used to, surprisingly, attach stuff to beams) but buy them now as a couple at a time. The next use is to attach an axle to the lever forge legs so I can add wheels and move it in/out of my make shift work shop..... a tent-like car port.

Regards, Zeke

[Frosty]

Don't apologize Zeke, I Yahoo'd it, pictures abound and they're available within a couple miles. I'm just a little embarrassed I didn't think of the things even if I spent time in school learning fabrication. So it was 45 years ago. Still it's a common device to NOT be aware of on a level to have it come to mind. I even have use for the things in my shop and I've been thinking of work arounds. 

Probably comes from too many years as a field guy who had to make do when things broke.

shop weathered in just before the accident so it's still lacking insulation, electric, etc. It's good though keeps my stuff mostly dry and I'm still kicking. 

Frosty The Lucky.