Good morning and/or afternoon and/or evening! I've gotten myself a better, non-galvanized pipe for my tuyere, but I need a grate. What can I use? Here are some photos of my JABOD as it is.

 

If you have the pipe coming in from the side, there's no need for a grate.

Exactly, what John said. A JABOD is a SIDE BLAST forge into a trench. What you've started on is an unworkable BOTTOM blast. Plastic directly below the fire will fail.

Frosty The Lucky.

I had it as a side blast before, but I couldn't get that to work, so I thought it might work better as a bottom blast. Was I wrong? Should I make it a side blast again?

Yes. A side blast is simpler to make and to repair. See the original JABOD thread for a good discussion of dimensions and setup.

What didn't work with your earlier setup? 

Yes. You have to learn fire management, the forge is literally just a fire place and can't do anything without the human hand.

Even a properly designed and built bottom blast takes more skill to manage and burns through charcoal like crazy regardless.

You'll probably get sick of hearing this from me but it's important to learn. NO tool is anything but highly refined dirt just waiting to return to the soil it can not do anything else. It's the human that does things with tools and that requires a little knowledge and a LOT of practice. There are no shortcuts or tricks.

A person can't practice this craft at a level of competent without investing sweat, sore muscles, cuts, burns and study. Read and study an idea and or technique means little until You take it to the anvil and develop the experience to put it to work for you.

It's just how the real world is. We're not trying to discourage you, we LOVE new folks taking up the craft and making things we can look at, admire and maybe copy. 

Frosty The Lucky.

Good to know, thanks. I guess I have more work to do... Better than sitting around doing nothing. The way I had it before, it didn't seem to be getting hot enough. I was able to get some rebar to a red heat one time, and then I heard somewhere(I forget where, maybe I should be more hesitant to trust information from uncertain sources...) that bottom blast was generally superior, so I figured that might work better. I'm glad I did switch it though, because it made me slow down and stop trying to use galv.

Fire management is key, and will vary depending on what fuel you're using. 

If you do keep it setup as a bottom blast, flip your “y” pvc coupler over and add a steel pipe section below it. That way any hot coals or clinker that falls in is more likely to drop straight through to a heat resistant section. PVC won’t last long with hot coals in it.

Keep it fun,

David 

Maybe it wasn't clear in the image, the PVC is open at the bottom, so in theory any coals that do fall will just fall through and land either in a steel bucket, or in a plastic bucket filled with water. I'm not quite sure why you think I should flip the y over, if I did that, wouldn't the air go down?

Geoffrey: The plastic pipe WILL NOT WORK. I don't know how many times experienced smiths have told you that already but I'm pretty sure this is #3 from me. 

Forget ANY plastic attached to the air grate, PERIOD, forget attaching it to the T in the air supply. 

If you're taking a welding class you're in luck the drawing below is an easy to make low cost and very effective air supply for a bottom blast forge. All that's necessary to add to the below is a flange welded to the exhaust pipe vertical section and and screw or rivet the flange to the pan or firepot and it's a done deal.

This is a rendering of one I made before I thought of an easy way to make the ash dump. An updated version has you visiting a truck exhaust shop and buying one each. Exhaust cap. Those are the caps on top of truck exhaust stacks that open when the engine is running and fall closed when it's not. Yes? While you're there ask for a piece of exhaust pipe it will fit. The commercial versions clamp to the pipe with a clamp similar to an exhaust clamp so you need the pipe it fits. A shop that works on truck exhaust systems should have plenty of drops (short cut offs) kept for places they'll fit so they don't have to cut a short piece out of a new length. 

The horizontal air supply pipe is 2" exhaust and only needs to be maybe 10" long and is welded to the vertical. It connects via a piece of vacuum cleaner hose to my hand crank blower or other smaller air supply, bellows, etc.

Things I learned making this one. The vertical pipe above the air supply only needs to be long enough to reach the bottom of the forge pan or firepot. The one in the pic is way too long. If you have hole saws simply drill a hole the vertical pipe barely fits through just far enough, 1/16" is plenty so it's easy to weld with a gmaw welder to make the mounting flange. Don't make the flange large, a couple inches wider is all you need for pop rivets and 4 is plenty.

Make the length of pipe below the air supply 8 maybe 10" below for the ash catcher, you want the hot clinker, coals, etc. far enough below the air supply it stays cool even if the air isn't blowing.

I welded the long extension to the exhaust cap thinking it would need the extra weight to close but the counter weight on the truck part is designed to close the cap and is long enough to reach under the forge with tongs, piece of stock, hammer, etc. and open to dump the ash.

Anyway, that's all it there is to it. pop rivet or use self tapping screws to attach it to the bottom of your forge table, firepot or whatever and your fire grate just lays on the opening. 

There's no need to weld one of these up, plumbing fittings work just fine but have you looked at the price of a 2" T lately!

My preference for a forge is a "Duck's Nest" which is basically a hole in a fire proof table covered in tamped field soil. The duck's nest is a space over the air supply scraped clean and covered with a grate. My grate is IIRC 4 or 5 pieces of 1.2" round steel a couple inches longer than the hole and loosely held in position by the compacted soil. The openings in the grate all being long narrow spaces makes cleaning easy my fire rake is a piece of square stock flattened at the working end with a small point that just fits between the grate bars. Scrape the grate with it flat and the junk comes right up and out if something is stuck the point picks it off the bars easily. If worse comes to worse, scrape the soil back and take the stuck bar(s) out and put fresh ones it.

It's all surprisingly EZ. PZ. and works a treat.

Frosty The Lucky.

I don't think I understand, what's the issue with using plastic? Even if coals fall through the grate, they won't touch any plastic, and if they do, as long as they don't go into the offshoot in the y joint, they won't touch it for long enough to do much if anything, since the PVC is open on the bottom and I'm going to put something underneath it that won't burn or melt.

You're need to "understand" the how and why largely comes from lack of knowledge and experience being a newcomer.

Seeing as you won't just take our word for it it's time you knock yourself out and give it a try. 

I don't have the patience to play Why why why.

Frosty The Lucky.

I'd lay heavy odds that at any reasonable level of blast, the air will change directions and exit through the bottom before it forces it way up through the fire.  And of course if you block off the bottom, you'll be trapping hot coals in the plastic pipe.

If you're determined to try this, submerging the end of the pipe a few inches deep in a bucket of water might create enough of a seal to force the air upward.  In addition to coals falling down the wrong pipe, you'd still need to deal with heat radiated down the steel pipe and conducted through its walls, as well as steam from coals quenching themselves and probably some other factors I haven't thought of.  But it might work long enough for you to learn something -- just make sure there's a fire extinguisher handy.

In theory, the pipe might not come in direct contact with hot coals. However, that would only happen if the bottom were open, and as Mike BR points out, that would allow the air to escape and make the whole thing useless. 

Even if by some miracle there were no direct contact, there’s going to be enough heat there to soften and degrade the plastic, and PVC gives off toxic chlorine gas as it degrades.

For a grate a couple holes drilled and a couple nails making an "X" is sufficient. Heck some do not even use a grate. But like has been said a bottom blast you should use coal.

I use a piece of grill from an old BBQ i had. 

You can also get a flat plate and drill a bunch of holes in it. 

What are you using for air supply? If you have too much air that will also keep the fire from getting hot enough. Too much air will just blow the heat out of the fire. Charcoal only needs a whisper of air to get to temp. 

Good call John, ABS and PVC or heck any plastic gives off Phosgene if heated enough to soften unless it's a "thermal plastic" and you don't want to know what phosgene poisoning is like. Probably a good thing to look up. Don't forget the images.

Frosty The Lucky.

One of the things I remember from firefighter training was how the PVC coating on all the wiring in modern buildings can release chlorine during a fire; hence WEAR YOUR AIRPACK!

Okay, I looked it up and you're right. Turns out phosgene would be a product of burning

plastics if the heat didn't break it down almost on creation into CO and CL2.

Where the ease of producing phosgene accidentally really sticks with me is it's formation with UV irradiation of CO and any chlorine containing chemical like the old style Carburator cleaner and spray degreasers. One of the guys in the drill shop was famous for walking up to the welding table and spraying degreaser or starting fluid on greasy parts. WHILE  I was welding! Use the solvent tank on the far end of the shop? Oh no, starting fluid worked faster. 

Finally I said his name while he was degreasing something while I was welding and just like his dim old self he didn't stop spraying when he looked at me and I got to strike an arc in the stream of starting fluid. WHOOSH!

I got called into the office for a stern talking to until I told them what doofus did andEY thought about degreasing things on the welding table. 

From then on he used starting fluid to degrease things outside. 

Frosty The Lucky.

Phosgene was used as a war gas in WW1 and according to Wiki was responsible for 85,000 deaths.  Based on my military chemical warfare training it is really nasty stuff and is worth avoiding at all costs. 

Back a few years ago we were restoring a '43 Pontiac Chieftain. We pulled the straight 8 out and were putting in a 327 with a powerglide. I was at the bench rebuilding the trans and happily spraying the valve body down with brake clean, back when it was trichlorethylene, while a freind was working inside the car happily grinding out the rusted parts of the floor board. That was when i felt the rapid increase in temp on my behind. I turned around and the sparks from the grinder had ignited the copious amount of brake clean on the floor. 

Phosgene is a horrific way to die, worse than mustard gas. Just the thought of suffocating while you bleed out through your dissolved lungs, sinuses, mouth, throat, etc. should be enough to make a person super careful. As in find an alternative.

We worked with several different types of TRICH as strong CO 3CL solvents were known as, in the Materials lab only needed a little UV, say sunshine. to start making people sick. 

Being extremely flammable is just a little bonus. Your friend's name wasn't Ralph was it Billy?

Frosty The Lucky.

I don't think I'm going to use the PVC pipe after hearing this...

Thanks for the warning, I'll get some fittings that won't kill me.

Good man, we WANT to see what cool stuff you make over the decades. We're greedy that way you know.

Frosty The Lucky.