Brand new here (and to the craft), just begun building a JABOD

[Frosty]

Another feature of a vertical rail anvil is when you've run out of things to grind into bottom tools, hardy, pic, bending fork, etc. you can flip it over and get to grinding on the other end.

Frosty The Lucky.

[Charles R. Stevens]

I shamelessly stole ideas from others for mine. Their is a thread “another rail iron anvil” or some such. I carved a pair of bicks on one flange (one round and one square) and the flange into a hot cut. The other end a pair of bending forks on the flange and a fuller for the flange. Down the side of the rail head are measurement marks and in the face of the head (the face that faces up when horizontal) I carved a shallow depression to aid in cold straitenning. I extended to carve shapes in the other edge as needed. 
this makes a nice travel and demo anvil.

[ThomasPowers]

I've decided that it's important that I demo with an improvised anvil as so many folks tell me the reason they don't try blacksmithing is that it's too expensive.  Showing them they could have a decent starter setup for much less than of the cost of their cell phone may lure some over to the dark side, (the Emperor will be *pleased*!)

[Randy Griffin]

Tommy, I just added my latest mod to the original Jabod thread. Take a look. Might give you some ideas.

[TommyVee]

Wow.  That is way more elaborate than mine!   Mine is just a box of cat litter and soil with a few firebricks and a pipe sticking out at this point --- but all that's left before I can fire it up is to mount up my bellows, which I hope to find time to do in the next couple days.  Yours seems very much more than "just a box of dirt"!

[Randy Griffin]

With the bells and whistles, it’s still just a box of dirt. 

Once you use yours for a while you’ll figure out things to make it better for you. Like I said, it’s easy to make changes.

[ThomasPowers]

Think of it as a prototyping tool. Once you figure out what works for you; you can transfer that knowledge to steel...

[TommyVee]

Hello again.

As I mentioned in the "Introduce Yourself" subforum, I got my JABOD and improvised anvil set up and did a forging last weekend.  I concluded that the hand-pumped mattress inflator was not going to be ideal for me as it moved too little air for too much work.  I replaced it days later with an electric blower that I can regulate using a ball valve in line with the tuyere.  I made my first forgings with it today.  To be scientific about it, I changed nothing else --- I am now able to move air through it more easily, but everything else is the same.

The electric blower was quite good at pushing air through the charcoal, and I did get a good, hot fire going.  It took a little longer than I expected, and most annoyingly of all, the hot spot was deeper in the fire box than I had hoped --- so I could not lay material flat over the forge and get to all the parts of a bar I wanted to heat unless the bar was short enough that I could just angle it down into the hot spot to get half hot, work it, then turn it around and get the other half hot.  It appears that the hot spot is only a couple of inches in diameter, right near the exit of the tuyere and about at the same level as the top of the tuyere.

After forging the first hook (below) a lot more of the fuel in the fire pot was involved in the heat, and with the blower going it was quite hot --- enough that at one point I overheated the tip of the second piece to sparking temperature.  But the hot spot was still down a little deeper than I wanted it.

In the first image, the drive-in hook was done from a piece of 36" long 3/8" round bar, but what I had been *hoping* to do was the S-hook.  I was unable to get to the full length of material I had hoped to use and then hot-cut off of the long bar.  I had to hot cut it shorter than planned and then just give up on the idea of doing an S-hook with that piece.

The second try I just cut the bar to 7" with a hacksaw and heated up what I could of it.

The sloppy twists are mostly due to my not having a proper vise, and using a crescent wrench as a twisting wrench.  My vise is not sturdy enough (it's a cheap, clamp-on vise I had for other purposes) and wouldn't hold the bar tight enough for a full 360° twist.  By the time I got it clamped down hard enough for a 180, it had cooled everything down pretty well.  So I know what bit of kit I need next.

But my main purpose for posting here now is that I want to make changes to the forge so that I can get that hot spot up higher, so that I can lay the work across and through it instead of digging down to it.  So I'll describe my current configuration once again and illustrate with some photos.

The firebox is made from cheap firebrick from the hardware store --- it's got one 9x4.5" firebrick for a bottom, is 4.5" wide, has two vertical firebricks on each side (left/right), and one horizontal firebrick front and back  So the depth of the pit is about 3.25", and the left and right sides are about 7.75" high.  I added one loose firebrick to seal off the back when I feel the need, and lay one brick across the top to hold some of the heat in.   The second photo shows the long view.  My tuyere comes in from the right about 1" above the bottom fire brick (third photo).

My fuel is lump charcoal, which so far has worked reasonably well.  I don't have an immediate source of bituminuous coal to try, but I do have a bag of Tractor Supply nut coal (anthracite) that I might try out (yes, I know it's not ideal, and yes, I've read JHCC's thread under the solid fuels subforum which I'll consult several more times before trying it).

 

Now, my question:  If this were your forge, and you found the hot spot down about an inch lower than you want it, would you:

    a) decrease the depth of the fire box by raising the bottom and the tuyere with it?

    b) raise the tuyere up an inch and leave the bottom of the box where it is?

    c) use a bigger tuyere (mine is 3/4" ID sched 40 black pipe, and it was suggested here that maybe 1" would be better)

    c) switch fuels?

    d) something else?

 

Last image is the full view of the forge.  No, I do not forge in this location --- this is after killing the fire dead and moving it back to its storage location.  The pile of charcoal is cold, and will be shoveled into a closed bucket when it dries out.  The scorch marks on the forge box are from laying the hot rake on it.

 

 

[Glenn]

Fuel does not make the fire hot, air makes the fire hot.  Use only as much gentle air as you need to get the heat you want from the fuel.  

Start by raising the air pipe up, say an inch at a  time.  Add more fuel to insulate and keep the heat down into the fire. Insert your metal horizontally and 90 degrees to the air pipe. Adjust as needed.  The fire may only allow a short section of the stock to get hot, so slide the stock in and out (through) the fire to get a longer heat.  You can only work 4-6 inches of hot metal at a time, so multiple heats may be required. 

Learning how to use YOUR forge takes practice and making ONE adjustment at a time until you get things to work the way you would like.  Patience and one adjustment at a time is the key.

[TommyVee]

Thank you, Glenn.  Moving the tuyere up a little is probably the easiest change I could possibly make, so I'm glad you've suggested that as the best thing to try first.

I knew that I could only work a short section of metal at a time --- my issue is that with the location of the hot spot that short section is always at the very end of the piece because it has to be angled down in the forge to get to the hot spot.  If I can move that hot spot up so I can lay the stock flat, I can get a short section away from the end, like you suggest.

[Glenn]

Look at the hot spot and then adjust the forge to move the hot spot to where you want it.  Keep an amount of fuel over the top of the hot spot so it replenished the burned fuel as you forge.

[TommyVee]

Well, yeah.  That's what I was getting at with my "a" and "b" parts of my question.  Like, would moving the bottom of the fire box and tuyere together  (so the entire mass of the fire is higher up in the forge) be better than just moving the tuyere alone (so that the part of the fuel that gets breathed on is higher)?  I think you've already indicated that moving the tuyere would be the first step, and that's going to be the first thing I try.

 

[Glenn]

You may want to look at the image of a side blast forge again.  The fire is above the height of the end of the air pipe, and the ash,  slag, etc collects below the end of the air pipe.  You are trying to limit the size of the fire by placing walls at the end of the air pipe, AND limiting the size of the fire with the away wall.  The fire will naturally be in front of the air pipe on its long axis.  With no away wall, the fire and fireball will be self limiting by the fuel and the air blast used anyway. Try putting the away wall so that you can get a tennis ball or larger fireball between the two walls. 

Changing your forge design may take a little playing the design, but that is part of understanding how the forge and fire works.  Easiest way to start is to remove the away wall, add more fuel, and then look at how the fire wants to work.  Once you get things working, you can add a stock rest so the stock naturally locates horizontally and 1/2 to 2/3 of the way up the fireball.  

 

[TommyVee]

Hmmmmm.  I see what you're saying, but at least *some* of what you say to do is what I've already done (obviously not all of it).  The away wall is 4.5 inches away from the end of the air pipe, so it would seem that the box is more than wide enough for a tennis ball sized fireball  --- are you saying that having it this wide could be forcing the fireball even smaller?  As it is, the fuel at the far side of the box doesn't seem to be burning very hot at all. 

The air pipe is just a bit back from the near wall to limit how much it gets burned and increase its lifespan, as many in the JABOD threads have advocated placing it.  And the fire seems to be limiting itself to something a good bit smaller than that.  I'd say the fireball is about 2" in diameter, and roughly level with the end of the air pipe rather than above it.

I'm no arteest, but here's what a side view of my forge looks like, sketched freehand.  The red blob is around where the hottest part of the fire is --- very close to the end of the air pipe, and very much *not* well above it as your diagram shows (and where I'd like it to be).  The cross section is through the air pipe, so the dashed boxes saying "fire brick" are well back from the plane of the image and provided only to show relative position. [EDIT:  after posting, I see that the forum has cropped the image and cut off the label at the very bottom showing the pot width to be 4.5"]

Now, my tuyere *is* angled down slightly (maybe 15° or less, the sketch is exaggerated) --- I angled it down like this precisely because other articles in these JABOD threads suggested it.  It's an inch above the bottom instead of right at the bottom to allow for the possibility that I might switch from charcoal to bituminous coal, to allow space for clinker to collect without clogging the pipe.  The dashed boxes marked "fire brick support" underneath the tuyere are just chunks of firebrick that serve as a base for the tuyere so it has something more firm than soil and kitty litter to keep it in place.

I've drawn fuel in there as deep as the front and back of my fire box (which are lower than the side walls to allow the work to be laid flat over the forge), but that's not exactly how I've been using it --- I *have* been trying to pile fuel above that level (and above the work piece) in practice to keep fresh fuel available to settle down  and to provide some insulation above.  Doing so does clearly make that hot spot much hotter, but it's still pretty deep.

Moving the air pipe another inch up would put it about 2" above the bottom and slightly closer to level, which may be just what the doctor's ordering.

I can certainly adjust the width and depth of the box and the location of the air pipe (it's mostly a JABOD after all), and will experiment with the variables.  I thank you for suggesting that my first variable to tweak should be the height of the air pipe, as that's the easiest to tweak anyway.  I'll also experiment with removing the far wall as you suggest, but that's a little trickier as that far wall is keeping the soil and kitty litter from trickling into the fire. 

Unfortunately, I'm only able to fire it up about once a week, weather permitting (more importantly, *wind* permitting), so may go through several weeks of experimenting  before I get it tuned right.  Thank you for your help focusing my experiments.

[Randy Griffin]

The first thing I would change is the angle of the tuyere. It needs to be level or slightly angled up. That should raise your hot spot.

The hot spot tends to be directly over the end of the tuyere so if it’s against a brick the hot spot will be against the brick. Look at my pictures again. The end of my tuyere is about middle of my duck nest and covered with clay. My hot spot can spread in all directions.

[TommyVee]

Ok.  Thanks for that.  I had seen a number of posts that said it should be angled down, so I'll adjust this.  I'll look at your pictures again, too.  I had not noticed that detail.

[TommyVee]

Thanks for the tips, everyone.  I have had one chance to forge since posting my query, and simply raising the tuyere to level and about an inch higher has adjusted my hotspot to a more workable place.   I can now lay material flat and get it hot wherever along its length that I I want to get it hot, which was the big problem I needed to solve. 

I'll make other tweaks to the geometry of the fire pit and location of the end of the tuyere one bit at a time until I am really happy with it. The comments here are pointing the way.